IR spectroscopy study of the amidation reaction of N-(1-azolecarbonyl)amino acids on L-phenylalanine derivative models

Behaviour of N-(1-azolecarbonyl)-L-phenylalanine (Azc-Phe-OH, 1a-d) and L-phenylalanine N-carboxy anhydride (L-Phe-NCA, 6) in the presence of triethylamine (TEA) or cyclohexylamine was followed by IR spectroscopy. IR spectra were recorded in acetonitrile solutions. Attention was focused on characteristic absorptions of CO2 (2340 cm–1) and Azc, COOH or the anhydride group (1850-1600 cm–1). The obtained results corroborate N-carboxy anhydride as an intermediate in amidation reactions of Azc-amino acids