(Tributyl phosphoranylidene)acetonitrile (428 μL, 1.50 mmol) was added to a solution of toluene (7 mL) containing N-(4-hydroxybenzoyl)glycine tert-butyl ester (264 mg, 1.05 mmol) prepared in Example 1 (1a) and 2-(4-methoxyphenyl)ethanol (176 mg, 1.16 mmol). The mixture was stirred at 100° C. for 3.5 hours, and then water was added thereto. The mixture was extracted with ethyl acetate. The organic layers were combined, washed with water and saturated brine, and dried over anhydrous magnesium sulfate. Then, the solvent was evaporated. The resulting residue was purified by silica gel column chromatography (hexane to hexane:ethyl acetate, 6:1, 4:1, and 3:1, v/v) to give an oily substance (358 mg). To a solution of dichloromethane (1 mL) containing this oily substance (358 mg, 0.929 mmol), trifluoroacetic acid (0.5 mL) was added. The mixture was stirred at room temperature for 1 hour, and then the solvent was evaporated. Diisopropyl ether was added to the resulting residue to suspend it. The produced precipitate was collected by filtration and was washed with diisopropyl ether to give 248 mg of the title compound (colorless crystalline solid, yield: 72%).
