Reaction Steps
To a stirred solution of 1′-{[(2S)-5-oxopyrrolidin-2-yl]methyl}-5,6-dihydrospiro[benzo[1,2-b:5,4-b′]difuran-3,3′-indol]-2′(1′H)-one (0.235 g, 0.623 mmol) in dry N,N-dimethylformamide (10 mL) was added sodium hydride (60% in mineral oil, 0.04 g, 1.04 mmol) at ambient temperature. The mixture was stirred for 15 min, and iodomethane (0.28 g, 2.0 mmol) was added in one portion. The reaction mixture was stirred at ambient temperature for 1 h, and concentrated to dryness. The residue was purified by flash chromatography (hexanes/ethyl acetate; gradient 0% to 30%) to afford 1′-{[(2S)-1-methyl-5-oxopyrrolidin-2-yl]methyl}-5,6-dihydrospiro[benzo[1,2-b:5,4-b′]difuran-3,3′-indol]-2′(1H)-one (0.15 g, 62%) as colorless solid: mp 72-76° C.; 1H NMR (300 MHz, CDCl3) δ7.33 (dd, J=7.5, 7.5 Hz, 1H), 7.20 (d, J=7.5 Hz, 1H), 7.09 (dd, J=7.5, 7.5 Hz, 1H), 6.91 (d, J=7.5 Hz, 1H), 6.46-6.38 (m, 2H), 4.77 (ABq, 2H), 4.53 (t, J=8.6 Hz, 2H), 4.03-3.75 (m, 3H), 3.11-2.83 (m, 5H), 2.61-2.42 (m, 1H), 2.42-2.27 (m, 1H), 2.26-2.07 (m, 1H), 2.03-1.84 (m, 1H); 13C NMR (75 MHz, CDCl3) δ178.4, 178.4, 175.1, 175.0, 161.8, 161.3, 161.2, 142.1, 141.9, 132.5, 132.4, 128.9 (2C), 124.3, 124.2, 123.7 (2C), 120.0, 119.9, 119.7, 119.6, 118.6, 118.5, 108.0, 93.2, 80.5, 72.3, 58.1, 58.0, 57.5 (2C), 43.0, 42.9, 29.3, 29.2, 28.9, 28.7 (2C), 22.6 (2C); MS (ES+) m/z 391.1 (M+1).
