Nucleophilic ring opening of aziridine-2-carboxylates with Wittig reagents; an enantioefficient synthesis of unsaturated amino acids

Reaction of N-tosyl- or N-acyl aziridine-(2S)-carboxylate esters with carbonyl stabilized Wittig reagents provides an isolable phosphorus ylide resulting from opening of the aziridine ring; this ylide reacts with carbonyl compounds to provide a novel synthesis of optically pure unsaturated amino acids, exemplified by enantioefficient syntheses of the naturally occuring (2S)-γ-methyleneglutamic acid and (E)-(2S)-4-ethylideneglutamic acid.