Citric Acid → 1-ethoxycarbonyl-3-(6-O-ethoxycarbonyl-beta-D-glucopyranosyl-oxy)-4-[(4-ethylthiophenyl)methyl]-5-methylpyrazole

To a solution of 4-[(4-ethylthiophenyl)methyl]-3-(β-D-glucopyranosyloxy)-5-methyl-1H-pyrazole (0.03 g) in 2,4,6-trimethylpyridine (0.5 mL) was added ethyl chloroformate (0.021 mL), and the mixture was stirred at room temperature overnight. To the reaction mixture was added 10% aqueous citric acid solution, and the resulting mixture was extracted with ethyl acetate. The organic layer was dried over anhydrous magnesium sulfate, and the solvent was removed under reduced pressure. The residue was purified by preparative thin layer chromatography on silica gel (eluent: dichloromethane/methanol=10/1) to give 1-ethoxycarbonyl-3-(6-O-ethoxycarbonyl-β-D-glucopyranosyloxy)-4-[(4-ethylthiophenyl)methyl]-5-methylpyrazole (0.023 g).