In 4 ml of methylene chloride was dissolved 80 mg of N-(2-methoxyphenyl)-3-(2,4-difluorophenyl)-2,2-difluoro-3-hydroxy-4-(1H-1,2,4-triazol-1-yl)butanamide. To the resulting solution were added 120 mg of ethanethiol and 130 mg of aluminum chloride at -5° to 0° C. The resulting mixture was subjected to reaction at 20°-25° C. for 20 hours. Then, the reaction mixture was introduced into a mixed solvent consisting of 10 ml of chloroform and 5 ml of water. The resulting solution was adjusted to pH 2.0 with 6N hydrochloric acid. The organic layer was separated, washed with a saturated aqueous sodium chloride solution, and then dried over anhydrous magnesium sulfate. Thereafter, the solvent was removed by distillation under reduced pressure. The residue thus obtained was purified by a column chromatography (eluant: chloroform/methanol=20/1) to obtain 30 mg of N-(2-hydroxyphenyl)-3-(2,4-difluorophenyl)-2,2-difluoro-3-hydroxy-4-(1H-1,2,4-triazol-1-yl)butanamide.
