3-Chloromethyl-5,6-dimethoxy-1-(1-trityl-4-imidazolyl)methyl-1H-indazole (165.0 g) was suspended in dimethyl sulfoxide (1,200 ml) and stirred at room temperature. To this was added potassium cyanate (43.6 g) which has been made into powder using a mortar. When the reaction solution was stirred at 70° C. for 1 hour, the reaction solution became uniform and transparent, and it was observed that the spot of the material almost disappeared on a thin layer chromatography (ethyl acetate/hexane=2/1). The reaction solution was cooled to room temperature and poured into water (15,000 ml) which was vigorously stirred, and the mixture was stirred for 1 hour. The thus precipitated solid substance was collected by suction filtration, washed with water (1,000 ml×3) and dissolved in chloroform (5,000 ml), the resulting solution was dried with sodium sulfate and filtered, and then the solvent was evaporated under a reduced pressure. The thus obtained residue was separated and purified by a silica gel column (ethyl acetate) to obtain 108.7 g of light brown solid. This solid substance was directly used in the subsequent reaction.
