[O:1]=[C:2]1[N:6]([CH2:7][CH2:8][O:9][C:10]2[CH:27]=[CH:26][C:13]([CH2:14][CH:15]([C:21]([O:23]CC)=[O:22])[C:16]([O:18]CC)=[O:17])=[CH:12][CH:11]=2)[C:5]2[CH:28]=[CH:29][CH:30]=[CH:31][C:4]=2[O:3]1.[OH-].[Na+]>O1CCCC1>[O:1]=[C:2]1[N:6]([CH2:7][CH2:8][O:9][C:10]2[CH:11]=[CH:12][C:13]([CH2:14][CH:15]([C:16]([OH:18])=[O:17])[C:21]([OH:23])=[O:22])=[CH:26][CH:27]=2)[C:5]2[CH:28]=[CH:29][CH:30]=[CH:31][C:4]=2[O:3]1Dissolve the compound obtained in Example 2 (1.5 g) in tetrahydrofuran (20 ml). Add 2N sodium hydroxide (8 ml) to the reaction mixture, cooled to 0° C. using an ice bath. Stir magnetically at ambient temperature for 72 hours. Remove the tetrahydrofuran by evaporation under reduced pressure. Take up the resulting residue in a 6N hydrochloric acid solution to pH 1 and extract twice with 50 ml of ether each time. Dry the organic phase over magnesium sulphate and remove the ether by evaporation under reduced pressure. Crystallise the resulting oil from isopropyl ether and recrystallise the resulting precipitate from cyclohexane.
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