Shortened analogs of somatostatin

Claim 1

A process for preparing a peptide of formula 1 ##STR13## in which R is hydrogen or NHR 1 wherein R 1 is a lower aliphatic acyl having from 1 - 6 carbon atoms, or benzoyl, which comprises: reacting a peptide hydrazide of formula (2) Trt--SCH 2 CH(R)CO--Lys--(Boc)--Asn--Phe--Phe--NHNH 2 in which R is as defined herein with a reagent which furnishes nitrous acid in situ in the presence of a strong acid to convert said peptide hydrazide to the corresponding peptide azide and reacting said azide with a hexapeptide of formula (3) H--Trp--Lys(Boc)--Thr(B + )--Phe--Thr(Bu + )--Ser(Bu + )--NHCH.sub.2 CH 2 S--Trt to obtain the linear peptide of formula (4) Trt--SCH 2 CH(R)CO--Lys(Boc)--Asn--Phe--Phe--Trp--Lys--(Boc)--Thr(Bu + )--Phe--Thr(Bu + )--Ser(Bu + )--NHCH 2 CH 2 S--Trt in which R is as defined herein, followed by oxidizing said linear peptide with iodine or thiocyanogen to obtain the corresponding cyclic disulfide derivative of formula (5) ##STR14## in which R is as defined herein and subsequently removing all remaining protecting groups under moderately acidic conditions to obtain the corresponding peptide of formula 1; or followed by subjecting said linear peptide (4) to treatment with either mercuric acetate, mercuric chloride, silver acetate or silver nitrate to remove selectively the sulfhydryl protecting groups to obtain the mercuric or disilver salt, respectively, of the corresponding disulfhydryl derivative; converting the latter salt to its corresponding free disulfhydryl derivative by treatment with hydrogen sulfide, oxidizing said last-named derivative by treatment with oxygen, 1,2-diiodoethane, sodium or potassium ferricyanide or iodine to obtain the corresponding cyclic disulfide derivative (5) and removing the remaining protecting groups under moderately acidic conditions to obtain the desired peptide of formula 1.