U.S. patent application number 10/500047 was filed with the patent office on 2005-06-09 for intermediates for lhrh antagonist synthesis, process for their production, and process for lhrh antagonist production.
Invention is credited to Fomsgaard, Jens, Hansen, Stefan, Rasmussen, Jon H., Rasmussen, Palle H., Wachs, Wolfgang O..
Application Number | 20050124788 10/500047 |
Document ID | / |
Family ID | 20286557 |
Filed Date | 2005-06-09 |
United States Patent
Application |
20050124788 |
Kind Code |
A1 |
Rasmussen, Jon H. ; et
al. |
June 9, 2005 |
Intermediates for lhrh antagonist synthesis, process for their
production, and process for lhrh antagonist production
Abstract
The novel tripeptides Ac-D-2Nal-D-4ClPhe-D-3Pal-OH and
Boc-D-2Nal-D-4ClPhe-D-3Pal-OH are intermediates useful in the
synthesis of LHRH analogs by coupling with suitable heptapeptides,
in particular with the heptapeptides
P.sup.1-Ser(P.sup.2)-NMeTyr(P.sup.3)-D-Lys(Nic)-Le- u-Lys(iPr,
P.sup.4)-Pro-D-AlaNH.sub.2 and P.sup.1-Ser(P.sup.2)-NMeTyr(P.su-
p.3)-D-Asn-Leu-Lys(iPr, P.sup.4)-Pro-D-AlaNH.sub.2.
Inventors: |
Rasmussen, Jon H.; (Lyngby,
DK) ; Rasmussen, Palle H.; (Bagsvaerd, DK) ;
Wachs, Wolfgang O.; (Wittmar, DE) ; Hansen,
Stefan; (Frederiksberg, DK) ; Fomsgaard, Jens;
(Farum, DK) |
Correspondence
Address: |
DICKSTEIN SHAPIRO MORIN & OSHINSKY LLP
1177 AVENUE OF THE AMERICAS (6TH AVENUE)
41 ST FL.
NEW YORK
NY
10036-2714
US
|
Family ID: |
20286557 |
Appl. No.: |
10/500047 |
Filed: |
February 8, 2005 |
PCT Filed: |
December 23, 2002 |
PCT NO: |
PCT/IB02/05583 |
Current U.S.
Class: |
530/331 ;
530/334 |
Current CPC
Class: |
C07K 5/0827 20130101;
C07K 1/02 20130101; C07K 7/23 20130101 |
Class at
Publication: |
530/331 ;
530/334 |
International
Class: |
C07K 005/06 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 29, 2001 |
SE |
0104463-5 |
Claims
1-13. (canceled)
14. A process for preparing a tripeptide, including a salt thereof,
of the formula (I) Ac-D-2Nal-D-4ClPhe-D-3Pal-OH (I) or (IX)
Boc-D-2Nal-D-4ClPhe-D-3Pal-OH (IX), comprising the following
consecutive steps for the preparation of (I): (a) Reacting
Boc-D-4ClPhe-OH with HONSu to form Boc-D-4ClPhe-OSu (VII); (b)
Reacting Boc-D-4ClPhe-OSu (VII) with H-D-3Pal-OH to form
Boc-D-4ClPhe-D-3Pal-OH (VIII); (c) Reacting Boc-D-4ClPhe-D-3Pal-OH
(VIII) with Boc-D-2Nal-OSu prepared by reacting Boc-D-2Nal-OH with
HONSu to form Boc-D-2Nal-D-4ClPhe-D-3Pal-OH (IX); (d) Reacting
Boc-D-2Nal-D-4ClPhe-D-3P- al-OH (IX) with acetic acid to form
Ac-D-2Nal-4ClPhe-D-3Pal-OH (I); or the consecutive steps (a)
through (c) for the preparation of (IX).
15. A process for preparing an LHRH antagonist or a
pharmaceutically acceptable salt thereof, comprising coupling a
tripeptide Ac-D-2Nal-D-4ClPhe-D-3Pal-OH (I) prepared according to
the process of claim 14 with a heptapeptide (IV) of the general
formula
P.sup.1-Ser(P.sup.2)-AA1-AA2-Leu-Lys(iPr,P.sup.4)-Pro-D-AlaNH.sub.2
(IV), wherein P.sup.1 is selected from H or amino protecting group,
P.sup.2 is H or OH-protecting group, P.sup.4 is H or an amino
protecting group such as Boc, AA1 is natural or synthetic amino
acid and AA2 is natural or synthetic amino acid or zero.
16. The process of claim 15, wherein the heptapeptide of the
general formula (IV) is a heptapeptide of the general formula
P.sup.1-Ser(P.sup.2)-NMeTyr(P.sup.3)-D-Lys(Nic)-Leu-Lys(iPr,P.sup.4)-Pro--
D-AlaNH.sub.2 (V) wherein P.sup.3 is H or --OH protecting
group.
17. The process of claim 15, wherein the heptapeptide of the
general formula (IV) is a heptapeptide of the general formula
P.sup.1-Ser(P.sup.2)-NMeTyr(P.sup.3)-D-Asn-Leu-Lys(iPr,P.sup.4)-Pro-D-Ala-
NH.sub.2 (Va). wherein P.sup.3 is H or --OH protecting group.
18. The process of claim 16, wherein the heptapeptide of the
general formula (V) is a heptapeptide of the formula
H-Ser(tBu)-NMeTyr-D-Lys(Nic)- -Leu-Lys(iPr,Boc)-Pro-D-AlaNH.sub.2
(VI).
19. The process of claim 17, wherein the heptapeptide of the
formula (VI) is a heptapeptide of the formula
H-Ser(tBu)-NMeTyr-D-Asn-Leu-Lys(iPr,Boc)- -Pro-D-AlaNH.sub.2
(VIa).
20. (New) A process for preparing an LHRH antagonist or a
pharmaceutically acceptable salt thereof, comprising coupling the
tripeptide Boc-D-2Nal-D-4ClPhe-D-3Pal-OH (IX) prepared by the
process of claim 14. with a heptapeptide (IV) of the general
formula Ser(P.sup.2)-AA1-AA2-Leu--
Lys(iPr,P.sup.4)-Pro-D-AlaNH.sub.2 (IV), wherein P.sup.1 is
selected from H or amino protecting group, P.sup.2 is H or
OH-protecting group, P.sup.4 is H or amino protecting group such as
Boc, AA1 is a natural or synthetic amino acid and AA2 is a natural
or synthetic amino acid or zero.
21. The process of claim 20, wherein the heptapeptide of the
general formula (IV) is a heptapeptide (V) of the general formula
P.sup.1-Ser(P.sup.2)-NMeTyr(P.sup.3)-D-Lys(Nic)-Leu-Lys(iPr,P.sup.4)-Pro--
D-AlaNH.sub.2 (V) wherein P.sup.3 is H or OH-protecting group.
22. The process of claim 21, wherein the heptapeptide of the
general formula (V) is the heptapeptide
H-Ser(tBu)-NMeTyr-D-Lys(Nic)-Leu-Lys(iPr,- Boc)-Pro-D-AlaNH.sub.2
(VI).
23. The process of claim 20, wherein the heptapeptide of the
general formula (IV) is a heptapeptide of the general formula
P.sup.1-Ser(P.sup.2)-NMeTyr(P.sup.3)-D-Asn-Leu-Lys(iPr,P.sup.4)-Pro-D-Ala-
NH.sub.2 (Va), followed by substituting the Boc group by an acyl
group, in particular an acetyl group.
24. The process of claim 23, wherein the heptapeptide of the
general formula (IV) is the heptapeptide
H-Ser(tBu)-NMeTyr-D-Asn-Leu-Lys(iPr,Boc)- -Pro-D-AlaNH.sub.2 (VIa),
followed by substituting the N-terminal Boc group by an acyl group,
in particular an acetyl group.
25. The tripeptide Ac-D-2Nal-D-4ClPhe-D-3Pal-OH (I) or a salt
thereof prepared by the process of claim 14.
26. The tripeptide Boc-D-2Nal-D-4ClPhe-D-3Pal-OH (IX) or a salt
thereof prepared by the process of claim 14.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to intermediates for the
synthesis of LHRH antagonists, to a process for the production of
these intermediates and to a process for the production of LHRH
antagonists.
BACKGROUND OF THE INVENTION
[0002] The luteinizing hormone-releasing hormone, LHRH, controls
the secretion of follicle stimulating hormone (FSH) and luteinizing
hormone (LH). LHRH antagonists are compounds capable of blocking
the secretion of FSH and LH. They are generally nona- and
decapeptides (but may be shorter or longer) comprising part of or
the entire structure of LHRH in which one or several amino acids
have been exchanged for other natural amino acids and/or amino
acids not found in nature.
[0003] Synthetic LHRH antagonists may be used for contraception and
in the treatment of benign hyperplasia of the prostate gland,
hormonal-dependent tumors of the breast and ovaries, dysmenorrhea,
endometriosis, and other conditions. These synthetic LHRH
antagonists have the general formula
Ac-D-2Nal-D-4ClPhe-D-3Pal-Ser-X--NH.sub.2,
[0004] wherein X is from 5 to 6 natural and/or synthetic amino acid
residues. More particularly they have the aforementioned general
formula wherein X is AA1-AA2-Leu-AA3-Pro-D-Ala, in particular
wherein AA1 is a natural or synthetic amino acid and AA2 is a
natural or synthetic amino acid or zero, AA3 is a natural or
synthetic amino acid.
[0005] While there are a number of synthetic methods for preparing
LHRH analogs known in the art, there is a need for improvement
since the total yield of LHRH analogs obtained from known processes
is not high and the products, in addition, may require extensive
purification. Moreover, the methods for the synthesis of LHRH
analogs known in the art are quite costly.
[0006] A synthesis strategy disclosed in U.S. Pat. No. 5,710,246
for making decapeptide or nonapeptide LHRH antagonists comprises
the coupling of an intermediate tripeptide representing amino
residues 1 to 3 (counting starts at the amino terminal of the
peptide) with a heptapeptide or a hexapeptide, respectively
representing amino acid residues 4-10 and 4-9, respectively. The
intermediate tripeptide disclosed in U.S. Pat. No. 5,710,246 A is
an ester, Boc-D-2Nal-D-4ClPhe-D-3Pal-O-Me or the corresponding
benzyl or allyl ester.
OBJECTS OF THE INVENTION
[0007] It is thus an object of the invention to provide a
tripeptide intermediate for the 3+7 and 3+6 synthesis of LHRH
analogs in which the yield and/or purity of the product is
improved.
[0008] It is another object of the invention to provide a process
for the production of such a tripeptide intermediate.
[0009] It is still another object of the invention to provide a
process for the production of LHRH analogs in which a tripeptide is
coupled to a hepta- or hexapeptide.
[0010] Further objects of the invention will become obvious from
the following summary of the invention, the description of
preferred embodiments, and the appended patent claims.
DEFINITIONS AND ABBREVIATIONS
[0011] For definitions and abbreviations used in this application
and which are generally accepted in the field of the invention
reference is made in particular to U.S. Pat. No. 5,710,246 A.
SUMMARY OF THE INVENTION
[0012] According to the invention is provided a tripeptide
representing amino acids 1-3 of an LHRH antagonist, the terminal
amino group of which is Boc- or Ac-protected and the terminal
carboxyl group of which (that is, the terminal group of amino acid
no. 3) is not protected.
[0013] According to the invention is disclosed the tripeptide
(I)
Ac-D-2Nal-D-4ClPhe-D-3Pal-OH (I)
[0014] which is a useful intermediate in a process for the
synthesis of an LHRH antagonist of the general formula (II)
Ac-D-2Nal-D-4ClPhe-D-3Pal-Ser-X--NH.sub.2 (II)
[0015] wherein X is from 5 to 7 natural and/or synthetic amino acid
residues, more preferred AA1-AA2-Leu-AA3-Pro-D-Ala, in particular
wherein AA1 is a natural or synthetic amino acid and AA2 is a
natural or synthetic amino acid or zero, AA3 is a natural or
synthetic amino acid.
[0016] Still preferred is the use of the tripeptide (I) in the
synthesis of a peptide of the general formula (IIa)
Ac-D-2Nal-D-4ClPhe-D-3Pal-Ser-AA1-AA2-Leu-Lys(iPr)-Pro-D-Ala-NH.sub.2
(IIa),
[0017] wherein AA1 and AA2 have the meaning given above, in
particular a LHRH antagonist of the formula (III)
Ac-D-2Nal-D-4ClPhe-D-3Pal-Ser-MeTyr-D-Lys(Nic)-Leu-Lys(iPr)-Pro-D-Ala-NH.s-
ub.2 (III)
[0018] or, even more preferred, of the formula (IIIa)
Ac-D-2Nal-D-4ClPhe-D-3Pal-Ser-MeTyr-D-Asn-Leu-Lys(iPr)-Pro-D-Ala-NH.sub.2
(IIIa).
[0019] According to the invention is also disclosed the
tripeptide
Boc-D-2Nal-D-4ClPhe-D-3Pal-OH (IX)
[0020] of same utility.
[0021] Furthermore, according to the invention is disclosed a
process for preparing a tripeptide of the formula (I)
Ac-D-2Nal-D-4ClPhe-D-3Pal-OH (I)
[0022] or (IX)
Boc-D-2Nal-D-4ClPhe-D-3Pal-OH (IX),
[0023] comprising the following consecutive steps for the
preparation of (I):
[0024] (a) Reacting Boc-D-4ClPhe-OH with HONSu to form
Boc-D-4ClPhe-OSu (VII);
[0025] (b) Reacting Boc-D-4ClPhe-OSu (VII) with H-D-3Pal-OH to form
Boc-D-4ClPhe-D-3Pal-OH (VIII);
[0026] (c) Reacting Boc-D-4ClPhe-D-3Pal-OH (VIII) with
Boc-D-2Nal-OSu prepared by reacting Boc-D-2Nal-OH with HONSu to
form Boc-D-2Nal-D-4ClPhe-D-3Pal-OH (IX);
[0027] (d) Reacting Boc-D-2Nal-D-4ClPhe-D-3Pal-OH (IX) with acetic
acid to form Ac-D-2Nal-4ClPhe-D-3Pal-OH (I);
[0028] or the consecutive steps (a) through (c) for the preparation
of (IX).
[0029] The process of the invention for preparing a LHRH antagonist
comprises the step of coupling the tripeptide (I) with a
heptapeptide (IV) of the general formula
P.sup.1-Ser(P.sup.2)-AA1-AA2-Leu-Lys(iPr,P.sup.4)-Pro-D-AlaNH.sub.2
(IV),
[0030] wherein P.sup.4 is H or an amino protecting group such as
Boc, wherein AA1 and AA2 have the aforementioned meaning, in
particular with a heptapeptide (V) of the general formula
P.sup.1-Ser(P.sup.2)-NMeTyr(P.sup- .3)-D-Lys(Nic)-Leu-Lys(iPr,
P.sup.4)-Pro-D-AlaNH.sub.2 (V), wherein P.sup.1 is selected from H
or amino protecting group and P.sup.2 and P.sup.3 are independently
selected from H and --OH protecting group, and P.sup.4 has the
meaning given above, for preparing the LHRH antagonist
Ac-D-2Nal-D-4ClPhe-D-3Pal-Ser-MeTyr-D-Lys(Nic)-Leu-Lys(iPr)-Pro-D-Ala-NH.-
sub.2 (III), more particularly with a heptapeptide (Va) of the
general. formula
P.sup.1-Ser(P.sup.2)-NMeTyr(P.sup.3)-D-Asn-Leu-Lys(iPr,
P.sup.4)-Pro-D-AlaNH.sub.2 (Va), wherein P.sup.1 is selected from H
or amino protecting group and P.sup.2 and P.sup.3 are independently
selected from H and --OH protecting group, and P.sup.4 has the
meaning given above, for preparing the LHRH antagonist
Ac-D-2Nal-D-4ClPhe-D-3Pal-Ser-Me-
Tyr-D-Asn-Leu-Lys(iPr)-Pro-D-Ala-NH.sub.2 (III).
[0031] The heptapeptide (V) is described in U.S. Pat. No. 5,710,246
A. The heptapeptide of the general formula (IV) including the
heptapeptide (Va) can be synthesized by routine modifications of
the synthesis of (V) or by coupling the corresponding Boc-amino
acids on a peptide synthesizer (Beckman Model 990), as described in
WO 94/40757 where also the LHRH antagonist (III) is disclosed.
[0032] Alternatively the process of the invention for preparing a
LHRH antagonist comprises the step of coupling the tripeptide
(IX)
Boc-D-2Nal-D-4ClPhe-D-3Pal--OH (IX)
[0033] with a heptapeptide (IV) of the general formula
P.sup.1-Ser(P.sup.2)-AA1-AA2-Leu-Lys(iPr,
P.sup.4)-Pro-D-AlaNH.sub.2 (IV),
[0034] wherein P.sup.1, P.sup.2, P.sup.4, AA1 and AA2 have the
meaning given above, in particular with a heptapeptide (V) of the
general formula
P.sup.1-Ser(P.sup.2)-NMeTyr(P.sup.3)-D-Lys(Nic)-Leu-Lys(iPr,
P.sup.4)-Pro-D-AlaNH.sub.2 (V)
[0035] or, even more preferred, with a heptapeptide of the general
formula (Va)
P.sup.1-Ser(P.sup.2)-NMeTyr(P.sup.3)-D-Asn-Leu-Lys(iPr,
P.sup.4)-Pro-D-AlaNH.sub.2 (Va),
[0036] wherein P.sup.1 is selected from H or amino protecting
group, P.sup.2 and P.sup.3 are independently selected from H and
--OH protecting group, P.sup.4 has the aforementioned meaning,
followed by substituting the N-terminal Boc group by an acyl group,
in particular an acetyl group.
[0037] More particularly, the heptapeptide of the general formula
(V) is the heptapeptide (VI)
H-Ser(tBu)-NMeTyr-D-Lys(Nic)-Leu-Lys(iPr,Boc)-Pro-D-AlaNH.sub.2
(VI),
[0038] or even more preferred, the heptapeptide (VIa)
H-Ser(tBu)-NMeTyr-D-Asn-Leu-Lys(iPr,Boc)-Pro-D-AlaNH.sub.2
(VIa)
[0039] A particular advantage with the method of the invention is
that a cheaper starting material, H-D-Pal-OH.2HCl, can be used
instead of the ester H-Pal-OR.2HCl; the protective group of the
starting material need not be removed. Therefore the synthesis of
the invention is one step shorter and avoids that material is lost
in the additional step. Another advantage is that the formation of
impurities in the saponification step is avoided. The formation of
such impurities is well known. For instance, the basic conditions
at the ester hydrolysis step cause partial racemization of D-Pal.
The other prior-art alternative of removing the ester group by
catalytic hydrogenation (in the case of allyl or benzyl ester
groups) risks to cause a loss of Cl from 4ClPhe producing Phe.
While allyl groups may be removed by still other reagents the full
removal is difficult to control.
[0040] The invention will now be explained in more detail by
reference to a preferred embodiment.
DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
[0041] Synthesis of Ac-D-2Nal-4ClPhe-D-3Pal-OH (I).
EXAMPLE 1
[0042] Boc-D-4ClPhe-OSu. Boc-D-4ClPhe-OH (299,75 g; 1,0 eq.) and
HONSu (184,1 g; 1,6 eq.) are dissolved in 2-propanol (4,5 L). The
mixture is cooled to 0.degree. C. and DIC (164,1 g; 1.3 eq.) is
added. The mixture is stirred for 16 h while warming to room
temperature. The product is filtered of, washed with 2-propanol
(1,5 L) and dried. Yield: 85%. HPLC purity: 98,8%.
EXAMPLE 2
[0043] Boc-D-4ClPhe-D-3Pal-OH. H-D-3Pal-OH, 2 HCl (251,1 g; 1,05
eq.) and Boc-D-4ClPhe-OSu (396,8 g; 1,0 eq.) are dissolved in DMSO
(3,33 L) and NMM (318,8 g; 3,15 eq.) is added. The mixture is
stirred for 16 h at room temperature. Water (17 L) is added and pH
is adjusted to 4-4,5 which causes the product to precipitate. The
mixture is filtered and the product is washed with water (3.times.5
L) to remove traces of DMSO, H-D-3Pal-OH and Boc-D-4ClPhe-OH. The
product is dried. Yield: 80%. HPLC purity: 97,8%
EXAMPLE 3
[0044] Boc-D-2Nal-OSu. Boc-D-2Nal-OH (315,4 g; 1,0 eq.) is
dissolved in 2-propanol (6,8 L) at -10.degree. C. and IBC (157 g;
1,15 eq.) and NMM (116 g; 1,15 eq.) is added. After stirring for
5-10 min a mixture of HONSu (230,1 g; 2,0 eq.) in 2-propanol (1,4
L) is added. Additional NMM (10,1 g; 0,1 eq.) is added. After half
an hour water (0,82 L) is added to dissolve precipitated
NMM.multidot.HCl. The product is isolated by filtration, washed
with 2-propanol (1 L), and dried. Yield.: 90%. HPLC purity:
98,3%.
EXAMPLE 4
[0045] Boc-D-Nal-D-4ClPhe-D-3Pal-OH.
[0046] (a) Deprotection. Boc-D-4ClPhe-D-3Pal-OH (447,93 g; 1,0 eq.)
is dissolved in a mixture of ethyl acetate (3,4 L), acetic acid
(675 ml) and MSA (454 mL; 7,0 eq.) at 0.degree. C. and kept at this
temperature for two hours. TEA (1669 ml; 12 eq.) is added.
[0047] b) Condensation. Boc-D-Nal-OSu (412,4 g; 1,0 eq.) is added
to the neutralized deprotection mixture at room temperature. The
reaction mixture is kept at this temperature for 2-4 h. Aq. 25%
NH.sub.3 (154 mL; 2,0 eq.) is added to quench remaining
hydroxysuccinimide ester. 1-Butanol (4,5 L) is added to prevent
precipitation in the subsequent extractions.
[0048] c) Purification and isolation. The reaction mixture is
extracted twice at pH 6 (2.times.4,5 L water) to remove TEA, at pH
9 (4,5 L water) to remove MSA and finally at pH 7 (4,5 L water).
The extractions are carried out at 40-45.degree. C. to prevent
precipitation. To the organic phase is added acetic acid (4,5 L; 1
vol.) and the mixture is concentrated in vacuo and co-evaporated
with acetic acid (4,5 L) to give a solid.
EXAMPLE 5
[0049] Ac-D-2Nal-D-4ClPhe-D-3Pal-ONa.
[0050] a) Deprotection. To the solid Boc-D-2Nal-D-4ClPhe-D-3Pal-OH
is added water (90 ml), acetic acid (1,8 L) and MSA (454 mL; 7,0
eq.) and the mixture is stirred for 1-2 h at room temperature. The
mixture is cooled to 0.degree. C. and neutralized with TEA (1071
ml; 7,7 eq.) . The solution is concentrated in vacuo and
co-evaporated twice with toluene (2.times.2,5 L) to give an
oil.
[0051] b) Acetylation. The oil from the deprotection step is
dissolve in toluene (2,0 L) and acetyl imidazole (132,14 g) is
added. The mixture is stirred at room temperature for 1 h and then
water (100 ml) is added to quench remaining acetyl imidazole.
[0052] d) Purification. The mixture from the acetylation is heated
to 30-35.degree. C. and 1-butanol (4,5 L) is added to prevent
precipitation The mixture is extracted twice at pH 5 (2.times.2,6 L
water), and twice at ph 11 (2.times.2,6 L water) using NaOH to
adjust pH to 11. Methanol (2,25 L) is added to the last extractions
to prevent precipitation. NaCl (130 g) is added to the first and
the last extraction to minimize loss of product in the aqueous
phases.
[0053] e) Isolation. To the vigorously stirred organic phase from
the extractions is added heptane (15 L) and the resulting
suspension is left at room temperature while stirring for at least
1 h. The mixture is filtered and the product is washed twice with
heptane (2.times.3,5 L) and dried. Yield: 75% (from
Boc-D-4ClPhe-D-3Pal-OH). HPLC purity: 92%. Amino acid analysis:
2Nal: 1.1; 4ClPhe: 1.0; 3Pal: 0.9. MS: MW 586. Na: 4.6%
EXAMPLE 6
[0054] Ac-D-2Nal-D-4ClPhe-D-3Pal-OH.DCHA
[0055] a) Deprotection. To the solid Boc-D-2Nal-D-4ClPhe-D-3Pal-OH
is added water (90 mL), acetic acid (1,8 L) and MSA (454 mL; 7,0
eq.) and the mixture is stirred for 1-2 h at room temperature. The
mixture is cooled to 0.degree. C. and neutralized with TEA (1071
mL; 7,7 eq.). The solution is concentrated in vacuo and
co-evaporated twice with toluene (2.times.2,5 L) to give an
oil.
[0056] b) Acetylation. The oil from the deprotection is dissolved
in toluene (2,0 L) and acetyl imidazole (132,14 g) is added. The
mixture is stirred at room temperature for 1 h followed by addition
of water (100 ml) to quench remaining acetyl imidazole.
[0057] c) Purification. The mixture is heated to 30-35.degree. C.
and 1-butanol (4,5 L) is added to prevent precipitation. The
mixture is extracted twice at pH 7 (2.times.2,6 L water), once at
pH 9-9,5 (2,6 L water) and once at pH 7 (2,6 L water). DCHA
(dicyclohexyl amine) is added and the mixture is concentrated in
vacuo. The product is suspended in 1-butanol (4,5 L) at 50.degree.
C. and slowly added to vigorously stirred heptane (27 L). The
mixture is stirred at 0.degree. C. over night, filtered and the
product washed twice with 1-butanol/heptane (1:3; 2.times.4,8 L)
and twice with heptane (2.times.4,5 L). Yield: 65% (from
Boc-D-4ClPhe-D-3Pal-OH). HPLC purity: 94,2%. Amino acid analysis:
2Nal: 1.1; 4ClPhe: 1.0; 3Pal: 0.9. MS: MW 586 (free peptide).
EXAMPLE 7
[0058] Ac-D-2Nal-D-4ClPhe-D-3Pal-OH.
[0059] a) Deprotection. To the solid Boc-D-2Nal-D-4ClPhe-D-3Pal-OH
is added water (90 mL), acetic acid (1,8 L) and MSA (454 ml; 7,0
eq.) and the mixture is stirred for 1-2 h at room temperature. The
mixture is cooled to 0.degree. C. and neutralized with TEA (1071
mL; 7,7 eq.). The solution is concentrated in vacuo and
co-evaporated twice with toluene (2.times.2,5 L) to give an
oil.
[0060] b) Acetylation. The oil from the deprotection is dissolved
in toluene (2,0 L) and acetyl imidazole (132,14 g) is added. The
mixture is stirred at room temperature for 1 h and then water (100
mL) is added to quench remaining acetyl imidazole.
[0061] c) Purification. The mixture from the acetylation is heated
to 30-35.degree. C. and 1-butanol (4,5 L) is added to prevent
precipitation The mixture is extracted twice at pH=7 (2.times.2,6 L
water), an once at pH=9-9,5 (2,6 L water) and once at pH=7 (2,6 L
water). The mixture is concentrated in vacuo to an oil, which is
dissolved in acetic acid (750 ml), concentrated, re-dissolved in
acetic acid (750 ml) and slowly added to vigorously stirred
heptane/ethyl acetate (3:1; 3,6 L). The mixture is left with
stirring at 0.degree. C. over night. The mixture is filtered, and
the product is washed twice with ethyl acetate/heptane (1:3;
2.times.3,6 L) and twice with heptane (2.times.3,6 L). Yield: 70%
(from Boc-D-4ClPhe-D-3Pal-OH). HPLC purity: 93,9%. Amino acid
analysis: Nal: 1.1; 4ClPhe: 1.0; 3Pal: 0.9 MS: MW 586 (free
peptide).
* * * * *