U.S. patent application number 15/498576 was filed with the patent office on 2017-08-10 for process for the purification of melphalan.
The applicant listed for this patent is FARMABIOS S.P.A.. Invention is credited to Valentina CANEVARI, Matteo Curti, Claudio Gianluca POZZOLI.
Application Number | 20170226047 15/498576 |
Document ID | / |
Family ID | 48748393 |
Filed Date | 2017-08-10 |
United States Patent
Application |
20170226047 |
Kind Code |
A1 |
POZZOLI; Claudio Gianluca ;
et al. |
August 10, 2017 |
PROCESS FOR THE PURIFICATION OF MELPHALAN
Abstract
A method for the purification and preparation of melphalan that
allows to obtain melphalan with purity higher than 99.5% is
described.
Inventors: |
POZZOLI; Claudio Gianluca;
(Gropello Cairoli (PV), IT) ; CANEVARI; Valentina;
(Gropello Cairoli (PV), IT) ; Curti; Matteo;
(Gropello Cairoli (PV), IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FARMABIOS S.P.A. |
Gropello Cairoli (PV) |
|
IT |
|
|
Family ID: |
48748393 |
Appl. No.: |
15/498576 |
Filed: |
April 27, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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14890540 |
Nov 11, 2015 |
9663450 |
|
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PCT/EP2014/060987 |
May 27, 2014 |
|
|
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15498576 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C07C 229/42 20130101;
C07C 227/40 20130101; C07C 269/08 20130101; C07C 227/20 20130101;
C07C 269/08 20130101; C07C 269/06 20130101; C07C 227/20 20130101;
C07C 269/06 20130101; C07C 229/36 20130101; C07C 229/36 20130101;
C07C 271/22 20130101; C07C 271/22 20130101 |
International
Class: |
C07C 229/42 20060101
C07C229/42 |
Foreign Application Data
Date |
Code |
Application Number |
May 31, 2013 |
IT |
MI2013A000896 |
Claims
1) Melphalan and melphalan hydrochloride having HPLC purity of
>99.5%.
2) Melphalan and melphalan hydrochloride according to claim 1
wherein impurity G is NMT 0.5%.
3) Melphalan and melphalan hydrochloride according to claim 1
having HPLC purity of >99.8%.
4) Melphalan and melphalan hydrochloride according to claim 1
wherein impurity G is NMT 0.2%.
5) Melphalan and melphalan hydrochloride according to claim 1
wherein impurity G is NMT 0.1%.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation of U.S. patent application Ser. No.
14/890,540, filed Nov. 11, 2015 which is a 371 of
PCT/EP2014/060987, filed May 27, 2014, which claims the benefit of
Italian Patent Application M12013A000896, filed May 31, 2013, the
disclosure of each of which is incorporated by reference.
FIELD OF INVENTION
[0002] The present invention relates to a method for the
purification of melphalan. Melphalan is the L enantiomer of
4-[bis(2-chloroethyl)amino]phenylalanine of formula I:
##STR00001##
[0003] This compound is also known with the name of L-PAM,
L-sarcolysine, NCS-8806, CB3025.
[0004] Melphalan is commercially known with the name of Alkeran.TM.
in the form of tablets or injectable preparations.
[0005] Melphalan is a compound known for its antitumor properties;
its D enantiomer and the racemic mixture also have antitumor
activity but of small degree.
[0006] Melphalan is particularly used in the treatment of multiple
myeloma and ovarian cancer.
[0007] Melphalan is synthesized according to the processes
disclosed in U.S. Pat. No. 3,032,584 and U.S. Pat. No. 3,032,585
starting from DL-phenylalanine with a process comprising the
following steps: [0008] 1. nitration in the presence of nitric acid
and sulfuric acid; [0009] 2. protection of the glycine amino group
as acetyl, formyl or phthtaloyl derivative followed by
esterification of the carboxy group; [0010] 3. reduction of the
nitro group to amine by hydrogenation; [0011] 4. hydroxyethylation
reaction of the amine on the aromatic ring in the presence of
ethylene oxide; [0012] 5. chlorination in the presence of
POCl.sub.3 or SOCl.sub.2; [0013] 6. resolution of the racemic
mixture and isolation of L-enantiomer; [0014] 7. deprotection of
the glycine amino group and hydrolysis of the ester. RO 57195
discloses the isolation of melphalan hydrochloride by adding
diethyl ether to the aqueous solution containing it, followed by
the addition of Na.sub.2CO.sub.3 or NaOAc to bring the pH to 0.5
and subsequently to 1.5-2. The purification is carried out by
dissolving in HCl melphalan hydrochloride obtained by the treatment
at pH=2. GB 750,155 discloses the synthesis of melphalan starting
from 4-[bis(hydroxyethyl)amino]phenylalanine ethyl ester by
reaction with POCl.sub.3 or SOCl.sub.2 in the optional presence of
an inert solvent to give the chlorine derivative followed by a
reaction with HCl to remove the protective groups.
[0015] GB 783,292 discloses the synthesis of melphalan starting
from its non optically active precursors by resolution of some
intermediates of the synthesis as brucine salts. It is particularly
disclosed the separation of brucine diastereomeric salts of
N-acetyl-4-nitro-DL-phenylalanine. The L-isomer, suitably purified
from the residues of brucine, is hydrolysed to give
4-nitro-phenylalanine, followed by the esterification with phthalic
anhydride, the reduction of the nitro group, the reaction of the
resultant amine with ethylene oxide, the reaction with POCl.sub.3
or SOCl.sub.2 to obtain the chlorine derivative, the removal of the
phthaloyl protective group and of the ethyl ester to give
4-bis-(2-chloroethyl)-aminophenylalanine.
[0016] CN 101100440 discloses a process for the preparation of
melphalan hydrochloride comprising: [0017] the esterification of
the carboxyl group of 4-nitrophenylalanine in EtOH [0018] the
protection of the amine in the presence of TEA to give the N-Boc
derivative [0019] the hydrogenation of the nitro group [0020] the
hydroxyethylation reaction in the presence of ethylene oxide [0021]
the chlorination reaction of the OH groups [0022] the deprotection
reaction of the amino group [0023] the hydrolysis reaction with
2M-6M hydrochloric acid to remove the protective groups and to
obtain the final compound.
[0024] EP 0 317 281 discloses the preparation of melphalan
hydrochloride by reaction of the N-phthaloyl derivative with
ethylene oxide, followed by chlorination, hydrolysis and subsequent
formation of melphalan hydrochloride.
[0025] WO 2009/117164 discloses a process for the synthesis of
melphalan characterized by the fact that the hydroxyethylation
reaction of the aromatic NH.sub.2 group is carried out without the
need to protect the glycine NH.sub.2 group.
[0026] US 2012/0190887 discloses a process for the preparation of
pharmaceutical grade melphalan hydrochloride comprising a
purification step by dissolving in hydrochloric acid, adding active
charcoal, adding alkali hydroxide, filtering and washing with
deionized water, slurrying with isopropyl ether.
[0027] US 2012/0116117 discloses a process for the preparation of
melphalan hydrochloride with HPLC purity>99% i.e. conforming to
drug regulation specifications.
[0028] In the processes described in the state of the art,
melphalan is isolated and purified through some steps that provide
a precipitation of melphalan in water saturated with sodium acetate
at pH=7 followed by one or more crystallizations from methanol or a
precipitation in the presence of diethylamine at pH=7, followed by
washing with methanol.
[0029] Most of the purification methods disclosed in the state of
the art need to bring the pH to neutrality after the treatment with
aqueous hydrochloric acid necessary for the removal of the amine
and carboxy protective groups, to allow the precipitation of
melphalan.
[0030] These purification methods yield melphalan with a purity
from 96% to 99%.
[0031] The precipitation of melphalan at pH=7, according to the
processes known in the state of the art, leads to the formation of
a highly unstable solid which is particularly hard to filter
because of its sponginess. The instability of said spongy solid
leads to the formation of an impurity, called "dimer" (impurity
G-4-[[2-[[4-[bis(2-chloroethyl)amino]-L-phenylalanine]oxy]ethyl]-(2-chlor-
oethyl)amino]-L-phenylalanine) according to European Pharmacopeia
2012, pages 4658-4659). The limit values of such impurity, reported
into the European Pharmacopeia, are high (limit NMT 1.0%) just
because of the difficult in the removal of the "dimer" in the
process for the production of melphalan.
SUMMARY OF INVENTION
[0032] We have now found a method for the purification of melphalan
that allows to obtain melphalan with much higher purity than that
required by the European Pharmacopeia, particularly with a purity
higher than 99.5%, preferably higher than 99.8%, in which each
single impurity identified by the European Pharmacopeia is NMT
0.5%, preferably NMT 0.2%. Particularly, the impurity G is
preferably NMT 0.2%, most preferably NMT 0.1%.
[0033] Melphalan obtained after the treatment at pH=2 in the
presence of water, methyl-tert-butyl ether and diethylamine is
characterized by the absence of ionizable chlorides by HPLC
analysis and will be herein after indicated as "melphalan
base".
DETAILED DESCRIPTION OF THE INVENTION
[0034] It is therefore an object of the present invention a process
for the purification of melphalan comprising: [0035] (a) the
treatment of a compound of formula IV
[0035] ##STR00002## [0036] wherein R is hydrogen or a linear or
branched C.sub.1-C.sub.6 alkyl group, preferably selected among
ethyl, methyl, propyl, most preferably ethyl and R.sup.1 is
hydrogen or an amine protective group, preferably selected among
phthaloyl or tert-butoxycarbonyl, more preferably
tert-butoxycarbonyl; or a hydrochloric salt or a dimeric form
thereof, in HCl 37% under reflux; [0037] (b) the isolation of the
compound obtained from step (a) in the presence of water,
methyl-tert-butyl ether and diethylamine at pH=2.
[0038] The process for the purification object of the present
invention is followed by washing the compound obtained from step
(b) with a linear or branched C.sub.1-C.sub.4 alcohol, preferably
selected among methanol, ethanol and isopropanol, more preferably
ethanol. Said washing allows to remove the diethylammonium salts
obtained from treatment (b). The product obtained by said washing
can be stored as such at low temperatures to avoid the formation of
dimerization products or can be salified with gaseous HCl which is
added as an ethanol solution in acetone to give melphalan
hydrochloride.
[0039] The process for the purification object of the present
invention allows to obtain melphalan with a HPLC purity greater
than 99.5%, preferably greater than 99.8%. The step (a) of the
process object of the present invention is preferably carried out
under reflux for at least 16 hours. The ratio HCl 37%/melphalan
(titrated) is preferably of about 4:1.
[0040] The step (b) is preferably taken at a temperature from
0.degree. C. to 10.degree. C.
[0041] The ratio water/melphalan (titrated) is preferably of about
10:1, the ratio methyl-tert-butyl ether/water is of about 2:1. In
step (b) of the process object of the present invention melphalan
with a HPLC purity greater than 99.5%, preferably greater than
99.8%, is obtained.
[0042] The method for the purification object of the present
invention comprises the treatment of melphalan or one of its
derivative of formula IV optionally in a protective and/or salified
form, or as a "dimer", both as a product or an isolated
intermediate of the synthesis, both as a reaction crude, in the
presence of HCl 37% under reflux, followed by the treatment at pH=2
of the resultant compound.
[0043] The treatment with HCl 37% under reflux allows to obtain
melphalan dissolved in solution with a purity greater than 99.5%,
preferably greater than 99.8%. Said treatment allows to hydrolyze
any protective groups on the molecule and to purify, at the same
time, the resultant product by hydrolysis of any impurities in the
reaction medium such for example esters, dimers, trimers of
melphalan.
[0044] The isolation of the product after the treatment with HCl
37% under reflux is carried out by treatment at pH=2 in the
presence of diethylamine and methyl-tert-butyl ether. The isolated
product is characterized by the absence of ionizable chlorides and
by a low ability to form undesirable by-products, such as for
example the "dimer" (impurity G).
[0045] The process for the purification object of the present
invention can be used to obtain melphalan with a high purity
(greater than 99.5%) both starting from a reaction crude and from
melphalan with a low purity degree or from a derivative of formula
IV thereof.
[0046] In a preferred embodiment the process for the purification
object of the present invention is carried out at the end of a
process of synthesis of melphalan which comprises: [0047] 1. the
alkylation reaction of a compound of formula II
[0047] ##STR00003## [0048] wherein R.sup.2 is a linear or branched
C.sub.1-C.sub.6 alkyl group, preferably selected among ethyl,
methyl, propyl, most preferably ethyl and PG is an amine protective
group, preferably selected among phthaloyl or tert-butoxycarbonyl
group, most preferably tert-butoxycarbonyl; [0049] in the presence
of an aprotic polar solvent, a base and an alkylating agent,
preferably selected among iodoethanol, chloroethanol or ethylene
oxide to give a compound of formula III
[0049] ##STR00004## [0050] wherein R.sup.2 and PG have the above
reported meanings; [0051] 2.the chlorination reaction of the
resultant compound of formula III in the presence of a chlorinating
agent preferably selected among POCl.sub.3 and SOCl.sub.2 in a
suitable solvent preferably selected among isopropylacetate or
ethylacetate, preferably isopropylacetate to give a compound of
formula IV-1
[0051] ##STR00005## [0052] wherein R.sup.2 and PG have the above
reported meanings.
[0053] It is therefore a further object of the present invention a
process for the preparation of melphalan comprising: [0054] 1. the
alkylation reaction of a compound of formula II
[0054] ##STR00006## [0055] wherein R.sup.2 is a linear or branched
C.sub.1-C.sub.6 alkyl group, preferably selected among ethyl,
methyl, propyl, most preferably ethyl and PG is an amine protective
group, preferably selected among phthaloyl or tert-butoxycarbonyl
group, most preferably tert-butoxycarbonyl; [0056] In the presence
of an aprotic polar solvent, a base and an alkylating agent,
preferably selected among iodoethanol and chloroethanol or ethylene
oxide to give a compound of formula III
[0056] ##STR00007## [0057] wherein R.sup.2 and PG have the above
reported meanings; [0058] 2.the chlorination reaction of the
resultant compound of formula III in the presence of a chlorinating
agent preferably selected among POCl.sub.3 and SOCl.sub.2 in a
suitable solvent preferably selected among isopropylacetate or
ethylacetate, preferably isopropylacetate to give a compound of
formula IV-1
[0058] ##STR00008## [0059] wherein R.sup.2 and PG have the above
reported meanings; [0060] 3.the isolation and purification of
melphalan comprising: [0061] (a) the treatment of a compound of
formula IV-1 in HCl 37% under reflux; [0062] (b) the isolation of
the compound obtained from step (a) in the presence of water,
methyl-tert-butyl ether and dietylamine at pH=2; [0063] (c) the
washing of the compound obtained from step (b) with a linear or
branched C.sub.1-C.sub.4 alcohol, preferably selected among
methanol, ethanol, isopropanol, most preferably ethanol; [0064]
4.the optional treatment of the compound obtained from step (c)
with a mineral acid, preferably with an ethanol solution of gaseous
HCI in acetone.
[0065] In step 1) of the process object of the present invention
the aprotic polar solvent is preferably selected among acetonitrile
and dichloromethane, acetonitrile is preferably used; the base is
preferably selected among Na.sub.2CO.sub.3, K.sub.2CO.sub.3,
Cs.sub.2CO.sub.3, CaO, Na.sub.2CO.sub.3 is most preferably
used.
[0066] In step 2) of the process object of the present invention
POCl.sub.3 in isopropylacetate is preferably used.
[0067] Preferably in step 4) of the process object of the present
invention an ethanol solution of gaseous HCl in acetone is used in
a concentration of from about 16% to about 25%.
[0068] A further preferred embodiment of the process object of the
present invention consists of the synthesis and purification of
melphalan comprising: [0069] 1) the alkylation reaction of the
amine group on the aromatic ring of N-BOC-L-phenylalanine ethyl
ester in the presence of acetonitrile, Na.sub.2CO.sub.3 and
iodoethanol to give
4-(bis(2-hydroxyethyl)-amino-N-BOC-L-phenylalanine ethyl ester;
[0070] 2) the chlorination reaction of the compound obtained in
step 1) in the presence of POCl.sub.3 and isopropylacetate; [0071]
3) the isolation and purification of melphalan comprising: [0072]
(a) the treatment of the compound obtained in step 2) in the
presence of HCl 37% under reflux; [0073] (b) the isolation of the
compound obtained in step a) with water, methyl-tert-butyl ether
and diethylamine at pH=2; [0074] (c) the washing of the compound
obtained in step b) with ethanol;
[0075] 4) the treatment of the compound obtained in step c) with an
ethanol solution of HCl in acetone
[0076] Melphalan and its hydrochloride salt having HPLC purity
>99.5%, preferably >99.8% are a further object of the present
invention.
[0077] The process object of the present invention allows to obtain
melphalan with a HPLC purity greater than the processes known in
the state of art. Particularly, the hydrolysis reaction reported in
step a) allows to obtain high purities through the removal of
further impurities in the mixture such as for example dimers,
trimers, esters etc.
[0078] The purity result is surprisingly obtained only by using HCl
37% under reflux. In fact, using HCl at different concentrations,
for example at 32%, melphalan with purity greater than 99.5% is not
obtained while operating under the same conditions of the
purification process according to the invention.
[0079] The subsequent isolation at pH=2 in step (b) surprisingly
allows to obtain a compound with a high purity and characterized by
a high stability in comparison to the spongy solid isolated under
the neutral conditions described in the known art. The greater
stability is probably given by a less capability to form the
"dimer" (impurity G) compared to melphalan obtained according to
the methods known in the state of art.
[0080] The washing of the compound reported in step (c) with
ethanol allows to remove diethylammonium chloride salts, residues
of step (b).
[0081] All the terms used in the present application, unless
otherwise indicated, are to be understood in their common meaning
as known in the art. Other more specific definitions for certain
terms, as indicated in this application, are underlined later and
are constantly applied for the whole description and the claims
unless a different definition provides specifically a wider
meaning.
[0082] The term "polar solvent" relates to a solvent which behave
as a proton donor, such as water; an alcohol, for example,
methanol, ethanol, propanol, iso-propanol, butanol, tert-butanol;
or a polarized solvent, such as esters, for example ethyl acetate,
butyl acetate, nitriles, for example acetonitrile; ethers, for
example, tetrahydrofuran, dioxane; ketones, for example, acetone,
methyl butyl ketone; and the like.
[0083] Further information about solvent can be found in organic
chemistry books or in specialized monographs, for example Organic
Solvents Physical Properties and Methods of Purification, 4th ed.,
John A.Riddik, et al., Vol II, in "Techniques of Chemistry Series",
John Wiley & Sons, NY, 1986. Such solvents are known to the
person skilled in the art and it is clear to the person skilled in
the art that different solvents and mixtures thereof can be
preferred, depending on the specific compounds and on the reaction
conditions, being their choice influenced, for example, by
solubility and reagent reactivity, by preferred temperature ranges.
Although the invention has been described in its characterizing
features, the equivalents and modifications obvious to the skilled
in the art are included in the following invention.
[0084] The present invention will now be illustrated by some
examples which have not to be seen as limiting the scope of the
invention.
EXAMPLE 1
Preparation of 4-(bis-(2-hydroxyethyl)-amino-N-BOC-L-phenylalanine
ethyl ester
[0085] Into a suitable reactor A, 2.0 kg of N-BOC-L-phenylalanine
ethyl ester and acetonitrile were loaded. The suspension was let
under stirring until complete dissolution, maintaining the
temperature at 23.degree. C. and 1.5 kg of sodium carbonate were
then added. Subsequently, 3.2 L of 2-iodoethanol were added
dropwise, the solution was heated up to 85.degree. C. and these
conditions were maintained for 2 hours. At the end of the reaction
the mixture was quickly cooled down to 20.degree. C.
[0086] In another suitable reactor B, 35L of water and 4 kg of
Celite.RTM. were loaded and the mixture was left under stirring for
at least 5 minutes. The compound obtained into reactor A was
transferred into reactor B and the suspension was kept under
stirring for an hour. The suspension was filtered and washed with
12L of water.
[0087] The wet Celite.RTM. obtained into the reactor B and 140 L of
ethyl acetate were loaded into a reactor C and the mixture was kept
under stirring for 30 minutes then filtered by collecting the
filtrate into a reactor D and letting the phases separate. The
organic phase was distilled at reduced pressure. The residue was
purified by chromatography using methylene chloride/ethyl acetate
about 2:1.
[0088] About 1.8 kg of
4-(bis-(2-hydroxyethyl)-amino-N-BOC-L-phenilalanine ethyl ester
were then obtained.
EXAMPLE 2
Preparation of Melphalan Hydrochloride
[0089] 4-(bis-(2-hydroxyethyl)-amino-N-BOC-L-phenilalanine ethyl
ester contained into the rich fractions was dissolved in 16 L of
isopropyl acetate and dropped into 4.6 L of phosphoryl chloride,
maintaining the temperature at 40.degree. C., in an inert
atmosphere. The solution was heated at 50.degree. C. and the
solution was kept under stirring for 2 hours and 30 minutes in an
inert atmosphere.
[0090] At the end of the reaction the solution was then transferred
into a separated funnel letting the phases separate for 30
minutes.
[0091] The phase containing the chlorinated product was dropped
into 8.8 L of 37% HCl and let under stirring at 130.degree. C.
under reflux for at least 12 hours. The solution was subsequently
cooled down to 50.degree. C.
[0092] At the end of the reaction the solution was cooled down to
20.degree. C. under stirring and subsequently concentrated at a
reduced pressure.
[0093] To the concentrated residue were added 9 L of water, 18 L of
methyl-tert-butyl ether and 2.6 L of diethylamine. The mixture was
kept under stirring up to stable pH=2 and these conditions were
maintained for 10 minutes, the mixture was subsequently filtered
and washed with 10 L of methyl-t-butyl ether.
[0094] The resultant product was transferred into a suitable
reactor and 18 L of ethanol at 99.9% were subsequently loaded. The
suspension was left under stirring for at least 10 minutes, then
filtered. The product was dried under vacuum for 8-12 hours
obtaining melphalan.
[0095] Into a suitable reactor were loaded 0.7 Kg of melphalan,
obtained as previously described, and 22 L of acetone, the solution
was cooled down and kept under stirring for 30 minutes. The
stoichiometric amount of gaseous HCl absorbed in ethanol was
subsequently added according to the titration. The suspension was
kept under stirring under cooling for a few hours. The suspension
was filtered and the solid washed with acetone and
methyl-tert-butyl ether.
[0096] The solid was dried under vacuum for one night.
[0097] About 0.7 kg of melphalan hydrochloride were obtained.
* * * * *