N-Acyl-2,3-didehydro-2-amino acid esters 3, 5, 7-12, with a great variety of N-substituents, are obtained in good yields by the perrhenate-catalyzed decomposition of methyl 2-azido carboxylates 1 in organic solvents in the presence of the corresponding acyl chlorides 2. By using methyl 2-azidoisovalerate (1a), the conditions (catalyst, solvent, temperature) for the reaction to give 3a were optimized. The reactivity of acyl chlorides can be strongly enhanced with equimolar amounts of dimethyl formamide, which allows a lowering of the decomposition temperature for this reaction. Under these mild reaction conditions also the unstable N-acyldehydroalanine derivative 5f can be obtained in good yield.
