Derivatives of retro-enantio-somatostatin, intermediates therefor, and

Abstract

Compounds of the formula 1 or 1a ##STR1## IN WHICH R is hydrogen or CONHCH.sub.2 CONHCH.sub.2 CH.sub.3 are disclosed. The compounds are obtained by a process which comprises the following step: preparing peptide fragments II, III, V and VII see below, by a series of condensations involving the reaction of an appropriately protected peptide having an activated ester group with an appropriately protected peptide having a free amino group; condensing ##STR2## by means of the azide method with ##STR3## followed by hydrogenolysis of the reaction product to obtain ##STR4## condensing the latter by means of the azide method with ##STR5## followed by treating the resulting compound with hydrazine hydrate to obtain ##STR6## condensing the latter by means of the azide method with ##STR7## in which R is hydrogen or CONHCH.sub.2 CONHCH.sub.2 CH.sub.3 to obtain the linear protected peptide ##STR8## in which R is as defined herein; thereafter said linear peptide is transformed into the desired cyclic peptide of formula 1 by deprotecting and oxidizing processes. In addition, the linear, reduced form of the peptide of formula 1a is obtained by deprotection of the aforementioned linear peptide or by reduction of the cyclic peptide. The peptides of formulae 1 and 1a are useful for the management of diabetes and the treatment of acromegaly. Methods for their use are also disclosed.