FORMATION OF OLIGOMERS ON N-ACYLATION OF TRIPEPTIDES . PROTON MAGNETIC RESONANCE SPECTRA OF PEPTIDES

The peptides L-Phe-Gly-L-Leu, L-Leu-L-Phe-L-Ala, and L-Ala-L-Phe-Gly-L-Leu were prepared via controlled acylation by amino acid N-carboxyanhydrides. Acylation of the tripeptides by benzyloxycarbonyl chloride resulted in extensive formation of tripeptide oligomers, indicating that the carboxylate anion of a free peptide competes favorably with the terminal amino group as a nucleophile. The proton magnetic resonance spectra of L-Leu-L-Phe-L-Ala and its oligomers and of L-Ala-L-Phe-Gly-L-Leu are reported and briefly discussed. © 1969, American Chemical Society. All rights reserved.