C[O:2][C:3]([C:5]1[CH:24]=[CH:23][C:8]2[N:9]([CH:18]([CH2:21][CH3:22])[CH2:19][CH3:20])[C:10]([CH2:12][C:13]3[S:14][CH:15]=[CH:16][CH:17]=3)=[N:11][C:7]=2[CH:6]=1)=[O:4].[OH-].[Na+].Cl>CO>[CH2:19]([CH:18]([N:9]1[C:8]2[CH:23]=[CH:24][C:5]([C:3]([OH:4])=[O:2])=[CH:6][C:7]=2[N:11]=[C:10]1[CH2:12][C:13]1[S:14][CH:15]=[CH:16][CH:17]=1)[CH2:21][CH3:22])[CH3:20]To 0.69 g of 1-(1-ethyl-propyl)-2-thiophen-2-ylmethyl-1H-benzoimidazole-5-carboxylic acid methyl ester 4 ml of methanol and 4 ml of 1 M aqueous sodium hydroxide solution were added and the reaction was heated in a microwave reactor to 110° C. for 5 min. The reaction mixture was adjusted to pH 5 by the addition of 2M aqueous hydrochloric acid and was extracted with ethyl acetate three times. The combined organic phases were dried over sodium sulphate and concentrated in vacuo. After crystallization from diisopropylether 0.46 g (96%) of 1-(1-ethyl-propyl)-2-thiophen-2-ylmethyl-1H-benzoimidazole-5-carboxylic acid were obtained.
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