Ammonium Acetate → N-Boc-pyrrolidine

Participants

Reaction Conditions

Reaction Steps

The mixture of Pyrrolidine-1,2-dicarboxylic acid 2-[2-(7-bromo-dibenzofuran-3-yl)-2-oxo-ethyl]ester 1-tert-butyl ester (200 mg) and ammonium acetate (860 mg, 11 mmol) in xylene (5 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 (DCM/EtOAc) gave 245-(7-Bromo-dibenzofuran-3-yl)-1H-imidazol-2-yl]-pyrrolidine-1-carboxylic acid tert-butyl ester (124 mg). m/z: 481.9 (M+1), 480.2 (M−1). 2-(5-{7-[2-(1-t-butoxycarbonyl-pyrrolidin-2-yl)-3H-benzoimidazol-5-yl]-dibenzofuran-3-yl}-1H-imidazol-2-yl)-pyrrolidine-1-carboxylic acid tert-butyl ester: To the solution of 2-[5-(7-Bromo-dibenzofuran-3-yl)-1H-imidazol-2-yl]-pyrrolidine-1-carboxylic acid tert-butyl ester (124 mg, 0.26 mmol) and 2-[6-(4,4,5,5-Tetramethyl-[1,3,2]dioxaborolan-2-yl)-1H-benzoimidazol-2-yl]-pyrrolidine-1-carboxylic acid tert-butyl ester (107 mg, 0.26 mmol) in DME (2.25 ml) and water (0.75 ml) was added potassium carbonate (72 mg, 0.52 mmol), followed by Pd(PPh3)4 (15 mg) and PdCl2(dppf)CH2Cl2 (15 mg). The mixture was heated at 90° C. for 6 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 (EtOAc) gave 2-(5-{7-[2-(1-t-butoxycarbonyl-pyrrolidin-2-yl)-3H-benzoimidazol-5-yl]-dibenzofuran-3-yl}-1H-imidazol-2-yl)-pyrrolidine-1-carboxylic acid tert-butyl ester (83 mg). m/z: 689.1 (M+1), 687.3 (M−1), 345.0 (M+2)/2. (1-{2-[5-(7-{2-[1-(2-Methoxycarbonylamino-3-methyl-butyryl)-pyrrolidin-2-yl]-3H-benzoimidazol-5-yl}-dibenzofuran-3-yl)-1H-imidazol-2-yl]-pyrrolidine-1-carbonyl}-2-methyl-propyl)-carbamic acid methyl ester: To the solution of 2-(5-{7-[2-(1-t-butoxycarbonyl-pyrrolidin-2-yl)-3H-benzoimidazol-5-yl]-dibenzofuran-3-yl}-1H-imidazol-2-yl)-pyrrolidine-1-carboxylic acid tert-butyl ester (82 mg, 0.12) in DCM (4 ml) was added TFA (2 ml). The mixture was stirred for 60 minutes, 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. To the solution of above powder (0.12 mmol) and MeOCO-Val-OH (42 mg, 0.24 mmol) in DMF (3.5 ml) was added HATU (95 mg, 0.25 mmol), followed by diisopropylethylamine (0.21 ml, 1.2 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/CH3CN/0.1% TFA/H2O) gave (1-{2-[5-(7-{2-[1-(2-Methoxycarbonylamino-3-methyl-butyryl)-pyrrolidin-2-yl]-3H-benzoimidazol-5-yl}-dibenzofuran-3-yl)-1H-imidazol-2-yl]-pyrrolidine-1-carbonyl}-2-methyl-propyl)-carbamic acid methyl ester (79 mg). m/z: 803.4 (M+1), 801.1 (M−1), 402.2 (M+2)/2. 1H NMR (CD3OD, 300 MHz) δ 8.25 (2H, m), 8.1-7.9 (5 H, m), 7.9-7.75 (3H, m), 5.4-5.2 (2H, m), 4.25 (2H, m), 4.2-3.8 (4H, m), 3.67 (6H, s), 2.60 (2 H, m), 2.4-2.0 (8H, m), 1.05-0.8 (12H, m).

Provenance & Evidence