[F:1][C:2]1[CH:7]=[CH:6][C:5]([C:8]([C:18]2[CH:23]=[CH:22][C:21]([CH:24]=[CH:25][C:26]([O:28]C)=[O:27])=[CH:20][CH:19]=2)=[C:9]([C:12]2[CH:17]=[CH:16][CH:15]=[CH:14][CH:13]=2)[CH2:10][CH3:11])=[CH:4][CH:3]=1.[OH-].[K+]>CO.C1COCC1>[F:1][C:2]1[CH:7]=[CH:6][C:5]([C:8]([C:18]2[CH:19]=[CH:20][C:21]([CH:24]=[CH:25][C:26]([OH:28])=[O:27])=[CH:22][CH:23]=2)=[C:9]([C:12]2[CH:17]=[CH:16][CH:15]=[CH:14][CH:13]=2)[CH2:10][CH3:11])=[CH:4][CH:3]=1To a solution of ester (5) (300 mg, 0.78 mmol) in methanol (25 mL) and THF (8 mL) was added 1N KOH (12 mL, 12 mmol). After stirring overnight the solvent was partially removed under reduced pressure, the mixture was acidified with 1N HCl, and was extracted with EtOAc. The combined organic layers were washed with brine and were dried (MgSO4). The solvent was removed under reduced pressure and the residue was chromatographed (silica gel, 5% methanol/CH2Cl2) to give the acid (6) as a white solid (270 mg, 93%): 1 H NMR (CDCl3) δ 7.60 (d, J=15.8 Hz, 1 H), 7.13 (m, 11 H), 6.87 (d, J=8.5 Hz, 2 H), 6.28 (d, J=15.8 Hz, 1 H), 2.47 (q, J=7.3 Hz, 2 H), 0.93 (t, J=7.3 Hz, 3 H); APcI m/z: 414 (M+H+CH3CN+, 100%).
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