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-α-d-glucopyranosyl-(1→3)-d-fructose (IS1), O-β-d-fructofuranosyl-(2→6)-d-glucose (IS2), and O-α-d-glucopyranosyl-β-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 α- or β-face. Keywords: Carbohydrates; authenticity; acid reversion; sucrose hydrolysis