Convenient Synthesis of Chiral Pyranones from Carbohydrates

Article abstract of DOI:10.1055/s-1988-27741

2-Acyloxyglycals (2-O-acyl-1,5-anhydrohex-1-enitols) having a D-arabino configuration (1a, b) react highly stereoselectively with alcohols in the presence of a stoichiometric amount of tin(IV) chloride at O-5 deg C to (2S,6S)-6-acyloxymethyl-2-alkoxy-2H-pyran-3(6H)-ones 2 together with furaldehyde by-products 3.In the case of 2-acyloxyglycals having a D-lyxo (1c, d) or an L-lyxo (4) configuration, reaction occurs readily at -20 deg C to form the desired pyranones 2 or 5 without the formation of furaldehydes.All reactions showed high stereoselectivity for α-anomersin the formation of the acetal linkage, except the reaction of the tri-O-benzoyl derivative 1d with methanol.The method reported allows the synthesis of chiral pyranones in higher yield and by a shorter route than the previously reported methods.