The one-pot syntheses of N-protected Δ1- and Δ2-dehydrodipeptide esters by the coupling of N-carboxy α-dehydroamino acid anhydride (ΔNCA) with several kinds of C- or N-protected L-α-amino acids are described. In addition, it was found that a similar coupling of ΔNCA with both C- and N-protected α-amino acids also took place to give Δ2-dehydrotripeptide derivatives, involving eight kinds of important