Stereoselective Synthesis of (4S,5S)-5-Vinyloxazolidin-2-one-4-carboxylate as a ß-Vinylserine Synthetic Equivalent by Vinyl Grignard Addition to an N-Tosyl Version of Garner's Aldehyde.

A highly efficient synthesis of a ß-vinylserine synthetic equivalent is reported that exploits the stereodirecting effect of the N-toluenesulfonamide in an anti-diastereoselective (8.5:1) vinyl Grignard addition to an analogue of Garner's aldehyde. Both aryl and alkyl Grignards are shown to give increased anti-selectivity compared with N-Boc Garner's aldehyde.