A mixture of 2-ethylhexyl 3-((2-(((2S)-2-acetamidopropyl)oxy)-5-nitropyridin-4-yl)sulfanyl)propanoate (3.38 g), reduced iron (2.07 g), ammonium chloride (0.397 g), ethanol (40 mL) and water (10 mL) was stirred overnight at 80° C. The precipitate was removed by filtration, and the filtrate was extracted with ethyl acetate. The combined organic layer were washed with saturated brine, and dried over anhydrous magnesium sulfate, and the solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography (hexane/ethyl acetate) to give the title compound (2.83 g).
