Sodium Hydroxide → {4-Chloro-2-[(2,4-dichlorophenyl)amino]-7-(1-ethylpropyl)-1H-benzimidazol-1-yl}acetic acid

To a solution of isopropyl {4-chloro-2-[(2,4-dichlorophenyl)amino]-7-(1-ethylpropyl)-1H-benzimidazol-1-yl}acetate (521 mg, 1.08 mmol) in methanol (4 mL) was added 8N aqueous sodium hydroxide (1 mL) at 0° C., and the mixture was stirred at the same temperature for 4 hours. Methanol was evaporated in vacuo, and the aqueous residue was adjusted to pH 4. Ethyl acetate was added to the mixture, followed by stirring at 0° C. for 1 hour. The resulting solid was collected by filtration and washed with water to give the title compound (330 mg, 0.749 mmol, 69%) as a colorless solid.