A new method of orthoesterification, under kinetic control, at non-anomeric 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 methyl glycosides is described as a new route to unusual cyclic orthoesters (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 resulting methoxyethylidene derivatives are very sensitive to hydrolysis, and mild conditions lead to hydroxyacetates that are potentially useful intermediates for carbohydrates synthesis.