Diastereoselective synthesis of all eight L-hexoses from L-ascorbic acid

A novel versatile method for the synthesis of all eight diastereomerically pure L-hexoses was developed. L-Ascorbic acid was converted to two diastereomers A. These alpha-hydroxy esters were transformed into four gamma-alkoxy-alpha,beta-unsaturated esters C via the intermediates B and subsequent Wittig olefination reactions. Each one of compounds C was subjected to dihydroxylation to provide a set of two diols D. Anti/lsyn-differentiation in diol formation was manipulated by using (DHQD)(2)PHAL and (DHQ)(2)PHAL as chiral ligands. Further two-step reaction sequence affords all eight diastereopure L-hexoses.