To a solution of methyl 3-(4-{acetyl[(2′,6′-dimethylbiphenyl-3-yl)methyl]amino}phenyl)propanoate (0.644 g, 1.55 mmol) in a mixture of methanol (8 mL) and tetrahydrofuran (8 mL) was added 2 M aqueous sodium hydroxide solution (2.5 mL), and the mixture was stirred at room temperature for 18 hr. Water was added to the reaction mixture, and the mixture was weakly acidified with 10% aqueous citric acid solution and extracted with ethyl acetate. The extract was washed with saturated brine, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The obtained residue was recrystallized from ethyl acetate to give the title compound (0.430 g, yield 69%) as colorless prism crystals.
