Scandium cation-exchanged montmorillonite catalyzed direct C-glycosylation of a 1,3-diketone, dimedone, with unprotected sugars in aqueous solution.

The condensation of dimedone with unprotected sugars in aqueous solution in the presence of a catalytic amount of Sc(3+)-montmorillonite (Sc(3+)-mont) gave 9-hydroxyalkyl-3,3,6,6,-tetramethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-diones in good yields, while the use of Sc(OTf)(3) instead of Sc(3+)-mont gave the hydroxyalkyl-6,7-dihydrobenzofuran-4(5H)-one derivatives in good yields. Furthermore, Sc(3+)-mont could be recycled without inactivation.