L-proline benzyl ester hydrochloride (0.745 mmoles, 180 mg) and diisopropylethyl amine (0.745 mmoles, 0.13 ml) were dissolved in 50 ml DMF. The solution was stirred at room temperature for 20 minutes. 1-Hydroxybenzotriazole (0.745 mmoles, 100 mg), 2-[5-[2-(2H-tetrazol-5-yl)phenyl]benzimidazol-1-yl]octanoic acid (0.745 mmoles, 300 mg) and dicyclohexylcarbodiimide (0.745 mmoles, 153 mg) were added sequentially. The reaction was stirred at room temperature for 12 days and poured into water. Ethyl acetate was added, washed with brine, dried over sodium sulfate, concentrated and purified by chromatography over silica gel eluted with ethyl acetate. The reaction yielded 250 mg of benzyl 1-[1-oxo-2-[5-[2-(2H-tetrazol-5-yl)phenyl]-1H-benzimidazole-1-yl]octyl]-L-proline benzyl ester. (MS)
