Reaction Steps
2-(4-Bromo-phenyl)-6-methoxy-benzo[b]thiophene was reported in the literature (Journal of Medicinal Chemistry, 2007, 50, 2682-2692). 2-(4-Bromo-phenyl)-benzo[b]thiophen-6-ol. To a stirred solution of 2-(4-bromo-phenyl)-6-methoxy-benzo[b]thiophene (80 mg, 0.25 mmol) was added BBr3 (0.5 mL of 1 M in DCM, 0.5 mmol) at 0° C. The mixture was stirred for 3 hours at ambient temperature. DCM was removed under vacuum, and the residue was dissolved in ethyl acetate (30 mL). The organic layer was washed with NaHCO3 solution, water and brine, dried over Na2SO4, filtered and concentrated in vacuo. The obtained residue was treated with hexane to give the product (67 mg, 88%). m/z 303.0, 305.0 (M−H)−. Trifluoro-methanesulfonic acid 2-(4-bromo-phenyl)-benzo[b]thiophen-6-yl ester. Tf2O was added slowly to a mixture of 2-(4-bromo-phenyl)-benzo[b]thiophen-6-ol (200 mg, 0.66 mol) in pyridine (3 mL) at 0° C. with stirring. The mixture was stirred at ambient temperature for 16 hours before quenched with NaHCO3 solution. The mixture was extracted with ethyl acetate (50 mL). The organic layer was washed with water and brine, dried over Na2SO4, filtered and concentrated in vacuo. The obtained residue was used for next step reaction without further purification. Pyrrolidine-1,2-dicarboxylic acid 1-tert-butyl ester 2-[2-(2-{4-[2-(1-Boc-pyrrolidine-2-carbonyloxy)-acetyl]-phenyl}-benzo[b]thiophen-6-yl)-2-oxo-ethyl]ester. Pd(Ph3)4 (43 mg, 0.037 mmol), PdCl2(Ph3)2 (26 mg, 0.037 mmol) and LiCl (78 mg, 1.8 mmol) were added to a mixture trifluoro-methanesulfonic acid 2-(4-bromo-phenyl)-benzo[b]thiophen-6-yl ester (200 mg, 0.46 mmol) and tributyl(1-ethoxyvinyl)tin (0.37 mL, 1.1 mmol) in 8 mL DMF. The reaction mixture was flushed with nitrogen, heated at 80° C. for 16 hours, then cooled to ambient temperature. Water (3 mL) and NBS (180 mg, 1.0 mmol) were added and the mixture was stirred at room temperature for 40 min, then diluted with ethyl acetate (300 mL). The ethyl acetate layer was washed with water and brine, dried over Na2SO4, filtered and concentrated in vacuo. The obtained residue was suspended in acetonitrile (30 mL). To it was added a solution of pyrrolidine-1,2-dicarboxylic acid 1-tert-butyl ester (792 mg, 3.7 mmol) and DIPEA (0.56 mL, 3.2 mmol) in 5 mL acetonitrile. The mixture was stirred at room temperature for 16 hours, diluted with ethyl acetate (100 mL). The organic layer was washed with NaHCO3 solution and water, dried over Na2SO4, filtered and concentrated in vacuo. The obtained residue was purified by flash chromatography to provide the desired product (90 mg, 27% over two steps). m/z 743.2 (M+Na)+. 2-[5-(2-{4-[2-(1-Boc-pyrrolidin-2-yl)-3H-imidazol-4-yl]-phenyl}-benzo[b]thiophen-6-yl)-1H-imidazol-2-yl]-pyrrolidine-1-carboxylic acid tert-butyl ester. A mixture of pyrrolidine-1,2-dicarboxylic acid 1-tert-butyl ester 2-[2-(2-{4-[2-(1-Boc-pyrrolidine-2-carbonyloxy)-acetyl]-phenyl}-benzo[b]thiophen-6-yl)-2-oxo-ethyl]ester (90 mg, 0.12 mmol) and ammonium acetate (192 mg, 2.5 mmol) in xylene (10 mL) was heated in a sealed tube at 140° C. for 1.5 hours under microwave condition. The volatile component was removed in vacuo, and the residue was dissolved in ethyl acetate (100 mL), washed with NaHCO3 solution, water and brine, dried over Na2SO4, filtered and concentrated in vacuo. The obtained residue was purified by flash chromatography to provide the desired product (60 mg, 70%). m/z 681.2 (M+H)+. [1-(2-{5-[2-(4-{2-[1-(2-Methoxycarbonylamino-3-methyl-butyryl)-pyrrolidin-2-yl]-3H-imidazol-4-yl}-phenyl)-benzo[b]thiophen-6-yl]-1H-imidazol-2-yl}-pyrrolidine-1-carbonyl)-2-methyl-propyl]-carbamic acid methyl ester. To a solution of 2-[5-(2-{4-[2-(1-Boc-pyrrolidin-2-yl)-3H-imidazol-4-yl]-phenyl}-benzo[b]thiophen-6-yl)-1H-imidazol-2-yl]-pyrrolidine-1-carboxylic acid tert-butyl ester (60 mg, 0.09 mmol) in methanol (3 mL) was added 4N HCl in 1,4-dioxane (0.4 mL, excess). The mixture was stirred for 2 hours at 50° C. and concentated under reduced pressure. The residue was dissolved in wather and freezing-dired overnight. The obtained white solid was dissoved in DMF (3 mL), to the solution was added 2-methoxycarbonylamino-3-methyl-butyric acid (34 mg, 0.19 mmol), HATU (84 mg, 0.22 mmol) and N,N-diisopropylethylamine (0.12 mL, 0.70 mmol). The mixture was stirred at ambient for 2 hours, and then the volatile component was removed in vacuo. The residue was dissolved in ethyl acetate (100 mL), washed with 1 N NaOH solution, water and brine, dried over Na2SO4, filtered and concentrated in vacuo. The obtained residue was purified by HPLC to provide the desired product as a TFA salt (45 mg, 64%). 1H-NMR (300 MHz, CD3OD) δ 8.26 (s, 1H), 8.00-7.70 (m, 9H), 5.30-5.20 (m, 2H), 4.23 (d, 2H), 4.18-4.10 (m, 2H), 3.95-3.80 (m, 2H), 3.75-3.60 (m, 6H), 2.65-2.50 (m, 2H), 2.35-2.00 (m, 8H), 1.00-0.80 (m, 12H); m/z 795.3 (M+H)+.
