Abstract
Aspartic and glutamic acids were selectively extended at each of the alternative C-terminals under mild conditions to afford diverse natural and unnatural N-protected dipeptides and tripeptides in yields of 73-96%. The reactions between N-protected (alpha-aminoacyl)benzotriazoles and free amino acids or dipeptides proceeded with complete retention of chirality as supported by parallel experiments involving D-Ala, L-Ala, and DL-Ala in the preparation of dipeptides and tripeptides, monitored by NMR and HPLC analyses.