N-bromobutanimide → pyrrolidine-1,2-dicarboxylic acid 2-[2-(7-bromo-9,9-difluoro-9H-fluoren-2-yl)-2-oxo-ethyl]ester 1-tert-butyl ester

Participants

Reaction Conditions

Reaction Steps

[1,1′-Bis(diphenylphosphino)ferrocene]dichloropalladium(II) (5%, 82 mg) and tetrakis(triphenylphosphine)palladium (5%, 115 mg) were added to the mixture of 2,7-dibromo-9,9-difluoro-9H-fluorene (720 mg, 3 mmol) and tributyl(1-ethoxyvinyl)tin (1 eq., 0.677 mL) in 12 mL dioxane. The reaction was heated to 70° C. under Argon for 4 hours. The reaction was cooled to room temperature. 3 mL water was added and followed by NBS (1 eq., 356 mg). The reaction was stirred at room temperature overnight. The reaction mixture was dissolved in ethyl acetate and washed with saturated sodium bicarbonate solution. The organic layer dried (MgSO4), concentrated down. The residue was dissolved in 15 mL anhydrous DMF. Boc-L-Pro-OH (4 eq., 1.72 g) was added, followed by DIEA (3.5 eq., 1.22 mL) in 5 mL MeCN and 5 mL DMF dropwise. The reaction was stirred at room temperature for 3 hours. The reaction crude was diluted with EtOAc and washed with saturated sodium bicarbonate solution. The organic layer dried (MgSO4), concentrated and purified by flash column chromatography (silica gel, 20 to 100% ethyl acetate/hexane) to give pyrrolidine-1,2-dicarboxylic acid 2-[2-(7-bromo-9,9-difluoro-9H-fluoren-2-yl)-2-oxo-ethyl]ester 1-tert-butyl ester (363 mg, yield 34%). LCMS-ESI−: calc'd for C25H24BrF2NO5: 536.36. Found: 560.0 (M+Na+), 535.9 (M−H). 2-[5-(7-Bromo-9,9-difluoro-9H-fluoren-2-yl)-1H-imidazol-2-yl]-pyrrolidine-1-carboxylic acid tert-butyl ester: 10 mL Xylenes was added to the mixture of pyrrolidine-1,2-dicarboxylic acid 2-[2-(7-bromo-9,9-difluoro-9H-fluoren-2-yl)-2-oxo-ethyl]ester 1-tert-butyl ester (363 mg, 0.677 mmol) and ammonia acetate (20 eq., 1.04 g). The mixture was heated in microwave at 140° C. for 90 minutes. The mixture was diluted with EtOAc and washed with sat.NaHCO3 aqueous solution. The organic layer was concentrated down and purified by flash column chromatography (silica gel, 20 to 80% ethyl acetate/hexane) to give 2-[5-(7-Bromo-9,9-difluoro-9H-fluoren-2-yl)-1H-imidazol-2-yl]-pyrrolidine-1-carboxylic acid tert-butyl ester (324 mg, yield 81%). LCMS-ESI−: calc'd for C25H24BrF2N3O2: 516.38. Found: 517.9 (M+H+). 2-(5-{9,9-Difluoro-7-[2-(1-Boc-pyrrolidin-2-yl)-3H-benzoimidazol-5-yl]-9H-fluoren-2-yl}-1H-imidazol-2-yl)-pyrrolidine-1-carboxylic acid tert-butyl ester: A mixture of 24547-Bromo-9,9-difluoro-9H-fluoren-2-yl)-1H-imidazol-2-yl]-pyrrolidine-1-carboxylic acid tert-butyl ester (137 mg, 0.265 mmol), 2-[6-(4,4,5,5-Tetramethyl-[1,3,2]dioxaborolan-2-yl)-1H-benzoimidazol-2-yl]-pyrrolidine-1-carboxylic acid tert-butyl ester (1 eq., 110 mg), [1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (5%, 11 mg), tetrakis(triphenylphosphine)palladium (5%, 16 mg) and potassium carbonate (2 eq., 73 mg) in 4 mL DME and 2 mL water was heated to 90° C. for 2 hours. The reaction mixture was cooled and dissolved in ethyl acetate and washed with saturated sodium bicarbonate solution. The organic layer dried (MgSO4), concentrated and purified by flash column chromatography (silica gel, 20 to 100% ethyl acetate/hexane) to give 2-(5-{9,9-Difluoro-7-[2-(1-Boc-pyrrolidin-2-yl)-3H-benzoimidazol-5-yl]-9H-fluoren-2-yl}-1H-imidazol-2-yl)-pyrrolidine-1-carboxylic acid tert-butyl ester (83 mg, yield 43%). LCMS-ESI″: calc'd for C41H44F2N6O4: 722.82. Found: 723.1 (M+H+). (1-{2-[5-(9,9-Difluoro-7-{2-[1-(2-methoxycarbonylamino-3-methyl-butyryl)-pyrrolidin-2-yl]-3H-benzoimidazol-5-yl}-9H-fluoren-2-yl)-1H-imidazol-2-yl]-pyrrolidine-1-carbonyl}-2-methyl-propyl)-carbamic acid methyl ester (Example DJ): TFA (2 mL) was added to 2-(5-{9,9-Difluoro-7-[2-(1-Boc-pyrrolidin-2-yl)-3H-benzoimidazol-5-yl]-9H-fluoren-2-yl}-1H-imidazol-2-yl)-pyrrolidine-1-carboxylic acid tert-butyl ester (83 mg, 0.115 mmol) and the reaction mixture was stirred at room temperature for 4 hours. The reaction mixture was concentrated and dried overnight under vacuum. The residue was dissolved in DMF (3 mL) and to this solution was added 2-Methoxycarbonylamino-3-methyl-butyric acid (2 eq., 40 mg), diisopropyl ethylamine (6 eq., 120 μL), followed by HATU (2 eq., 88 mg). Reaction mixture was stirred at 0° C. for 30 minutes. The reaction mixture was dissolved in ethyl acetate and washed with saturated sodium bicarbonate solution. The organic layer was dried (MgSO4), 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-(9,9-Difluoro-7-{2-[1-(2-methoxycarbonylamino-3-methyl-butyryl)-pyrrolidin-2-yl]-3H-benzoimidazol-5-yl}-9H-fluoren-2-yl)-1H-imidazol-2-yl]-pyrrolidine-1-carbonyl}-2-methyl-propyl)-carbamic acid methyl ester (Example DJ) (37 mg, 39%).

Provenance & Evidence