Synthesis of Peptides with α,β‐Dehydroamino Acids, II. Synthesis of tert‐Butyloxycarbonyldipeptides of Dehydroalanine and Dehydrophenylalanine

Abstract
Condensation of amides of Boc‐amino acids3) with pyruvic acid leads to Boc‐dipeptides 1 – 3 of dehydroalanine and 1‐Boc‐5‐alkyl‐2‐methyl‐4‐oxo‐2‐imidazolidinecarboxylic acids 8 – 10. The amides, however, do not condense with phenylpyruvic acid. Boc‐dipeptides of dehydroalanine (1 – 3) and dehydrophenylalanine (4 – 7) are synthesized using (Boc)2O and dehydrodipeptides with a free unmasked N‐terminal amino group.