C([O:3][C:4](=[O:21])[CH:5]=[CH:6][CH:7]=[CH:8][CH2:9][CH:10]([O:19][CH3:20])[C:11]1[CH:16]=[CH:15][C:14]([O:17][CH3:18])=[CH:13][CH:12]=1)C.[Li+].[OH-]>CO>[CH3:20][O:19][CH:10]([C:11]1[CH:16]=[CH:15][C:14]([O:17][CH3:18])=[CH:13][CH:12]=1)[CH2:9][CH:8]=[CH:7][CH:6]=[CH:5][C:4]([OH:21])=[O:3]To a stirred solution of diene ester 3 (0.36 g, 1.24 mmol) in methanol (10 mL) at rt was added aqueous LiOH 0.5 N solution (3.4 mL, 1.7 mmol). After being stirred at 40° C. for 16 h, methanol was removed under reduced pressure and the resulting aqueous solution was acidified with 3N HCl (pH=ca. 4), extracted with ethyl acetate (25×3 mL), dried (MgSO4), and concentrated under reduced pressure to give the desired carboxylic acid 4 (0.30 g, 92% yield). Without further purification, the crude product was used in the next step: 1H NMR (300 MHz, CD3OD): δ 7.23 (d, J=9.0 Hz, 2H), 7.00 (dd, J=15.3, 10.5 Hz, 1H), 6.93 (d, J=9.0 Hz, 2H), 6.17 (dd, J=15.3, 10.5 Hz, 1H), 5.93 (dd, J=15.3, 10.5 Hz, 1H), 5.85 (d, J=15.3 Hz, 1H), 4.20 (br t, J=6.6 Hz, 1H), 3.82 (s, 3 H ), 3.20 (s, 3H), 2.61 (m, 1H), 2.48 (m, 1H).
Wird geladen…
