2-n-Propyl-5-(2-aminoethyl)-3-[2'-(1-trityl-1H-tetrazol-5-yl)biphenyl-4-yl]methylimidazole (1.01g) is dissolved in tetrahydrofuran (10 ml), and thereto is added ethyl glyoxylate hydrate (195 mg), and the mixture is stirred at room temperature overnight. The mixture is heated at 50° C. for 30 minutes, and after cooling, 7% hydrochloric acid-methanol solution (3 ml) and chloroform (10 ml) are added to the mixture, which is refluxed for 20 minutes. The mixture is evaporated under reduced pressure to remove the solvent, and the resulting residue is dissolved in chloroform (30 ml). To the mixture are added acetic anhydride (290 mg) and a solution of sodium hydrogen carbonate (1.2 g) in water (20 ml), and the mixture is stirred at room temperature overnight. The mixture is acidified with citric acid, and extracted with chloroform. The extract is washed with water, dried, and evaporated. To the residue are added fumaric acid (100 mg) and ethanol (35 ml), and the mixture is refluxed for 5 hours. Then, the reaction mixture is evaporated under reduced pressure, and the residue is recrystallized from methanol/ether to give ethyl 2-n-propyl-5-acetyl-3-[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl-4,5,6,7-tetrahydroimidazo[4,5-c]pyridine-4-carboxylate 1/2 fumarate (728 mg).
