A 2.0 mol/L aqueous solution of sodium hydroxide (0.27 mL) was added to a 2-propanol (1.5 mL) suspension of the obtained methyl 2-(2-hydroxy-5-(1-isopropylpiperidin-4-yl)benzamido)-4-phenylbenzoate (0.086 g), followed by stirring at 50° C. for 1 hour. A 2.0 mol/L aqueous solution of sodium hydroxide (0.091 mL) was added to the reaction mixture, followed by stirring at 50° C. for 30 minutes. The reaction mixture was cooled to room temperature, and water was added thereto. After adjusting the pH to 6.0 with 1.0 mol/L hydrochloric acid, the solid substance was collected by filtration to obtain 0.062 g of 2-(2-hydroxy-5-(1-isopropylpiperidin-4-yl)benzamido)-4-phenylbenzoic acid as a light yellow solid.
