Compound 2 (51 mg, 0.13 mmol) obtained in Example 2 was dissolved in dichloromethane (0.65 mL), and furan-2-carboxylic acid chloride (0.025 mL, 0.26 mmol) and pyridine (0.041 mL, 0.51 mmol) were added thereto, followed by stirring at 0° C. for 3 hours. A saturated aqueous sodium bicarbonate solution was added to the reaction mixture, followed by extraction with ethyl acetate twice. The organic layer was dried over anhydrous sodium sulfate, and concentrated under reduced pressure. A residue obtained by concentrating the organic layer under reduced pressure was purified by preparative thin layer chromatography to obtain the title compound (65 mg, 100%).
