(E)-4-[2-(1H-indazol-3-yl)vinyl]benzoic acid (0.18 g, 0.67 mmol) obtained in Step 6 of Example 1 was dissolved in THF (4 mL), and the solution was added with N-(2-methoxyethyl)methylamine (0.11 mL, 1.00 mmol), 1-hydroxybenzotriazole monohydrate (0.12 g, 0.85 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.18 g, 0.92 mmol), followed by stirring at room temperature for 2 hours. The reaction mixture was added with a saturated aqueous sodium hydrogencarbonate solution, was extracted with ethyl acetate, the organic layer was sequentially washed with water and saturated brine, was dried over anhydrous magnesium sulfate, and the solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography (chloroform/methanol=25/1) to obtain Compound 5 (0.22 g, 99%).
