A variety of hydroxylic aglycones can be glucuronidated directly with methyl 2, 3, 4-tri-O- acetylglucopyranuronate (4a), activated with trimethyhilyl trifluoromethanesulfonate (Me3Si- OTf). This reaction provides mostly/3, and sometimes a, glucopyranosiduronic acid derivatives (referred to as glucuronides) rapidly and at low temperatures. The epimeric ratio depends on the relative aglycone nucleophilicity vs. its tendency to form a stabilized ...
