β-selective C-arylation of silyl protected 1,6-anhydroglucose with arylalanes: the synthesis of SGLT2 inhibitors.

The stereoselective arylation of hydroxy protected 1,6-anhydro-beta-d-glucose with arylalanes to provide beta-C-arylglucosides is reported. Modification of triarylalanes, Ar3Al, with strong Bronsted acids (HX) or AlCl3 produced more reactive arylating agents, Ar2AlX, while the incorporation of alkyl dummy ligands into the arylating agents was also viable. Me3Al and i-Bu2AlH were found useful in the in situ blocking of the C3-hydroxyl group of 2,4-di-O-TBDPS protected 1,6-anhydroglucose. The utility of the method was demonstrated by the synthesis of the SGLT2 inhibitor, canagliflozin.