U.S. patent application number 09/767140 was filed with the patent office on 2002-09-26 for processes for large scale production of tetrapyrroles.
This patent application is currently assigned to Miravant Pharmaceuticals, Inc.. Invention is credited to Garcia, Barbara A., Robinson, Byron C..
Application Number | 20020137924 09/767140 |
Document ID | / |
Family ID | 25078596 |
Filed Date | 2002-09-26 |
United States Patent
Application |
20020137924 |
Kind Code |
A1 |
Robinson, Byron C. ; et
al. |
September 26, 2002 |
Processes for large scale production of tetrapyrroles
Abstract
Processes for the large scale production of tetrapyrrolic
compounds useful as photosensitizers in photodynamic therapy, such
as meso-formyl porphyrins, meso-acrylate porphyrins, purpurins and
benzochlorins. In particular, tin ethyl etiopurpurin (SnET2) and
the intermediates necessary for its production without
chromatography are disclosed.
Inventors: |
Robinson, Byron C.; (Santa
Barbara, CA) ; Garcia, Barbara A.; (Ventura,
CA) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT &
DUNNER LLP
1300 I STREET, NW
WASHINGTON
DC
20005
US
|
Assignee: |
Miravant Pharmaceuticals,
Inc.
|
Family ID: |
25078596 |
Appl. No.: |
09/767140 |
Filed: |
January 23, 2001 |
Current U.S.
Class: |
540/145 ;
548/518 |
Current CPC
Class: |
A61K 41/0071 20130101;
C07D 487/22 20130101 |
Class at
Publication: |
540/145 ;
548/518 |
International
Class: |
C07D 487/22; C07D
43/14 |
Claims
What we claim is:
1. A process for isolating a mono-formylated tetrapyrrolic compound
comprising: a) contacting a reaction product containing mono- and
di-formylated tetrapyrrolic compounds with a solvent to form a
solution thereof; b) adding an alkylcarboxylic acid precipitating
solvent to the solution; c) distilling all or a sufficient portion
of the first solvent from the solution to precipitate from the
solution formylated tetrapyrrolic compounds having a smaller
proportion of di-formylated tetrapyrrolic compounds than was
present in the reaction product; and d) isolating formylated
tetrapyrrolic compounds from the resulting distillate having a
smaller proportion of di-formylated tetrapyrrolic compounds than
was present in the reaction product.
2. The process of claim 1, wherein steps a), b), c), and d) are
repeated.
3. The process of claim 1, wherein the solvent is selected from
dichloroethane, dichloromethane, ethyl acetate, tetrahydrofuran,
acetonitrile, acetone, benzene, toluene and ether.
4. The process of claim 3, wherein the precipitating solvent is
selected from acetic acid, propionic acid, butyric acid, pentanoic
acid, hexanoic acid, heptanoic acid, and octanoic acid.
5. The process of claim 4, wherein the solvent is methylene
chloride and the precipitating solvent is acetic acid.
6. The process of claim 1, wherein the formyl tetrapyrrolic
compound is a meso-formylated tetrapyrrolic compound.
7. The process of claim 1, wherein the formyl tetrapyrrolic
compound is a .beta.-formylated tetrapyrrolic compound.
8. The process of claim 1, wherein the formyl tetrapyrrolic
compound is Nickel (II) meso-formyl etioporphyrin I.
9. The process of claim 1, wherein the formyl tetrapyrrolic
compound is Nickel (II) meso-formyl octaethylporphyrin.
10. The process of claim 1, wherein the formyl tetrapyrrolic
compound is a metallo-derivative with Copper (II) or Nickel (II)
bound to the central inner nitrogens.
11. The process of claim 1, wherein the formyl tetrapyrrolic
compound is a meso-formyl porphyrin selected from Copper (II)
etioporphyrin I, Nickel (II) etioporphyrin I, Copper (II)
etioporphyrin II, Nickel (II) etioporphyrin II, Copper (II)
octaethylporphyrin Nickel (II) octaethylporphyrin I, Copper (II)
coproporphyrin I tetra-alkyl ester, Nickel (II) coproporphyrin I,
tetra-alkyl ester, Copper (II) coproporphyrin II, tetra-alkyl
ester, Nickel (II) coproporphyrin II, tetra-alkyl ester, Copper
(II) mesoporphyrin di-alkyl ester, Nickel (II) mesoporphyrin
di-alkyl ester, Nickel .beta.-formyl tetraphenyl porphyrin, Nickel
.beta.-formyl tetrakis((4'-methyl)phenyl))porphyrin, and Nickel
.beta.-formyl tetrakis((4'-carbomethoxy)phenyl) porphyrin.
12. The process of claim 1, wherein the formyl tetrapyrrolic
compound is selected from a metallo-meso-formyl chlorin, a
metallo-meso-formyl bacteriochlorin, a metallo-meso-formyl
iso-bacteriochlorin, a metallo-meso-formyl corrole, a
metallo-meso-formyl porphyracene, and a metallo-meso-formyl
azaporphyrin.
13. The process of claim 6, wherein the formyl tetrapyrrolic
compound is selected from a meso-formyl chlorin, a meso-formyl
bacteriochlorin, a meso-formyl iso-bacteriochlorin, a meso-formyl
corrole, a meso-formyl porphyracene, and a meso-formyl
azaporphyrin.
14. A process for formylating a metallo-tetrapyrrolic compound
comprising: a) dissolving or partially dissolving a reaction
product containing a metallo-tetrapyrrolic compound in a solvent
that includes dichloromethane; b) adding a Vilsmeier reagent to the
reaction product mixture; c) heating the reaction product mixture
to a temperature and at a pressure sufficient to form the iminium
salt intermediate of the metallo-tetrapyrrolic compound; d)
hydrolyzing the resulting tetrapyrrolic iminium salt at a
temperature and pressure sufficient to produce the desired formyl
metallo-tetrapyrrolic compound.
15. The process of claim 14, wherein the metallo-tetrapyrrolic
reaction product mixture is heated past the boiling point of the
solvent or solvents.
16. The process of claim 14, wherein the solvent is
dichloromethane.
17. The process of claim 14, wherein the temperature of the
reaction product mixture is maintained at 35-65.degree. C. during
the Vilsmeier reaction.
18. The process of claim 17, wherein the temperature of the
reaction product mixture is maintained at 50-60.degree. C. during
the Vilsmeier reaction.
19. The process of claim 14, wherein the metallo-tetrapyrrolic
compound is selected from Nickel (II) etioporphyrin I, Nickel (II)
octaethylporphyrin, and Nickel (II) coproporphyrin I tetraalkyl
ester.
20. A process for formylating a metallo-tetrapyrrolic compound
comprising: a) dissolving or partially dissolving a
metallo-tetrapyrrolic reaction product in dichloromethane; b)
adding a Vilsmeier reagent to the metallo-tetrapyrrolic reaction
product mixture; c) refluxing the solution at a temperature and
pressure sufficient to form the iminium salt intermediate of the
metallo-tetrapyrrolic compound; d) hydrolyzing the resulting
tetrapyrrole iminium salt at a temperature and pressure sufficient
to produce the desired formyl tetrapyrrolic compound.
21. The process of claim 20, wherein the metallated tetrapyrrolic
compound is selected from Nickel (II) etioporphyrin I, Nickel (II)
octaethylporphyrin, and Nickel (II) coproporphyrin I tetraalkyl
ester.
22. The process of claim 20, wherein the metallated tetrapyrrolic
compound has a symmetrical peripheral substitution pattern.
23. A process for producing a mono- or di-acrylate tetrapyrrolic
compound comprising: a) contacting a mono- or di-formyl
tetrapyrrolic compound, a Wittig reagent, and dimethylformamide to
form a slurry; b) melting the slurry under an inert atmosphere at a
temperature sufficient to produce the corresponding mono or
di-acrylate tetrapyrrolic product.
24. The process of claim 23, wherein the weight of
dimethylformamide ranges from about 90% to about 110 % of the
weight of the starting mono or di-formyl tetrapyrrole.
25. The process of claim 23, wherein the dimethylformamide
functions to keep any unreacted Wittig or mono- or diformyl
tetrapyrrolic compound in the reaction melt.
26. A process for isolating a mono or di-acrylate tetrapyrrolic
compound comprising: a) contacting a reaction product containing a
mono or di-acrylate tetrapyrrolic compound with a solvent to form a
solution thereof; b) adding a precipitating solvent to the
solution; c) distilling a portion of the solvent from the solution;
d) isolating the mono or di-acrylate tetrapyrrolic compound from
the resulting solution.
27. The process of claim 26, wherein the steps a), b), c), d) are
repeated.
28. The process of claim 26, wherein both the solvent and the
precipitating solvent are halogenated solvents.
29. The process of claim 26, wherein the solvent is a
non-halogenated solvent and the precipitating solvent is a
halogenated solvent.
30. The process of claim 26, wherein both the solvent and the
precipitating solvent are non-halogenated solvents.
31. The process of claim 26, wherein the solvent is a halogenated
solvent and the precipitating solvent is a non-halogenated
solvent.
32. The process of claim 26, wherein the solvent is selected from
dichloroethane, dichloromethane, ethyl acetate, tetrahydrofuran,
acetonitrile, acetone, benzene, toluene and ether.
33. The process of claim 26, wherein the precipitating solvent is
selected from acetic acid, propionic acid, methanol, ethanol,
1-propanol, 2-propanol, 1-butanol, hexanes, acetonitrile, ethyl
acetate and iso-octane.
34. The process of claim 26, wherein the solvent is methylene
chloride and the precipitating solvent is ethanol or methanol.
35. The process of claim 26, wherein the mono- or di-acrylate
tetrapyrrolic compound is a mono or di-meso-acrylate tetrapyrrolic
compound.
36. The process of claim 26, wherein the mono or di-acrylate
tetrapyrrolic compound is a .beta.-substituted mono or di-acrylate
tetrapyrrolic compound.
37. The process of claim 26, wherein the mono or di-acrylate
tetrapyrrolic compound is both .beta.- and meso-acrylate
substituted.
38. The process of claim 26, wherein the mono-acrylate
tetrapyrrolic compound is selected from Nickel (II) meso-acrylate
etioporphyrin I, Nickel (II) meso-acrylate octaethylporphyrin,
Nickel (II) meso-acrylate coproporphyrin I tetra ester, Copper (II)
meso-acrylate etioporphyrin I, Copper (II) meso-acrylate
octaethylporphyrin, and Copper (II) meso-acrylate coproporphyrin I
tetra ester.
39. The process of claim 26, wherein the di-acrylate tetrapyrrolic
compound is selected from Nickel (II) 5, 15 -diacrylate
etioporphyrin I Nickel (II) 5, 10 -diacrylate etioporphyrin I,
Nickel (II) 5, 15-diacrylate octaethylporphyrin, Nickel (II) 5,
10-diacrylate octaethylporphyrin, Nickel (II) 5, 15-diacrylate
coproporphyrin I tetra ester, Nickel (II) 5, 10-coproporphyrin I
tetra ester, Copper (II) 5, 15-diacrylate octaethylporphyrin,
Copper (II) 5, 10-diacrylate octaethylporphyrin, Copper (II) 5,
15-diacrylate coproporphyrin I tetra ester, and Copper (II) 5,
10-diacrylate coproporphyrin I tetra ester.
40. The process of claim 26, wherein the mono or di-acrylate
tetrapyrrolic compound is a metallo-derivative with Copper (II) or
Nickel (II) bound to the central inner nitrogens.
41. The process of claim 26, wherein the precipitating solvent
decreases the amount of impurities in the resulting product.
42. The process of claim 26, wherein the mono-acrylate
tetrapyrrolic compound is a metallo-mono-meso-acrylate porphyrin
selected from Copper (II) meso-formyl coproporphyrin I tetra ester,
Nickel (II) meso-formyl coproporphyrin I tetra ester, Copper (II)
meso-formyl coproporphyrin II tetra ester, Nickel (II) meso-formyl
coproporphyrin II tetra ester, Copper (II) meso-formyl
mesoporphyrin di-ester, and Nickel (II) meso-formyl mesoporphyrin
di-ester.
43. The process of claim 26, wherein the mono or di-acrylate
tetrapyrrolic compound is selected from a metallo-mono- or
di-acrylate chlorin, a metallo- mono- or di-acrylate
bacteriochlorin, a metallo- mono- or di-acrylate
iso-bacteriochlorin, a metallo- mono- or di-acrylate corrole, a
metallo- mono- or di-acrylate porphyracene, and a metallo- mono-or
di-acrylate azoporphyrin.
44. A process for demetallating a metallo-tetrapyrrolic compound
comprising: a) dissolving the metallo-tetrapyrrolic compound in a
solvent or mixture of solvents that is not water soluble; b) adding
an acid capable of removing the central co-ordinated metal of the
metallo-tetrapyrrolic compound to the solvent or mixture of
solvents containing the metallo-tetrapyrrolic compound with
stirring or agitation; and c) waiting a period of time sufficient
to effect the demetallation.
45. The process of claim 44, wherein said demetallation is effected
when the solvent or mixture of solvents becomes essentially
colorless.
46. The process of claim 44 wherein the solvent or mixture of
solvents is selected from dichloromethane, chloroform,
1,2-dichloroethane, 1,1-dichloroethane, toluene, xylene, benzene,
hexane, and ether.
47. The process of claim 44, wherein the acid is selected from
sulfuric acid, hydrochloric acid, and phosphoric acid.
48. The process of claim 44, wherein the weight of acid added
ranges from about 90% to about 110% of the initial dry weight of
the metallo-tetrapyrrolic compound.
49. The process of claim 44, wherein the metallo-tetrapyrrolic
compound is selected from Nickel (II) meso-acrylate etioporphyrin
I, Copper (II) meso-acrylate etioporphyrin I, Nickel (II)
meso-acrylate octaethylporphyrin, Copper (II) meso-acrylate
octaethylporphyrin, Nickel (II) meso-acrylate coproporphyrin I or
II tetra-ester, and Copper (II) meso-acrylate coproporphyrin I or
II tetra ester.
50. The process of claim 49, wherein the metallo-tetrapyrrolic
compound is a metallated di-acrylate porphyrin.
51. A process for demetallating a metallo-tetrapyrrolic compound
comprising: a) adding an acid capable of removing the central
coordinated metal of a metallo-tetrapyrrolic compound to a reactor
vessel with stirring or agitation; b) dissolving a
metallo-tetrapyrrolic compound in a solvent or mixture of solvents
that is not water soluble; c) adding the solution of
metallo-tetrapyrrolic compound to the reactor vessel containing the
acid with stirring or agitation; and d) waiting a period of time
sufficient to effect said demetallation.
52. The process of claim 51, wherein said demetallation is effected
when the solvent or mixture of solvents becomes essentially
colorless.
53. The process of claim 51, wherein the solvent or mixture of
solvents is selected from dichloromethane, chloroform,
1,2-dichloroethane, 1,1-dichloroethane, toluene, xylene, benzene,
hexane, and ether.
54. The process of claim 51, wherein the acid is selected from
sulfuric acid, hydrochloric acid, and phosphoric acid.
55. The process of claim 51, wherein the weight of acid added
ranges from about 90% to about 110% of the initial dry weight of
the metallo-tetrapyrrolic compound.
56. The process of claim 51, wherein the metallo-tetrapyrrolic
compound is selected from Nickel (II) meso-acrylate etioporphyrin
I, Copper (II) meso-acrylate etioporphyrin I Nickel (II)
meso-acrylate octaethylporphyrin, Copper (II) meso-acrylate
octaethylporphyrin, Nickel (II) meso-acrylate coproporphyrin I or
II tetra-ester, and Copper (II) meso-acrylate coproporphyrin I or
II tetra ester.
57. The process of claim 51, wherein the metallo-tetrapyrrolic
compound is a metallated di-acrylate porphyrin.
58. A process for demetallating a metallo-tetrapyrrolic compound
comprising: a) forming a solution of a metallo-tetrapyrrole in a
solvent or mixture of solvents that is not water soluble; b)
simultaneously adding said solution and an acid that is capable of
removing the central co-ordinated metal of a metallo-tetrapyrrolic
compound to a reactor vessel with stirring or agitation; and c)
waiting a period of time sufficient to effect said
demetallation.
59. The process of claim 58, wherein said demetallation is effected
when the solvent or mixture of solvents becomes essentially
colorless.
60. The process of claim 58, wherein the acid is selected from
sulfuric acid, hydrochloric acid, and phosphoric acid.
61. The process of claim 58, wherein the weight of acid added
ranges from about 90% to about 110% of the initial dry weight of
the metallo-tetrapyrrolic compound.
62. The process of claim 58, wherein the metallo-tetrapyrrolic
compound is selected from Nickel (II) meso-acrylate etioporphyrin
I, Copper (II) meso-acrylate etioporphyrin I, Nickel (II)
meso-acrylate octaethylporphyrin, Copper (II) meso-acrylate
octaethylporphyrin, Nickel (II) meso-acrylate coproporphyrin I or
II tetra-ester, and Copper (II) meso-acrylate coproporphyrin I or
II tetra ester.
63. The process of claim 62, wherein the metallo-tetrapyrrolic
compound is a metallated di-acrylate porphyrin.
64. A process for isolating a mono or di-acrylate tetrapyrrolic
compound from a demetallation reaction mixture comprising: a)
adding water to a reaction mixture containing a solvent or mixture
of solvents that is not water soluble, a demetallated tetrapyrrolic
compound, and an acid; b) neutralizing or partially neutralizing
the aqueous phase of the mixture; c) separating the organic phase
of the mixture from the aqueous phase; d) adding a precipitating
solvent or mixture of precipitating solvents to the organic phase;
e) distilling the solvent or mixture of solvents at least partially
from the reaction mixture to induce precipitation or
crystallization; and f) separating the solid from the remaining
solution and isolating the desired mono or di-acrylate
tetrapyrrolic compound.
65. The process of claim 64, wherein steps a), b), c), d) are
repeated.
66. The process of claim 64, wherein both the solvent or mixture of
solvents and the precipitating solvent or mixture of solvents
includes a halogenated solvent.
67. The process of claim 64, wherein the solvent or mixture of
solvents includes a non-halogenated solvent and the precipitating
solvent or mixture of solvents includes a halogenated solvent.
68. The process of claim 64, wherein both the solvent or mixture of
solvents and the precipitating solvent or mixture of solvents
includes a non-halogenated solvent.
69. The process of claim 64, wherein the solvent or mixture of
solvents includes a halogenated solvent and the precipitating
solvent or mixture of solvents includes a non-halogenated
solvent.
70. The process of claim 64, wherein the solvent is methylene
chloride and the precipitating solvent is ethanol or methanol.
71. The process of claim 64, wherein the mono- or di-acrylate
tetrapyrrole is a mono or di-meso-acrylate tetrapyrrolic
compound.
72. The process of claim 64, wherein the mono or di-acrylate
tetrapyrrolic compound is a .beta.-substituted mono or di-acrylate
tetrapyrrolic compound.
73. The process of claim 64, wherein the mono or di-acrylate
tetrapyrrolic compound is .beta.- and meso-acrylate
substituted.
74. A process for cyclizing a mono-meso-acrylate tetrapyrrolic
compound to the corresponding purpurin comprising heating a
solution of a mono-meso-acrylate tetrapyrrolic molecule in a
solvent or mixture of solvents having a boiling point greater than
about 80.degree. C. in the presence of a non-nucleophilic base with
a pKa greater than about 10.8 under conditions sufficient to form
the cyclized purpurin.
75. The process of claim 74, wherein said non-nucleophilic base is
selected from 1,5-diazabicyclo[4.3.2]non-5-ene,
1,8-diazabicyclo[5.4.0]un- dec-7-ene, tetramethylguanidine,
piperidine, and pyrrolidine.
76. The process of claim 74, wherein the solvent is toluene.
77. A process for isolating a purpurin from an acetic acid or base
catalyzed cyclization reaction of a tetrapyrrolic compound
comprising: a) removing all or substantially all of the liquid from
the cyclization reaction product; b) forming a solution of the
remaining reaction product in a solvent or mixture of solvents; c)
adding a precipitating solvent or mixture of solvents to the
solution; d) removing the solvent or mixture of solvents at least
partially from the reaction mixture to induce precipitation or
crystallization of the desired purpurin; e) separating the solid
from the remaining solution and isolating the desired purpurin
compound.
78. The process of claim 77, wherein steps b), c), d), e) are
repeated.
79. The process of claim 77, wherein the solvent or mixture of
solvents contains a halogenated solvent and the precipitating
solvent or mixture of solvents contains a non-halogenated
solvent.
80. The process of claim 77, wherein the both the solvent or
mixture of solvents and the precipitating solvent or mixture of
solvents contain a halogenated solvent.
81. The process of claim 77, wherein both the solvent or mixture of
solvents and the precipitating solvent or mixture of solvents
contain a non-halogenated solvent.
82. The process of claim 77, wherein the solvent or mixture of
solvents contains a non-halogenated solvent and the precipitating
solvent or mixture of solvents contains a halogenated solvent.
83. The process of claim 77, wherein the solvent or mixture of
solvents is selected from dichloromethane, ether,
1,2-dichloroethane, chloroform, toluene, acetone, tetrahydrofuran,
ethyl acetate, and benzene.
84. The process of claim 77, wherein the precipitating solvent is
selected from methanol, ethanol, 1-propanol, 2-propanol, 1-butanol,
acetone, acetonitrile, hexane, heptane, octane, cyclohexane, and
isopropyl ether.
85. The process of claim 77, wherein the solvent is dichloromethane
and the precipitating solvent is acetonitrile or acetone.
86. The process of claim 77, wherein the isolated purpurin is ethyl
etiopurpurin I, the solvent is dichloromethane, and the
precipitating solvent is acetonitrile.
87. The process of claim 77, wherein the isolated purpurin is ethyl
etiopurpurin I, the solvent is dichloromethane and the
precipitating solvent is acetone.
88. A process for isolating methyl etiopurpurin from a base
catalyzed or acetic acid catalyzed cyclization reaction of
meso-acrylate etioporphyrin I comprising: a) removing all or
substantially all of the liquid from the cyclization reaction; b)
forming a solution of the remaining reaction product in a first
solvent or mixture of solvents; c) adding sodium acetate and a
solution of stannous chloride or stannous acetate predissolved in
dimethylformamide to the solution; d) warming the solution to about
30-80.degree. C. until no more meso-acrylate etioporphyrin I or
metal free porphyrinic impurities are visible by TLC; e) distilling
the solution at atmospheric or reduced pressure to remove all or
substantially all of the liquid; f) redissolving the crude solid in
a second solvent or mixtures of solvents; g) passing the solution
over a silica gel or alumina column, while eluting with a third
solvent or mixture of solvents and collecting the purpurin fraction
thereby removing the highly polar tin porphyrin impurities from the
crude reaction mixture; h) distilling the solution to remove all or
substantially all of the liquid from the purpurin fraction at
atmospheric or reduced pressure; i) redissolving the remaining
solid in a fourth solvent; j) adding a precipitating solvent or
mixture of solvents and distilling all or substantially all of the
fourth solvent from the solution to induce precipitation of the
methyl etiopurpurin; and k) isolating the methyl etiopurpurin by
filtration.
89. The process of claim 88, wherein the first solvent or mixture
of solvents is selected from 1,2-dichloromethane, acetic acid, and
propionic acid; the second solvent is selected from
dichloromethane, a dichloromethane/ethylacetate mixture, a
dichloromethane/methanol mixture, a dichloromethane/acetone
mixture, and a dichloromethane/ethanol mixture; the third solvent
is selected from a dichloromethane/ethylacetate mixture, a
dichloromethane/methanol mixture, a dichloromethane/acetone
mixture, and a dichloromethane/ethanol mixture; the fourth solvent
is selected from dichloromethane, tetrahydrofuran, and ether; and
the precipitating solvent is selected from methanol, ethanol,
1-butanol, t-butanol, 1-propanol, 2-propanol, isooctane, isopropyl
ether, and hexane.
90. The process of claim 88 wherein steps i), j), and k), are
repeated more than once.
91. A process for reducing the ester of an ester-containing
tetrapyrrolic compound comprising: a) dissolving the
ester-containing tetrapyrrolic compound in a first cholorinated
solvent or mixture of solvents; b) adding diisobutylaluminium
hydride in toluene to the solution to reduce the ester to the
corresponding alcohol; and c) quenching the reaction with a second
solvent or mixture of solvents.
92. The process of claim 91, wherein the tetrapyrrolic molecule is
selected from esters of protoporphyrin IX, esters of mesoporphyrin
IX, esters of meso-acrylate etioporphyrin I esters of meso-acrylate
octaethylporphyrin, and esters of meso-acrylate coproporphyrin I or
II.
93. The process of claim 91, wherein the first solvent is selected
from dichloromethane and 1,2-dichloroethane.
94. The process of claim 91, wherein the second solvent is selected
from isopropanol and methanol.
95. The process of claim 91, wherein the reaction is carried out at
a temperature ranging from about -80.degree. C. to about
-35.degree. C.
96. A process for converting the ester of a meso-acrylate
tetrapyrrolic compound to a benzochlorin comprising: a) dissolving
the meso-acrylate tetrapyrrolic compound in a first solvent or
mixture of solvents; b) adding diisobutylaluminium hydride in
toluene to the tetrapyrrolic molecule in the first solvent or
mixture of solvents; c) quenching the reaction with a second
solvent or mixture of solvents; d) adding an acid or mixture of
acids to the solution and distilling off the organic solvents from
the reaction while the temperature of the reaction is increased to
about 60-1 30.degree. C.; e) holding the reaction at 60-1
30.degree. C. until no more starting material remains; f) adding an
amount of water to the reaction sufficient to selectively
precipitate the benzochlorin, while leaving impurities in the
acidic aqueous solution; g) isolating the benzochlorin by
filtration; h) dissolving the crude benzochlorin in a third solvent
or mixture of solvents; i) adding a precipitating solvent or
mixture of solvents and distilling at least part of the third
solvent from the reaction to induce precipitation of the
benzochlorin; and j) isolating the benzochlorin by filtration.
97. The process of claim 96, wherein the meso-acrylate
tetrapyrrolic molecule is selected from an ester of a meso-acrylate
octaalkylporphyrin, an ester of a meso-acrylate octaethylporphyrin,
an ester of meso-acrylate etioporphyrin I or II, and an ester of
meso-acrylate coproporphyrin I or II.
98. The process of claim 96, wherein the first solvent or mixture
of solvents is selected from dichloromethane, tetrahydrofuran,
toluene, and dichloroethane.
99. The process of claim 96, wherein the second solvent or mixture
of solvents contains an alcohol, an ester, an acid or water.
100. The process of claim 96, wherein the acid or mixture of acids
is selected from phosphoric acid, methane sulfonic acid, and
hydrochloric acid.
101. The process of claim 96, wherein the fourth solvent or mixture
of solvents is selected from dichloromethane, tetrahydrofuran,
toluene, dichloroethane, acetone, benzene, N,N-dimethylformamide,
acetonitrile, and xylene.
102. The process of claim 96, wherein the precipitating solvent or
mixture of solvents in step i) is selected from water, alcohol,
hexane, isopropyl ether, iso-octane, and acetonitrile.
103. The process of claim 96, wherein the precipitating solvent is
also used to wash the benzochlorin in each of steps g) and j).
104. A method for cyclizing a
meso-((2-hydroxymethyl)vinyl)porphyrin or an alcohol protected
derivative thereof to a benzochlorin comprising contacting the
meso-((2-hydroxymethyl)vinyl)porphyrin or an alcohol protected
derivative thereof with an acid catalyst selected from phosphoric
acid, methane sulfonic acid, and hydrochloric acid under conditions
sufficient to effect the cyclization reaction.
105. A method for cyclizing a
meso-((2-hydroxymethyl)vinyl)tetrapyrrolic compound or an alcohol
protected derivative thereof to form a tetrapyrrolic compound
possessing an annelated six membered ring comprising contacting the
meso-((2-hydroxymethyl)vinyl)tetrapyrrolic compound or an alcohol
protected derivative thereof with an acid catalyst selected from
phosphoric acid, methane sulfonic acid, and hydrochloric acid under
conditions sufficient to effect the cyclization reaction.
106. A method of demetallating a metallo-benzochlorin compound
comprising contacting the metallo-benzochlorin compound with
methane sulfonic acid for a time and at a temperature sufficient to
achieve demetallation.
107. A method of demetallating a metallo-isobacteriobenzochlorin or
a metallo-bacteriobenzochlorin compound comprising contacting the
metallo-isobacteriobenzochlorin or metallo-bacteriobenzochlorin
compound with methane sulfonic acid for a time and at a temperature
sufficient to achieve demetallation.
108. A method for producing a tin (IV) tetrapyrrolic complex from
the corresponding non-metallated compound comprising: (a)
contacting the non-metallated tetrapyrrolic compound with a
solvent; and (b) bubbling an oxygen containing gas into the solvent
before or after the non-metallated tetrapyrrolic compound is
contacted by the solvent.
109. A method for producing a tin (IV) tetrapyrrolic complex
comprising: a) dissolving or suspending a metal free tetrapyrrolic
macrocycle in a solvent or mixture of solvents; b) adding a tin
salt and a proton scavenger to the solvent or mixture of solvents
before or after step (a); c) introducing an oxygen containing gas
into the solvent or mixture of solvents before or after step (a);
and d) heating the solution or suspension in the presence of the
tin salt and the proton scavenger under conditions sufficient to
form the tin (IV) tetrapyrrolic complex.
110. The method of claim 109, wherein the solvent or mixture of
solvents is selected from acetic acid, propionic acid, pyridine,
dimethylformamide, 1,2-dichloroethane, chloroform,
1,1-dichloroethane, and a halogenated solvent.
111. The method of claim 109, wherein the tin salt is selected from
SnCl.sub.2, Sn(OAc).sub.2, and Sn(acac).sub.2.
112. The method of claim 109, wherein the proton scavenger is
sodium acetate.
113. A method for producing a tin (IV) tetrapyrrolic complex
comprising: a) dissolving or suspending a metal free tetrapyrrolic
macrocycle in a first solvent or mixture of solvents; b) adding a
tin salt pre-dissolved in a second solvent and a proton scavenger
to the first solvent or mixture of solvents before or after step
(a); c) introducing an oxygen containing gas into the first solvent
or mixture of solvents before or after step (a); and d) heating the
solution or suspension in the presence of the tin salt and the
proton scavenger under conditions sufficient to form the tin (IV)
tetrapyrrolic complex.
114. The method of claim 113, wherein the first and second solvents
are selected from acetic acid, propionic acid, pyridine, and
dimethylformamide.
115. The method of claim 113, wherein the first and second solvents
are different.
116. The method of claim 113, wherein the first and second solvents
are the same.
117. The method of claim 1 13, wherein the proton scavenger is
sodium acetate.
118. A method for producing a tin (IV) tetrapyrrolic complex
comprising: a) adding a solid or pre-dissolved tin salt to a
solvent; b) heating the combination of solvent and tin salt to form
a heated solution; c) introducing an oxygen containing gas into the
solvent before or after step (a); and d) adding a metal free
tetrapyrrolic macrocycle to the solution under conditions
sufficient to form the tin (IV) tetrapyrrolic complex.
119. The method of claim 118, wherein the solvent and predissolving
solvent are selected from acetic acid, propionic acid, pyridine,
and dimethylformamide.
120. The method of claim 118, wherein the tin salt is selected from
SnCl.sub.2, Sn(OAc).sub.2, and Sn(acac).sub.4.
121. The method of claim 118, wherein a proton scavenger is added
to the solvent prior to or during step (d).
122. The method of claim 121, wherein the proton scavenger is
sodium acetate.
123. A method for producing a tin (IV) tetrapyrrolic complex
comprising: a) dissolving or suspending a cadmium tetrapyrrolic
macrocycle in a solvent or mixture of solvents; b) adding a tin
salt and a proton scavenger to the solvent; c) introducing an
oxygen containing gas into the solvent before or after step (a);
and d) heating the solution or suspension under conditions
sufficient to form the tin (IV) tetrapyrrolic complex.
124. The method of claim 123, wherein the solvent or mixture of
solvents is selected from acetic acid, propionic acid, pyridine,
and dimethylformamide.
125. The method of claim 123, wherein the tin salt is selected from
SnCl.sub.2, Sn(OAc).sub.2, and Sn(acac).sub.4.
126. A method for producing a tin (IV) tetrapyrrolic complex
comprising: a) dissolving or suspending a cadmium tetrapyrrolic
macrocycle in a solvent or mixture of solvents; b) adding a solid
or pre-dissolved tin salt to a solvent; c) introducing an oxygen
containing gas into the solvent before or after step (a); and d)
heating the solution or suspension under conditions sufficient to
form the tin (IV) tetrapyrrolic complex.
127. The method of claim 126, wherein a proton scavenger is added
to the solvent prior to or during step (d).
128. The method of claim 126, wherein the solvent or mixture of
solvents and the pre-dissolving solvent are selected from acetic
acid, propionic acid, pyridine, and dimethylformamide.
129. The method of claim 128, wherein the solvent and
pre-dissolving solvent are different.
130. The method of claim 128, wherein the solvent and
pre-dissolving solvent are the same.
131. The method of claim 126, wherein the tin salt is selected from
SnCl.sub.2, Sn(OAc).sub.2, and Sn(acac).sub.4.
132. A method for producing a tin (IV) tetrapyrrolic complex
comprising: a) adding a solid or predissolved tin salt to a
solvent; b) heating the tin salt and solvent to form a heated
solution; c) introducing an oxygen containing gas into the solvent
before or after step (a); and d) adding a cadmium tetrapyrrolic
macrocycle to the tin containing solution containing under
conditions sufficient to form the tin (IV) tetrapyrrolic
complex.
133. The method of claim 132, wherein a proton scavenger is added
to the solvent prior to or during step (d).
134. The method of claim 132, wherein the solvent and predissolving
solvent are selected from acetic acid, propionic acid, pyridine,
and dimethylformamide.
135. The method of claim 132, wherein the tin salt is selected from
SnCl.sub.2, Sn(OAc).sub.2, and Sn(acac).sub.4.
136. The method of claim 109, wherein the metal free tetrapyrrole
is selected from ethyl etiopurpurin I protoporphyrin IX, a
protoporphyrin IX ester, a protoporphyrin IX amide, octaethyl
benzochlorin, and methyl pyrropheophorbide.
137. The method of claim 113, wherein the metal free tetrapyrrole
is selected from ethyl etiopurpurin I protoporphyrin IX, a
protoporphyrin IX ester, a protoporphyrin IX amide, octaethyl
benzochlorin, and methyl pyrropheophorbide.
138. The method of claim 118, wherein the metal free tetrapyrrole
is selected from ethyl etiopurpurin I protoporphyrin IX, a
protoporphyrin IX ester, a protoporphyrin IX amide, octaethyl
benzochlorin, and methyl pyrropheophorbide.
139. The method of claim 109, wherein the metal free tetrapyrrole
is selected from a porphyrin, a corrole, a chlorin, a
bacteriochlorin, and an iso-bacteriochlorin.
140. The method of claim 113, wherein the metal free tetrapyrrole
is selected from a porphyrin, a corrole, a chlorin, a
bacteriochlorin, and an iso-bacteriochlorin.
141. The method of claim 118, wherein the metal free tetrapyrrole
is selected from a porphyrin, a corrole, a chlorin, a
bacteriochlorin, and an iso-bacteriochlorin.
142. The method of claim 109, wherein the metal free tetrapyrrole
is selected from a pheophorbide derivative, a purpurin derivative,
a benzochlorin derivative, a benzoporphyrin derivative, a chlorin
e6 derivative, a chlorin e4 derivative, a rhodin g7 derivative, a
bacteriochlorin e6 derivative, and a bacteriopheophorbide
derivative.
143. The method of claim 113, wherein the metal free tetrapyrrole
is selected from a pheophorbide derivative, a purpurin derivative,
a benzochlorin derivative, a benzoporphyrin derivative, a chlorin
e6 derivative, a chlorin e4 derivative, a rhodin g7 derivative, a
bacteriochlorin e6 derivative, and a bacteriopheophorbide
derivative.
144. The method of claim 118, wherein the metal free tetrapyrrole
is selected from a pheophorbide derivative, a purpurin derivative,
a benzochlorin derivative, a benzoporphyrin derivative, a chlorin
e6 derivative, a chlorin e4 derivative, a rhodin g7 derivative, a
bacteriochlorin e6 derivative, and a bacteriopheophorbide
derivative.
145. A method of recrystallizing or reprecipitating a tin
tetrapyrrolic compound comprising: a) dissolving the tin
tetrapyrrolic compound in a solvent or mixture of solvents; b)
adding a precipitating solvent to the solution; and c) removing the
solvent or mixture of solvents by distillation or evaporation under
conditions sufficient to effect crystallization or precipitation of
the tin tetrapyrrolic compound from the solution.
146. The method of claim 145, wherein the tin tetrapyrrolic
compound is SnET2.
147. The method of claim 145, wherein the solvent or mixture of
solvents is selected from dichloromethane, ether, dichloroethane,
chloroform, toluene, and benzene.
148. The method of claim 145, wherein the precipitating solvent is
selected from acetic acid, acetone, ethanol, methanol,
dimethylformamide, and acetonitrile.
149. The method of claim 148, wherein the precipitating solvent is
selected from acetic acid, acetone, and ethanol.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to processes especially
suitable for the large scale production of tetrapyrrolic compounds,
such as meso-formyl porphyrins, meso-acrylate porphyrins, purpurins
and benzochlorins. In particular, tin ethyl etiopurpurin (SnET2),
sometimes called rostaporfin, and the intermediates necessary for
its production without chromatography are disclosed. In addition,
much of the chemistry disclosed is applicable to the large scale
manufacturing of benzochlorins. Purpurins, benzochlorins and
several of the intermediates in the synthesis may be useful as
photosensitizers in photodynamic therapy, or as porphyrin building
blocks in the synthesis of other porphyrinic materials.
BACKGROUND OF THE INVENTION
[0002] Photodynamic therapy is a procedure that uses photoactive
(light-activated) drugs to target and destroy diseased cells.
Photoactive drugs transform light energy into chemical energy in a
manner similar to the action of chlorophyll in green plants. The
photoactive drugs are inactive until irradiated by light of a
specific wavelength, thereby enabling physicians to target specific
groups of cells and control the timing and selectivity of
treatment. The result of this process is that diseased or unwanted
cells are destroyed with less damage to surrounding normal tissues.
For a more detailed description of photodynamic therapy, see U.S.
Pat. Nos. 5,225,433, 5,198,460, 5,171,749, 4,649,151, 5,399,583,
5,459,159, and 5,489,590, the disclosures of which are incorporated
herein by reference.
[0003] A large number of naturally occurring and synthetic dyes are
currently being evaluated as potential photoselective compounds in
the field of photodynamic therapy. Perhaps the most widely studied
class of photoselective dyes in this field are the tetrapyrrolic
macrocyclic compounds generally called tetrapyrroles, some of which
are shown below. 1
[0004] In particular, and relevant to this invention, are the
chlorin ring systems called purpurins and benzochlorins. Purpurins
are a class of chlorin in which an annelated five membered
cyclopentenyl ring is directly attached to the reduced pyrrole
ring. A notable example of a metallo-purpurin that is showing great
promise in the field of photodynamic therapy is tin dichloride
ethyl etiopurpurin I (7) (currently prepared by Scheme 1). An older
method for synthesis of (7) was outlined in U.S. Pat. No.
5,051,415, the disclosure of which is incorporated herein by
reference.
[0005] Benzochlorins on the other hand have an annelated benzene
ring directly attached to the reduced pyrrole ring. A notable
example of a benzochlorin is octaethylbenzochlorin (13) (prepared
by Scheme 2) which serves as a starting chlorin for many promising
photosensitizers (see U.S. Pat. Nos. 5,552,134; 5,438,051;
5,250,668; 5,109,129; 4,988,808; 5,514,669; 6,008,211; 5,856,515;
5,744,598; 5,512,559; and 5,424,305, the disclosures of which are
incorporated herein by reference). To date, very inefficient routes
to the synthesis of purpurins and benzochlorin ring systems have
been reported and there exists no reported satisfactory method of
manufacturing these materials on a large scale. 2 3
[0006] As a result, a method that enables the synthesis of
compounds having these two ring systems, the purpurins and the
benzochlorins and their intermediates, on a large scale is of
immense value. The present invention provides processes for the
large scale preparation of meso-formyl porphyrins, meso-acrylate
porphyrins, metal free meso-acrylate porphyrins,
metallo-porphyrins, purpurins, metallated purpurins and
benzochlorin compounds, the purification steps of which are
achieved simply by fractional crystallizations.
[0007] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory only and are not restrictive of the present
invention as claimed.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0008] The present invention relates to processes for synthesizing
meso-formyl porphyrins, .beta.-formyl porphyrins, metallo
meso-acrylate porphyrins, metal free meso-acrylate porphyrins,
purpurins, metallo-purpurins, metallo-porphyrins and benzochlorins
and isolating these compounds simply by fractional crystallization
techniques that are amenable to large scale syntheses of such
compounds. Processes for the isolation of such compounds will be
set forth in the following detailed descriptions of each of the
steps of schemes 1 and 2. These processes require no
chromatographic separations or additional chemical reactions and
are therefore suitable for use on a large scale. The present
invention is also particularly relevant to the formylation of
metallo-tetrapyrrolic molecules, the reaction of formyl
tetrapyrrolic compounds with Wittig reagents, the demetallation of
metallo-tetrapyrrolic compounds, the cyclization of meso-acrylate
tetrapyrroles to purpurin compounds, the reduction of meso-acrylate
tetrapyrrolic compounds, the cyclization of
meso-(3-hydroxypropenyl) tetrapyrrolic compounds to benzochlorins
and the tin metallation of tetrapyrrolic molecules, all on large
scale.
[0009] As used herein, the term "tetrapyrrole" or "tetrapyrrolic
compound" is intended to encompass a large number of compounds with
at least three joined pyrrolic rings having widely differing
functionality as described in the literature (for example, see
"Porphyrins and Metalloporphyrins" Ed. K. Smith, Elsevier, 1975,
N.Y.; "The Porphyrins", Ed. D. Dolphin, Vol. I-V, Academic Press,
1978; and "The Porphyrin Handbook", Ed. K. Kadish, K. M. Smith, R.
Guilard, Academic Press, 1999). These compounds contain various and
ranging substituents on the .beta.-pyrrole positions or
meso-positions of the tetrapyrrolic rings, either symmetrically or
asymmetrically substituted on the tetrapyrrolic macrocycle. Simple
tetrapyrrolic ring systems include porphyrins, chlorins,
iso-bacteriochlorins and bacteriochlorins. Additionally, molecules
resembling porphyrins such as corroles, porphodimethenes,
phthalocyanines, naphthalocyanines, azoporphyrins, phlorins,
texaphyrins, porphyrin "isomers" (such as porphycenes,
porphacyanine, homoporphyrins, corrphycenes, vinylogous corroles,
vinylogous porphyrins, sapphyrins, pyriporphyrins, smaragdyrins,
isosmaragdyrins, ozaphyrins, pentaphyrins, heteropentaphyrins,
orangarins, dehydropentaphyrins, rubyrins, bronzaphyrins,
octaphyrins, and the like ) have been developed with a wide range
of functionality both at the peripheral positions and at the
internal heterocyclic "core" of these molecules. All of these
compounds are considered to be within the scope of the term
"tetrapyrrole" or "tetrapyrrolic compound" as used herein.
[0010] In many of these macrocycles the inner heteroatoms have been
replaced by O, S, Se, Te forming new macrocycles with interesting
properties. Many of these materials are capable of coordinating
metals and will undoubtedly find commercial uses in the fields of
medicine and industry and thus are applicable to the inventions set
forth in the specification, particularly with regard to
formylation, Wittig reactions, demetallation and metallation with
tin. Accordingly, there will be a need for highly pure material,
especially in pharmaceuticals, which can be made on a large
scale.
[0011] Examples of the various substituents that can be present on
the .beta.-pyrrole or meso-positions of the tetrapyrrolic compounds
of the invention include functional groups having a molecular
weight less than about 100,000 daltons and can be a biologically
active group or organic. Examples are, but are not limited to: (1)
hydrogen; (2) halogen, such as fluoro, chloro, iodo and bromo (3)
lower alkyl, such as methyl, ethyl, n-propyl, butyl, hexyl, heptyl,
octyl, isopropyl, t-butyl, n-pentyl and the like groups; (4) lower
alkoxy, such as methoxy, ethoxy, isopropoxy, n-butoxy, t-pentoxy
and the like; (5) hydroxy; (6) carboxylic acid or acid salts, such
as --CH.sub.2COOH, --CH.sub.2COONa,--CH.sub.2CH.sub.2COO- H,
--CH.sub.2CH.sub.2COONa, --CH.sub.2CH.sub.2CH(Br)COOH,
--CH.sub.2CH.sub.2CH(CH.sub.3)COOH, --CH.sub.2CH(Br)COOH,
--CH.sub.2CH(CH.sub.3)COOH, --CH(Cl)CH.sub.2CH(CH.sub.3)COOH,
--CH.sub.2CH.sub.2C(CH.sub.3).sub.2COOH,
--CH.sub.2CH.sub.2C(CH.sub.3).su- b.2COOK,
--CH.sub.2CH.sub.2CH.sub.2CH.sub.2COOH, C(CH.sub.3).sub.2COOH,
CH(Cl).sub.2COOH and the like; (7) carboxylic acid esters, such as
--CH.sub.2CH.sub.2COOCH.sub.3,
--CH.sub.2CH.sub.2COOCH.sub.2CH.sub.3,--CH-
.sub.2CH(CH.sub.3)COOCH.sub.2CH.sub.3,
--CH.sub.2CH.sub.2CH.sub.2COOCH.sub- .2CH.sub.2CH.sub.3,
--CH.sub.2CH(CH.sub.3).sub.2COOCH.sub.2CH.sub.3,
--CH.sub.2CH.sub.2COOCH.sub.2CH.sub.2OH,
--CH.sub.2CH.sub.2COOCH.sub.2CH.- sub.2 N(CH.sub.3).sub.2 and the
like; (8) sulfonic acid or acid salts, for example, group I and
group II salts, ammonium salts, and organic cation salts such as
alkyl and quaternary ammonium salts; (9) sulfonylamides such as
--SO.sub.2NH(alkyl), --SO.sub.2N(alkyl).sub.2,
--SO.sub.2NH(alkyl-OH), --SO.sub.2N(alkyl-OH).sub.2,
--SO.sub.2NH(alkyl)-N(alkyl).sub.2,
--SO.sub.2N(alkyl-N(alkyl).sub.2).sub- .2,
SO.sub.2NH(alkyl)-N(alkyl).sub.3.sup.+Z.sup.-) and the like,
wherein Z.sup.31 is a counterion), --SO.sub.2NHCH.sub.2CO.sub.2H,
substituted and unsubstituted benzene sulfonamides and
sulfonylamides of aminoacids and the like; (10) sulfonic acid
esters, such as SO.sub.3(alkyl), SO.sub.3(alkyl-OH),
SO.sub.3(alkyl-N(alkyl).sub.2),
SO.sub.3(alkyl-N(alkyl).sub.3.sup.+Z.sup.31 ) and the like, wherein
Z .sup.31 is a counterion), SO.sub.3CH.sub.2CO.sub.2H, and the like
(11) amino, such as unsubstituted or substituted primary amino,
methylamino, ethylamino, n-propylamino, isopropylamino, butylamino,
sec-butylamino, dimethylamino, trimethylamino, diethylamino,
triethylamino, di-n-propylamino, methylethylamino,
dimethyl-sec-butylamino, 2-aminoethoxy, ethylenediamino,
cyclohexylamino, benzylamino, phenylethylamino, anilino,
N-methylanilino, N,N-dimethylanilino, N-methyl-N-ethylanilino,
3,5-dibromo-4-anilino, p-toluidino, diphenylamino,
4,4'-dinitrodiphenylamino and the like; (12) cyano; (13) nitro; or
(14) a biologically active group; (15) amides, such as
--CH.sub.2CH.sub.2CONHCH.sub.3,--CH.sub.2CH.sub.2CONHCH.sub.2CH.sub.3,
--CH.sub.2CH.sub.2CON(CH.sub.3).sub.2,
--CH.sub.2CH.sub.2CON(CH.sub.2CH.s- ub.3) .sub.2,
--CH.sub.2CONHCH.sub.3, --CH.sub.2CONHCH.sub.2CH.sub.3,
--CH.sub.2CON(CH.sub.3).sub.2,
--CH.sub.2CON(CH.sub.2CH.sub.3).sub.2 and amides of amino acids and
the like; or (16) iminium salts for example
CH.dbd.N(CH.sub.3).sub.2.sup.+Z.sup.31; and the like, wherein
Z.sup.31 is a counterion), (17) Boron containing complexes, (18)
carbon cage complexes (e.g., C60 and the like), (19) metal cluster
complexes, for example derivatives of EDTA, crown ethers, cyclams,
cyclens, (20) other porphyrin, chlorin, bacteriochlorin,
isobacteriochlorin, azoporphyrin, tetraazoporphyrin,
phthalocyanine, naphthalocyanine, texaphyrins, tetrapyrrolic
macrocycles or dye class and the like (21) alkynyl, including
alkyl, aryl, acid and heteroatom substituted alkynes, and (22)
haloalkyl where one or more halogens are substituted onto the alkyl
carbon chain, the length of the carbon chain being from C1 to C20;
and (23) any other substituent that increases the hydrophilic,
amphiphilic or lipophilic nature or stability of the compounds.
[0012] The term "biologically active group" as used herein can be
any group that selectively promotes the accumulation, elimination,
binding rate, or tightness of binding in a particular biological
environment. For example, one category of biologically active
groups is the substituents derived from sugars, specifically, (1)
aldoses such as glyceraldehyde, erythrose, threose, ribose,
arabinose, xylose, lyxose, allose, altrose, glucose, mannose,
gulose, idose, galactose, and talose; (2) ketoses such as
hydroxyacetone, erythrulose, rebulose, xylulose, psicose, fructose,
sorbose, and tagatose; (3) pyranoses such as glucopyranose; (4)
furanoses such as fructo-furanose; (5) O-acyl derivatives such as
penta-O-acetyl-.alpha.-glucose; (6) O-methyl derivatives such as
methyl .alpha.-glucoside, methyl .beta.-glucoside, methyl
.alpha.-glucopyranoside, and
methyl-2,3,4,6-tetra-O-methyl-glucopyranosid- e; (7) phenylosazones
such as glucose phenylosazone; (8) sugar alcohols such as sorbitol,
mannitol, glycerol, and myo-inositol; (9) sugar acids such as
gluconic acid, glucaric acid and glucuronic acid,
.delta.-gluconolactone, .delta.-glucuronolactone, ascorbic acid,
and dehydroascorbic acid; (10) phosphoric acid esters such as
.alpha.-glucose 1-phosphoric acid, .alpha.-glucose 6-phosphoric
acid, .alpha.-fructose 1,6-diphosphoric acid, and .alpha.-fructose
6-phosphoric acid; (11) deoxy sugars such as 2-deoxy-ribose,
rhammose (deoxy-mannose), and fructose (6-deoxy-galactose); (12)
amino sugars such as glucosamine and galactosamine; muramic acid
and neurarninic acid; (13) disaccharides such as maltose, sucrose
and trehalose; (14) trisaccharides such as raffinose (fructose,
glucose, galactose) and melezitose (glucose, fructose, glucose);
(15) polysaccharides (glycans) such as glucans and mannans; and
(16) storage polysaccharides such as .alpha.-amylose, amylopectin,
dextrins, and dextrans.
[0013] Amino acid derivatives are also useful biologically active
substituents, such as those derived from valine, leucine,
isoleucine, threonine, methionine, phenylalanine, tryptophan,
alanine, arginine, aspartic acid, cystine, cysteine, glutamic acid,
glycine, histidine, proline, serine, tyrosine, asparagine and
glutamine. Also useful are peptides, particularly those known to
have affinity for specific receptors, for example, oxytocin,
vasopressin, bradykinin, LHRH, thrombin and the like.
[0014] Another useful group of biologically active substituents are
those derived from nucleosides, for example, ribonucleosides such
as adenosine, guanosine, cytidine, and uridine; and
2'-deoxyribonucleosides, such as 2'-deoxyadenosine,
2'-deoxyguanosine, 2'-deoxycytidine, and 2'-deoxythymidine.
[0015] Another category of biologically active groups that is
particularly useful is any ligand that is specific for a particular
biological receptor. The term "ligand specific for a receptor"
refers to a moiety that binds a receptor at cell surfaces, and thus
contains contours and charge patterns that are complementary to
those of the biological receptor. The ligand is not the receptor
itself, but a substance complementary to it. It is well understood
that a wide variety of cell types have specific receptors designed
to bind hormones, growth factors, or neurotransmitters. However,
while these embodiments of ligands specific for receptors are known
and understood, the phrase "ligand specific for a receptor", as
used herein, refers to any substance, natural or synthetic, that
binds specifically to a receptor.
[0016] Examples of such ligands include: (1) the steroid hormones,
such as progesterone, estrogens, androgens, and the adrenal
cortical hormones; (2) growth factors, such as epidermal growth
factor, nerve growth factor, fibroblast growth factor, and the
like; (3) other protein hormones, such as human growth hormone,
parathyroid hormone, and the like; (4) neurotransmitters, such as
acetylcholine, serotonin, dopamine, and the like; and (5)
antibodies. Any analog of these substances that also succeeds in
binding to a biological receptor is also included.
[0017] Particularly useful examples of substituents tending to
increase the amphiphilic nature of the compounds include: (1) short
or long chain alcohols, for example,--C.sub.12H.sub.24--OH where
--C.sub.12H.sub.24 is hydrophobic; (2) fatty acids and their salts,
such as the sodium salt of the long-chain fatty acid oleic acid;
(3) phosphoglycerides, such as phosphatidic acid, phosphatidyl
ethanolamine, phosphatidyl choline, phosphatidyl serine,
phosphatidyl inositol, phosphatidyl glycerol, phosphatidyl
3'-O-alanyl glycerol, cardiolipin, or phosphatidal choline; (4)
sphingolipids, such as sphingomyelin; and (5) glycolipids, such as
glycosyldiacylglycerols, cerebrosides, sulfate esters of
cerebrosides or gangliosides. It would be apparent to those skilled
in the art what other groups or combinations of the groups
described would be suitable to the invention.
Meso-Formylation of Metallo-Tetrapyrroles
[0018] It is well established in the literature that many
metallated tetrapyrrolic compounds such as Nickel
octaethylporphyrin (OEP) and Nickel etioporphyrin I (NiEtio I)
undergo electrophilic substitution at the meso position with a
Vilsmeier reagent according to schemes 1 and 2 to give compounds
(2) and (9). In compounds where all the meso-positions are
substituted and free .beta.-pyrrolic positions exist, for example
Nickel or Copper tetraphenyl porphyrin derivatives, Vilsmeier
formylations occur at the .beta.-pyrrolic positions. Generally on
the laboratory scale (grams), the reactions are carried out in hot
1,2-dichloroethane (55-60.degree. C.) and the resulting iminium
salt intermediate is hydrolyzed with saturated sodium acetate
solution at this elevated temperature. The solution is cooled to
room temperature and the organic layer is separated from the
aqueous layer. The organic layer is then dried, filtered and
evaporated to dryness. The crude residue is best purified by
chromatography on silica.
[0019] In addition to the mono-meso-formylated products,
significant amounts of di-formylated products (Scheme 3) are
produced in the reaction in yields between 9-20%. Longer reaction
times produce more di-formylated products. 4
[0020] Current literature (K. M. Smith et al., J. Chem. Soc Perk I,
p.581, 1982; K. M. Smith et al, Teft. Lett., vol.21, p.3747,1980;
G. V. Ponomarev et al, Kimiya Geterotsiklicheskikh Soedinenii,
vol.6, p.776, 1979; G. V. Ponomarev et al, Kimiya
Geterotsiklicheskikh Soedinenii, vol.6, p.767, 1979; E. Watanabe et
al, Tetrahedron, vol.31, p.1385, 1975; K. M. Smith et al, J. Chem.
Soc. Perk I, p.439, 1983; G. V. Ponomarev et al, Kimiya
Geterotsiklicheskikh Soedinenii, vol.9, p.1215, 1970; A. W. Nichol,
J. Chem. Soc. (C) p.903, 1970; G. V. Ponomarev et al, Kimiya
Geterotsiklicheskikh Soedinenii, vol.4, p.479, 1984; G. V.
Ponomarev et al, Kimiya Geterotsiklicheskikh Soedinenii, vol.11,
p.1507, 1982; J. W. Buchler, Leibigs Annalen Chemie, p.43, 1988; A.
W. Johnson, J. Chem. Soc., p.4, 1966; H. Brockmann, Leibigs Annalen
Chem, vol.148, p.718,1968; R. Grigg, J. Chem. Soc., p.1789,1972;;
R. Grigg, J. Chem. Soc. CC1, p.557, 1979) and patent disclosures
(U.S. Pat. Nos. 5,051,415; 5,216,012; 4,877,872; and 5,534,506, the
disclosures of which are incorporated herein by reference) in
general use chromatography or precipitation from methanol to
isolate compounds (2) and (9) in particular from their
di-formylated counterparts.
[0021] As chromatography on a large scale is an expensive
alternative for purification of tetrapyrrolic molecules, the
present inventors studied the precipitation of the crude formylated
tetrapyrrolic compounds from methanol, ethanol and acetic acid. In
this instance, the inventors chose to study compounds (2) and (9).
Precipitation of the crude formylated reaction mixture of (2) from
dichloromethane/methanol or dichloromethane/ethanol via
distillation of the lower boiling solvent was found to be
inefficient at removing the di-formylated impurity products from
the precipitated product. Approximately the same ratio of
diformylated products to mono-formylated products (Table 1 for
etioporphyrin series) remained using this procedure.
[0022] However, the inventors have found that when alkylcarboxylic
acids, such as acetic acid, are used as a precipitating solvent,
and the dichloromethane distilled as before, the di-formyl
by-products were successfully reduced by approximately 10% per
precipitation. This is due to the fact that the di-formylated
products possessed greater solubility in the alkylcarboxylic acids
than in methanol or ethanol.
[0023] The use of alkylcarboxylic acid solvents like acetic acid
has several additional advantages. Aqueous residues, which may
contain sodium acetate from the hydrolysis step, that have
inadvertently found their way into the organic layer during the
extraction and separation process are soluble in alkylcarboxylic
acids. This is particularly useful in large scale manufacturing
where separation of the organic and aqueous phases is sometimes
difficult. Additionally, metal free porphyrins, for example
etioporphyrin I which is observed as a minor impurity with Nickel
etioporphyrin I (due to incomplete Nickel insertion), has
solubility in alkylcarboxylic acids and hence may be reduced in
percentage in the final isolated Nickel meso-formyl etioporphyrin I
The fact that many metal-free tetrapyrrolic compounds are soluble
in alkylcarboxylic acids enables an efficient means of reducing
this impurity in metallated porphyrin derivatives, which in general
are less soluble in alkylcarboxylic acids. Additionally, polymeric
material produced in the reaction is also soluble in
alkylcarboxylic acids.
1TABLE 1 HPLC of the crude reaction mixture and precipitations
(single) Crude Methanol Ethanol Acetic acid Mixture pptn pptn pptn
Ni meso-formyl 79.6% 80% 76% 90.1% etioporphyrin Ni meso-diformyl
16% 15% 16% 6.8% etioporphyrins Etioporphyrin 2.4% 3.0% 2.6% 1.6%
Ni etioporphyrin 0.9% 1.3% 1.2% 1.2%
[0024] Yet another major advantage lies with the boiling point of
alkylcarboxylic acids. Once the 1,2-dichloromethane has been
separated from the aqueous phase, it may be effectively distilled
from a mixture of alkylcarboxylic acid/dichloromethane, affecting
the precipitation of the desired meso-formyl porphyrin.
[0025] Similar observations were made for the formylation of Nickel
octaethylporphyrin. The di-formylated Nickel octaethylporphyrin
impurities were reduced by levels of 10-15% by a single
precipitation from dichloromethane/acetic acid.
[0026] Similar results have been obtained for a large number of
meso-formylporphyrins, including Nickel meso-formyl etioporphyrin I
and II Copper meso-formyl etioporphyrin I and II Nickel meso-formyl
coproporphyrin I and II tetra-alkyl esters, Copper meso-formyl
coproporphyrin I and II tetraalkyl esters, Nickel .beta.-formyl
tetraphenyl porphyrin, Nickel .beta.-formyl
tetrakis((4'-methyl)phenyl))p- orphyrin, Nickel .beta.-formyl
tetrakis((4'-carbomethoxy)phenyl) porphyrin, Copper (II)
octaethylporphyrin, Nickel (II) octaethylporphyrin, Copper
mesoporphyrin dialkyl ester, and Nickel mesoporphyrin dialkyl
ester. It is envisaged that this procedure is generally applicable
to the purification of any formylated metallo-tetrapyrrolic
compound on a large scale that is not soluble, or has limited
solubility in alkylcarboxylic acids. The scope of the invention is
not limited to the examples provided herein.
[0027] In accordance with another embodiment of the present
invention, as embodied and broadly described herein, we have found
that the formylation of metallo tetrapyrrolic compounds may be
undertaken in a solvent other than 1,2-dichloroethane. As
1,2-dichloroethane is listed as a class 1 solvent by the
International Conference on Harmonization (ICH), it would be
advantageous on a large-scale to use a less toxic solvent for the
formylation of metallo-tetrapyrroles. Toward this goal we used
dichloromethane.
[0028] Formylation of Nickel etioporphyrin or Nickel
octaethylporphyrin with Vilsmeier reagent occurs only slowly at
room temperature. In refluxing dichloromethane at atmospheric
pressure, the formation of the desired intermediate iminium salt
progresses slowly, being complete after approximately 13-24 hours.
If the same reaction is undertaken in dichloromethane in a glass
lined metal reactor at an elevated temperature such as
35-60.degree. C., preferably 50-60.degree. C., under pressurized
conditions, the reaction proceeds smoothly in 3-6 hours. Hence it
is possible to replace 1,2-dichloroethane with the less toxic
dichloromethane in standard large-scale reactor equipment that is
capable of sustaining pressure. Metal glass lined reactor vessels
are well suited and designed for such reactions. This procedure is
generally applicable to the synthesis of any formylated
metallo-tetrapyrrolic compound on a large scale, including but not
limited to porphyrins, azoporphyrins, chlorins,
iso-bacteriochlorins and bacteriochlorins. The applicability of
this process to other formylated metallo-tetrapyrrolic compounds
would be within the knowledge of those skilled in the art.
Wittig Reactions on Meso-Formyl Tetrapyrroles
[0029] It is well established in the literature that the formyl
group on metallated meso-formyl porphyrins such as meso-formyl
Nickel etioporphyrin I (2) and meso-formyl Nickel
octaethylporphyrin (9) or on .beta.-formylated porphyrins undergoes
Wittig reactions with a large number of Wittig reagents such as,
for example, (ethoxycarbonylmethylene)- triphenylphosphorane or
(methoxycarbonylmethylene)-triphenylphosphorane or the like, to
produce the corresponding Wittig addition product porphyrins like
meso-acrylate porphyrins (Scheme 4). It should be noted that the
term meso-acrylate as used herein is broadly defined as including
the following groups: --CH.dbd.CHCO.sub.2Et; --CH.dbd.CHCO.sub.2Me;
--CH.dbd.CH(ester); --CH.dbd.CH(amide); --CH.dbd.CHCHO;
--CH.dbd.CHCH(Oalkyl).sub.2; --CH.dbd.CHCH(Ocyclicalkyl).sub.2.;
--(CH.dbd.CH).sub.n(ester) where n =2, 3; --(CH.dbd.CH).sub.n(CHO)
where n=2, 3;--=CHCN; and --.dbd.CHCO.sub.2H. There are a number of
"stabilized" Wittig reagents that can be isolated as powders with
defined melting points. Such Wittig reagents are useful in the
present invention. Also useful are stabilized Wittig reagents that
are liquids.
[0030] In literature preparations, the Wittig reaction of
(ethoxycarbonylmethylene)-triphenylphosphorane or
(methoxycarbonylmethyle- ne)triphenyl phosphorane or the like on
meso-formyltetrapyrroles is carried out in refluxing xylenes (bp
138-145.degree. C.) under atmospheric conditions (generally
overnight) where upon completion of the reaction, the xylene is
removed by rotary evaporation and the viscous gummy residue
dissolved in dichloromethane. The solution is then chromatographed
on silica to remove the desired meso-acrylate porphyrin from the
tars and triphenylphosphine oxide produced in the reaction as
outlined in the literature (D. P. Arnold, J. Chem. Soc. Perk. I,
p.1660, 1978; H. Callott, Bull. Soc. Chim. France. p.3413, 1973; A.
R. Morgan et al, J. Org. Chem., vol.51, p.1347, 1986; A. R. Morgan
et al, J. Med. Chem., vol.34, p.2126, 1991) and in several patents
(U.S. Pat. Nos. 5,051,415 and 5,534,506). 5
[0031] The present inventors have discovered that the reported
procedures suffer from a number of disadvantages when going from
bench scale (1-5 g) to larger scale. First, it was found that when
the reaction was performed in xylene, a large excess of Wittig
reagent (typically more than 5 equivalents) was always required to
complete the reaction. Even at small scales the reaction was
generally slow, requiring at least 15-18 hours of reflux. It was
also noted that amounts as high as 10% of Nickel etioporphyrin (or
Nickel octaethylporphyrin) were produced during the reaction via
deformylation of the starting material. Chromatography of the
reaction often yielded the metallated meso-acrylate porphyrin
contaminated with triphenyl phosphine oxide due to tailing of the
latter through the column. It should be noted that metal-free
formyl tetrapyrrolic compounds can also be reacted with Wittig
reagents under the same conditions, thereby producing the metal
free meso-acrylate compounds directly. These compounds also suffer
the disadvantages on purification described above.
[0032] As chromatography on a large scale is an expensive
alternative for purification of such molecules and because of the
problems described, the reaction conditions were modified to best
optimize for time, purity, amount of Wittig reagent used, and ease
of isolation of the final product. We investigated the reaction in
a different solvent, dimethylformamide (DMF), under argon or
another inert atmosphere. Under similar conditions as those
described by the prior art, it was found that no appreciable
amounts of Nickel etioporphyrin I were produced in the reaction. It
was also discovered that reducing the volume of DMF in the reaction
dramatically decreased the time taken to complete the reaction. In
fact, it was found that the reaction could be performed as a melt
in which a very small volume of the solvent was present and the
temperature was slowly increased to 135.degree. C. over an hour or
so with adequate stirring. In this case the reaction was complete
in 3-6 hours. Under these conditions, a 2 molar equivalent of
phosphorane was used, dramatically reducing the amount of Wittig
reagent required from the reported procedure. It was found optimal,
however, to have a small amount of solvent (DMF) in the reaction,
specifically within about 10% of the weight of the starting
meso-formyl tetrapyrrole. The solvent aids in the initial
dissolution of the melt and assists in bringing powdered starting
material on the sides of the reactor flask into the reaction melt.
It is envisaged that this procedure is generally applicable to the
Wittig reaction of any formylated tetrapyrrolic compound on a large
scale. It is further envisaged that this procedure is particularly
applicable to any Wittig reaction where the Wittig reagent is a
stable solid or liquid at room temperature. The scope of the
invention is not limited to the examples provided herein, but is
realized to be generally applicable to metallo or metal free formyl
tetrapyrrolic molecules possessing at the .beta.-pyrrole positions,
or meso- positions, the functionality described at pages 8-12
herein.
[0033] The next challenge was to purify the Nickel meso-acrylate
porphyrin from the reaction melt. This was achieved very
successfully simply by optionally removing as much of the DMF as
possible, allowing the solution to cool, dissolving the crude
residue in a solvent and adding a precipitating solvent.
Distillation of the solvent with stirring resulted in the
precipitation of the desired Nickel meso-acrylate etioporphyrin.
The porphyrin can then be filtered directly and optionally washed
with the precipitating solvent. The yields from such a procedure
are generally about 90% and the purity greater than 98%. Comparable
results are obtained with the octaethylporphyrin series and the
following meso-formyl tetrapyrrolic compounds: meso-formyl
etioporphyrin I; Nickel meso-formyl etioporphyrin I and II Copper
meso-formyl etioporphyrin I and II Nickel meso-formyl
coproporphyrin I and II; Copper meso-formyl coproporphyrin I and II
tetramethyl esters; Nickel .beta.-formyl tetraphenyl porphyrin;
Nickel .beta.-formyl tetrakis((4'-methyl)phenyl))porphyrin; Nickel
.beta.-formyl tetrakis((4'-carbomethoxy)phenyl) porphyrin; and the
purification of their acrylate analogues. The precipitation
technique described is believed to be applicable to any
meso-acrylate (or similar) tetrapyrrolic compound on a large scale
that is not soluble, or has limited solubility in alcohols with the
functionality described at pages 7-12.
[0034] In accordance with the invention, the solvent in the above
described precipitation procedure can be halogenated or
non-halogenated and is preferably selected from dichloroethane,
dichloromethane, ethyl acetate, tetrahydrofuran, acetonitrile,
acetone, benzene, toluene, and ethers. The precipitating solvent
can also be halogenated or non-halogenated and is preferably
selected from acetic acid, propionic acid, methanol, ethanol,
1-propanol, 2-propanol, 1-butanol, hexanes, acetonitrile, ethyl
acetate, and iso-octane.
[0035] Of particular interest is the composition of the mother
liquors of the Wittig reaction on Nickel meso-formyl etioporphyrin
I They are largely enriched in Nickel etioporphyrin, etioporphyrin,
and the Nickel meso-diacrylate etioporphyrins (produced in the
reaction from the Nickel di-formyl etioporphyrins). Thus, the
alcoholic mother liquors, rich in triphenylphosphine oxide,
effectively remove up to 20% of di-formyl etioporphyrin impurities
(as their di-acrylate derivatives) carried over in the meso-formyl
porphyrin solid of the formylation step, as well as other
impurities.
[0036] It should be noted that pure di-formyl porphyrins undergo
conversion to the di-acrylate porphyrins using the melt conditions
described. Additionally, they may be precipitated and purified
according to the precipitation technique outlined above. It should
be noted that this precipitation technique works especially well
for 5, 15 di-acrylate porphyrins as they are generally less soluble
in organic solvents. The corresponding 5, 10- diacrylate porphyrins
are somewhat more soluble and suffer larger losses to the
precipitation technique.
Demetallation of Tetrapyrrolic Compounds on a Large Scale
[0037] It is well known in the literature that the centrally
coordinated metal of many metallated porphyrins can be removed by
treating the complex with strong acids. Nickel, copper or cobalt
porphyrins generally require strong acids, such as sulfuric acid to
liberate the metal from the complex. Organic acids, like
trifluoroacetic acid, are seldom strong enough to demetallate these
complexes, or are very slow at demetallating the complex. Other
metals such Zn, In, Ga, Ge, and TI, for example, are rapidly
removed from the tetrapyrrolic macrocycles using sulfuric acid,
hydrochloric acid, methane sulfonic acid, trifluoroacetic acid, and
the like.
[0038] In literature preparations, demetallation reactions of
nickel or copper porphyrins or other tetrapyrrolic complexes are
usually carried out using a large excess of neat sulfuric acid. The
acid is either added to the porphyrin or the porphyrin added to the
acid. Table 2 gives some literature examples. The solution is then
generally added to a neutralizing solution (for example a
NaHCO.sub.3 solution) and the porphyrin extracted with a solvent
and purified. Such procedures are routinely used to demetallate all
tetrapyrrolic classes, including porphyrins, chlorins,
isobacteriochlorins and bacteriochlorins.
2TABLE 2 Literature examples of molar ratios of acid/porphyrin Acid
amount Compound/amount (molar equivalents) Reference Meso-acrylate
NiOEP 10 mL H.sub.2SO.sub.4 ( .about.92 eq) U.S. Pat. No. (Et
ester) (621 mg) 4,877,872 Meso-acrylate NiOEP 5 mL H.sub.2SO.sub.4
( .about.306 eq) D. P. Arnold et al, (Me ester) (100 mg) J. Chem.
Soc, 1660, 1978 Meso-acrylate NiEtio 3 mL H.sub.2SO.sub.4 (
.about.334 eq) D. P. Arnold et al, (Me ester) (50 mg) J. Chem. Soc,
1660, 1978 5,10-Diacrylate 2 mL H.sub.2SO.sub.4 ( .about.579 eq) A.
R. Morgan et al, NiOEP(Et ester) (25 J. Med. Chem., 34 (7), mg)
2126, 1991 5,15-Diacrylate 2 mL H.sub.2SO.sub.4 ( .about.579 eq) A.
R. Morgan et al, NiOEP(Et ester) (25 J. Med. Chem., 34 (7), mg)
2126, 1991
[0039] We have discovered that the reported procedures suffer from
a number of disadvantages when going from bench scale (1 g) to
larger scale. In the literature procedures, even on small scale, a
large excess of acid is generally required to demetallate the
porphyrinic compounds (Table 2). Besides the expense related to
using large volumes of acid on large scale, the hazards of handling
and neutralizing acid wastes becomes a crucial issue. It would be
advantageous to use the minimum amount of acid to effect
demetallation so that safety and disposal become more
manageable.
[0040] A theoretically possible solution to this problem is to
"increase the loading" or decrease the equivalents of acid to the
starting metal complex. Unfortunately, this approach does not work
well with the demetallation of tetrapyrrolic compounds. Regardless
of whether the tetrapyrrolic powder is added to the acid or vice
versa, severe clumping of the powder occurs. In fact, the powder
forms solid clumps that are difficult to disperse under rapid
stirring and often stick to the sides of the reactor vessel. This
dramatically impacts the amount of demetallation that takes place
in the reaction and isolated "demetallated" tetrapyrrolic compound
product is invariably contaminated with large amounts of the
metallated starting material. The clumping problem makes it
virtually impossible to predict when the demetallation reaction is
complete.
[0041] Another serious limitation in the reported processes
involves the neutralization of the acidic solution. The addition of
sodium bicarbonate to a highly acidic solution on large scale would
be a hazardous undertaking, as a large amount of carbon dioxide is
released in the neutralization process (which must be processed
accordingly). In addition, extensive frothing and foaming of the
solution occurs, which even on a small scale is difficult to
control. Total or over neutralization of the solution with NaOH,
for example, may cause ester cleavage of tetrapyrroles with ester
groups.
[0042] We have been able to successfully overcome these problems by
utilizing a simple process involving the pre-dissolution of the
metallo-tetrapyrrolic compound in a non-water-soluble solvent.
Examples of non-water-soluble solvents include 1,2-dichloroethane,
1,1- dichloroethane, dichloromethane, chloroform, benzene, toluene,
ether, hexane, xylene, and the like. Initial dissolution of Nickel
meso-acrylate porphyrin, for example, in a halogenated solvent like
dichloromethane occurs readily. The temperature of the reactor is
lowered to approximately 0.degree. C., and the slow addition of an
acid with vigorous stirring or agitation results in the acid being
dispersed onto the sides of the reaction vessel (as it is not
soluble in dichloromethane). The lowering of the temperature avoids
any exotherm due to the demetallation reaction. The metallated
porphyrin dissolved in the dichloromethane passes over the acid
layer and demetallates. It is immediately drawn into the acid layer
as its tetraprotonated species. Over a matter of 0.5-1 hour, the
metallated porphyrin is continually drawn out of the
dichloromethane layer and demetallated.
[0043] The completion of the demetallation reaction is easily
visualized when the dichloromethane layer is essentially colorless.
At this point, water is added to the solution which enables the
protonated porphyrin to enter the organic layer (probably as its
diprotonated species) and the solution is at least partially
neutralized with sodium hydroxide. The organic layer is separated
from the at least partially neutralized aqueous layer and reduced
in volume by distillation. A precipitating solvent such as, for
example, ethanol or methanol is added and the remaining
dichloromethane removed by distillation. The precipitating solvent
in this instance also acts as a proton sponge, efficiently
deprotonating the porphyrin. The thick precipitate is collected by
filtration and washed with ethanol. The metal-free meso-acrylate
porphyrin isolated is greater than 99% pure. This procedure works
equally well with Nickel meso-acrylate octaethylporphyrin.
[0044] Using this procedure, it is possible to demetallate a large
amount of metallo-tetrapyrrole with very small amounts of acid.
Over 240 grams of Nickel meso-acrylate etioporphyrin 1 (3) can be
demetallated with only 250 ml of H.sub.2SO.sub.4. Here,
approximately 5 equivalents of acid are required to effect
demetallation in approximately 1 hour. Identical results are
achieved with a large number of different porphyrins. The process
is believed to be generally applicable to the demetallation of any
metallo-porphyrin, metallo-chlorin, metallo-isobacteriochlorin,
metallo-bacteriochlorin, or other metallo-tetrapyrrolic compound
that has a co-ordinated metal able to be removed with sulfuric
acid. It is also applicable to metallo-tetrapyrroles that are
capable of being demetallated with hydrochloric acid or phosphoric
acid (for example zinc, indium, gallium, thallium, germanium).
Included among the tetrapyrrolic metal complexes suitable for
demetallation via this process are those outlined by Johann Walter
Buchler in "The Porphyrins", Ed. D. Dolphin, Volume I, Chapter 10,
p.389-483, Academic Press, New York, 1978. It is envisaged that
such tetrapyrrolic molecules may possess on the .beta.-pyrrolic or
meso positions the functionality or combination thereof discussed
earlier herein at pages 7-12.
[0045] It would be within the general skill and knowledge of those
of ordinary skill in the art as to what other functional groups
would be amenable to the inventive process or what modifications to
the disclosed procedure could be made without departing from the
scope of the invention.
Cyclization of Meso-Acrylate Tetrapyrroles to Purpurins
[0046] Historically in the literature, the cyclization reaction of
meso-acrylate porphyrins to give purpurins has been performed using
two different methods. Meso-acrylate octaalkylporphyrins, as shown
in Scheme 6, have historically been cyclized to purpurins under
acidic conditions, using acetic acid under an inert atmosphere. The
cyclization process is slow, requiring typically 24 hours of reflux
to attain an equilibrium where approximately 5-10% of starting
material is present in the final product. The reaction is also
highly sensitive to the presence of oxygen, which causes the
formation of other purpurin types that are difficult to remove from
the desired product. A significant amount of decomposition also
occurs such that the yield of desired product in the presence of
oxygen is halved. 6
[0047] Alternatively, 5,15-Bis aryl 10-acrylate porphyrins (shown
in Scheme 7) undergo cyclization to give 5,15-Bis aryl purpurins
under basic conditions (Et.sub.3N, KSCN or NaOH). Surprisingly,
they do not cyclize under acidic conditions. The cyclization
reaction is not sensitive to oxygen and there does not appear to be
an equilibrium established between starting material and product.
Meso-acrylate octaalkylporphyrins (Scheme 6) do not cyclize using
triethylamine or sodium hydroxide as bases. 7
[0048] Clearly, the chemistry related to the large scale
manufacturing of purpurins from meso-acrylate octaalkylporphyrins
needs significant improvement to make it commercially feasible. In
addition, meso-acrylate octaalkylporphyrins, such as meso-acrylate
etioporphyrin I (or meso-acrylate coproporphyrin I), which bear
different alkyl substituents on either side of the meso-acrylate
group (scheme 1 at page 4 of the specification) suffer from the
formation of cyclization isomers. An example of this is shown in
Scheme I with the cyclization of meso-acrylate etioporphyrin I (4).
Here, cyclization occurs toward an ethyl group on a pyrrole ring to
give ethyl etiopurpurin I (5) or toward a methyl group on a pyrrole
ring to give methyl etiopurpurin I (6). The product obtained from
the acetic acid cyclization route of meso-acrylate etioporphyrin I
consists of a mixture of (4), (5) and (6) in a ratio of 3: 9: 8 and
each of (4) and (6) must be separated from (5) for the production
of SnET2 (7). See, U.S. Pat. No. 5,051,415. U.S. Pat. No. 5,051,415
does not indicate that (6) is produced in the synthesis, nor does
it describe how (4) and (6) are removed from (5).
[0049] Over the course of the development of the cyclization
process, we investigated base catalysis as an alternative to the
acetic acid conditions for cyclizing mono-meso-acrylate
tetrapyrrolic compounds to the corresponding purpurin. We
investigated a large number of bases and solvents to find the
optimal conditions necessary to generate maximal amounts of (5).
Table 3 outlines the conditions used. MAE in Table 3 is
meso-acrylate etioporphyrin I (4), ET2 is ethyl etiopurpurin (5),
and MET2 is methyl etiopurpurin (6).
[0050] While we found many of the bases were effective or partially
effective at producing purpurin formation, the most effective bases
of those we tested were the non-nucleophilic bases
1,5-diazabicyclo[4.3.0]no- n-5-ene (DBN),
1,5-diazabicyclo[5.4.0]non-5-ene (DBU), tetramethyl guanidine, and
pyrrolidine, generally in higher boiling solvents like toluene. The
reactions were not sensitive to air (oxygen), and after short
reflux times of 4-6 hours, levels of starting material MAE (4)
present in the mixture were generally equal to or less than those
seen in the long acetic acid reflux cyclization reaction. DBU
appeared to give the greatest ratio of ET2 (5):MET2(6):MAE (4),
about 72:21:7. In addition to 1,5-diazabicyclo[4.3.0]non-5-ene
(DBN), 1,5-diazabicyclo[5.4.0]non-5-e- ne (DBU), tetramethyl
guanidine, and pyrrolidine, the non-nucleophilic base piperidine
would also be expected to give similar favorable results.
3TABLE 3 Base catalysized Cyclization of meso-acrylate
etioporphyrin I (MAE) Base MAE Wt Solvent Reflux time MAE (%) ET2
(%) MET2 (%) DBU 100 mg Toluene 4 hr .about.7% 72% 21% DBN 100 mg
Toluene 4 hr <10% 55% 35% Pyrrolidine 100 mg Toluene 4 hrs
<7% 71% 22% Et.sub.3N 100 mg Toluene 24 hr 100% NR NR DMAP 100
mg Toluene 24 hrs 94% 4% 2% Pyridine 100 mg neat 24 hrs 100% NR NR
4-DMAP 100 mg Toluene 24 hrs 75% 15% 5% Tetra- 100 mg Toluene 6 hrs
7% 70% 23% methyl guanidine DMAP = Dimethylaminopyridine
[0051] The challenge then came to separate the two isomeric
purpurins ET2 (5) and MET2 (6) without chromatography. Our
investigations into the solubility of both compounds led to the
discovery that MET2 (6) was much more soluble in acetonitrile and
acetone, than was ET2 (5). In fact, we found that ET2 (5) has only
limited solubility in hot acetonitrile. Additionally, the starting
porphyrin meso-acrylate etioporphyrin I (4) was found to have
solubility in acetonitrile and acetone. These discoveries enabled
us to develop a simple precipitation process to effectively
separate ET2 (5) from MAE (4) and MET2 (6). This process is
suitable for use in both traditional acetic acid cyclization
reactions as well as the base catalyzed cyclization reactions
disclosed herein.
[0052] In accordance with the invention, the crude reaction mixture
from the base catalyzed or acetic acid cyclization reaction can be
evaporated to dryness or near dryness and the residue dissolved in
a solvent or mixture of solvents such as dichloromethane. A
precipitating solvent such as acetonitrile or acetone can then be
introduced, and the solvents(s) removed by distillation. The
precipitated product is then filtered rapidly from the warm
solution. The mother liquors are rich in small amounts of MAE (4)
and mostly MET2 (6). Preferably, the process is repeated until the
solid ET2 (5) is sufficiently pure by TLC (0.5%
ethylacetate/dichloromethane) or HPLC to proceed to the metallation
step and the production of SnET2 (7). In general, three
precipitations in this manner has been found to be sufficient to
obtain pure product. It would be understood by those skilled in the
art that this process may be carried out with a variety of solvents
and precipitation solvents in the same or similar manner. Both the
solvent and the precipitating solvent can be halogenated or
non-halogenated. Preferably, the solvent is dichloromethane, ether,
1,2-dichloroethane, chloroform, toluene, acetone, methanol,
ethanol, tetrahydrofuran, ethyl acetate, benzene, or mixtures
thereof. The precipitating solvent is preferably methanol, ethanol,
1-propanol, 2-propanol, 1-butanol, t-butanol, acetone,
acetonitrile, hexane, heptane, isooctane, cyclohexane, or isopropyl
ether.
[0053] The isolation of MET2 (6) from the acetonitrile or acetone
mother liquors above is a relatively straightforward process. The
biggest challenge to overcome lies with the separation of MAE (4)
from the MET2 (6). In our tin metallation reactions described
earlier, we have observed that free base porphyrins can be
metallated effectively at temperatures where the chlorin cannot be
metallated (typically 60-80.degree. C.) (see following tin
metallation section) in solvents like 1,2-dichloroethane or acetic
acid. If the mother liquors of the ET2 precipitation technique
described above are evaporated and dissolved in either
1,2-dichloroethane or acetic acid containing a tin salt (preferably
SnCl.sub.2 predissolved in dimethylformamide) and sodium acetate,
any metal-free porphyrins in the crude mixture can be metallated at
30-80.degree. C. with little or no metallation of the chlorin. The
crude reaction mixture can then be evaporated to dryness and
redissolved in a solvent suitable for chromatography of the
material. This method is preferable if the metallation is
undertaken in acetic acid or the like.
[0054] Alternatively, if the metallation reaction is carried out in
1,2-dichloroethane the solution may be either reduced in volume and
chromatographed or directly chromatographed. As tin compounds bind
particularly tightly to either silica or alumina, the crude chlorin
solution from the metallation reaction can be passed over a small
pad of silica or alumina. The tin porphyrins remain on the silica
while the chlorin fraction may be eluted from the column under most
chromatographic conditions. Such a selective metallation and
purification process enables the separation of porphyrinic
impurities from chlorins or bacteriochlorins in general.
Alternatively, other metals that increase the polarity of the
porphyrinic compound on silica or alumina may be used. The metal
salts most preferable are those that are readily incorporated into
porphyrins at or between 60-80.degree. C. including
Sn.sup.2+In.sup.3+, Ga.sup.3+, TI.sup.3+, etc., because these metal
salts, when complexed to a tetrapyrrolic molecule, possess an axial
ligand that enhances polarity on silica or alumina and enhances the
ability to separate the chlorin or bacteriochlorin from the
porphyrin impurity. MET2 can then be isolated by chromatography and
the resulting MET2 purified by precipitation or crystallization
from a solvent such as dichloromethane or a mixture of solvents,
and a precipitating solvent in which MET2 is not soluble. In this
instance, the solvent can be removed by slow or rotary evaporation
resulting in the precipitation of MET2.
[0055] The base catalyzed cyclization of meso-acrylate
tetrapyrrolic compounds to give purpurins or purpurin type
compounds is believed to be applicable to any meso-acrylate (or
similar) tetrapyrrolic compound on a large scale. The functionality
on the periphery of the meso-acrylate tetrapyrrolic molecule,
either at the meso or .beta.-pyrrolic positions may be varied
widely as outlined earlier herein at pages 7-12. It would be within
the knowledge of those skilled in the art what other functional
groups or modifications to this procedure could be made to utilize
the invention described.
Large Scale Synthesis of Octaethylbenzochlorin.
[0056] A variety of methods have been reported for the synthesis of
octaethylbenzochlorin. U.S. Pat. No. 5,552,134 and literature
references (Arnold, D. P., Gaete-Holmes, R., Johnson, A. W., Smith,
R. P., Williams, G. A., J. Chem. Soc. Perkin I, 1660-1670, 1978;
Morgan, A. R., Skalkos, D., Maguire, G., Rampersaud, A., Garbo, G.,
Keck, R., Selman, S. H., Photochem. Photobiol. Vol. 55, No.1,
133-136, 1992) outline the synthesis of octaethylbenzochlorin from
Nickel meso-(.beta.-formylvinyl)-octaethylp- orphyrin (14) or from
the metal free meso-(.beta.-hydroxymethylvinyl)porph- yrin (12)
(Scheme 8).
[0057] Historically, the formation of octaethylbenzochlorin (OEBC)
has been via two routes. First, the metallated meso-acrolein
porphyrins (14) and (15) have been cyclized under acidic conditions
to give Nickel OEBC (17) (or copper benzochlorin if the copper
meso-acrolein porphyrin is used). Demetallation of (17) (or Copper
OEBC) is difficult and demetallation with sulfuric acid generally
produces OEBC (13) and its sulfonic acid derivative (18) after 3
hours at room temperature. 8
[0058] An alternative route outlined by Morgan et al (Morgan, A.
R., Skalkos, D., Maguire, G., Rampersaud, A., Garbo, G., Keck, R.,
Selman, S. H., Photochem. Photobiol. Vol. 55, No.1, 133-136, 1992)
involves the reduction of the meso-acrylate porphyrin (11) with
diisobutyl aluminium hydride in tetrahydrofuran (THF) at low
temperature to give the meso-(.beta.-hydroxymethylvinyl)porphyrin
(12). This compound is then treated with sulfuric acid for 5
minutes to effect the cyclization and give OEBC (13). Longer
reaction times in sulfuric acid leads to significant production of
the sulfonated derivative (18).
[0059] Neither of these two routes is suitable for manufacturing
OEBC on a large scale. The first route gives low yields of the
Nickel or copper benzochlorin, generally not greater that 50%, and
demetallation of the strongly bound metals (Nickel and Copper) has
historically used sulfuric acid. As sulfonation of OEBC occurs
rapidly in sulfuric acid (within 3 hours), demetallation of (17)
invariably results in the formation of the sulfonated analog, which
must be separated by chromatography. The yields thus are
disappointing.
[0060] The use of diisobutyl aluminium hydride (DIBALH) to reduce
the ester functionality of the meso-acrylate porphyrin (11)
following Morgan's exact methodology as reported, [(200 mg (11) in
THF (100 mL; dry), -78.degree. C./N.sub.2; add DIBALH in THF (20 mL
of 1M solution (63 equivalents)), stir 1 hr at -78.degree. C.; add
water (100 mL) followed by 10% NaOH solution (100 mL) and water
(200 mL)] does not work. When we repeated this reported protocol
only starting material was isolated. Indeed, the starting material
precipitates out of the THF on the addition of water and sodium
hydroxide solution. There are no organic layers formed as reported
and no appreciable amounts of (12) formed by NMR or TLC. We have
observed that the reduction of the ester functionality in THF is an
extremely slow reaction, requiring more that 2 days stirring (under
Morgan's conditions) to see any appreciable amount of (12). Even
under these conditions, the product is mostly (11). Reactions using
LiAlH.sub.4 under a variety of conditions give unsatisfactory
quantities of (12), which are invariably contaminated with other
multiple products by TLC.
[0061] An alternative route to the synthesis of NiOEBC has been
described by Arnold and co-workers (Scheme 9). In this methodology,
the Nickel derivatives (10) or (14) are reduced to (19) with
LiAlH.sub.4 or NaBH.sub.4 respectively. Reduction of (10) produces
(19) in 36% yield. Treatment of (19) with acid gives Nickel OEBC in
28% yield. 9
[0062] All of the known reported methods for the synthesis of
NiOEBC or OEBC directly, suffer from low yields or products that
require chromatography to purify. Indeed, the cyclization of the
porphyrin precursors in sulfuric acid form sulfonated products like
(18). As a result, none of the reported methods is suitable for
manufacturing OEBC on a large scale. We have discovered methods
that give excellent yields of OEBC from either (11) or NiOEBC,
which are described below in detail.
Production of OEBC from meso-acrylate octaethylporphyrin (11)
[0063] The reduction of the ester group in (11) using DIBALH in THF
has been shown to be prohibitively slow for use on a large scale
(or even a small scale). We have discovered that the reduction
reaction rate is entirely dependent on the solvents utilized in the
reaction. If the reduction is undertaken in dichloromethane, using
DIBALH in toluene (2.5 equivalents) as the reducing agent, large
quantities (>100 g) of (11) are efficiently transformed to (12)
in about 4 hours. If THF is used instead of dichloromethane to
dissolve (11) and DIBALH in toluene is added to the reaction under
the same conditions, the reaction is 1.5 to 2 times slower. Thus,
it appears that the reduction of (11) with DIBALH is dependent on
the solvent in which the DIBALH is dissolved. The inventors believe
that this reaction proceeds most efficiently using a chlorinated
solvent such as dichloromethane or 1,2-dichloroethane. The
reduction is also dependant on the temperature of the reaction. If
the addition of the DIBALH is not closely monitored and the
temperature is allowed to rise, significant by-products occur in
the reaction. In particular, metallated porphyrins are formed,
presumably aluminium porphyrins, at higher temperatures
(>-35.degree. C.). It is preferred that the reaction be carried
out between about -80.degree. C. and about --35.degree. C.
[0064] Literature methods (Morgan et al) have reported isolating
the alcohol (12) from the reduction reaction prior to cyclization
to give OEBC. We have found that it is not necessary to isolate the
alcohol (12) prior to cyclization. During the course of the
reduction reaction, small aliquots are taken from the reaction
mixture and neutralized with acetic acid/water or ethylacetate and
ammonium hydrochloride solution. TLC indicates whether the reaction
is complete or not. Once complete, excess DIBALH is quenched with
isopropanol/methanol and an acid such as, for example, phosphoric
acid (85%) is added. The organic volatiles (dichloromethane and
toluene) are removed by distillation (rotoevaporation or other) and
the phosphoric acid solution is heated at 60-130.degree. C.,
preferably at about 100.degree. C. for 3 hours to effect
cyclization of (12) to OEBC. The OEBC is conveniently isolated from
the phosphoric acid solution by precipitation with water
(1.5.times.the H.sub.3PO.sub.4 volume). The OEBC is simply filtered
from the acidic aqueous liquors. Any porphyrinic impurities remain
protonated and soluble in the acidic aqueous mother liquors. The
OEBC solid is then dissolved in dichloromethane and reprecipitated
as before (using phosphoric acid/water) or from methanol or
ethanol, via the distillation of the dichloromethane. The OEBC
obtained in this manner is sufficiently pure to be used further
(>97%) and is typically obtained in 70-75% yields. In addition
to phosphoric acid, acids that can be preferably used in the above
method include, for example, methane sulfonic acid and hydrochloric
acid.
[0065] If the alcohol (12) needs to be isolated, we have found it
convenient to quench the reaction with aqueous ammonia
hydrochloride solution. Care must be taken during the quenching
process to make sure that the quenching solution is acidic, as it
appears that aluminium can be incorporated into the porphyrin. It
should be noted also that TFA will not cyclize (12) to OEBC.
[0066] OEBC made in this way can be conveniently sulfonated at
large scale to produce (18), by dissolving OEBC in sulfuric acid
(with or without oleum). After the reaction is complete, (18) is
conveniently isolated simply by adding the sulfuric acid to chilled
water which precipitates the sulfonated product. It is then
filtered and dried in a vacuum oven.
[0067] Both the reduction reaction and the acid catalyzed
cyclization described in this section are believed to be applicable
to any meso-acrylate (or similar) tetrapyrrolic compound on a large
scale. The functionality on the periphery of the meso-acrylate
tetrapyrrolic molecule, either at the meso or .beta.-pyrrolic
positions, can be varied widely as described earlier herein at
pages 7-12. It would be within the knowledge of those skilled in
the art what other functional groups are susceptible to
modification via the reduction conditions or what modifications to
this procedure could be made to utilize the invention
described.
Demetallation of NiOEBC or CuOEBC without Sulfonation
[0068] The centrally coordinated metal (nickel or copper) of
metallated benzochlorin or benzochlorin-type compounds requires
strong acid conditions for removal (usually concentrated sulfuric
acid) and long reaction times at room temperature (usually
overnight). Unfortunately, sulfonation of the benzochlorin occurs
readily in this solvent. It is thus very difficult to control the
conditions necessary to obtain high yields of demetallated
benzochlorins such as OEBC, without concomitant production of the
corresponding sulfonated product (18). We have found that the
central metal (nickel or copper) of OEBC can be efficiently removed
by warming the compound to, for example, 80.degree. C. in methane
sulfonic acid. The reaction can be monitored by neutralizing small
aliquots of the reaction, dissolving in dichloromethane and
evaluating by TLC (30% hexane/dichloromethane). When deemed
complete, the reaction can be diluted with ice water (equal volume)
and the solid collected by filtration. The solid is washed with
methanol or ethanol, redissolved in dichloromethane and
precipitated from methanol, to give OEBC in about 80-90% yield,
sufficiently pure to undergo further reactions (>97%).
[0069] The demetallation reaction described above is believed to be
applicable to any benzochlorin or similar tetrapyrrolic compound on
a large scale. The functionality on the periphery of the
meso-acrylate tetrapyrrolic molecule, either at the meso or
.beta.-pyrrolic positions, can be varied widely as described
earlier herein at pages 7-12. It would be within the knowledge of
those skilled in the art what other functional groups could be used
in order to use this demetallation reaction.
Tin Insertion into Tetrapyrrolic Compounds
[0070] The formation of metallated porphyrins, chlorins,
bacteriochlorins and iso-bacteriochlorins is well established in
the literature. Incorporation of metals into these tetrapyrrolic
macrocycles can change the photophysical and pharmacokinetic
attributes, distribution, metabolism and toxicology of the
metallated compound from that of the parent metal-free molecule. In
particular, one such metal, tin, has been incorporated into a
number of tetrapyrrolic macrocycles that are of interest in
medicine or phototherapy. Examples of these compounds include, for
example, tin (dichloride) ethyl etiopurpurin I (SnET2;
Rostaporfin), tin protoporphyrin (IX) [SnPP(IX)] and tin
meso-porphyrin (IX) [SnMPP(IX)] (shown below). SnET2 is currently
being evaluated as a photosensitizer in the treatment of age
related macular degeneration. SnPP(IX) and SnMPP(IX), as their
disodium salts, are currently being evaluated as heme oxygenase
inhibitors that decrease the production of bilirubin in infants
suffering from hyperbilirubinemia. While there have been few human
studies thus far with SnPP(IX) in this role, promising results have
been obtained. As the general applicability of photomedicine is
realized in disease indications, there will be an increasing need
for pure tin tetrapyrrolic macrocyclic compounds. 10
[0071] The invention described herein relates to the insertion of
tin (II) complexes into tetrapyrrolic macrocycles to form tin (IV)
metallo-tetrapyrrolic macrocycles. Such compounds, in addition to
medicine or phototherapy, may also be useful as molecular wires or
as templates for molecular or chiral recognition. In addition,
these compounds may also be useful as pharmaceuticals, data storage
devices, molecular switches or mimics of biosynthetic
processes.
[0072] To achieve the advantages in accordance with the purpose of
the invention, as embodied and broadly described therein, the
inventors have found that a necessary component in the successful
formation of highly pure tin (IV) metalloporphyrin complexes, is
the abundance of molecular oxygen in the reaction mixture. In deed,
tin insertion into a porphyrin molecule may be achieved at
relatively low temperatures provided that an abundance of molecular
oxygen is present in the reaction mixture.
[0073] Work in our laboratory has explored in detail the chemistry
of tin insertion into tetrapyrrolic macrocycles. While there exists
many reported methods for inserting tin into tetrapyrrolic
macrocycles, we have discovered that even at relatively small
scales (grams) the classical methods of inserting tin (II) into
tetrapyrrolic macrocycles often lead to the formation of "reduced"
tetrapyrrolic side products. Such products are often undesired and
are extremely difficult to remove from the desired metallated
products as purification of tin tetrapyrroles by chromatography on
silica or alumina is extremely difficult. Scheme 10 represents a
typical tin insertion reaction into a tetrapyrrolic macrocycle.
11
[0074] In the metal insertion process, Sn (II) is believed to be
inserted into the tetrapyrrolic core as a Sn (II) cation, whereupon
rapid oxidation occurs by oxygen or traces of oxidizing impurities
to produce the isolated Sn (IV) tetrapyrrolic species. Evidence for
the formation of Sn (II) tetrapyrrole complexes has been observed
by the isolation of a Sn (II) phthalocyanine. Sn (II) complexes of
porphyrins are relatively unknown.
[0075] In the metallation reaction, oxidation of Sn (II) to Sn (IV)
occurs via oxygen present in the reaction, or other electron rich
molecules according to the following equation: 1 2 Sn 2 + 2 Sn 4 +
+ 4 e - E 0 N = - 0.151 O 2 + 4 H + 4 e - 2 H 2 O E 0 N = + 1.229 2
Sn 2 + O 2 2 Sn 4 + + 2 H 2 O E 0 N = + 1.078
[0076] Unfortunately, while the reaction sequence appears
relatively straightforward, problems occur when tin metallation is
attempted under normal atmospheric conditions in concentrations
desirable for large scale manufacturing (or even manufacturing at
small scale.about.1 g). First, metal insertion is usually
undertaken in solvents like glacial acetic acid, dimethylformamide
or pyridine at, or close to, their boiling points in the presence
of a proton scavenger that absorbs protons of metallation. A
particularly preferred proton scavenger is sodium acetate, but
others such as salts of other organic acids or amines could also be
used effectively. The solvents quickly degas under elevated
temperature conditions. In large-scale reactors, the volume between
the reaction solvent and the top of the reactor vessel is called
headspace. In order to maximize operating efficiency and lower the
cost of plant production of the material, headspace is preferably
kept to a minimum. Reactions are generally carried out at the
highest concentrations of reactants possible in order to maximize
efficiency. The combination of solvent degassing, solvent saturated
headspace at the reflux temperature, and highly concentrated
reaction solutions, leads to less than optimal results in the
formation of pure Sn (IV) tetrapyrroles.
[0077] The driving force for tin insertion into the macrocycle is
the reduction of Sn (II) to Sn (IV). As the metal desires to
incorporate into the macrocycle, tetrapyrroles with reducible bonds
undergo reductions. Such reductions typically occur on the ring of
the macrocycle or at groups on the periphery of the molecule (such
as vinyl groups etc.). The following are observed examples of
unwanted reactions at the porphyrin periphery, which adequately
illustrate the observed problem.
Tin metallation of Methyl pyrropheophorbide (20)
[0078] Attempts to insert SnCl.sub.2 into (20) under standard
reaction conditions (500 mg of (20) in 70 mL of AcOH, 5 equivalents
of NaOAc, 7 equivalents of SnCl.sub.2, followed by reflux) results
in the formation of the desired tin metallated pyrropheophorbide
(21) and 12
[0079] appreciable amounts (>20%) of (22) in which the
peripheral vinyl group has been reduced. If pyridine or
dimethylformamide is used as solvent instead of acetic acid, the
major product of the reaction is (22).
Tin metallation of Ethyl etiopurpurin (7)
[0080] 13
[0081] Attempts to insert SnCl.sub.2 into (5) under standard
reaction conditions (1 g of (5) in 100 mL of AcOH, 5 equivalents of
NaOAc, 7 equivalents of SnCl.sub.2, followed by reflux) results in
the formation of the desired tin metallated purpurin (SnET2) (7)
and appreciable amounts (5-10%) of SnET2H2 (24) in which the
peripheral vinyl group of the isocyclic ring has been reduced. If
pyridine or dimethylformamide is used as solvent instead of acetic
acid, the major product of the reaction is (24). Additionally, the
reaction slows substantially if adequate oxygen is not present. We
have found that the formation of the impurity (24) is reduced to
levels below the limit of quantitation by HPLC if air (or other
oxygen containing gas) is bubbled through the solution during the
metallation reaction.
Tin metallation of meso-acrylate etioporphyrin I
[0082] 14
[0083] Attempts to insert SnCl.sub.2 into (4) under standard
reaction conditions (1 g of (4) in 100 mL of AcOH, 5 equivalents of
NaOAc, 5 equivalents of SnCl.sub.2, followed by reflux) results in
some formation of the desired tin metallated porphyrin (25),
however the major product of the reaction is (26) in which the
peripheral vinyl group of the acrylate has been reduced. If
pyridine or dimethylformamide is used as the solvent instead of
acetic acid, the major product of the reaction is (26). We have
found that the meso-acrylate tin porphyrin (25) can only be formed
in high purity when dichloroethane is used as a solvent and a
vigorous stream of air (or other oxygen containing gas) is bubbled
through the solution.
Tin metallation of protoporphyrin IX, dimethyl ester (27)
[0084] 15
[0085] Attempts to insert SnCl.sub.2 into (27) under standard
reaction conditions (1 g of (27) in 100 mL of AcOH, 5 equivalents
of NaOAc, 7 equivalent of SnCl.sub.2, followed by reflux) results
in the formation of the desired tin metallated porphyrin (28).
However, by NMR at least 2 major impurities (ranging from 5-15%)
are observed. These may be compounds (29) to (31). If pyridine or
dimethylformamide is used as the solvent instead of acetic acid,
the impurity products increase to 15-25%. The formation of these
impurities is limited substantially (to undetectable levels by NMR
(<0.4%)) if air (or another oxygen containing gas) is vigorously
bubbled through the solution during the metallation reaction. As
the solubility of tin salts in a number of common metallation
solvents is low, the inventors have also found it advantageous to
pre-dissolve the tin salt in a suitable solvent like
dimethylformamide, prior to addition to the bulk reaction. This
enables rapid incorporation of the tin salt into the macrocycle.
Other examples of tin salts that can be used in the invention in
addition to SnCl.sub.2 include, for example, Sn(Oac).sub.2 and
Sn(acac).sub.2. In addition to dimethylformamide, predissolving
solvents suitable for use in this process include, for example,
acetic acid, propionic acid, or pyrridine.
[0086] Additionally, it is recognized in the art that some
metallo-tetrapyrrolic macrocycles such as cadmium tetrapyrrolic
will exchange the coordinated metal for a second metal. Such metal
exchange reactions are encompassed within the present
invention.
[0087] In accordance with the invention, as embodied and broadly
described herein, the inventors have found that if adequate air is
used in the reaction, high purity tin tetrapyrrolic compounds are
formed from their corresponding non-metallated tetrapyrrolic
compounds. It should be noted that a gas with an oxygen content of
at least about 14% by weight is particularly advantageous. In
general, many of these compounds crystallize or precipitate from
the reaction mixture itself, enabling effective isolation by
filtration.
[0088] The inventors have found that to obtain highly pure product
(>99%), excess salts or impurities can be effectively removed
from the reaction mixture on a large scale by precipitation
techniques. In the case of tin ethyl etiopurpurin I (7), for
example, the crude precipitate of (7) from the metallation reaction
can be reprecipitated by first dissolving the purpurin in
dichloromethane, adding acetic acid and removing the
dichloromethane by distillation. In addition to dichloromethane,
other solvents can be used to dissolve the purpurin, such as ether,
dichloroethane, chloroform, toluene, or benzene. Other solvents in
addition to acetic acid that have been found effective at
precipitating the tin purpurin product include, for example,
acetone, ethanol, methanol, dimethylformamide and acetonitrile. Of
these, acetone and ethanol are preferred. This precipitation
technique works similarly with almost all tin tetrapyrrolic
compounds on a larger scale (>100 g). In particular, this
precipitation technique works effectively with (21), (24), (25),
(28) and (31) on scales greater than 50 grams. Of particular note
is that the use of high quality solvents with low water contents
(especially in the alcohols and acetone) greatly lowers the
potential of ligand exchange on the centrally coordinated tin
compounds.
[0089] It would be within the knowledge of those skilled in the art
that other solvents can be used to effectively precipitate the tin
tetrapyrrolic complexes. These would include hexanes and the like,
ethers and the like, and other alcohols. Examples set forth in the
experimental section highlight the general applicability of the
precipitation technique.
[0090] Described above are general procedures for the large scale
manufacturing of tetrapyrrolic compounds such as meso-formyl
porphyrins, meso-acrylate porphyrins, purpurins, tin metallated
tetrapyrroles and benzochlorins. Purification is readily achieved
by a series of fractional crystallizations. Additional advantages
of the invention will be set forth in the detailed examples that
follow, and in part will be obvious from the description supplied
or may be learned by practice of the invention. The advantages of
the invention can be realized and attained by means of the elements
and combinations particularly pointed out in the appended claims.
The following examples are included to highlight the advantages
over the existing methods and are in no way intended to limit the
invention.
EXAMPLES
[0091] A) Large Scale Formylations of Metalloporphyrins
Example 1
Preparation of Nickel (II) meso-Formyl Etioporphyrin I (2)-Method
A
[0092] 1,2-Dichloroethane (DCE, 8 L) was charged into a 22 L
jacketed reaction vessel, followed by Nickel (II) etioporphyrin I
(250.0 g, 0.47 mole), and the mixture was stirred slowly to
dissolve the solid. During the dissolution, a Vilsmeier reagent
[(chloromethylene)dimethylammonium chloride (200.5 g, 1.57 mole)]
was added to the Nickel(II) etioporphyrin I solution, followed by
DCE (300 mL) to rinse the residual solid from the sides of the
vessel. The reaction was warmed to 50-60.degree. C. and held for
approximately 5 hours, when the iminium salt formation was
determined to be complete by TLC. Subsequently, aqueous sodium
acetate (NaOAc.3H.sub.2O, 744.0 g, 5.47 moles; H.sub.2O, 4L) was
added over 46 minutes to hydrolyze the excess Vilsmeier reagent.
The mixture was heated to 50-60.degree. C. and held for
approximately 45 minutes with rapid stirring, when the hydrolysis
was determined to be complete by TLC.
[0093] After allowing the two phase system to separate over
approximately 14 hours, the organic layer was collected and the
aqueous layer was back extracted three times with DCE (2.times.1000
mL, 1.times.750 mL). Each back extraction required an additional
1000 mL of purified water to facilitate layer separation. The
combined organic layers were then evaporated to dryness at reduced
pressure on a rotary evaporator (260-180 mbar, 60 -67.degree. C.).
DCE (300 mL) was used to rinse the final residue from flasks that
contained the original DCE organic layer. This DCE rinse was then
added to the rotary evaporation flask. Methylene chloride
(CH.sub.2Cl.sub.2, 3000 mL) was added to the solid residue and the
mixture was warmed in a water bath (.about.35.degree. C.) for about
30 minutes. Acetic acid (1500 mL) was added slowly with swirling to
the CH.sub.2Cl.sub.2 solution and the CH.sub.2Cl.sub.2 was removed
slowly on the rotary evaporator (600-378 mbar, 37-59.degree. C.).
The resulting slurry was cooled to ambient temperature over 10
minutes and was then vacuum filtered on a Buchner funnel with
hardened qualitative filter paper. The solid was slurried and
rinsed in portions with ethanol (2000 mL) and dried in the filter
for another 35 minutes. The solid was checked by TLC and then
transferred to a vacuum oven and dried to a constant weight at
40-57.degree. C. at a vacuum 29.5-30" Hg for about 21 hours to
afford 239.6 g (91.1% yield) of Nickel (II) meso-formyl
etioporphyrin I (2).
Example 2
Preparation of Nickel (II) meso-Formyl Etioporphyrin I (2)-Method
B
[0094] 1,2-Dichloromethane (DCM, 8 L) was charged into a 10 gal
glass lined jacketed metal reactor, followed by Nickel (II)
etioporphyrin I (250.0 g, 0.47 mole), and the mixture was stirred
slowly to dissolve the solid. During the dissolution, the Vilsmeier
reagent [(chloromethylene)dimethylammonium chloride (200.0 g, 1.56
mole)] was added to the Nickel(II) etioporphyrin I solution,
followed by DCM (300 mL) to rinse the residual solid from the sides
of the vessel. The reactor was sealed and warmed to 50-60.degree.
C. and held for approximately 5 hours, whereby the reactor was
cooled to 10.degree. C. A sample taken from the reactor was
analyzed by TLC (DCM) which showed the absence of starting material
and iminium salt formation.
[0095] Aqueous sodium acetate (NaOAc.3H.sub.2O, 744.0 g, 5.47
moles; H.sub.2O, 4L) was added over 45 minutes to hydrolyze excess
Vilsmeier reagent while maintaining the temperature below
20.degree. C. The reactor was then sealed and the solution
vigorously stirred at 35.degree. C. over night. After allowing the
two phase system to separate, the organic layer was collected into
a second reactor and the aqueous layer in reactor 1 was back
extracted three times with DCM (2.times.1000 mL, 1.times.750 mL)
with the organic layer at each extraction being added to the second
reactor. Acetic acid (1500 mL) was added slowly with swirling to
the CH.sub.2Cl.sub.2 solution in reactor 2 and the CH.sub.2Cl.sub.2
was removed slowly by distillation. The resulting slurry was cooled
to ambient temperature and was then line filtered onto a filter
disk. Ethanol (2000 mL) was added to the second reactor and the
solution rapidly stirred to wash any remaining solid from the sides
of the reactor vessel. The solution was again line filtered onto
the filter disk containing the product. The product was collected
and dried in a vacuum oven to constant weight at 40-60.degree. C.
at a vacuum 29.5-30" Hg for about 21 hours to afford 235.0 g (89%
yield) of Nickel (II) meso-formyl etioporphyrin I (2).
Example 3
Preparation of Nickel (II) meso-Formyl Octaethylporphyrin (9)
[0096] 1,2-Dichloroethane (DCE, 8 L) was charged into a 22 L
jacketed reaction vessel, followed by Nickel (II)
octaethylporphyrin (250.0 g, 0.42 mole), and the mixture was
stirred slowly to dissolve the solid. During the dissolution,
Vilsmeier reagent [(chloromethylene)dimethylammon- ium chloride
(200.5 g, 1.57 mole)] was added to the Nickel(II)
octaethylporphyrin solution, followed by DCE (300 mL) to rinse the
residual solid from the sides of the vessel. The reaction was
warmed to 50-60.degree. C. and held for approximately 5 hours, when
the iminium salt formation was determined to be complete by TLC.
Subsequently, aqueous sodium acetate (NaOAc.3H.sub.2O, 744.0 g,
5.47 moles; H.sub.2O, 4L) was added over 40 minutes to hydrolyze
the excess Vilsmeier reagent. The mixture was heated to
50-60.degree. C. and held for approximately 45 minutes with rapid
stirring, when the hydrolysis was determined to be complete by
TLC.
[0097] After allowing the two phase system to separate over
approximately 14 hours, the organic layer was collected and the
aqueous layer was back extracted three times with DCE (2.times.1000
mL, 1.times.750 mL). Each back extraction required an additional
1000 mL of purified water to facilitate layer separation. The
combined organic layers were then evaporated to dryness at reduced
pressure on a rotary evaporator (260-180 mbar, 60 -67.degree. C.).
DCE (300 mL) was used to rinse the final residue from flasks that
contained the original DCE organic layer. This DCE rinse was then
added to the rotary evaporation flask. Methylene chloride
(CH.sub.2Cl.sub.2, 3000 mL) was added to the solid residue and the
mixture was warmed in a water bath (.about.35.degree. C.) for -30
minutes. Acetic acid (1500 mL) was added slowly with swirling to
the CH.sub.2Cl.sub.2 solution and the CH.sub.2Cl.sub.2 was removed
slowly on the rotary evaporator (600-380 mbar, 40-60.degree. C.).
The resulting slurry was cooled to ambient temperature over 10
minutes and was then vacuum filtered on a Buchner funnel with
hardened qualitative filter paper. The solid was slurried and
rinsed in portions with ethanol (2000 mL) and dried in the filter
for another 35 minutes. The solid was checked by TLC and then
transferred to a vacuum oven and dried to a constant weight at
40-57.degree. C. at a vacuum 29.5-30" Hg for about 21 hours to
afford 240.2 g (91.6% yield) of Nickel (II) meso-formyl
octaethylporphyrin (9).
[0098] B) Large Scale Wittig Reaction on meso-Formylporphyrins
Example 4
Preparation of Nickel (II) meso-Acrylate Etioporphyrin I (3)
[0099] Nickel (II) meso-formyl etioporphyrin I (237.2 g, 0.42
mole), N,N-dimethylformamide (275 mL) and (carbethoxymethylene)
triphenylphosphorane (293.4 g, 0.84 mole) were combined in a 3 L
round bottom flask and heated at 137-153.degree. C. under an argon
blanket for approximately 4 hours. TLC was used to monitor the
completion of the reaction. The reaction was cooled to
approximately 80.degree. C. and transferred to an evaporation flask
with the aid of DMF (300 mL). After the majority of the solvent was
removed under vacuum (200 -15 mbar) at 74 to 92.degree. C., the
residue was heated at .gtoreq.80.degree. C under vacuum (.ltoreq.70
mbar) for an additional 28 minutes. To the resulting solid, which
was cooled in an ambient water bath, methylene chloride (1750 mL)
was added and the mixture was warmed to 35-40.degree. C. for 35
minutes to dissolve the solid. Then ethanol (2000 mL) was added
with swirling and the methylene chloride was slowly removed under
vacuum (700-400 mbar, 40-49.degree. C.) to precipitate the product.
The slurry was cooled to ambient temperature over 7 minutes and the
product collected by vacuum filtration on a Buchner funnel with
hardened qualitative filter paper, slurried and rinsed in portions
with ethanol (2500 mL) and dried until the solid caked. The solid
was checked by TLC and then transferred to a vacuum oven and dried
at 40-55.degree. C., 28.5-30" Hg for approximately 21 hours to a
constant weight to afford 239.2 g (89.7% yield) of Nickel (II)
meso-acrylate etioporphyrin I (3).
Example 5
Preparation of Nickel (II) meso-Acrylate Octaethylporphyrin
(10)
[0100] Nickel (II) meso-formyl octaethylporphyrin (237.2 g, 0.40
mole), N,N-dimethylformamide (275 mL) and (carbethoxymethylene)
triphenylphosphorane (278.7 g, 0.80 mole) were combined in a 3 L
round bottom flask and heated at 137-153.degree. C. under an argon
blanket for approximately 4 hours. TLC was used to monitor the
completion of the reaction. The reaction was cooled to
approximately 80.degree. C. and transferred to an evaporation flask
with the aid of DMF (300 mL). After the majority of the solvent was
removed under vacuum (200-15 mbar) at 74 to 92.degree. C., the
residue was heated at >80.degree. C under vacuum (.ltoreq.70
mbar) for an additional 25 minutes. To the resulting solid, which
was cooled in an ambient water bath, methylene chloride (1750 mL)
was added and the mixture was warmed to 35-40.degree. C. for 35
minutes to dissolve the solid. Then ethanol (2000 mL) was added
with swirling and the methylene chloride was slowly removed under
vacuum (700-400 mbar, 40-49.degree. C.) to precipitate the product.
The slurry was cooled to ambient temperature over 10 minutes and
the product collected by vacuum filtration on a Buchner funnel with
hardened qualitative filter paper, slurried and rinsed in portions
with ethanol (2500 mL) and dried until the solid caked. The solid
was checked by TLC and then transferred to a vacuum oven and dried
at 40-55.degree. C., 28.5-30" Hg for approximately 21 hours to a
constant weight to afford 240.2 g (90% yield) of Nickel (II)
meso-acrylate octaethylporphyrin (10).
Example 6
Preparation of meso-Acrylate Etioporphyrin I (4)
[0101] A solution of methylene chloride (3250 mL) and Nickel (II)
meso-acrylate etioporphyrin I (237.1 g, 0.37 mole), plus an
additional 250 mL of CH.sub.2Cl.sub.2 to rinse the sides of the
vessel, was cooled to 0.degree. C. in a jacketed 22 L reaction
vessel. Then, concentrated H.sub.2SO.sub.4 (250 mL, .about.4.5
moles) was added slowly with vigorous stirring, followed by 300 mL
of CH.sub.2Cl.sub.2 to rinse the sides of the vessel. The stirring
was continued for a total of 33 minutes, and then cold water (5 L)
was slowly added to the reaction vessel with moderate stirring,
maintaining the temperature at .ltoreq.11.degree. C. The reaction
was cooled to 2.degree. C., and then aqueous NaOH (NaOH, 230.0 g,
5.75 mole; H.sub.2O, 2000 mL) was added slowly, maintaining the
temperature at .ltoreq.10.degree. C.
[0102] The layers were separated and the aqueous layer was back
extracted twice with CH.sub.2Cl.sub.2 (2.times.1000 mL). The
organic layers were combined and concentrated under vacuum (700-660
mbar, 35-40.degree. C.) until approximately 1500 mL of
CH.sub.2Cl.sub.2 remained. During the solvent removal,
CH.sub.2Cl.sub.2 (300 mL) was used to rinse the organic layer
collection flasks and was added to the CH.sub.2Cl.sub.2 solution.
Ethanol (1700 mL) was then added with swirling, and the remaining
CH.sub.2Cl.sub.2 was removed under vacuum (600-335 mbar,
42-50.degree. C.) to precipitate the product. The slurry was cooled
over approximately 1 hour and the product was vacuum filtered on a
Buchner funnel with hardened qualitative filter paper. The solid
was slurried and rinsed in portions with ethanol (2000 mL), and
then dried under vacuum until the solid caked. The product was
checked by TLC and then dried for approximately 27 hours under
vacuum (29-29.5" Hg) at an end temperature of 56.degree. C. to a
constant weight, affording 206.6 g (95.7% yield) of meso-acrylate
etioporphyrin I (4).
Example 7
Preparation of meso-Acrylate Octaethylporphyrin I (II)
[0103] A solution of methylene chloride (3250 mL) and Nickel (II)
meso-acrylate octaethylporphyrin (240 g, 0.35 mole), plus an
additional 250 mL of CH.sub.2Cl.sub.2 to rinse the sides of the
vessel, was cooled to 0.degree. C. in a jacketed 22 L reaction
vessel. Then, concentrated H.sub.2SO.sub.4 (250 mL, .about.4.5
moles) was added slowly with vigorous stirring, followed by 300 mL
of CH.sub.2Cl.sub.2 to rinse the sides of the vessel. The stirring
was continued for a total of 35 minutes, and then cold water (5 L)
was slowly added to the reaction vessel with moderate stirring,
maintaining the temperature at .ltoreq.10.degree. C. The reaction
was cooled to 0.degree. C., and then aqueous NaOH (NaOH, 230.0 g,
5.75 mole; H.sub.2O, 2000 mL) was added slowly, maintaining the
temperature at .ltoreq.10.degree. C.
[0104] The layers were separated and the aqueous layer was back
extracted twice with CH.sub.2Cl.sub.2 (2.times.1000 mL). The
organic layers were combined and concentrated under vacuum (700-660
mbar, 35-40.degree. C.) until approximately 1500 mL of
CH.sub.2Cl.sub.2 remained. During the solvent removal,
CH.sub.2Cl.sub.2 (300 mL) was used to rinse the organic layer
collection flasks and was added to the CH.sub.2Cl.sub.2 solution.
Ethanol (1700 mL) was then added with swirling, and the remaining
CH.sub.2Cl.sub.2 was removed under vacuum (600-335 mbar,
40-50.degree. C.) to precipitate the product. The slurry was cooled
over approximately 1 hour and the product was vacuum filtered on a
Buchner funnel with hardened qualitative filter paper. The solid
was slurried and rinsed in portions with ethanol (2000 mL), and
then dried under vacuum until the solid caked. The product was
checked by TLC and then dried for approximately 27 hours under
vacuum (29-29.5" Hg) at an end temperature of 60.degree. C. to a
constant weight, affording 211.8. g (95.7% yield) of meso-acrylate
octaethylporphyrin (II).
Example 8
Preparation of Ethyl Etiopurpurin I (5)-Method A
[0105] Meso-acrylate etioporphyrin I (4) (204.7 g, 0.36 mole),
toluene (3750 mL) and 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU, 20
mL, 0.13 mole) were combined in a 12 L round bottom reaction vessel
and purged with argon for 21 minutes, brought to reflux and stirred
for approximately 5 hours under an argon atmosphere. TLC was used
to monitor the completion of the reaction. The reaction was cooled
to ambient temperature, transferred to an evaporation flask with
the aid of additional toluene (210 mL) and the solvent was removed
under vacuum (98-30 mbar, 60-70.degree. C.).
[0106] Methylene chloride (4000 mL) was added to the solid and the
mixture was warmed with swirling at 35-41.degree. C. for 35
minutes. Acetonitrile (2500 mL) was added in portions with swirling
as the CH.sub.2Cl.sub.2 was removed at reduced pressure (700-408
mbar, 45-55.degree. C.). The slurry was vacuum filtered while still
warm on a Buchner funnel with hardened qualitative filter paper and
the solid was slurried and rinsed in portions with acetonitrile
(1750 mL), and then dried until the solid caked. The solid was
transferred to an evaporation flask with CH.sub.2Cl (4000 mL) and
the mixture was warmed with swirling at 35-45.degree. C. for 30
minutes. Acetonitrile (2500 mL) was added in portions with swirling
as the CH.sub.2Cl was removed at reduced pressure (695-460 mbar,
45-55.degree. C.). The warm slurry was vacuum filtered on a Buchner
funnel with hardened qualitative filter paper and the solid was
slurried and rinsed in portions with acetonitrile (1500 mL), then
dried until the solid caked. The solid was transferred to an
evaporation flask with CH.sub.2Cl (4000 mL) and the mixture was
warmed with swirling at 40-44.degree. C. for 30 minutes.
Acetonitrile (2500 mL) was added in portions with swirling as the
CH.sub.2Cl was removed at reduced pressure (700-466 mbar,
45-55.degree. C.). The warm slurry was vacuum filtered on a Buchner
funnel with hardened qualitative filter paper and the solid was
slurried and rinsed in portions with acetonitrile (1500 mL), then
dried until the solid caked. The solid was analyzed by TLC to
determine the purity and then dried under vacuum (30" Hg) at
52-57.degree. C. for approximately 21 hours to a constant weight to
yield 130.3 g (63.7% yield) of ethyl etiopurpurin I (5).
Example 9
Preparation of Ethyl Etiopurpurin I (5)-Method B
[0107] Meso-acrylate etioporphyrin I (4) (205.0 g, 0.36 mole),
toluene (3750 mL) and 1,8-diazabicyclo [5.3.0] undec-5-ene (DBN, 20
mL, 0.16 mole) were combined in a 12 L round bottom reaction vessel
and purged with argon for 20 minutes, brought to reflux and stirred
for approximately 5 hours under an argon atmosphere. TLC was used
to monitor the completion of the reaction. The reaction was cooled
to ambient temperature, transferred to an evaporation flask with
the aid of additional toluene (210 mL) and the solvent was removed
under vacuum (98-30 mbar, 60-70.degree. C.).
[0108] Methylene chloride (4000 mL) was added to the solid and the
mixture was warmed with swirling at 35-40.degree. C. for 35
minutes. Acetonitrile (2500 mL) was added in portions with swirling
as the CH.sub.2Cl.sub.2 was removed at reduced pressure (700-400
mbar, 45-55.degree. C.). The slurry was vacuum filtered while still
warm on a Buchner funnel with hardened qualitative filter paper and
the solid was slurried and rinsed in portions with acetonitrile
(1750 mL), and then dried until the solid caked. The solid was
transferred to an evaporation flask with CH.sub.2Cl.sub.2 (4000 mL)
and the mixture was warmed with swirling at 35-45.degree. C. for 30
minutes. Acetonitrile (2500 mL) was added in portions with swirling
as the CH.sub.2Cl.sub.2 was removed at reduced pressure (700-460
mbar, 45-55.degree. C.). The warm slurry was vacuum filtered on a
Buchner funnel with hardened qualitative filter paper and the solid
was slurried and rinsed in portions with acetonitrile (1500 mL),
then dried until the solid caked. The solid was transferred to an
evaporation flask with CH.sub.2Cl.sub.2 (4000 mL) and the mixture
was warmed with swirling at 40-42.degree. C. for 30 minutes.
Acetonitrile (2500 mL) was added in portions with swirling as the
CH.sub.2Cl.sub.2 was removed at reduced pressure (700-460 mbar,
45-55.degree. C.). The warm slurry was vacuum filtered on a Buchner
funnel with hardened qualitative filter paper and the solid was
slurried and rinsed in portions with acetonitrile (1500 mL), then
dried until the solid caked. The solid was analyzed by TLC to
determine the purity and then dried under vacuum (30" Hg) at
52-59.degree. C. for approximately 21 hours to a constant weight to
yield 125.4 g (61.2% yield) of ethyl etiopurpurin I (5).
Example 10
Preparation of Ethyl etiopurpurin I (5)-Method C
[0109] Meso-acrylate etioporphyrin I (4) (205.1 g, 0.36 mole) and
acetic acid (3750 mL) were combined in a 12 L round bottom reaction
vessel and purged with argon for 22 minutes, brought to reflux and
stirred for approximately 24 hours under an argon atmosphere. The
reaction was cooled to ambient temperature, transferred to an
evaporation flask with the aid of dichloromethane (200 mL) and the
solvents were removed under vacuum. Ethanol (500 mL) was added and
removed by rotoevaporation. Methylene chloride (4000 mL) was added
to the solid and the mixture was warmed with swirling at 35
-40.degree. C. for 30 minutes. Acetonitrile (2500 mL) was added in
portions with swirling as the CH.sub.2Cl.sub.2 was removed at
reduced pressure (700-400 mbar, 45-55.degree. C.). The slurry was
vacuum filtered while still warm on a Buchner funnel with hardened
qualitative filter paper and the solid was slurried and rinsed in
portions with acetonitrile (1750 mL), and then dried until the
solid caked. The solid was transferred to an evaporation flask with
CH.sub.2Cl.sub.2 (4000 mL) and the mixture was warmed with swirling
at 35-45.degree. C. for 30 minutes. Acetonitrile (2500 mL) was
added in portions with swirling as the CH.sub.2Cl.sub.2 was removed
at reduced pressure (700-460 mbar, 45-55.degree. C.). The warm
slurry was vacuum filtered on a Buchner funnel with hardened
qualitative filter paper and the solid was slurried and rinsed in
portions with acetonitrile (1500 mL), then dried until the solid
caked. The solid was transferred to an evaporation flask with
CH.sub.2Cl.sub.2 (4000 mL) and the mixture was warmed with swirling
at 36 -40.degree. C. for 30 minutes. Acetonitrile (2500 mL) was
added in portions with swirling as the CH.sub.2Cl.sub.2 was removed
at reduced pressure (700-460 mbar, 45-55.degree. C.). The warm
slurry was vacuum filtered on a Buchner funnel with hardened
qualitative filter paper and the solid was slurried and rinsed in
portions with acetonitrile (1500 mL), then dried until the solid
caked. The solid was analyzed by TLC to determine the purity and
then dried under vacuum (30" Hg) at 50-57.degree. C. for
approximately 21 hours to a constant weight to yield 102.2 g (50%
yield) of ethyl etiopurpurin I (5).
Example 11
Preparation of Ethyl etiopurpurin I (5)-Method D
[0110] Meso-acrylate etioporphyrin I (4) (205.0 g, 0.36 mole),
toluene (3750 mL) and 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU, 20
mL, 0.13 mole) were combined in a 12 L round bottom reaction vessel
and purged with argon for 21 minutes, brought to reflux and stirred
for approximately 5 hours under an argon atmosphere. TLC was used
to monitor the completion of the reaction. The reaction was cooled
to ambient temperature, transferred to an evaporation flask with
the aid of additional toluene (210 mL) and the solvent was removed
under vacuum (98-30 mbar, 60-70.degree. C.).
[0111] Methylene chloride (4000 mL) was added to the solid and the
mixture was warmed with swirling at 35-41.degree. C. for 35
minutes. Acetone (2000 mL) was added in portions with swirling as
the CH.sub.2Cl.sub.2 was removed at reduced pressure (700-690 mbar,
45-50.degree. C.). The slurry was vacuum filtered on a Buchner
funnel with hardened qualitative filter paper and the solid was
slurried and rinsed in portions with acetonitrile (1750 mL), and
then dried until the solid caked. The solid was transferred to an
evaporation flask with CH.sub.2Cl.sub.2 (4000 mL) and the mixture
was warmed with swirling at 35-45.degree. C. for 30 minutes.
Acetone (2000 mL) was added in portions with swirling as the
CH.sub.2Cl.sub.2 was removed at reduced pressure (700 -690 mbar,
45-50.degree. C.). The slurry was vacuum filtered on a Buchner
funnel with hardened qualitative filter paper and the solid was
slurried and rinsed in portions with acetonitrile (1500 mL), then
dried until the solid caked. The solid was analyzed by TLC to
determine the purity (a third precipitation may be undertaken) and
then dried under vacuum (30" g) at 52-60.degree. C. for
approximately 21 hours to a constant weight to yield 122.3 g (59%
yield) of ethyl etiopurpurin I (5).
Example 12
Preparation of Tin Dichloride Ethyl Etiopurpurin (7) (Method A)
[0112] Ethyl etiopurpurin I (128.0 g, 0.22 mole), anhydrous sodium
acetate (45.5 g, 0.55 mole) and glacial acetic acid (7500 mL) were
combined in a 12 L round bottom reaction vessel and purged with
compressed air for 36 minutes via a wide bore glass bubbler. Then
anhydrous tin chloride (231.6 g, 1.22 mole), predissolved with heat
in N,N-dimethylformamide (139 mL), was added to the solution and
the reaction mixture was heated to 105.degree. C. with stirring and
constant purging with air, for approximately 3.5 hours. Upon
completion of the reaction by UV/Vis and TLC, the reaction was
cooled to 75.degree. C. with stirring at which point stirring was
stopped and the solution was allowed to cool to ambient
temperature. The solid crystalline product was vacuum filtered on a
Buchner funnel with hardened qualitative filter paper, and rinsed
in portions with acetic acid (1600 mL), and dried until the solid
caked. The solid was then transferred to another filter funnel
containing hardened qualitative filter paper, and CH.sub.2Cl.sub.2
(5000 mL, in portions) was used to dissolve the solid in the filter
funnel and the CH.sub.2Cl.sub.2 solution was vacuum filtered
through the funnel. The CH.sub.2Cl.sub.2 solution was transferred
to an evaporation flask with the aid of 300 mL of additional
CH.sub.2Cl.sub.2 and the solution was concentrated to approximately
3500 mL under vacuum (695 mbar, 41-42.degree. C.). Acetic acid
(1250 mL) was added with swirling and the CH.sub.2Cl.sub.2 was
removed under vacuum (695-390 mbar, 42-52.degree. C.). The
resulting slurry was cooled to ambient temperature and vacuum
filtered on a Buchner funnel with hardened qualitative filter
paper. The solid was slurried and rinsed in portions with acetic
acid (1000 mL) and then rinsed with 500 mL of acetone. The product
was then dried in a vacuum oven (30" Hg) at 48-62.degree. C. for
approximately 54.5 hours to a constant weight. The solid was
transferred to an evaporation flask with CH.sub.2Cl.sub.2 (4500 mL)
and the mixture was warmed at 35-42.degree. C. for 30 minutes.
Acetone (2540 mL) was added with swirling as the CH.sub.2Cl.sub.2
was removed under vacuum (700-697 mbar, 42-50.degree. C.). The
resulting slurry was cooled to ambient temperature over 19
minutes.
[0113] The product was collected by vacuum filtration on a Buchner
funnel with hardened qualitative filter paper, slurried and rinsed
in portions with acetone (1010 mL), and dried in a vacuum oven (30"
Hg) at 56 -58.degree. C. for 28.5 hours to a constant weight. The
solid was then dried an additional 23 hours to give 149.0 g (90.8%
yield) of tin dichloride ethyl etiopurpurin (7) (purity>99% by
HPLC).
Example 13
Preparation of Tin Dichloride Ethyl Etiopurpurin (7) (Method B)
[0114] Ethyl etiopurpurin I (128.0 g, 0.22 mole), anhydrous sodium
acetate (45.5 g, 0.55 mole) and glacial acetic acid (7500 mL) were
combined in a 12 L round bottom reaction vessel and purged with
compressed air for 30 minutes via a wide bore glass bubbler. Then
anhydrous tin chloride (231.6 g, 1.22 mole), predissolved with heat
in N,N-dimethylformamide (139 mL), was added to the solution and
the reaction mixture was heated to 105.degree. C. with stirring and
constant purging with air, for approximately 3.5 hours. Upon
completion of the reaction by UV/Vis and TLC, the reaction was
cooled to 75.degree. C. with stirring at which point stirring was
stopped and the solution was allowed to cool to ambient temperature
for approximately 16.5 hours. The solid crystalline product was
vacuum filtered on a Buchner funnel with hardened qualitative
filter paper, and rinsed in portions with acetic acid (1600 mL),
and dried until the solid caked. The solid was then transferred to
another filter funnel containing hardened qualitative filter paper,
and CH.sub.2Cl.sub.2 (5000 mL, in portions) was used to dissolve
the solid in the filter funnel and the CH.sub.2Cl.sub.2 solution
was vacuum filtered through the funnel. The CH.sub.2Cl.sub.2
solution was transferred to an evaporation flask with the aid of
300 mL of additional CH.sub.2Cl.sub.2 and the solution was
concentrated to approximately 3500 mL under vacuum (700 mbar, 40
-42.degree. C.). Acetic acid (1250 mL) was added with swirling and
the CH.sub.2Cl.sub.2 was removed under vacuum (700-390 mbar,
42-52.degree. C.). The resulting slurry was cooled to ambient
temperature and vacuum filtered on a Buchner funnel with hardened
qualitative filter paper. The solid was slurried and rinsed in
portions with acetic acid (1000 mL) and then rinsed with 500 mL of
ethanol (anhydrous). The product was then dried in a vacuum oven
(30" Hg) at 50-62.degree. C. for approximately 58 hours to a
constant weight. The solid was transferred to an evaporation flask
with CH.sub.2Cl.sub.2 (4500 mL) and the mixture was warmed at
35-42.degree. C. for 30 minutes. Ethanol (2500 mL, anhydrous) was
added with swirling as the CH.sub.2Cl.sub.2 was removed under
vacuum (600-340 mbar, 40-50.degree. C.). The resulting slurry was
cooled to ambient temperature over 19 minutes.
[0115] The product was collected by vacuum filtration on a Buchner
funnel with hardened qualitative filter paper, slurried and rinsed
in portions with ethanol (1000 mL), and dried in a vacuum oven (30"
Hg) at 56 -60.degree. C. for 30 hours to a constant weight. The
solid was then dried an additional 23 hours to give 148.9 g (90.8%
yield) of tin dichloride ethyl etiopurpurin (7) (purity >99% by
HPLC).
Example 14
Preparation of Tin dichloride Ethyl Etiopurpurin I (7) (Method
C)
[0116] The procedure of Example 13 method B was repeated except
that acetonitrile replaced ethanol and the volume of acetonitrile
used was half that of ethanol. Yield of tin dichloride ethyl
etiopurpurin (7)=80%.
Example 15
Preparation of Tin dichloride Ethyl Etiopurpurin (7) (Method D)
[0117] The procedure of Example 13 method B was repeated except
that dry dimethylformamide replaced ethanol and the volume of
dimethylformamide used was half that of ethanol. Yield of tin
dichloride ethyl etiopurpurin (7)=70%.
Example 16
Isolation of MET2 (6)
[0118] The acetonitrile mother liquors from the ET2 (5)
precipitations (Example 8, method A) were rotoevaporated to
dryness. The solid was redissolved in dichloroethane (1000 mL) and
to this solution was added SnCl.sub.2 (20 g; anhydrous)
predissolved in DMF (25 mL). Sodium acetate (8 g; anhydrous) was
added. The solution was warmed at 55-60.degree. C. for 4 hours
after which time the solution was cooled to room temperature and
washed with water (2.times.1000 mL). The organic layer was
evaporated to dryness and the residue redissolved in
dichloromethane (200mL). The solution was chromatographed on a
short pad of silica (1 Kg), eluting with 5%
ethylacetate/dichloromethane. The tin metallated porphyrin
impurities remained at the baseline on the column. The major band
was collected and recrystallized from dichloromethane/isooctane.
Yield of MET2 (6) =27%, purity >98%.
Example 17
Preparation of Octaethylpurpurin (32)
[0119] Meso-acrylate octaethylporphyrin (11) (20.4 g, 0.032 mole),
toluene (375 mL) and 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU, 2
mL, 0.013 mole) were combined in a 2 L round bottom reaction vessel
and purged with argon for 21 minutes, brought to reflux and held
for approximately 5 hours under an argon atmosphere. TLC was used
to monitor the completion of the reaction. The reaction was cooled
to ambient temperature, transferred to an evaporation flask with
the aid of additional toluene (20 mL) and the solvent was removed
under vacuum (98-30 mbar, 60-70.degree. C.).
[0120] Methylene chloride (400 mL) was added to the solid and the
mixture was warmed with swirling at 35-41.degree. C. for 35
minutes. Acetonitrile (250 mL) was added in portions with swirling
as the CH.sub.2Cl.sub.2 was removed at reduced pressure (700-408
mbar, 45-55.degree. C.). The slurry was vacuum filtered while still
warm on a Buchner funnel with hardened qualitative filter paper and
the solid was slurried and rinsed in portions with acetonitrile
(175 mL), and then dried until the solid caked. The solid was
transferred to an evaporation flask with CH.sub.2Cl.sub.2 (400 mL)
and the mixture was warmed with swirling at 35-45.degree. C. for 30
minutes. Acetonitrile (250 mL) was added in portions with swirling
as the CH.sub.2Cl.sub.2 was removed at reduced pressure (695-460
mbar, 45-55.degree. C.). The warm slurry was vacuum filtered on a
Buchner funnel with hardened qualitative filter paper and the solid
was slurried and rinsed in portions with acetonitrile (150 mL),
then dried until the solid caked. The solid was analyzed by TLC to
determine the purity and then dried under vacuum (30" Hg) at 52
-57.degree. C. for approximately 21 hours to a constant weight to
yield 18.3 g (90% yield) of octaethylpurpurin (32).
Example 18
Preparation of Octaethylbenzochlorin (13)-Method A
[0121] Meso-acrylate octaethylporphyrin (11 ) (100 g, 0.16 mole)
and dichloromethane (4000 mL) were combined in a 10 L round bottom
reaction vessel equipped with a mechanical stirrer and a
thermocouple. The solution was purged with nitrogen for 21 minutes.
The reaction was cooled to -78.degree. C. under nitrogen using an
acetone/CO.sub.2 bath. DIBALH (270 mL, 1.5M in toluene) was added
dropwise via a dropping funnel to the reaction at a rate as to
maintain the temperature between -78.degree. C. and -75.degree. C.
After the addition of the DIBALH, the reaction was monitored until
all starting material had been consumed [TLC, Acetone/DCM (1%)].
Excess DIBALH was quenched with dropwise addition of isopropanol
(100 mL) followed by MeOH (100 mL). H.sub.3PO.sub.4 (1800 mL, 85%)
was added to the cold solution and the flask warmed to room
temperature. The dichloromethane/methanol was distilled and the
phosphoric acid solution warmed at 100.degree. C. for 3 hours after
which time the reaction was deemed complete by TLC (DCM). The
solution was cooled to room temperature and water (2800 mL) was
added with vigorous stirring. The solid precipitate was vacuum
filtered and rinsed with portions of methanol (3.times.200 mL), and
then dried until the solid caked. The solid was air dried
overnight, redissolved in phosphoric acid (85%, 1500 mL) and
reprecipitated with water (2500 mL). The crude OEBC was collected
by filtration, washed with MeOH (300 mL) and air dried overnight.
The solid was dissolved in CH.sub.2Cl.sub.2 (2000 mL) into a 5L
distillation flask and MeOH (1500 mL) was added. The
CH.sub.2Cl.sub.2 was removed by distillation with stirring and the
solid precipitate was collected by filtration, and washed with MeOH
(200 mL). The solid was vacuum dried to constant weight. Yield of
octaethylbenzochlorin (13) =69 g (72%).
Example 19
Preparation of Octaethylbenzochlorin (13)-Method B
[0122] Nickel (II) octaethylbenzochlorin (1 g, 0.0017mol) was
dissolved in dichloromethane (30 mL). Methane sulfonic acid (10 mL)
was added and the dichloromethane was removed by rotary
evaporation. The methane sulfonic acid solution was warmed to
80.degree. C. under nitrogen and the reaction monitored hourly
until complete by TLC (after neutralization of a small aliquot, 30%
hexane/DCM). Once complete, the solution was diluted with ice cold
water (15 mL) and the solid precipitate collected by filtration and
washed with MeOH (30 mL). The solid was redissolved in
dichloromethane (50 mL) and MeOH (50 mL) was added. The
dichloromethane was removed by rotoevaporation and the solid
collected by filtration and washed with MeOH (20 mL). Yield of
octaethylbenzochlorin (13) =0.7 g (73%). The solid was sufficiently
pure to be used further, if desired. Additional OEBC may be
isolated from the methanol mother liquors by chromatography if
required.
Example 20
Tin Dichloride Pheophorbide Methyl Ester (21)
[0123] Pyropheophorbide methyl ester (20) (1.0 g) was dissolved in
glacial acetic acid (100 ml) and sodium acetate (0.74 g, anhydrous)
was added. SnCl.sub.2 (2.4 g, anhydrous) was predissolved in
dimethylformamide (5 mL) and added to the solution. A wide bore
glass bubbling tube was added to the reaction vessel such that air
was efficiently purged into the bottom of the acetic acid solution.
A moderate stream of air was bubbled through the solution over the
entire reaction. The solution was heated to 105-110.degree. C.
until the reaction was complete by UV/Vis and by TLC (1 %
acetone/dichloromethane). The reaction was cooled and the acetic
acid was removed by rotoevaporation. The residue was dissolved in
dichloromethane (100 L) and washed several times with 1N HCl
solution (4.times.100 L). The organic layer was collected and dried
over sodium sulfate. The organic layer was filtered and evaporated
to dryness. The residue was dissolved in dichloromethane (50 L) and
ethanol (50 L) was added. The dichloromethane was removed by rotary
evaporation and the precipitated product (21) collected by
filtration and dried under high vacuum. Yield=1.21 g (90%); Purity
>98% by HPLC.
Example 21
Tin Dichloride Meso-acrylate Etioporphyrin I (25)
[0124] SnCl.sub.2 (6.54 g, anhydrous) was dissolved in
dimethylformamide (8 mL). Dichloroethane (200 mL) was added to the
tin solution and sodium acetate (1.54 g, anhydrous) was added. The
solution was stirred at 30.degree. C. for 30 minutes with
compressed air bubbling through the solution moderately via a wide
bore glass tube. Meso-acrylate etioporphyrin I (4.0 g) dissolved in
dichloroethane (80 mL) was added slowly to the solution and the
solution warmed at 55-60.degree. C. for 5 hours until complete by
TLC. (2% acetone/dichloromethane). The solution was cooled and
filtered to remove excess salts. The salts were washed with a small
amount of dichloromethane (20 mL). The combined organic solution
was washed three times with dilute HCl (1N). The organic layer was
dried over sodium sulfate and filtered. The sodium sulfate was
washed with a small amount of dichloromethane (20 mL). The solvent
was removed by rotary evaporation and the crude residue dissolved
in dichloromethane (50 mL) and acetic acid (50 mL) was added. The
dichloromethane was removed by rotary evaporation and the solid
precipitate was collected by filtration and dried under high
vacuum. Yield of tin dichloride meso-acrylate etioporphyrin I
(25)=3.7 g (70%). An HPLC of the material showed it to be >98%
pure with no reduced porphyrin (26).
Example 22
Tin Dichloride Protoporphyrin IX, Dimethyl Ester (28)
[0125] Protoporphyrin IX dimethyl ester (27) (5.0 g) was dissolved
in pyridine (200 mL). SnCl.sub.2 (8.0 g, anhydrous) was added and
the solution was aerated with compressed air moderately bubbling
through the solution via a wide bore glass tube. The solution was
heated to 100.degree. C. for 3 hours after which the reaction was
cooled to room temperature. The pyridine was removed by rotary
evaporation and the residue dissolved in dichloromethane (500 mL)
and washed three times with dilute HCl (1N, 100 mL). The organic
layer was dried over sodium sulfate, filtered and evaporated to
approximately 100 mL. Acetic acid (100 mL) was added and the
dichloromethane was removed by rotary evaporation. The precipitated
solid was collected by filtration and dried under high vacuum.
Yield of tin dichloride protoporphyrin IX, dimethyl ester (28)=4.7
g (71%). Analysis of the product showed it to be >99% pure.
[0126] It will be apparent to those skilled in the art that various
modifications and variations can be made in the compounds and
methods of the present invention without departing from the spirit
or scope of the invention. Thus, it is intended that the present
description cover the modifications and variations of this
invention provided that they come within the scope of the appended
claims and their equivalents.
* * * * *