To the compound (170 mg, 0.745 mmol) of Step 2, methyl 3-(bromomethyl)benzoate (256 mg, 1.12 mmol), and potassium carbonate (206 mg, 1.49 mmol), DMF (4 mL) was added, and stirred overnight. The solvent was distilled away under reduced pressure, and after diluted with ethyl acetate, the resultant was washed with the water and saturated brine, and then dried over anhydrous magnesium sulfate. The solvent was distilled away under reduced pressure. The resulting residue was purified by silica gel chromatography (hexane/ethyl acetate). To the resulting compound (267 mg, 0.709 mmol), methanol (5 mL) and THF (5 mL) were added. A 1 N lithium hydroxide aqueous solution (1.5 mL) was added thereto under ice-cooling, and stirred at room temperature overnight. After a 1N hydrochloric acid aqueous solution (2 mL) were added thereto under ice-cooling, the solid obtained by concentrating the solvent was collected by filtration to thus obtain the title compound.
