4-[3-[1(S)-(4-Chlorophenyl)ethyl]1-(4-cyclohexylphenyl)ureidomethyl]benzoic acid (1.0 g, 2.04 mmol) was dissolved in DMF (8 ml) and HOBt (410 mg, 3.05 mmol), and EDAC (580 mg, 3.05 mmol) were added. The solution was stirred at room temperature for 30 min. A solution of 3-aminopropionic acid methyl ester hydrochloride (310 mg, 3.05 mmol) and N,N-diisopropylethylamine (530 μl, 3 mmol) in DMF (2 ml) was added, and the reaction mixture was stirred at ambient temperature over night. The reaction mixture was partitioned between ethyl acetate (70 ml) and water (3×50 ml). The organic phase was dried with anhydrous sodium sulfate and evaporated to dryness to afford 1.17 g (99%) of 3-{4-[3-[1(S)-(4-chloro-phenyl)ethyl]1-(4-cyclohexylphenyl)ureidomethyl]benzoylamino}propionic acid methyl ester. HPLC-MS (method A): m/z=576 (M+1); Rt=5.47 min.
