AMINO-ACIDS .16. SYNTHESIS OF N-ACYL-2,3- DIDEHYDRO-2-AMINO ACID-ESTERS

N-Acyl-2,3-didehydro-2-amino acid esters 3, S, 7-12, with a great vari ety of N-substituents, are obtained in good yields by the perrhenate-c atalyzed decomposition of methyl 2-azido carboxylates 1 in organic sol vents in the presence of the corresponding acyl chlorides 2. By using methyl 2-azidoisovalerate (1a), the conditions (catalyst, solvent, tem perature) for the reaction to give 3a were optimized. The reactivity o f acyl chlorides can be strongly enhanced with equimolar amounts of di methyl formamide, which allows a lowering of the decomposition tempera ture for this reaction. Under these mild reaction conditions also the unstable N-acyldehydroalanine derivative 5f can be obtained in good yi eld.