C[O:2][C:3]([C:5]1[CH:15]=[N:14][C:8]2[S:9][CH2:10][C:11](=[O:13])[NH:12][C:7]=2[CH:6]=1)=[O:4].[OH-].[Na+]>O1CCCC1>[O:13]=[C:11]1[CH2:10][S:9][C:8]2[N:14]=[CH:15][C:5]([C:3]([OH:4])=[O:2])=[CH:6][C:7]=2[NH:12]1A solution of the ester (b) (2.8 g) in tetrahydrofuran (50 ml) was treated with 1M sodium hydroxide (30 ml). After 2 hours the mixture was concentrated to near dryness and acidified with 2M hydrochloric acid. Filtration and washing with water afforded a solid (2.5 g).
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