A suspension of sodium hydride (purity: 60%, 60 mg) in tetrahydrofuran (1.0 mL) was added to a solution of 2-oxazolidinone (153 mg) in tetrahydrofuran (1.0 mL) under ice-cooling, and the mixture was stirred at room temperature for 30 minutes. 6-[(1E)-3-Bromo-1-(4-tert-butylphenyl)prop-1-en-1-yl]-3-chloro-2-methoxypyridine obtained in Reference Example 4-5 (303 mg) was added thereto, and the mixture was stirred at room temperature for 20 hours. Water was added to the reaction solution, followed by extraction with ethyl acetate. The organic layer was washed with brine and dried over sodium sulfate. After filtration, the solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography (hexane:ethyl acetate=9:1→3:2) to give 3-[(2E)-3-(4-tert-butylphenyl)-3-(5-chloro-6-methoxypyridin-2-yl)prop-2-en-1-yl]-1,3-oxazolidin-2-one as a light brown powder (298 mg, 98%).
