Serendipitous Discovery of Peptide Dialkyl Peroxides

In an attempt to synthesize a homologous series of peptide peresters, we investigated the reaction of the oxazol-5(4H)-ones of Pht-(Aib)n-OH (n=2–8) and tert-butyl hydroperoxide in the presence of 4-(dimethylamino)pyridine. Unexpectedly, the major product isolated in each case proved to be the peptide dialkyl peroxide. This novel class of peptide derivatives was characterized by FT-IR, 1H-NMR, MS, cyclic voltammetry, and X-ray diffraction. On the basis of the experimental data, a plausible mechanism is proposed for this reaction.