Reaction Steps
A solution of 5-[(2′-oxo-2,3-dihydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indol]-1′(2′H)-yl)methyl]furan-2-carboxylic acid (0.42 g, 1.00 mmol), dimethylamine hydrochloride (0.17 g, 2.04 mmol), N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (0.26 g, 1.35 mmol), 1-hydroxybenzotriazole hydrate (0.21 g, 1.54 mmol) and 4-methylmorpholine (0.30 mL, 2.7 mmol) in N,N-dimethylformamide (10 mL) was stirred at ambient temperature for 16 h. The solvent was removed under reduced pressure, the residue was taken up into ethyl acetate (75 mL) and washed sequentially with 1 M hydrochloric acid (2×50 mL), water (50 mL) and brine (50 mL). The organic phase was further diluted with dichloromethane until all the material was in solution, then was dried over sodium sulfate, filtered and concentrated under reduced pressure. Purification by flash column chromatography with dichloromethane/methanol (29:1) afforded N,N-dimethyl-5-[(2′-oxo-2,3-dihydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indol]-1′(2′H)-yl)methyl]furan-2-carboxamide (0.34 g, 77%) as a colorless solid: mp 224-226° C. (diethyl ether/hexanes); 1H NMR (300 MHz, DMSO-d6) δ7.32 (dd, J=7.5, 7.5 Hz, 1H), 7.22-7.14 (m, 2H), 7.05 (dd, J=7.8, 7.5 Hz, 1H), 6.96 (m, 1H), 6.62 (m, 1H), 6.51 (s, 1H), 6.06 (s, 1H), 5.06 (d, J=16.4 Hz, 1H), 4.97 (d, J=16.4 Hz, 1H), 4.76 (d, J=9.3 Hz, 1H), 4.66 (d, J=9.3 Hz, 1H), 4.22-4.14 (m, 2H), 4.14-4.06 (m, 2H), 3.05 (br s, 3H), 2.94 (br s, 3H); 13C NMR (75 MHz, DMSO-d6) δ176.4, 158.9, 154.6, 150.8, 147.2, 144.2, 141.8, 137.8, 131.6, 128.8, 123.6, 123.3, 121.2, 116.5, 111.0, 109.9, 109.4, 98.8, 79.3, 64.2, 63.6, 57.2, 37.7, 36.7, 35.8; MS (ES+) m/z 446.9 (M+1).
