To a mixture of ethyl 3-{[(4-{[2-ethyl-1-(5-methoxy-3-methyl-1-benzofuran-2-yl)butyl]amino}phenyl)carbonyl](methyl)amino}propanoate (261 mg) synthesized above, tetrahydrofuran (5 mL) and ethanol (5 mL) was added 1N aqueous sodium hydroxide solution (1.00 mL), and the mixture was stirred at room temperature for 1 hr, and concentrated under reduced pressure. The residue was dissolved in water (10 mL), and 1N hydrochloric acid (1.00 mL) was added at 0° C. The resulting precipitate was collected by filtration to give the title object compound (231 mg, 94%) as a pale-brown solid.
