In a mixture of 14 ml of methanol and 14 ml of dioxane was dissolved 1.8 g of methyl 4-(1-benzyloxycarbonylaminocyclopropyl)-2,3,5,6-tetrafluorobenzoate. To the resulting solution was added 14 ml of a 1N aqueous sodium hydroxide solution. The resulting mixture was stirred at room temperature for 1 hour. To the reaction mixture was added 50 ml of water. The resulting mixture was adjusted to pH 1 with 2N hydrochloric acid, and 50 ml of ethyl acetate was added thereto. The organic layer was separated, washed with water and a saturated aqueous sodium chloride solution in this order, and dried over anhydrous magnesium sulfate. The solvent was removed by distillation under reduced pressure, and n-hexane was added to the residue obtained. The resulting crystals were collected by filtration to obtain 1.7 g (yield: 97.7%) of 4-(1-benzyloxycarbonylaminocyclopropyl)-2,3,5,6tetrafluorobenzoic acid.
