transglycosylation

Transglycosylation is a chemical and biochemical process in which a glycosyl group is transferred from a donor molecule to an acceptor, forming a new glycosidic bond and releasing the original leaving group. The reaction can occur under enzymatic control or in purely chemical synthesis, and it is often discussed in contrast to hydrolysis, which converts a glycoside back to a sugar and aglycone.

In biological systems, transglycosylation is commonly mediated by glycoside hydrolases that, under certain conditions, favor transfer of the glycosyl residue to an acceptor over water. Retaining glycosidases, and some glycosyltransferases that use activated sugar donors, can catalyze the formation of new glycosidic bonds to diverse acceptors such as alcohols, phenols, or sugars, producing non-native glycosides or glycoconjugates. Water activity, donor and acceptor reactivity, and enzyme specificity all influence the balance between hydrolysis and transglycosylation.

In chemical synthesis, transglycosylation refers to the transfer of a glycosyl unit from a glycosyl donor to an acceptor in the presence of promoters or catalysts. Common donor types include glycosyl halides, thioglycosides, and trichloroacetimidates, with promoters such as Lewis acids or Brønsted acids. Acceptor scope includes alcohols, phenols, or other nucleophiles. Controlling the reaction environment to minimize hydrolysis and maximize transfer is a central challenge.

Applications of transglycosylation include the synthesis of oligosaccharides, glycosides, and glycoconjugates for research, pharmaceuticals, and functional foods.