Trifluoroacetic acid → 6-[6-methoxy-2-(1-methylcyclopropyl)-1H-indol-3-ylmethyl]pyridine-2-carbonitrile

To a solution of tert-butyl {2-[1-(6-cyanopyridin-2-ylmethyl)-2-(1-methylcyclopropyl)-2-oxoethyl]-5-methoxyphenyl}carbamate (270 mg) in acetonitrile/dichloromethane (2.1 mL/2.1 mL) was added trifluoroacetic acid (2.1 mL) under ice-cooling, and the mixture was stirred at room temperature for 44.5 hours. The reaction mixture was concentrated under reduced pressure. The residue was dissolved in ethyl acetate and the resulting mixture was washed with a saturated aqueous sodium hydrogen carbonate solution. The organic layer was dried over anhydrous sodium sulfate, and then concentrated under reduced pressure. The residue was purified by silica gel column chromatography (eluting solvent: ethyl acetate-hexane), and then purified by aminopropylated silica gel column chromatography to obtain the title compound (163 mg). 1H-NMR (CDCl3) δ ppm: 0.70-0.78 (2H, m), 0.81-0.89 (2H, m), 1.33 (3H, s), 3.82 (3H, s), 4.39 (2H, s), 6.70 (1H, dd, J=2.3, 8.5 Hz), 6.80-6.85 (1H, m), 7.12-7.22 (2H, m), 7.47-7.53 (1H, m), 7.59 (1H, t, J=7.8 Hz), 7.87 (1H, br s).