A 2.0 mol/L aqueous solution of sodium hydroxide (0.11 mL) was added to a 2-propanol (1.0 mL) suspension of the obtained methyl 2-(5-(2-(azetidin-1-yl)ethoxy)-2-hydroxybenzamido)-4-phenylbenzoate (0.032 g), followed by stirring at 50° C. for 1 hour. 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. Ethyl acetate (1.5 mL) and a 4.0 mol/L hydrogen chloride-dioxane solution (0.10 mL) were added to the obtained solid substance, followed by stirring at room temperature for 1 hour and 30 minutes. The solid substance was collected from the reaction mixture by filtration to obtain 0.021 g of 2-(5-(2-(azetidin-1-yl)ethoxy)-2-hydroxybenzamido)-4-phenylbenzoic acid hydrochloride as a light yellow solid.
