To a solution of 4-bromo-3-hydroxy-3-(6-hydroxy-1,3-benzodioxol-5-yl)-1-pentyl-1,3-dihydro-2H-indol-2-one (34.9 g, 80.4 mmol) in dichloromethane (100 mL) was added trifluoroacetic acid (18.7 g, 161 mmol) and triethylsilane (18.3 g, 161 mmol). The brown solution was stirred at ambient temperature for 3 h and concentrated in vacuo to dryness. The residue was diluted with dichloromethane (200 mL), washed with saturated ammonium chloride solution (50.0 mL), brine (3×50.0 mL), dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated in vacuo to dryness. The residue was crystallized from ether to give the title compound (16.5 g, 49%) as a brown solid: 1H NMR (300 MHz, CDCl3) δ 7.29-7.21 (m, 2H), 7.14 (dd, 1H), 6.58 (s, 1H), 6.10 (s, 1H), 5.85 (dd, 2H), 5.01 (s, 1H), 3.75-3.55 (m, 2H), 1.69-1.56 (m, 2H), 1.35-1.21 (m, 4H), 0.86 (t, 3H); 13C NMR (75 MHz, CDCl3) δ 177.9, 150.9, 147.6, 145.4, 141.6, 130.3 127.1 126.8, 120.8, 113.3 108.0, 106.7, 101.5, 101.2, 59.9, 48.6, 40.7, 28.9, 26.9, 22.3 13.9; MS (ES+) m/z 418.3 (M+1), 420.3 (M+1).
