To a solution of ethyl 2,3-dibromo-3-(5-((2-phenoxybenzyl)oxy)-2-pyridinyl)propanoate (159.3 mg) in tetrahydrofuran (1 ml), 32 mg of hydroxyamine hydrochloride, 0.6 ml of 2.5N sodium hydroxide/methanol solution and 0.078 ml of water were added, and the reaction solution was stirred at room temperature for 2 hours and then heated to reflux overnight. The reaction solution was cooled, then diluted with water, acidified with 10% aqueous citric acid, then extracted with chloroform, and dried over anhydrous magnesium sulfate. The solvent was distilled off under reduced pressure, and the residue obtained was purified through reversed phase medium pressure liquid chromatography (ODS-AS-360-CC (by YMC), mobile phase: water-acetonitrile-0.1% trifluoroacetic acid). The solvent of the resultant fraction was distilled off under reduced pressure, and then purification by preparative thin layer chromatography (Kieselgel™ 60 F254, Art5744, made by Merck & Co., chloroform/methanol (9:1)) was carried out to afford the title compound as a white solid.
