To a solution of tert-butyl 3-[6-((E)-2-cyanovinyl)pyridin-2-ylmethyl]-6-methoxy-2-phenyl-1H-indole-1-carboxylate (100 mg) in acetonitrile/dichloromethane (1 mL/1 mL) was added trifluoroacetic acid (1 mL) under ice-cooling, and the mixture was stirred at room temperature overnight. To the reaction mixture were added ethyl acetate and a saturated aqueous sodium hydrogen carbonate solution. The organic layer was separated, washed with saturated brine, dried over anhydrous magnesium sulfate, and then concentrated under reduced pressure. The residue was purified by silica gel column chromatography (eluting solvent: ethyl acetate-hexane) to obtain the title compound (68.7 mg). 1H-NMR (CDCl3) δ ppm: 3.86 (3H, s), 4.40 (2H, s), 6.60 (1H, d, J=16.1 Hz), 6.76 (1H, dd, J=2.1, 8.7 Hz), 6.91 (1H, d, J=2.1 Hz), 7.07-7.16 (2H, m), 7.32-7.49 (5H, m), 7.50-7.63 (3H, m), 8.05 (1H, br s).
