Aziridine-mediated asymmetric synthesis of quaternary β-amino acids using 2H-azirine 2-carboxylate esters

Regioselective hydrogenation of enantiopure 3-substituted and 3,3-disubstituted aziridine 2-carboxylate esters affords β-amino acids and quaternary β-amino acids, respectively, in good yield. The aziridines are prepared via an aza-Darzens reaction of α-bromoenolates with enantiopure sulfinimines (N-sulfinyl imines) and by addition of Grignard reagents to 2H-azirine 2-carboxylate esters.