Reaction Steps
Following the procedure as described in EXAMPLE 15 and making non-critical variations using ethyl {4-[(2′-oxo-5,6-dihydrospiro[benzo[1,2-b:5,4-b′]difuran-3,3′-indol]-1′(2′H)-yl)methyl]phenoxy}acetate to replace ethyl {3-[(2′-oxo-5,6-dihydrospiro[benzo[1,2-b:5,4-b′]difuran-3,3′-indol]-1′(2′H)-yl)methyl]phenoxy}acetate, {4-[(2′-oxo-5,6-dihydrospiro[benzo[1,2-b:5,4-b′]difuran-3,3′-indol]-1′(2′H)-yl)methyl]phenoxy}acetic acid was obtained (88%) as a colorless solid: mp 265-266° C.; 1H NMR (300 MHz, DMSO-d6) δ 12.99 (s, 1H), 7.33-7.21 (m, 3H), 7.19-7.14 (m, 1H), 7.05-6.98 (m, 2H), 6.93-6.86 (m, 2H), 6.43 (s, 1H), 6.41 (s, 1H), 4.86 (q, J=15.5 Hz, 2H), 4.79 (ABq, J=38.0, 9.3 Hz, 2H), 4.65 (s, 2H), 4.55-4.46 (m, 2H), 3.04-2.90 (m, 2H); 13C NMR (75 MHz, DMSO-d6) δ 177.0, 170.1, 161.1, 160.6, 157.0, 142.1, 132.1, 128.7, 128.5, 123.6, 122.9, 120.4, 119.8, 118.8, 114.6, 109.4, 92.4, 79.8, 72.0, 64.3, 56.9, 42.4, 28.3; MS (ES+) m/z 443.8 (M+1).
