N-phthaloylation of chloro- and hydroxy-2-amino-acids

Abstract

Because of displacement and amide–hydroxy neighbouring group reactions, 2-amino-acids bearing 4-substituents, (halogen, hydroxy) are difficult to acylate. New synthetic techniques designed to minimise these side reactions and to allow N-phthaloylation of chloro- and hydroxy-amino-acids are discussed. N-Phthaloylation of 4-chloro-and 4-hydroxylysines in aprotic solvents has been found to occur in high yield, and preferential attack at the 6-amino-function of these 4-substituted lysines has been observed.