Transglucosidation of methyl and ethyl d-glucofuranosides by alcoholysis Original Research Article

The acid catalyzed ethanolysis of methyl 5-O-methyl-α- and -β-d-glucofuranoside and the analogous methanolysis of ethyl 5-O-methyl-α- and -β-d-glucofuranoside have been investigated. For all four reactions, the primarily formed transglycosylation product was a single glycoside that had the opposite anomeric configuration to the starting material. This strongly indicates that a d-glucose methyl ethyl acetal is first formed and is then ring closed by a nucleophilic attack by HO-4, giving either the starting material or a transglycosylation product with the opposite anomeric configuration. Low percentages of the methyl ethyl acetals and of dimethyl acetals were also observed in the reaction product during the methanolysis reactions.