t-Butyldimethylsilyl chloride (42.24 mg, 0.28 mmol) and imidazole (47.7 mg, 0.701 mmol) were added to a solution of 5-{4-[1-ethyl-1-(4-hydroxy-3-methyl-phenyl)-propyl]-2-methyl-phenyl}-furan-2-carboxylic acid methyl ester (Example 19-(1); 55 mg, 0.14 mmol) in N,N-dimethylformamide (0.2 mL) at room temperature, and the mixture was stirred at room temperature for 0.2 hour. Diethyl ether was added to the reaction solution. The organic layer was washed with distilled water and brine and dried over anhydrous magnesium sulfate, and then the solvent was distilled off under reduced pressure. The residue was purified by silica gel chromatography (n-hexane/ethyl acetate=95/5 to ethyl acetate only) to give the title compound (61 mg, 86%).
