Preparation of some acylated 4-deoxyhex-3-enopyranosiduloses and γ-pyrone formation therefrom

Acylated 4-deoxyhex-3-enopyranosiduloses carrying benzoyl and/or acetyl groups (i.e., enolones 9, 10, and 14) were prepared by methyl sulfoxide-acetic anhydride oxidation of methyl 3,4,6-tri-O-acetyl-β-D-glucoside and of methyl 3-O-benzoyl-4,6-O-benzylidene-α-D-glucoside, the latter reaction being followed by debenzylidenation, acylation, and β-elimination of a carboxylic acid. The enolones, as well as the intermediate hexosiduloses, were readily characterized by spectral data and as their 2,4-dinitrophenylhydrazones. In basic and, less readily, in acidic medium, the enolones 9, 10, and 14 are converted into the γ-pyrone system. The mechanistic implications of these conversions are discussed.