Ethyl6-hydroxyindazole-3-carboxylate (1.457 g) which can be prepared according to the method described in Reference example 17, etc. was dissolved in dehydrated DMF (15.6 mL; manufactured by Kanto Chemical Co., Inc.), added with imidazole (1.425 g; manufactured by Tokyo Chemical Industry, Co., Ltd.) and TBDPSCl (4.06 mL), followed by stirring overnight at room temperature. The reaction solution was poured to a saturated aqueous solution of sodium hydrogen carbonate and extracted twice with ethyl acetate. The organic layer was washed with brine and insoluble matters were filtered using Celite. The organic layer was washed twice with water and dried over anhydrous magnesium sulfate. After the solvent was evaporated under reduced pressure, the residue was purified by column chromatography (“COLUMN-A”; n-hexane:ethyl acetate=81:19→60:40) to obtain the title compound (1.467 g).
