An Efficient Synthesis of N-Boc-D-diphenylalanine from a Chiral Azirdine-2-carboxylate

N-Boc-D-diphenylalanine was prepared from a commercially available aziridine-2(S)-carboxylate through alkylation, regiospecific aziridine ring opening, and benzylic deoxygenation followed by oxidation in 57% overall yield.Enantiomerically pure unnatural amino acids attract attentions from many fields for the syntheses of peptide-based biologically active compounds. 1Especially peptide bearing diphenylalanine as a core unnatural amino acid possesses high biological activity. 2The best-known examples are the analogs of angiotensin II with high binding affinities for rat uterus and brain receptors 3 because they have diphenylalanine instead of phenylalanine.