PRACTICAL SYNTHESIS OF OPTICALLY PURE 3,4-EPOXY-5-METHYLDIHYDRO-2(3H)-FURANONES FROM D-XYLOSE BY REGIOSELECTIVE AND STEREOSELECTIVE FUNCTIONALIZATION

The known 1,2-O-isopropylidene-5-O-p-tolylsulfonyl-alpha-D-xylofuranose was converted into its 3-p-nitrobenzoate (13a) and 3-methanesulfonate (13b). (-)-(3S,4S,5R)-3,4-Epoxy-5-methyldihydro-2(3H)-furanone [(-)-8] was synthesized from 13a in 5 steps by conversion of 13a into its methyl glycoside, 3-O-mesylation, glucosidic cleavage with CF3CO2H, epoxide formation with sodium methoxide and PCC-oxidation. (+)-(3R,4R,5R)-3,4-Epoxy-5-methyldihydro-2(3H)-furanone [(+)-9] was prepared from 13b in 3 steps by deacetonation with CF3CO2H, epoxide formation with sodium methoxide, and PCC oxidation. These epoxides may be useful intermediates for the total synthesis of natural products of the alpha-alkyl-beta-hydroxy-gamma-methylbutyrolactone type (1).