O-Glycosidic bond exocyclic cleavage of difructose led by acidic proton migration: Density functional theory calculation study

We investigate proton migrations from (H2O)n (n = 1–3) to difructose, α-d-fructofuranose-β-d-fructofuranose-2,3′, using density functional theory. The proton migrations result in O-glycosidic bond cleavage. The highest transition barrier for proton migrations taking place from (H2O)3 to difructose is 11.67 kcal mol−1. The barriers are much lower than those for the direct breaking of a covalent bond in a difructose linkage. In addition, an autocatalysis process is also studied. An excess proton can migrate from a fructose molecule to a difructose molecule, leading to O-glycosidic bond cleavage. The transition barrier energy for this proton migration is 5.35 kcal mol−1.