Concise Synthesis of Vinyl Glycines

Significance

A concise asymmetric synthesis of (E)-vinyl glycines 7 has been achieved. Enantio­selective α-sulfenylation of aldehydes 1 catalyzed by α,α-diaryl prolinol ether 2 followed by stereoselective in situ olefination of intermediates 4 allowed ready access to optically enriched allylic sulfides 5. Subsequent amination of 5, accomplished by using oxaziridine 6 and stereospecific [2,3]-sigmatropic rearrangement of the resulting allylic sulfimides, furnished products 7 in good overall yields with essentially complete chirality transfer. Rapid and clean N-S bond cleavage took place on treatment with P(OEt)₃ and Et₃N. Finally, a one-pot amination-rearrangement-desulfurization sequence directly giving N-Boc-protected (E)-vinyl glycines could be realized.