Synthesis of oligopeptides having alternate L-leucyl and L-methionyl residues

Abstract

A series of oligopeptides having alternate L-leucyl and L-methionyl residues which are interesting from a conform-ational aspect have been prepared by a method involving use of an N-o-nitrophenylsulphenyl-N-carboxy-α-amino-acid anhydride (Nps-NCA). The peptides were assembled stepwise, with L-methionine ethyl ester as the starting amino-acid; L-leucyl residues were introduced in high yields by the ‘Nps-NCA’ method, and L-methionyl residues in moderate yields by the dicyclohexylcarbodi-imide method. The usefulness of the Nps-NCA method for peptide synthesis is demonstrated.