Peptides by extension at the N- or C-terminii of lysine.

Dipeptides 3a-g, (3a + 3a'), (3d + 3d'), (3l + 3l')a and tripeptides 6a-e, (6b + 6b'), (6e + 6e') incorporating Z(epsilon)-Lys were prepared in high yields (70-95%) and enantiopurity (> or =97%) in partially aqueous acetonitrile solution by coupling using (i) Z(epsilon)-Lys with N-(Z- and Fmoc-aminoacyl)benzotriazoles 1a-g, (ii) Z(epsilon)-Lys with N-Z-dipeptidoylbenzotriazoles 5a-c, and (iii) N-Fmoc(alpha)-Z(epsilon)-l-Lys-Bt 1h and amino acids 2a,c-e. Unnatural dipeptides 3h-j, (3h + 3h') and tripeptides 6f were similarly prepared from Z(alpha)-Lys. Retention of chirality was demonstrated by parallel experiments involving l-Ala, dl-Ala, l-Met, and dl-Met by NMR and HPLC analysis.