Reaction Steps
To a stirred solution of {3-[(2′-oxo-5,6-dihydrospiro[benzo[1,2-b:5,4-b′]difuran-3,3′-indol]-1′(2′H)-yl)methyl]phenoxy}acetic acid (0.22 g, 0.5 mmol) in dry chloroform (5 mL) was added at ambient temperature oxalyl chloride (0.43 mL, 5.0 mmol) followed by 1 drop of N,N-dimethylformamide. The mixture was stirred at ambient temperature for 2 h and evaporated to dryness in vacuo to afford crude {3-[(2′-oxo-5,6-dihydrospiro[benzo[1,2-b:5,4-b′]difuran-3,3′-indol]-1′(2′H)-yl)methyl]phenoxy}acetyl chloride. The crude product was dissolved in dry dichloromethane (5 mL), and used in the next step. To a solution of methylamine hydrochloride (0.07 mg, 1.0 mmol) in dry dichloromethane (5 mL) containing triethylamine (0.35 mL, 2.5 mmol) was added at 0° C. 5.0 mL (0.50 mmol) of the stock solution of {3-[(2′-oxo-5,6-dihydrospiro[benzo[1,2-b:5,4-b′]difuran-3,3′-indol]-1′(2′H)-yl)methyl]phenoxy}acetyl chloride. The mixture was stirred at ambient temperature for 16 h, diluted with dichloromethane (20 mL), washed with 7% aqueous solution of citric acid (10 mL), water (10 mL), and brine (10 mL). The organic layer was dried over anhydrous magnesium sulfate, filtered, and concentrated in vacuo. The residue was purified by column chromatography (hexanes/ethyl acetate 1:3) to afford N-methyl-2-{3-[(2′-oxo-5,6-dihydrospiro[benzo[1,2-b:5,4-b′]difuran-3,3′-indol]-1′(2′H)-yl)methyl]phenoxy}acetamide (0.09 g, 40%) as a colorless solid: mp 175-176° C.; 1H NMR (300 MHz, CDCl3) δ 7.34-7.17 (m, 3H), 7.09-6.98 (m, 2H), 6.90 (s, 1H), 6.87-6.76 (m, 2H), 6.55 (br s, 1H), 6.48 (s, 1H), 6.44 (s, 1H), 5.09-4.96 (m, 2H), 4.88-4.79 (m, 1H), 4.75-4.69 (m, 1H), 4.60-4.51 (m, 2H), 4.47 (s, 2H), 3.11-2.92 (m, 2H), 2.92-2.88 (m, 3H); 13C NMR (75 MHz, CDCl3) δ 177.9, 168.4, 161.9, 161.3, 157.6, 142.0, 137.9, 132.7, 130.3, 128.7, 123.9, 123.5, 121.0, 120.1, 120.0, 118.8, 113.9, 113.6, 109.1, 93.3, 80.6, 72.4, 67.2, 57.7, 43.9, 29.0, 25.7; MS (ES+) m/z 457.0 (M+1).
