N-Bromosuccinimide assisted oxidation of tripeptides and their amino acid analogs: Synthesis, kinetics, and product studies

Abstract

Three tripeptides (TPs), Gly–Val–Gly, Ala–Val–Gly and Gyl–Phe–Gly, were synthesized and characterized. The kinetics of oxidation of the TPs and their constituent amino acids (AAs) by N-bromosuccinimide (NBS) was studied in the presence of perchloric acidic medium at 28 °C by following the reaction spectrophotometricaly at λ max = 240 nm. In all cases, the kinetics of reactions was first-order with respect to each [NBS] and [AA] or [TP]. Increased [H +], succinimide (the reduction product of NBC), chloride and perchlorate concentrations had no effect on the rate of reactions. However, the reaction rate was increased with increased dielectric constant of the medium and with the hydrophobicity of AAs and TPs. Activation parameters for each of the substrate were considerably different. Analysis of the oxidation products indicated that the amino acids and peptides underwent oxidative deamination and decarboxylation to form corresponding aldehydes. Based on these data, plausible mechanisms for the oxidation AAs and TPs are proposed.