Novel Route to L‐Hexoses from L‐Ascorbic Acid: Asymmetric Synthesis of L‐Galactopyranose and L‐Talopyranose Preliminary Communication

A novel route with L ‐ascorbic acid as a single common starting material to asymmetric synthesis of all eight diastereomers of L ‐hexoses is described. Assessment of this new approach is demonstrated by the expedient synthesis of L ‐galactopyranose and L ‐talopyranose derivatives. Key steps involve stereoselective preparation of chiral (E)‐ and (Z)‐γ‐hydroxy‐α,β‐unsaturated esters and their stereo‐controlled dihydroxylation by OsO₄.