Synthesis of glycyrrhizin analogues containing fluorinated beta(1-->2)-linked disaccharides

For studies on the recognition mechanisms for Glycyrrhizin-induced biological activities, seven Glycyrrhizin analogues with 3'-, 4'-, 6'-, 3-, and 4-fluorinated 2-O-beta-D-glucopyranosyl-beta-D-glucopyranoses (1-5) and 3- and 4-fluorinated 2-O-beta-D-glucopyranuronosyl-beta-D-glucopyranoses (6 and 7) were synthesized through a stepwise glycosylation procedure. 1,2-Di-O-acetyl-4,6-di-O-benzyl-3-deoxy-3-fluoro- (13) and 1,2-di-O-acetyl-3,6-di-O-benzyl-4-deoxy-4-fluoro-D-glucopyranose (14) were employed for the first beta-glycosylation of methyl glycyrrhetate, promoted with trimethylsilyl trifluoromethanesulfonate.