Reaction Steps
To a cold (0° C.) solution of Boc-Lys(Z)—OH (Bachem, 10.0 g, 26.3 mmol) in dimethylformamide (80 mL) was added hydroxybenzotriazole-hydrate (4.3 g, 31.6 mmol), triethylamine (7.3 mL, 52.6 mmol) and EDAC (6.1 g, 31.6 mmol). After stirring at 0° C. for 1 h, 2-aminomethylpyridine (3.0 mL, 28.9 mmol) was added to the mixture. The mixture was warmed to room temperature and stirred for an additional 17 h. The mixture was diluted with aqueous saturated NaHCO3 and extracted with ethyl acetate. The organic phase was dried (MgSO4), filtered and concentrated in vacuo. The crude residue was purified by silica gel chromatography (0% to 5% methanol/CHCl3) to afford the desired product 27: 1H NMR (d6-DMSO) δ 8.43 (d, J=4.0 Hz, 1H), 8.39 (t, J=5.6 Hz, 1H), 7.68 (t, J=7.6 Hz, 1H), 7.34-7.19 (m, 8H), 6.94 (d, J=7.6 Hz, 1H), 4.96 (s, 2H), 4.31 (d, J=5.6 Hz, 2H), 3.90-3.83 (m, 1H), 2.95-2.90 (m, 2H), 1.60-1.25 (m, 6H), 1.35 (s, 9H); ESI+ MS: m/z (rel intensity) 471.2 (100, [M+H]+). Step b: Preparation of (S)-tert-butyl-5-amino-6-oxo-6-(pyridin-2-ylmethyl-amino)hexylcarbamate (28). To a solution of (S)-benzyl 6-((tert-butoxycarbonyl)-amino)-1-oxo-1-(pyridin-2-ylmethylamino)hexan-2-ylcarbamate, 27, (3.8 g, 8.2 mmol) in methanol (80 mL) was added palladium (10 wt % on carbon, 0.5 g). The mixture was stirred under a hydrogen atmosphere for 2 h. The mixture was filtered through Celite and washed with methanol. The resulting filtrate was concentrated in vacuo. The crude residue was used without further purification: ESI+ MS: m/z (rel intensity) 337.2 (100, [M+H]+). Steps c and d: Preparation of tert-butyl(S)-6-oxo-6-(pyridin-2-ylmethylamino)-5-(5,6,7,8-tetrahydroquinolin-8-ylamino)hexylcarbamate (29). To a solution of (S)-tert-butyl 5-amino-6-oxo-6-(pyridin-2-ylmethyl-amino)hexylcarbamate, 28, (2.16 g, 6.43 mmol) in ethanol (14 mL) was added 6,7-dihydroquinolin-8(5H)-one (0.90 g, 6.12 mmol). The mixture was heated in microwave reactor at 150° C. for 13 min. After cooling the reaction to room temp., NaBH4 (0.46 g, 12.24 mmol) was added to the mixture. The reaction mixture was stirred at room temp for 1 h. The mixture was diluted with aqueous saturated NaHCO3, extracted twice with ethyl acetate. The organic phase was dried (MgSO4), filtered and concentrated in vacuo. The crude residue was purified by silica gel chromatography (5% to 25% methanol/CH2Cl2) to afford the desired product 29: 1H NMR (d6-DMSO) δ 8.44 (d, J=4.4 Hz, 1H), 8.40 (m, 1H), 8.32-8.31 (m, 1H), 7.66 (t, J=7.2 Hz, 1H), 7.45 (d, J=7.6 Hz, 1H), 7.24 (d, J=8.0 Hz, 1H), 7.20 (t, J=4.8 Hz, 1H), 7.13 (dd, J=8.0, 4.2 Hz, 1H), 6.94 (d, J=7.6 Hz, 1H), 4.32 (d, J=5.6 Hz, 2H), 3.95-3.89 (m, 1H), 3.62-3.57 (m, 1H), 2.69 (d, J=4.8 Hz, 2H), 2.61-2.56 (m, 2H), 1.99-1.95 (m, 1H), 1.89-1.83 (m, 1H), 1.63-1.28 (m, 8H), 1.35 (s, 9H); ESI+ MS: m/z (rel intensity) 468.3 (100, [M+H]+). Step e: Preparation of (2S)-6-amino-N-(pyridin-2-ylmethyl)-2-(5,6,7,8-tetrahydro-quinolin-8-ylamino)hexanamide tetrahydrochloride (AZ). To a solution of tert-butyl(S)-6-oxo-6-(pyridin-2-ylmethylamino)-5-(5,6,7,8-tetrahydroquinolin-8-ylamino)-hexylcarbamate, 29, (1.07 g, 2.29 mmol) in methanol (50 mL) was bubbled HCl gas (generated from H2SO4 and NaCl). The reaction mixture was stirred at room temp. for 20 minutes. The mixture was concentrated in vacuo to afford the desired product. The tetrahydrochloride salt was used without further purification: ESI+ MS: m/z (rel intensity) 368.2 (100, [M+H]+).
