[OH-].[Na+].[O:3]1[C:7]2[CH:8]=[CH:9][CH:10]=[CH:11][C:6]=2[C:5]([CH2:12][C:13]([N:15]2[CH2:20][CH2:19][CH:18]([C:21]([O:23]CC)=[O:22])[CH2:17][CH2:16]2)=[O:14])=[CH:4]1>C(O)C>[O:3]1[C:7]2[CH:8]=[CH:9][CH:10]=[CH:11][C:6]=2[C:5]([CH2:12][C:13]([N:15]2[CH2:20][CH2:19][CH:18]([C:21]([OH:23])=[O:22])[CH2:17][CH2:16]2)=[O:14])=[CH:4]1200 ml of 1N sodium hydroxide solution are added to a solution of 42.1 g of the product obtained in Step A in 200 ml of ethanol. After 8 hours' stirring at room temperature, the ethanol is removed by evaporation, the mixture is washed with ether, and the aqueous phase is rendered acidic with 1N hydrochloric acid. After extraction with dichloromethane, decanting and drying, concentration under reduced pressure enables the expected product to be isolated.
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