Abstract Condensation of amides of N-(benzyloxycarbonyl)-and N-(trifluoroacetyl) amino acid with pyruvic and phenylpyruvic acid yields, in the presence of p-toluenesulfonic acid as a catalyst, N-(benzyloxycarbonyl)-and N-(trifluoroacetyl) dehydro dipeptides with C-terminal Δ Ala and ΔPhe, respectively (Table 2 and 3).