Isolation and identification of select oligosaccharides from commercially produced total invert sugar with a proposed mechanism for their formation

Three disaccharides were isolated and purified from a commercial total invert sugar (TIS). The structures of these compounds were determined by a combination of acid and enzymatic hydrolysis studies, chromatographic comparison to standards, and nuclear magnetic resonance spectroscopy. These carbohydrates were identified as O-alpha-D-glucopyranosyl-(1 -> 3)-D-fructose (IS1), O-beta-D-fructo-furanosyl-(2 -> 6)-D-glucose (IS2), and O-alpha-D-glucopyranosyl-beta-D-glucopyranoside (IS3). On the basis of these structures a mechanism for the hydrochloric acid catalyzed hydrolysis of sucrose is proposed: protonation of the glycosidic oxygen of sucrose leading to the formation of glucopyranosyl and fructofuranosyl oxonium ions Of D-glucose or D-fructose, respectively, followed by nucleophilic attack of these ions by D-glucose or D-fructose at either the alpha- or beta-face.