To a mixture of 2-[5-benzyloxy-4-methoxy-2-(5-methyl-[1,2,4]oxadiazol-3-yl)phenyl]N-cyclohexyl-2-oxoacetamide (reference example 14-15) (860 mg) and N,N-dimethylformamide (6 mL) was added sodium hydride (60%, 92 mg). After stirring at room temperature for 20 minutes, iodomethane (0.48 mL) was added to the mixture. After stirring at room temperature for 8 hours, the mixture was poured into a mixture of 2 mol/L hydrochloric acid and ice-water. Ethyl acetate was added to the mixture. The separated organic layer was washed with water, an aqueous solution of sodium bicarbonate and brine successively, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (eluent: 0%-50% ethyl acetate/hexane, gradient elution) to give the title compound (605 mg).
