From methyl -glucopyranoside to methyl -allopyranoside via the Mitsunobu reaction

Methyl β--glucopyranoside reacted with a 4-molar excess of the Mitsunobu reagents (triphenylphosphine–diethyl azodicarboxylate–benzoic acid) under Weinges et al. [Carbohydr. Res., 164 (1987) 453–458] conditions to furnish four differently benzoylated methyl β--allopyranosides in a very good overall yield. The same reaction applied to methyl α--glucopyranoside yielded allosides in a low yield and nine other sugar products. These results give an insight into the course of the Mitsunobu esterification–inversion reaction.