Carbohydrate-active enzyme-catalyzed stereoselective glycosylation of complex natural product glycosides

Natural products and their derivatives are precious resources with extensive applications in various industrial fields. Enzymatic glycosylation is an efficient approach for chemical structure diversification and biological activity alternation of natural products. Herein, we reported a stereoselective glycosylation of complex natural product glycosides catalyzed by two carbohydrate-active enzymes (CAZys). ASP OleD, a mutant of glycosyltransferase OleD from Streptomyces antibioticus, catalyzed an explicit β-1,x-linkage glycosylation of the OH group of the glycosyl moiety of the representative plant-derived complex natural product glycosides, protodioscin (1) and epimedin C (2), producing two complex glycoside derivatives. The glycoside hydrolase Δ27ThCGT, a truncated cyclodextrin glucanotransferase from Thermoanaerobacter sp., exhibited a definite α-1,x-linkage glycosylation of the OH group of the glycosyl moiety of the glycosides 1, 2, and astragaloside IV (3), generating four complex glycoside derivatives. The chemical structures and absolute configurations of these enzymatic glycosylation products were determined by analysis of their HRMS and NMR data. The present study expands the enzymatic glycosylation diversification of complex glycosides catalyzed by the CAZys.