Reaction Steps
Following the procedure as described in EXAMPLE 9 and making non-critical variations using 5,6-dihydrospiro[benzo[1,2-b:5,4-b′]difuran-3,3′-indol]-2′(1′H)-one to replace 3-methylspiro[furo[3,2-f][1,2]benzisoxazole-5,3′-indol]-2′(1H)-one, and (S)-(5-oxopyrrolidin-2-yl)methyl 4-methylbenzenesulfonate to replace 2-(bromomethyl)-5-(trifluoromethyl)furan, 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 was obtained (47%) as a colorless solid: mp 133-136° C.; 1H NMR (300 MHz, CDCl3) δ7.35-7.27 (m, 1H), 7.24-7.14 (m, 1H), 7.14-7.03 (m, 1H), 7.00-6.85 (m, 1H), 6.54-6.42 (m, 1H), 6.42-6.37 (m, 1H), 4.93 (t, J=9.3 Hz, 1H), 4.67 (dd, J=9.3, 3.0 Hz, 1H), 4.53 (t, J=8.5 Hz, 2H), 4.18-4.04 (m, 1H), 3.93 (dt, J=13.9, 4.6 Hz, 1H), 3.72 (dt, J=13.9, 4.6 Hz, 1H), 3.07-2.80 (m, 3H), 2.42-2.15 (m, 3H), 2.06-1.81 (m, 1H); 13C NMR (75 MHz, CDCl3) δ178.6, 178.5, 161.8 (2C), 161.3, 161.2, 142.2, 142.1, 132.6, 132.5, 129.0 (2C), 128.9, 128.8, 124.1, 123.6, 119.9 (3C), 119.7, 118.8, 108.3, 93.2, 93.1, 80.6, 80.5, 72.3, 57.5, 53.2, 53.1, 45.2 (2C), 29.6, 29.6, 28.9, 24.7 (2C); MS (ES+) m/z 377.1 (M+1).
