Stereoselective epoxidation of vinyl sulfones and N-(p-tolylsulfonyl)vinylsulfoximines derived from isopropylideneglyceraldehyde: synthesis of chiralbuilding blocks

Epoxidation of N-(p-tolylsulfonyl)vinylsulfosimines using metal alkyl perox ides proceeds with varying degrees of stereoselectivity, depending both on the metal cation and the steric bulk of the alkyl peroxide group. The stere ochemical outcome of the epoxidation of substrates bearing an allylic asymm etric centre is also dependent upon the epoxidising agent, and very high le vels of stereoselectivity may be obtained in the formation of sulfonyloxira ne 8a. This oxirane was subsequently converted into the sulfonyloxirane 15, a precursor to a useful chiral functionalised acyl anion equivalent. In ad dition, the optically pure alpha-bromothioester 20 was also prepared.