0.007 ml of diethylaminosulfur trifluoride was added to a chloroform (1 ml) solution of 21 mg of 1-(1-(6-(4-methanesulfonyl-phenoxy)-2-pyridin-2-yl-3H-benzimidazol-5-yl)-pyrrolidin-2-yl)-ethanol diastereomer A obtained in Example 354, at −78° C., and the reaction liquid was stirred at −78° C. for 1 hour. The reaction liquid was heated up to room temperature, and aqueous saturated sodium bicarbonate was added to the reaction liquid, and then extracted with ethyl acetate, and dried with anhydrous magnesium sulfate. The solvent was evaporated away, and the resulting residue was purified through partitioning thin-layer chromatography (Kieselgel™ 60F254, Art 5744 (by Merck), chloroform/methanol=10/1) to obtain the entitled compound as a pale yellow solid.
