STEREOSPECIFIC AND STEREOSELECTIVE REACTIONS - IX. PREPARATION OF ETHYL (2E,7R)-7-ACETOXY-4-OXO-2-OCTENOATE FROM D-GLUCOSE.

Article abstract of DOI:10.1246/bcsj.56.1803

Reaction of methyl 2,3-anhydro-4,6-dideoxy-a-D-ribo-hexopyranoside with MgI//2 exclusively afforded methyl 3,4,6-trideoxy-3-iodo-a-D-xylo-hexopyranoside which was dehalogenated by treatment with LiAlH//4 to give methyl 3,4,6-trideoxy-a-D-erythro-hexopyranoside (2). Hydrolysis of 2 and subsequent treatment with ethoxycarbonylmethylenetriphenylphosphorane gave ethyl (2E, 4R, 7R)-4,7-dihydroxyl-2-octenoate (10). Oxidation of 10 by active MnO//2 resulted in the formation of an equilibrium mixture of ethyl (2E, 7R)-7-hydroxy-4-oxo-2-octenoate (the carbon skeleton of pyrenophorin) and cyclic hemiacetal. On treatment with acetic anhydride, the mixture affords dethyl (2E, 7R)-7-acetoxy-4-oxo-2-octenoate.