Acylation of aldonolactones for long periods, or treatment of their peracylated derivatives under alkaline conditions, lead to the formation of unsaturated lactones via β-elimination processes. Aldono-1,4-lactones undergo multiple eliminations, affording polyunsaturated furan-2-one derivatives. Under the same conditions, aldono-1,5-lactones, but more vigorous conditions are required. Alternatively, pyrones are readily obtained by the Lewis acid promoted elimination from 2-enonolactones. The catalytic hydrogenation of the furanones and pyranones is stereoselective, affording deoxyaldonolactones, which are readily converted into the corresponding deoxysugars by reduction of the lactone carbonyl group. The sequence β-elimination-catalytic hydrogenation- lactone reduction was employed for the synthesis of deoxysugars of biological significance. Also, aldonolactones and deoxyaldonolactones undergo oxidative degradation by treatment with ceric sulfate in M sulfuric acid, to yield the aldose with one less carbon. Partially substituted aldonolactones have been used as glycosylating agents of peracylated monosaccharides. Employing tin(IV) chloride as catalyst of the condensation, the glycosylic linkage was stereoselectively constructed. The resulting glycosylaldono-1,4-lactones are precursors of disaccharides having one or both monosaccharide units in a furanoid configuration. Antigenic disaccharides, constituents of glycoconjugates of plants and microorganisms, have been synthesized.
Buy this Article