Amino-acids and peptides. Part XXXIII. Synthesis of Val5-angiotensin-II by the picolyl ester method

Abstract

A further example of the use of 4-picolyl esters to facilitate peptide synthesis is provided in a synthesis of protected Val⁵-angiotensin-II (overall yield 38%). The side-chain 4-picolyl esters of benzyloxycarbonyl- and t-butoxy-carbonyl-aspartic and -glutamic acids, and derivatives, are described, and in a further synthesis of protected Val⁵-angiotensin-II the aspartic acid was introduced as its β-4-picolyl ester, so facilitating the separation procedure. Hydrogenation of both protected octapeptides gave biologically active Val⁵-angiotensin-II.