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 α-hydroxy esters were transformed into four γ-alkoxy-α,β-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/syn-differentiation in diol formation was manipulated by using (DHQD)2PHAL and (DHQ)2PHAL as chiral ligands. Further two-step reaction sequence affords all eight diastereopure l-hexoses.