ClCCl.C[O:5][C:6]1[C:15]2[C:10](=[C:11]([CH2:16][CH3:17])[CH:12]=[CH:13][CH:14]=2)[CH:9]=[CH:8][CH:7]=1.B(Br)(Br)Br>O>[CH2:16]([C:11]1[CH:12]=[CH:13][CH:14]=[C:15]2[C:10]=1[CH:9]=[CH:8][CH:7]=[C:6]2[OH:5])[CH3:17]Anhydrous dichloromethane (20 mL) was added to 8 (870 mg, 4.6 mmol). After cooling to 0° C., BBr3 (boron tribromide 1.0M in dichloromethane) (14 mL, 14 mmol) was added dropwise. The reaction mixture was heated to reflux for 5 h. After cooling, a large amount of water was slowly added and the mixture was extracted three times with dichloromethane. The organic layer was evaporated and the residue was purified on MPLC to afford compound 9c, 75% yield; MS-ESI− (m/z, %): 171 (M+−1, 100), 172 (M+, 45); 1H NMR δ 1.37 (3H, t, J=7.8 Hz, CH3CH2—), 3.10 (2H, q, J=7.8 Hz, CH3CH2—), 5.19 (1H, s, OH), 6.82 (1H, d, J=7.8 Hz, H-2), 7.31-7.45 (3H, m, H-3, 6, 7), 7.65 (1H, d, J=8.7 Hz, H-4), 8.06 (1H, d, J=8.1 Hz, H-8).
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