Chelation-controlled regioselectivity in the lanthanum-promoted monobenzoylation of monosaccharides in water

Abstract

Monosaccharides are selectively converted to monobenzoates in a base-catalyzed reaction with benzoyl methyl phosphate (BzMP) and a lanthanum salt in water. Yields are reported in terms of formation of the ester, which competes with hydrolysis of BzMP, to give an estimate of the efficiency of the conversion of the sugar. Higher conversions can be achieved using excess reagent. Regioselectivity is influenced by the structure of the glycoside. For example, the reaction leads to different product distributions from α- and β-anomers of the glycosides. The reaction combination provides a basis for efficient ester formation in specific geometric situations, providing a means of identification as well as modification.