Patent GB-1527252-A (GB)
Title: Cyclization of peptides via cystine linkages
IPC: A61K38/23
Filed: 1975-09-10
Abstract: 1527252 Peptide cyclization process ARMOUR PHARMACEUTICAL CO 10 Sept 1975 [12 Sept 1974] 37226/75 Heading C3H Per se a non-cyclic peptide having an amino acid chain which contains two cysteine moieties, one of which has its sulphydryl function protected by an n-alkylthio group, whilst the second sulphydryl function may be protected by BZ may be prepared by a process which comprises coupling one cysteine moiety into an amino acid chain wherein the sulphydryl group of said moiety is protected with BZ, and coupling a second cysteine moiety into said chain, whilst protecting said sulphydryl function of said second moiety with an n-alkylthio group, and treating the peptide so formed with an acid to cleave said BZ without effecting said nalkylthio group. The non-cyclic peptide is held in solution (preferably aqueous or aqueous alcoholic) substantially free of oxygen (preferably in a stream of inert gas such as nitrogen), preferably at a pH of 5 to 10, until cyclization via a cystine linkage occurs. In the examples, condensation is effected using a solid phase synthesis or a polystyrene resin, with removal of the BOC group after each condensation; Ex. (A) (9) Boc-Gly-OH; (8) Boc-Leu-OH; (7) Boc-Pro-OH; (6) Boc- Cys(S-SEt)-OH; (5) Boc-Asn-OpNp; (4) Boc- Gln-OpNp; (3) Boc-Ile-OH; (2) Boc-Tyr(Bzl). OH; (1) Boc-Cys(S-pMeBzl)-OH to give Boc- Cys(S-pMeOBzl) - Tyr(Bzl) - Ile - Gln - Asn- Cys(S-SEt) - Pro - Leu - Gly - NHCH(C 6 H 5 )-X which is treated with HF to give H-Cys-Tyr- Ile - Gln - Asn - Cys(S-SEt) - Pro - Leu - Gly- NH 2  which, on cyclization, yields OXYTOCIN. Ex. (B) (32) Boc-Pro-OH; (31) Boc-Ala-OH; (30) Boc-Gly-OH; (29) Boc-Val-OH; (28) Boc-Gly-OH; (27) Boc-Ile-OH; (26) Boc-Ala- OH; (25) Boc-Thr(Bzl)-OH; (24) Boc-Gln- OpNp; (23) Boc-Pro-OH; (22) Boc-Phe-OH; (21) Boc-Thr(Bzl)-OH; (20) Boc-His(Z)-OH; (19) Boc-Phe-OH; (18) Box-Lys(Z)-OH; (17) Boo-Asn-OpNp; (16) Boc-Phe-OH; (15) Boc- Asp(OBzl)-OH; (14) Boc-Gln-OpNp; (13) Boc- Thr(Bzl)-OH; (12) Boc-Tyr(Bzl)-OH; (11) Boc- Thr(Bzl)-OH; (10) Boc-Gly-OH; (9) Boc-Leu- OH; (8) Boc-Met-OH; (7) Boc-Cys(S-SEt)-OH; (6) Boc-Thr(Bzl)-OH; (5) Boc-Ser(Bzl)-OH; (4) Boc-Leu-OH; (3) Boc-Asn-OpNp; (2) Boc- Gly-OH; (1) Boc-Cys(pMeOBzl)-OH which, on treatment as in Ex. (A) yields HUMAN CALCITONIN. Similarly there may be prepared: (1) H-Ala- Gly - Cys(SR) - Lys(V) - Asn - Phe - Phe - Trp- Lys(V) - Thr(Bzl) - Phe - Thr(Bzl) - Ser(Bzl)- Cys(3,4DiMeBzl) - OCH 2 X or H - Ala - Gly- Cys(SR) - Lys(V) - Asn - Phe - Phe - Trp- Lys(V) - Thr(Bz) - Phe - Thr(Bz) - Ser(Bz)- Cys(Bz) - OCH 2 X which yields SOMATOSTATIN. (2) H - Cys(Bzl) - Thr(Bz) - Phe - Gln - Asn- Cys(SR) - Pro - Arg(T) - Gly - NH - CH(C 6 H 5 ) -X which yields VASOPRESSIN. (3) H - Cys(Bz) Ser(Bz) - Asn - Leu- Ser(Bz) - Thr(Bz) - Cys(SR) - Val - Leu- Ser(Bz) - Ala - Tyr(W) - Trp - Arg(T) - Asn- Leu - Asn - Asn - Phe - His(V) - Arg(T) - Phe- Ser(Bz) - Gly - Met - Gly - Phe - Gly - Pro- Gly(Bz) - Thr(Bz) - Pro - NHCH(C 6 H 5 )-X which yields PORCINE CALCITONIN. (4) H - Cys(Bz) - Ser(Bz) - Asn - Leu- Ser(Bz) - Thr(Bz) - Cys(SR) - Val - Leu- Ser(Bz) - Ala - Tyr(W) - Trp - Lys(V) - Asp(Bz)- Leu - Asn - Asn - Tyr(W) - His(V) - Arg(T)- Phe - Ser(Bz) - Gly - Met - Gly - Phe - Gly- Pro - Glu(Bz) - Thy(Bz) - Pro - NHCH(C 6 H 5 ) -X which yields BOVINE CALCITONIN. (Bz, benzyl, 4-methoxybenzyl, 4-methylbenzyl, 3,4-dimethylbenzyl, 4-chlorobenzyl, 2,6 - dichlorobenzyl, 4-nitrobenzyl or benzhydryl; W, hydrogen Bz, benzyloxycarbonyl, 2 - chlorobenzyloxycarbonyl or 2 - bromobenzyloxycarbonyl; T, nitro or tosyl; V, benzyloxycarbonyl, 2 - chlorobenzyloxycarbonyl, 2 - bromobenzyloxycarbonyl or 3,4- dimethylbenzyloxycarbonyl; SR, n-alkylthio; X, polystyrene resin.)