Triethylamine → 5-Aza-spiro[2.4]heptane-5,6-dicarboxylic acid 5-benzyl ester 6-[2-(7-bromo-dibenzofuran-3-yl)-2-oxo-ethyl]ester

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Reaction Steps

To the solution of (s) 5-aza-spiro[2.4]heptane-5,6-dicarboxylic acid 5-benzyl ester (138 mg, 0.5 mmol) and triethylamine (65 μl, 0.47 mmol) in acetonitrile (3 ml) was added slowly a solution of 2-bromo-1-(7-bromo-dibenzofuran-3-yl)-ethanone (143 mg, 0.39 mmol) in DMF (4 ml). The mixture was stirred for 12 hours, and the solvent was evaporated. The mixture was diluted with EtOAc, and washed with 1.0 N NaOH solution, water and brine, and was dried with sodium sulfate. Concentration gave 5-Aza-spiro[2.4]heptane-5,6-dicarboxylic acid 5-benzyl ester 6-[2-(7-bromo-dibenzofuran-3-yl)-2-oxo-ethyl]ester (210 mg) 6-[5-(7-Bromo-dibenzofuran-3-yl)-1H-imidazol-2-yl]-5-aza-spiro[2.4]heptane-5-carboxylic acid benzyl ester: The mixture of 5-aza-spiro[2.4]heptane-5,6-dicarboxylic acid 5-benzyl ester 6-[2-(7-bromo-dibenzofuran-3-yl)-2-oxo-ethyl]ester (210 mg, 0.39 mmol) and ammonium acetate (330 mg, 4.3 mmol) in xylene (3 ml) was heated at 140 C for 80 minutes under microwave. The mixture was quenched with water, 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 (EtOAc) gave 645-(7-bromo-dibenzofuran-3-yl)-1H-imidazol-2-yl]-5-aza-spiro[2.4]heptane-5-carboxylic acid benzyl ester (150 mg). m/z: 542.1 (M+1), 540.1 (M−1). 3-(6-{7-[2-(5-Benzyloxycarbonyl-5-aza-spiro[2.4]hept-6-yl)-3H-imidazol-4-yl]-dibenzofuran-3-yl}-1H-benzoimidazol-2-yl)-2-aza-bicyclo[2.2.1]heptane-2-carboxylic acid tert-butyl ester: To the solution of 6-[5-(7-bromo-dibenzofuran-3-yl)-1H-imidazol-2-yl]-5-aza-spiro[2.4]heptane-5-carboxylic acid benzyl ester (150 mg, 0.28 mmol) and 3-[6-(4,4,5,5-Tetramethyl-[1,3,2]dioxaborolan-2-yl)-1H-benzoimidazol-2-yl]-2-aza-bicyclo[2.2.1]heptane-2-carboxylic acid tert-butyl ester (160 mg, 0.36 mmol) in DME (2.25 ml) and water (0.75 ml) was added potassium carbonate (78 mg, 0.56 mmol), followed by Pd(PPh3)4 (15 mg) and PdCl2(dppf)CH2Cl2 (15 mg). The mixture was heated at 90 C for 16 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-(6-{7-[2-(5-benzyloxycarbonyl-5-aza-spiro[2.4]hept-6-yl)-3H-imidazol-4-yl]-dibenzofuran-3-yl}-1H-benzoimidazol-2-yl)-2-aza-bicyclo[2.2.1]heptane-2-carboxylic acid tert-butyl ester (190 mg). m/z: 775.2 (M+1), 773.3 (M−1), 338.2 (M+2)/2. (1-{6-[5-(7-{2-[2-(2-Methoxycarbonylamino-3-methyl-butyryl)-2-aza-bicyclo[2.2.1]hept-3-yl]-3H-benzoimidazol-5-yl}-dibenzofuran-3-yl)-1H-imidazol-2-yl]-5-aza-spiro[2.4]heptane-5-carbonyl}-2-methyl-propyl)-carbamic acid methyl ester: To the solution of 3-(6-{7-[2-(5-benzyloxycarbonyl-5-aza-spiro[2.4]hept-6-yl)-3H-imidazol-4-yl}-dibenzofuran-3-yl]-1H-benzoimidazol-2-yl)-2-aza-bicyclo[2.2.1]heptane-2-carboxylic acid tert-butyl ester (185 mg, 0.24 mmol) in DCM (3.6 ml) was added slowly 33% HBr/HOAc (1 ml). The mixture was stirred for two hours, and the solvent and reagent were removed under reduced pressure to give a brown solid. The solid was suspended in DCM/Et2O (2.5 ml/25 ml) and was stirred. The solid was collected through filtration. To the solution of above solid (0.24 mmol) and MeOCO-Val-OH (84 mg, 0.48 mmol) in DMF (7.0 ml) was added HATU (192 mg, 0.50 mmol), followed by diisopropylethylamine (0.42 ml, 2.4 mmol). The mixture was stirred for ten hours and was evaporated and then 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/CH3CN/0.1% TFA/H2O) gave (1-{6-[5-(7-{2-[2-(2-methoxycarbonylamino-3-methyl-butyryl)-2-aza-bicyclo[2.2.1]hept-3-yl]-3H-benzoimidazol-5-yl}-dibenzofuran-3-yl)-1H-imidazol-2-yl]-5-aza-spiro[2.4]heptane-5-carbonyl}-2-methyl-propyl)-carbamic acid methyl ester (151 mg). m/z: 855.3 (M+1), 853.2 (M−1), 428.4 (M+2)/2.

Provenance & Evidence