Hydrochloric Acid → {8-Methyl-3-{1-[4-(6-methylpyridin-3-yl)phenyl]cyclopropyl}-5,6,8,9-tetrahydro[1,2,4]triazolo[4,3-d][1,4]thiazepin-8-yl}methanol

A solution of the compound (342 mg, 0.66 mmol) obtained in Example 18-1) and 4 M hydrochloric acid (1,4-dioxane solution, 2 mL) in methanol (2 mL) was stirred at room temperature for 14 h. The reaction mixture was concentrated under reduced pressure, saturated aqueous sodium hydrogencarbonate was added to the residue, the mixture was extracted with dichloromethane, and the organic layer was washed with saturated sodium chloride solution and dried with anhydrous sodium sulfate. After filtration, the filtrate was concentrated under reduced pressure, and the residue was purified by silica gel chromatography (Isco Combiflash, 12 g, methanol:ethyl acetate=0:100 to 40:60, gradient) to obtain the title compound (215 mg, 81%) as a colorless solid.