25 ml of 4 N solution of hydrogen chloride in dioxane and 12.5 ml of dioxane were added to 2.54 g (4.34 mmol) of 3-[(2S)-3-[4-[1-(benzyloxycarbonyl)-4-piperidyloxy]phenyl]-2-(t-butoxycarbonylamino)propoxy]benzonitrile. After stirring at room temperature for 24 hours, the solvent was distilled off under reduced pressure. The residue was dissolved in 40 ml of DMF. 1.77 ml (13.0 mmol) of diisopropylethylamine and 1.97 g (6.51 mmol)) of 4-iodobenzenesulfonyl chloride were added to the solution at 0° C. 30 minutes after, the temperature was elevated to room temperature, and the reaction mixture was stirred for 19 hours. Ater the same isolation process as that of step 1 in Example 1 with ethyl acetate as the extractant, the crude product was obtained, which was purified by the silica gel column chromatography to obtain the title compound.
