Sodium Hydroxide → 3-({[4-({Cyclohexyl[2-ethyl-5-(1-hydroxy-2-methylpropyl)thiophen-3-yl]methyl}amino)phenyl]carbonyl}amino)propanoic acid

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To a mixture of 4-({cyclohexyl[2-ethyl-5-(1-hydroxy-2-methylpropyl)thiophen-3-yl]methyl}amino)benzoic acid (150 mg) synthesized above, ethyl β-alaninate hydrochloride (83.3 mg), 1-hydroxybenzotriazole monohydrate (83.0 mg) and triethylamine (76 μL) in N,N-dimethylformamide (10 mL) was added 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (104 mg), and the mixture was stirred at room temperature overnight. Saturated aqueous ammonium chloride solution was added to quench the reaction, and the mixture was extracted with ethyl acetate. The extract was washed with saturated aqueous sodium hydrogen carbonate solution and saturated brine, dried over magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (50% ethyl acetate/hexane) to give colorless oil. To a mixture of the obtained oil, tetrahydrofuran (5 mL) and ethanol (5 mL) was added 1N aqueous sodium hydroxide solution (1 mL), and the mixture was stirred at room temperature for 2.5 hr, and concentrated under reduced pressure. The residue was dissolved in water (10 mL), and 1N hydrochloric acid (1 mL) was added at 0° C. The resulting precipitate was collected by filtration to give the title compound (135 mg, 77%) as a white solid. The obtained resultant product was a mixture of two diastereomers.

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