Polypeptides. Part XVII. The synthesis of some sequential polypeptides of γ-benzyl D-glutamate and L-leucine

Abstract

The succinimidyl esters of mono-, di-, tri-, and tetra-γ-benzyl-D-glutamyl-L-leucine (VII; n= 1–4) have been prepared from the corresponding acids (V; n= 1–4), which were synthesised by the dicyclohexylcarbodi-imide method; the t-butoxycarbonyl group was used for amino-group protection and the 2-methylthioethyl ester group for carboxy-protection. Polymerisation of these esters gave satisfactory yields of the corresponding sequential polypeptides (I; n= 1–4) with molecular weights of between 11,000 and 31,000. Little racemisation (1–2%) accompanies the polymerisations, and the method is recommended as a procedure of choice for the synthesis of sequential polypeptides.