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.