[OH-].[Na+].[Cl:3][C:4]1[CH:25]=[C:24]([Cl:26])[CH:23]=[CH:22][C:5]=1[CH2:6][N:7]1[C:11]2[CH:12]=[C:13]([C:16]([O:18]CC)=[O:17])[CH:14]=[CH:15][C:10]=2[N:9]=[C:8]1[CH3:21].Cl>C(O)C>[C:16]([C:13]1[CH:14]=[CH:15][C:10]2[N:9]=[C:8]([CH3:21])[N:7]([CH2:6][C:5]3[CH:22]=[CH:23][C:24]([Cl:26])=[CH:25][C:4]=3[Cl:3])[C:11]=2[CH:12]=1)([OH:18])=[O:17]10% sodium hydroxide aqueous solution (3.10 g) and ethanol (10 ml) are added to 1-(2,4-dichlorobenzyl)-6-ethoxycarbonyl-2-methylbenzimidazole (0.94 g) (example 70), and the solution is refluxed by heating for 1 hour. Its acidity is adjusted to pH 6 with 10% hydrochloric acid. The precipitated crystals are separated through filtration, dried, and thus, 6-carboxy-1-(2,4-dichlorobenzyl)-2-methylbenzimidazole (0.68 g) is obtained. 1H-NMR (DMSO-d6, δ): 2.52 (3H, s), 5.61 (2H, s), 6.54 (1H, d, J=8.4 Hz), 7.33 (1H, dd, J=8.4 and 2.1 Hz), 7.64 (1H, d, J=8.4 Hz), 7.74 (1H, d, J=2.1 Hz), 7.81 (1H, dd, J=8.4 and 1.5 Hz), 7.98 (1H, s), 12.72 (1H, s).
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