Peptide synthesis using o‐nitrophenylsulfenyl N‐carboxy α‐amino acid anhydrides. Sequential oligopeptides having alternate γ‐methyl L ‐glutamyl and L ‐phenylalanyl residues

A series of sequential oligopeptides having the sequence alternating γ‐methyl L‐glutamyl and L‐phenylalanyl residues have been successfully prepared by a rapid method involving the reaction of o‐nitrophenylsulfenyl N‐carboxy α‐amino acid anhydrides with amino acid and peptide esters. The sequential oligopeptides, which are interesting from a conformational aspect, were obtained in optical pure forms above 74% yields. This result demonstrates that the o‐nitrophenylsulfenyl N‐carboxy α‐amino acid anhydride method is especially useful for easy synthesis of protected oligopeptides with o‐nitrophenylsulfenyl group.