Asymmetric synthesis of 2H-Azirine 2-carboxylate esters

2H-Azirine 2-carboxylate esters (5), the smallest unsaturated nitrogen hete rocycle, are readily prepared in enantiomerically pure form via the base-in duced elimination of sulfenic acid (RSOH) from nonracemic N-sulfinylaziridi ne 2-carboxylate esters (4). Optimum yields were obtained when the aziridin e was treated with TMSCl at -95 degrees C followed by LDA, which was attrib uted to the improved leaving group ability of an silicon-oxonium species. B y using this new methodology the first asymmetric syntheses of the marine c ytotoxic antibiotics (R)-(-)- and (S)-(+)-dysidazirine (2) were accomplishe d.