Stannic tetrachloride catalysed glycosylation of 8-ethoxycarbonyloctanol by cellobiose, lactose, and maltose octaacetates; synthesis of α- and β-glycosidic linkages

Abstract

The 1,2-trans-octaacetates of cellobiose, lactose, and maltose were converted to β-glycosides of 8-ethoxycarbonyloctanol in good yield by a single step reaction. A 1,2-acetoxonium ion generated by stannic tetrachloride in dichloromethane at −10 °C leads initially to β-glycosides via 1,2-orthoacetate intermediates. Insitu anomerisation of the β-maltoside occurred during reaction (4 h) at room temperature and provided a preparative route to this α-glycoside of the disaccharide. The β-lactose and cellobiose glycosides were also anomerised to the respective α-glycosides. The three β- and three α-disaccharide glycosides of the disaccharides have been functionalised for conversion to artificial carbohydrate antigens.