A General Asymmetric Synthesis of syn- and anti-β-Substituted Cysteine and Serine Derivatives

A stereodivergent synthetic route has been developed to make the optically pure anti- and syn-beta-substituted cysteine and serine derivatives. In this approach, the key intermediates, > 94% enantiomerically pure cyclic sulfates 3 and aziridines 7, were prepared from alpha,beta-unsaturated esters 1, employing the Sharpless asymmetric dihydroxylation. The high regio- and stereoselective ring-opening reactions of cyclic sulfates and aziridines provided enantiomerically pure beta-substituted cysteine and serine derivatives.