A NEW METHOD OF ORTHOESTERIFICATION, UNDER KINETIC CONTROL, AT NONANOMERIC POSITIONS - APPLICATION TO THE D-GLUCOSE AND D-MANNOSE SERIES AND SELECTIVE HYDROLYSIS OF THE CORRESPONDING ORTHOESTERS

The reaction of ketene acetals with D-glucose, D-mannose, and their me thyl glycosides is described as a new route to unusual cyclic orthoest ers (at non anomeric positions). The reaction proceeds by preferential attack of the reagent on the primary hydroxyl group. The synthesis of strained rings (2,3-diequatorial orthoester) is possible. The resulti ng methoxyethylidene derivatives are very sensitive to hydrolysis, and mild conditions lead to hydroxyacetates that are potentially useful i ntermediates for carbohydrates synthesis.