Tetrahydrofuran → 3-{[(4-{[Cyclohexyl(3-methylthieno[2,3-b]pyridin-2-yl)methyl]amino}phenyl)carbonyl]amino}propanoic acid

To a mixture of ethyl 3-[{(4-{[cyclohexyl(3-methylthieno[2,3-b]pyridin-2-yl)methyl]amino}phenyl)carbonyl]amino}propanoate (335 mg) synthesized above, tetrahydrofuran (5 mL) and ethanol (5 mL) was added 1N aqueous sodium hydroxide solution (2.00 mL), and the mixture was stirred at room temperature for 2 hr, and concentrated under reduced pressure. The residue was dissolved in water (10 mL), and 1N hydrochloric acid (2.00 mL) was added at 0° C. The resulting precipitate was collected by filtration to give the title object compound (281 mg, 89%) as a white solid.