Depsipeptide synthesis by accelerated active ester coupling

Abstract

Protected amino acid active esters react with α-hydroxy acid esters in the presence of several equivalents of imidazole to form aminoaoyl hydroxy acid derivatives in high yield. p-Nitrophenyl, 8-quinolyl, and cyanomethyl esters have been employed as activated carboxyl components in the reaction. Several depsipeptide derivatives were synthesized using the accelerated active ester coupling procedure. Pentamethylbenzyl was used extensively as a carboxyl-protecting group in this work.