Under an argon atmosphere, to a solution of N-(2-{6,6-dimethyl-1-[2-(trimethylsilyl)ethoxymethyl]-4,5,6,7-tetrahydro-1H-indazol-3-yl}-1-[2-(trimethylsilyl)ethoxymethyl]-1H-indol-6-yl)-N-methylamine (100 mg, 0.18 mmol) and triethylamine (75 μl, 0.54 mmol) in chloroform (1.5 ml) was added acetyl chloride (19 μl, 0.27 mmol) at room temperature, and the mixture was stirred for 2 hr. Water was added to the reaction mixture, and the mixture was extracted three times with ethyl acetate. The combined organic layers were washed successively with water and saturated brine, and dried over sodium sulfate. Sodium sulfate was removed by filtration, and the filtrate was concentrated under reduced pressure to give N-(2-{6,6-dimethyl-1-[2-(trimethylsilyl)ethoxymethyl]-4,5,6,7-tetrahydro-1H-indazol-3-yl}-1-[2-(trimethylsilyl)ethoxymethyl]-1H-indol-6-yl)-N-methylacetamide. A solution of the obtained N-(2-{6,6-dimethyl-1-[2-(trimethylsilyl)ethoxymethyl]-4,5,6,7-tetrahydro-1H-indazol-3-yl}-1-[2-(trimethylsilyl)ethoxymethyl]-1H-indol-6-yl)-N-methylacetamide in N,N-dimethylformamide (1.4 ml) was added to tetrabutylammonium fluoride (1.8 ml, 1.8 mmol) concentrated in advance under reduced pressure. Ethylenediamine (0.7 ml) was added, and the mixture was stirred with heating at 90° C. for 24 hr. After cooling, water and ethyl acetate were added, and the organic layer was separated. Then, the aqueous layer was extracted twice with ethyl acetate. The combined organic layers were washed successively with water and saturated brine, and dried over sodium sulfate. Sodium sulfate was removed by filtration, and the filtrate was concentrated under reduced pressure. The residue was purified by thin layer silica gel chromatography to give the title compound (26 mg, yield 42%).
