Reaction Steps
To the solution of 2-amino-1-(4-bromo-phenyl)-ethanone (HCl salt, 1.0 g, 4 mmol) and 2-aza-bicyclo[2.2.1]heptane-2,3-dicarboxylic acid 2-tert-butyl ester (0.98 g, 4 mmol) in DMF (13 ml) was added HATU (1.64 g, 4.3 mmol), followed by slow addition of diisopropylethylamine (2.2 ml, 12.7 mmol). The mixture was stirred for 4 hours and was diluted with EtOAc. The organic phase was washed with 1 N NaOH solution, water, and brine, and was dried with sodium sulfate. Concentration and purification by flash column chromatography (hexane/EtOAc) gave 342-(4-bromo-phenyl)-2-oxo-ethylcarbamoyl]-2-aza-bicyclo[2.2.1]heptane-2-carboxylic acid tert-butyl ester (1.7 g). m/z: 460.9 (M+Na)+. 3-[5-(4-Bromo-phenyl)-1H-imidazol-2-yl]-2-aza-bicyclo[2.2.1]heptane-2-carboxylic acid tert-butyl ester: The mixture of 342-(4-bromo-phenyl)-2-oxo-ethylcarbamoyl]-2-aza-bicyclo[2.2.1]heptane-2-carboxylic acid tert-butyl ester (1.7 g, 4 mmol), acetic acid (24 μl ), and ammonium acetate (1.54 g, 20 mmol) in xylene (20 ml) was heated at 140° C. for 20 hours. The mixture was quenched with saturated sodium carbonate solution, and extracted with EtOAc. The organic phase was washed with water and brine, and was dried with sodium sulfate. Concentration and purification by flash column chromatography (hexanes/EtOAc) gave 3-[5-(4-bromo-phenyl)-1H-imidazol-2-yl]-2-aza-bicyclo[2.2.1]heptane-2-carboxylic acid tert-butyl ester (1.21 g). m/z: 417.9 (M+H)+. 3-{5-[4-(4,4,5,5-Tetramethyl-[1,3,2]dioxaborolan-2-yl)-phenyl]-1H-imidazol-2-yl}-2-aza-bicyclo[2.2.1]heptane-2-carboxylic acid tert-butyl ester: To the solution of 345-(4-Bromo-phenyl)-1H-imidazol-2-yl]-2-aza-bicyclo[2.2.1]heptane-2-carboxylic acid tert-butyl ester (667 mg, 1.6 mmol) and bis(pinacolato)diboron (813 mg, 3.2 mmol) in 1,4-dioxane (12.5 ml) was added potassium acetate (401 mg, 4.1 mmol), followed by Pd(PPh3)4 (78 mg). The mixture was heated at 80° C. for 12 hours. The mixture was diluted with EtOAc, and was washed with water and brine, and was dried with sodium sulfate. Concentration and purification by flash column chromatography (hexanes/EtOAc) gave 3-{5-[4-(4,4,5,5-Tetramethyl-[1,3,2]dioxaborolan-2-yl)-phenyl]-1H-imidazol-2-yl}-2-aza-bicyclo[2.2.1]heptane-2-carboxylic acid tert-butyl ester (560 mg). m/z: 466.1 (M+H)+. 4,4′-Bis-[2-(2-tert-butoxycarbonyl-2-aza-bicyclo[2.2.1]hept-3-yl)-3H-imidazol-4-yl]-biphenyl: To the solution of 3-{5-[4-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-phenyl]-1H-imidazol-2-yl}-2-aza-bicyclo[2.2.1]heptane-2-carboxylic acid tert-butyl ester (560 mg, 1.22 mmol) and 3-[5-(4-bromo-phenyl)-1H-imidazol-2-yl]-2-aza-bicyclo[2.2.1]heptane-2-carboxylic acid tert-butyl ester (535 mg, 1.28 mmol) in 1,2-dimethoxyether (11 ml) and water (3.5 ml) was added sodium bicarbonate (343 mg, 4 mmol), followed by Pd(PPh3)4 (55 mg). The mixture was heated at 80° C. for 7 hours. The mixture was diluted with EtOAc, and was washed with water and brine, and was dried with sodium sulfate. Concentration and purification by flash column chromatography (DCM/MeOH) gave 4,4′-bis-[2-(2-tert-butoxycarbonyl-2-aza-bicyclo[2.2.1]hept-3-yl)-3H-imidazol-4-yl]-biphenyl (50 mg). m/z: 677.2 (M+H)+. (1-{3-[5-(4′-{2-[2-(2-Methoxycarbonylamino-3-methyl-butyryl)-2-aza-bicyclo[2.2.1]hept-3-yl]-3H-imidazol-4-yl}-biphenyl-4-yl)-1H-imidazol-2-yl]-2-aza-bicyclo[2.2.1]heptane-2-carbonyl}-2-methyl-propyl)-carbamic acid methyl ester: To the solution of 4,4′-Bis42-(2-tert-butoxycarbonyl-2-aza-bicyclo[2.2.1]hept-3-yl)-3H-imidazol-4-yl]-biphenyl (50 mg, 0.07 mmol) in MeOH (2 ml) was added hydrochloric acid (0.24 ml, 1.48 mmol) The mixture was heated at 50° C. for 5 hours, and the solvent and reagent were removed under reduced pressure. The mixture was diluted with acetonitrile and water, and was freezer-dried to give brown powder. m/z: 477.2 (M+1), 239.1 (M+2)/2. To the solution of above powder (29 mg, 0.047 mmol) and MeOCO-Val-OH (20 mg, 0.0.113 mmol) in DMF (1.5 ml) was added HATU (40 mg, 0.10 mmol), followed by diisopropylethylamine (50 ml, 0.28 mmol). The mixture was stirred for 90 minutes and was diluted with EtOAc. The organic phase was washed with 1 N NaOH solution, water, and brine, and was dried with sodium sulfate. Concentration and purification by HPLC (0.1% TFA/C H3CN/0.1% TFA/H2O) gave (1-{3-[5-(4′-{2-[2-(2-Methoxycarbonylamino-3-methyl-butyryl)-2-aza-bicyclo[2.2.1]hept-3-yl]-3H-imidazol-4-yl}-biphenyl-4-yl)-1H-imidazol-2-yl]-2-aza-bicyclo[2.2.1]heptane-2-carbonyl}-2-methyl-propyl)-carbamic acid methyl ester (15 mg). m/z: 791.2 (M+1), 396.5 (M+2)/2. 1H NMR (CD3OD, 300 MHz) δ 7.92-7.82 (10H, m), 4.82 (2H, m), 4.32 (2H, m), 4.05 (2H, m), 3.65 (6H, m), 2.85 (2 H, m), 2.3-1.6 (14H, m), 1.05-0.85 (12H, m).
