[Cl:1][C:2]1[CH:3]=[C:4]([CH:19]=[CH:20][C:21]=1[C:22]([O:24]C)=[O:23])[C:5]([NH:7][CH2:8][C:9]1[NH:13][C:12]2[CH:14]=[CH:15][C:16]([Cl:18])=[CH:17][C:11]=2[N:10]=1)=[O:6].[OH-].[Na+]>C(O)(C)C>[Cl:1][C:2]1[CH:3]=[C:4]([CH:19]=[CH:20][C:21]=1[C:22]([OH:24])=[O:23])[C:5]([NH:7][CH2:8][C:9]1[NH:13][C:12]2[CH:14]=[CH:15][C:16]([Cl:18])=[CH:17][C:11]=2[N:10]=1)=[O:6]2.15 g of 3-chloro-N-(5-chloro-1H-benzimidazol-2-ylmethyl)-4-methoxycarbonylbenzamide is dissolved in 50 mL of isopropanol, and 50 mL of 1 molar sodium hydroxide solution is added and the mixture is stirred for 3 hours at ambient temperature. Then it is poured into 250 mL ice water and extracted twice with ethyl acetate. The aqueous phase is adjusted to pH 4 with 1 molar hydrochloric acid and the precipitate formed is separated off by filtration. The solid is washed with a little demineralized water and dried at 40° C. Then the solid obtained is treated with 150 mL of solvent mixture comprising petroleum ether/diethyl ether/ethyl acetate and dried again. Yield: quantitative; C16H11Cl2N3O3 (364.19); mass spectrum: (M+H)+=364/66/68 (chlorine isotope).
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