A novel entry to naturally occurring 5-alkenyl alpha,beta-unsaturated delta-lactones from D-glucose: syntheses of (+)-acetylphomalactone and (+)-asperlin

A bicyclic pyranosidic glycoside 6, readily obtained from D-glucose, has been used as the key intermediate in enantioselective syntheses of (+)-acetylphomalactone and (+)-asperlin, in which the configuration at C-5 corresponds to that of the hexopyranosides in the L-sugar series.