To a solution of 4,7-dichloro-3-(6-hydroxy-1,3-benzodioxol-5-yl)-3-(hydroxymethyl)-1-pentyl-1,3-dihydro-2H-indol-2-one (0.69 g, 1.57 mmol) in anhydrous tetrahydrofuran (15.0 mL) was added triphenylphosphine (0.54 g, 2.04 mmol) followed by slow addition of diisopropyl azodicarboxylate (0.41 g, 2.04 mmol) at 0° C. The brown reaction mixture was stirred at ambient temperature for 16 h and quenched with ammonium chloride solution (2.00 mL). The organic solvent was removed in vacuo. The residue was dissolved in ethyl acetate (20.0 mL), washed with 10% aqueous HCl solution (10.0 mL), dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated in vacuo to dryness. The residue was subjected to column chromatography eluting with ethyl acetate/hexane (35%) to give a solid, which was crystallized from ethyl acetate/ether to give the title compound (0.13 g, 20%) as a colorless solid: mp 106-108° C.; 1H NMR (300 MHz, CDCl3) δ 7.24-7.16 (m, 1H), 6.81 (d, 1H), 6.44 (s, 1H), 6.07 (s, 1H), 5.86 (dd, 2H), 4.87 (dd, 2H), 4.12-4.07 (m, 2H), 1.76-1.66 (m, 2H) 1.36-1.31 (m, 4H), 0.89 (t, 3H); 13C NMR (75 MHz, CDCl3) δ 177.5, 157.0, 149.2, 142.1, 140.0, 132.3, 131.0, 130.2, 124.6, 116.0, 113.8, 102.3, 101.5, 93.3, 77.2, 58.5, 42.1, 29.5, 28.7, 22.3, 14.0; MS (ES+) m/z 420.4 (M+1).
