Trifluoroacetic acid 3.0 mL solution of tert-butyl 2-(4-fluoroanilino)-4-(isoquinolin-4-yl)benzoate 110 mg was stirred at room temperature for 1 hour. Water and ethyl acetate were added to the reaction mixture, and it was adjusted to pH6.0 with 1.0 mol/L sodium hydroxide aqueous solution. The organic layer was separated and collected,dried over anhydrous magnesium sulfate after washing with saturated sodium chloride aqueous solution, and the solvent was removed under reduced pressure. Hexane and diisopropyl ether were added to the obtained residue, and solid matter was filtrated to give 2-(4-fluoroanilino)-4-(isoquinolin-4-yl)benzoic acid 50 mg of pale green solid.
