Conversion of β-d-C-glucopyranosyl phloroacetophenone to a spiroketal compound

Treatment of β-d-C-glucopyranosyl phloroacetophenone in water in the presence of a catalytic amount of p-TsOH afforded a spiroketal product. This is the first demonstration of ring conversion in aryl C-glycoside. The structure of the product was determined by 1H-1H COSY, HMQC, HMBC, NOESY, and single crystal X-ray analysis of the corresponding acetylated compound.