(E)-[2-(2-Propylbenzimidazol-1-yl)methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5-ylidene]acetonitrile (467 mg, 1.16 mmol) obtained in Example 1 was dissolved in ethanol (11 mL), hydroxylamine (50% aqueous solution, 2.13 mL, 34.7 mmol) was added, and the mixture was heated under reflux for 16 hr, and concentrated under reduced pressure. The obtained residue was dissolved in DMF (5.5 mL), pyridine (112 μL, 1.39 mmol) and ethyl chlorocarbonate (133 μL, 1.39 mmol) were added at 0° C., and the mixture was stirred at room temperature for 1 hr. Ethyl acetate and saturated aqueous sodium hydrogen carbonate solution were added to the mixture. The organic layer was washed with brine, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The obtained residue was dissolved in toluene (11 mL), potassium tert-butoxide (195 mg, 1.74 mmol) was added, and the mixture was stirred at room temperature for 15 min. Ethyl acetate was added to the mixture, and the organic layer was washed with 5% aqueous citric acid solution, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (chloroform/methanol=99/1) to give the title compound (compound 5) (295 mg, 55%).
