4-Methylmorpholine → 2-(6-bromo-1H-benzimidazol-2-yl)pyrrolidine-1-carboxylic acid tert-butyl ester

Temperature

120 °C

To a mixture of 4-Bromo-benzene-1,2-diamine (5.0 g), Boc-L-proline (6.0 g), and 4-methylmorpholine (5.88 mL) in DMF (100 mL) was added HATU (10.7 g). Reaction mixture was stirred for 16 hours and then concentrated. Residue was dissolved in ethyl acetate and washed with 5% lithium chloride solution (2×), brine and dried (MgSO4), concentrated and purified by flash column chromatography (silica gel, 30 to 60% ethyl acetate/hexanes) to a dark brown foam. Brown foam was dissolved in ethanol (100 mL) and heated in a sealed tube at 110-130° C. for 2 days. Reaction mixture was cooled and concentrated. Residue was dissolved in ethyl acetate and extracted with 1N HCl (3×). Aqueous layer was basified with 50% NaOH solution to pH 10 and extracted with ethyl acetate (2×). The organic layer was dried (MgSO4), concentrated and purified by flash column chromatography (silica gel, 0 to 10% isopropanol/hexanes) to give 2-(6-Bromo-1H-benzoimidazol-2-yl)-pyrrolidine-1-carboxylic acid tert-butyl ester (6.5 g) as an off-white foam: LCMS-ESI+: calc'd for C16H21BrN3O2: 367.26 (M+H+). Found: 365.8, 367.8 (M+H+). 2-{6-[4-(4,4,5,5-Tetramethyl-[1,3,2]dioxaborolan-2-yl)-phenyl]-1H-benzoimidazol-2-yl}-pyrrolidine-1-carboxylic acid tert-butyl ester: A mixture 2-(6-Bromo-1H-benzoimidazol-2-yl)-pyrrolidine-1-carboxylic acid tert-butyl ester (0.257 g), 1,4-benzenediboronic acid, pinacol ester (1.158 g), Pd(PPh3)4 (0.041 g) and potassium carbonate (0.485 g) in H2O (2.0 mL)/dimethoxyethane (5.0 mL) was heated in microvave at 120° C. for 30 minutes. Reaction mixture was cooled and diluted with ethyl acetate, washed with brine, dried (MgSO4), concentrated and purified by flash column chromatography (silica gel, 20 to 70% ethyl acetate/hexanes) to give 2-{6-[4-(4,4,5,5-Tetramethyl-[1,3,2]dioxaborolan-2-yl)-phenyl]-1H-benzoimidazol-2-yl}-pyrrolidine-1-carboxylic acid tert-butyl ester (0.187 g): LCMS-ESI+: calc'd for C28H37BN3O4: 490.42 (M+H+). Found: 490.0 (M+H+). 2-(6-{4-[2-(1-tert-butylcarbamyl-pyrrolidin-2-yl)-3H-imidazol-4-yl]-phenyl}-1H-benzoimidazol-2-yl)-pyrrolidine-1-carboxylic acid tert-butyl ester: A mixture of 2-{6-[4-(4,4,5,5-Tetramethyl-[1,3,2]dioxaborolan-2-yl)-phenyl]-1H-benzoimidazol-2-yl}-pyrrolidine-1-carboxylic acid tert-butyl ester (0.116 g), 2-(5-Bromo-1H-imidazol-2-yl)-pyrrolidine-1-carboxylic acid tert-butyl ester (0.112 g, prepared according to WO2008021927 A2) and Pd(PPh3)4 (0.014 g) in 2.0M potassium carbonate solution (0.35 mL) and dimethoxyethane (1.0 mL) was heated at 90° C. for 6 hours. Additional Pd(PPh3)4 (0.014 g) was added and reaction continued for 12 hours. Reaction mixture was cooled, diluted with ethyl acetate, washed with H2O, brine, dried (MgSO4), concentrated and purified by flash column chromatography (silica gel, 1 to 30% isopropanol/hexanes) and preparative reverse phase HPLC (Gemini, 5 to 100% ACN/H2O+0.1% TFA) to give 2-(6-{4-[2-(1-tert-butylcarbamyl-pyrrolidin-2-yl)-3H-imidazol-4-yl]-phenyl}-1H-benzoimidazol-2-yl)-pyrrolidine-1-carboxylic acid tert-butyl ester (0.035 g) as a bis-TFA salt: LCMS-ESI+: calc'd for C34H43N6O4: 599.74 (M+H+). Found: 599.1 (M+H+). A reaction side-product was also isolated and determined to be 2-(6-{4′-[2-(1-tert-butylcarbamyl-pyrrolidin-2-yl)-3H-benzoimidazol-5-yl]-biphenyl-4-yl}-1H-benzoimidazol-2-yl)-pyrrolidine-1-carboxylic acid tert-butyl ester (0.013 g) as the bis-TFA salt: LCMS-ESI+: calc'd for C44H49N6O4: 725.89. (M+H+). Found: 725.1 (M+H+). (1-{2-[5-(4-{2-[1-(2-Methoxycarbonylamino-3-methyl-butyryl)-pyrrolidin-2-yl]-3H-benzoimidazol-5-yl}-phenyl)-1H-imidazol-2-yl]-pyrrolidine-1-carbonyl}-2-methyl-propyl)-carbamic acid methyl ester: 2-(6-{4-[2-(1-tert-butylcarbamyl-pyrrolidin-2-yl)-3H-imidazol-4-yl]-phenyl}-1H-benzoimidazol-2-yl)-pyrrolidine-1-carboxylic acid tert-butyl ester (0.035 g) in dichloromethane (1.0 mL) was treated with 4N HCl in dioxane (1.0 mL) for 1 hour at ambient temperature. Reaction mixture was concentrated and dried under vacuum. The residue was dissolved in DMF (1.0 mL) and to this solution was added 2-Methoxycarbonylamino-3-methyl-butyric acid (0.0155 g), 4-methylmorpholine (0.023 mL), followed by HATU (0.033 g). Reaction mixture was stirred for 1 hour at ambient temperature and then diluted with ethyl acetate and washed with dilute sodium bicarbonate solution, 5% lithium chloride solution, brine and dried (MgSO4). Organic layer was concentrated and purified by preparative reverse phase HPLC (Gemini, 5 to 100% ACN/H2O+0.1% TFA). Product was lyophilized to give (1-{2-[5-(4-{2-[1-(2-Methoxycarbonylamino-3-methyl-butyryl)-pyrrolidin-2-yl]-3H-benzoimidazol-5-yl}-phenyl)-1H-imidazol-2-yl]-pyrrolidine-1-carbonyl}-2-methyl-propyl)-carbamic acid methyl ester as the bis-TFA salt (0.0226 g).

1. customReaction mixture
2. concentrationconcentrated
3. dissolutionResidue was dissolved in ethyl acetate
4. washwashed with 5% lithium chloride solution (2×), brine
5. dry with materialdried (MgSO4)
6. concentrationconcentrated
7. custompurified by flash column chromatography (silica gel, 30 to 60% ethyl acetate/hexanes) to a dark brown foam
8. dissolutionBrown foam was dissolved in ethanol (100 mL)
9. customReaction mixture
10. temperaturewas cooled
11. concentrationconcentrated
12. dissolutionResidue was dissolved in ethyl acetate
13. extractionextracted with 1N HCl (3×)
14. extractionextracted with ethyl acetate (2×)
15. dry with materialThe organic layer was dried (MgSO4)
16. concentrationconcentrated
17. custompurified by flash column chromatography (silica gel, 0 to 10% isopropanol/hexanes)

ORD record

ord-c3b0a87331014434a7a44da0ba2cdd0c

Source dataset

uspto-grants-2012_09

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08273341B2