[CH3:1][C:2]1[C:3]([C:16]([C:18]2[CH:27]=[CH:26][C:21]([C:22]([O:24]C)=[O:23])=[CH:20][CH:19]=2)=[CH2:17])=[CH:4][C:5]2[C:6]([CH3:15])([CH3:14])[CH2:7][CH2:8][C:9]([CH3:13])([CH3:12])[C:10]=2[CH:11]=1.[OH-].[K+].Cl>CO>[CH3:1][C:2]1[C:3]([C:16]([C:18]2[CH:27]=[CH:26][C:21]([C:22]([OH:24])=[O:23])=[CH:20][CH:19]=2)=[CH2:17])=[CH:4][C:5]2[C:6]([CH3:15])([CH3:14])[CH2:7][CH2:8][C:9]([CH3:12])([CH3:13])[C:10]=2[CH:11]=1To a suspension of the ester 32 (0.058 g, 0.16 mmol) in 75% aqueous methanol (2 mL) was added one pellet of potassium hydroxide (0.1 g). The mixture was stirred at 70° C. for 1 h during which time the material dissolved. The solution was cooled to room temperature, acidified with 1N aqueous hydrochloric acid, and then extracted with 80% ethyl acetate/hexane. The combined organic layers were dried over anhydrous MgSO4, filtered, and concentrated to afford a white solid. Recrystallization from dichloromethane/hexane afforded the desired acid 33 as a white, crystalline solid (42 mg, 91%): m.p. 230°-231° C. The structure of the product was also confirmed using IR, 1H NMR and mass spectroscopy.
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