N-Cbz-or N-Tos-α-dehydroamino acid (DHA) and its ester were prepared by the condensation of 2-oxo carboxylic acid or ester with benzyl carbamate or p- toluenesulfonamide. Subsequently, the N-protected DHA and its N-free ester thus obtained were coupled with several L-α-amino acid esters and N-protected (Boc or Cbz)-L-α-amino acid respectively by the usual peptide synthetic methods to give a number of different ...
