Reaction Steps
Hydrochloric acid (HCl) in dioxane (4 M, 25 mL) was added to the solution of compound 3.3 (4.34 g, 10 mmol) in dioxane (25 mL). The resulting mixture was then stirred for 4 h, rotovapped, washed with ether and dried under vacuum to obtain 4.02 g (99%) of (S)-2-(pyrrolidin-2-yl)-5-{4-[(trimethylsilyl)buta-1,3-diynyl]phenyl}-1H-imidazole dihydrochloride (3.8). The LC-MS molecular ion peak was at 334 (M+H)+. 1H NMR (DMSO-d6, 400 MHz) δ 10.35 (br s, 1H), 9.74 (br s, 1H), 8.12 (m, 1H), 7.95 (m, 2H), 7.67 (d, J=8.0 Hz, 2H), 4.98 (m, 1H), 3.43 (m, 1H), 3.36 (m, 1H), 2.44 (m, 2H), 2.18 (m, 1H), 2.00 (m, 1H), 0.22 (s, 9H). The mixture of compound 3.8 (406 mg, 1 mmol), N-Moc-L-valine (184 mg, 1.05 mmol) and HATU (418 mg, 1.1 mmol) in DMF (4 mL) was stirred in a fridge for 0.5 h, then DIPEA (517 mg, 4 mmol, 0.697 mL) was added, and the resulting mixture was continuously stirred in a fridge for 2 h. The mixture was diluted with 20 mL of benzene, washed twice with a 5% Na2CO3 solution, dried over Na2SO4, rotovapped and subjected to dry flash chromatography on silica gel (EtOAc) to obtain 314 mg (64%) of methyl (S)-3-methyl-1-oxo-1-[(S)-2-(5-{4-[(trimethylsilyl)buta-1,3-diynyl]phenyl}-1H-imidazol-2-yl)pyrrolidin-1-yl]butan-2-ylcarbamate (3.9). The LC-MS molecular ion peak was at 491 (M+H)+. Potassium carbonate (K2CO3) (265 mg, 1.92 mmol) was added to the solution of compound 3.9 (314 mg, 0.64 mmol) in THF (10 mL) and methanol (10 mL), and the reaction mixture was stirred under an argon atmosphere (aa) for 2 h, then filtered and rotovapped. Triethylamine (2 mL), tert-butyl (S)-2-(5-iodo-1H-imidazol-2-yl)-pyrrolidine-1-carboxylate (3.5) (232 mg, 0.64 mmol), Pd(PPh)4 (37 mg, 0.032 mmol) and CuI (12 mg, 0.064 mmol) were added to the solution of the obtained compound 5 in THF (8 mL). The resulting mixture was then stirred under aa at 40° C. for 15 h. After the reaction was completed, the mixture was rotovapped, dissolved in DCM, filtered, washed with a sat. NH4Cl solution, rotovapped again and subjected to column chromatography on silica gel (gradient toluene/dioxane from 5:1 to 3:2) to obtain 276 mg (66%) of (S)-tert-butyl 2-(5-{[4-(2-{(S)-1-[(S)-2-(methoxycarbonylamino)-3-methylbutanoyl]pyrrolidin-2-yl}-1H-imidazol-5-yl)phenyl]buta-1,3-diynyl}-1H-imidazol-2-yl)pyrrolidine-1-carboxylate (3.10). The LC-MS molecular ion peak was at 654 (M+H)+. Compound 3.10 was treated according to the procedure given above for compound 3.8 to obtain methyl (S)-3-methyl-1-oxo-1-{(S)-2-[5-(4-{[2-((S)-pyrrolidin-2-yl)-1H-imidazol-5-yl]buta-1,3-diynyl}phenyl)-1H-imidazol-2-yl]pyrrolidin-1-yl}butan-2-ylcarbamate trihydrochloride (3.11). Yield 257 mg (92%). The LC-MS molecular ion peak was at 554 (M+H)+. The mixture of compound 3.11 (133 mg, 0.2 mmol) and N-Moc-(R)-2-phenylglycine2 (44 mg, 0.21 mmol) in DMF (4 mL) was cooled to −10° C. and HATU (84 mg, 0.22 mmol) was added. After dissolution the mixture was left in a freezer for 0.5 h, then DIPEA (129 mg, 1 mmol, 0.174 mL) was added, and the resulting mixture was left in a freezer for 3 h. After the reaction completed (LC-MS check) the mixture was diluted with 20 mL of benzene, washed twice with a 5% Na2CO3 solution, dried over Na2SO4, rotovapped and subjected to HPLC to obtain 70 mg (47%) of methyl (R)-[(S)-2-(5-{4-[4-(2-{(S)-1-[(S)-2-(methoxycarbonylamino)-3-methylbutanoyl]pyrrolidin-2-yl}-3H-imidazol-4-yl)buta-1,3-diynyl]phenyl}-1H-imidazol-2-yl)pyrrolidin-1-yl]-2-oxo-1-phenylethylcarbamate (1.2). It was dissolved in acetone (2 mL), treated with 10% excess of 4M HCl solution in ethyl acetate and with ether (6 mL), the precipitate was centrifuged off and dried in vacuum to obtain 72 mg (94%) of methyl (R)-[(S)-2-(5-{4-[4-(2-{(S)-1-[(S)-2-(methoxycarbonylamino)-3-methylbutanoyl]pyrrolidin-2-yl}-3H-imidazol-4-yl)buta-1,3-diynyl]phenyl}-1H-imidazol-2-yl)pyrrolidin-1-yl]-2-oxo-1-phenylethylcarbamate dihydrochloride (1.2•2HCl). The LC-MS molecular ion peak was at 745 (M+H)+.
