Polypeptides. Part XI. Tetrazole analogues of the C-terminal tetrapeptide amide sequence of the gastrins

Abstract

The synthesis is described of two analogues of N-benzyloxycarbonyl-L-tryptophyl-L-methionyl-L-aspartyl-L-phenylalanine amide (a physiologically active derivative of the C-terminal tetrapeptide amide sequence of the gastrins) wherein the aspartyl β-carboxy-group or the terminal carboxamide group of the tetrapeptide amide are replaced by a tetrazol-5-yl residue. The optically active amino-acid analogues (carboxy replaced by tetrazol-5-yl) required in these syntheses were prepared without special difficulties, and they could be utilised in peptide synthesis without protection of the tetrazole unit.