Reaction Steps
1-bromo-7-phenylheptan-2-one (1.00 g, 3.71 mmol) was placed in a 50 mL round bottomed flask with a stir bar and dissolved in 10 mL of DMF. Boc guanidine (1.77 g, 11.13 mmol) was then added to the reaction mixture and it was allowed to stir for 48 hours. Water was then added to the reaction mixture and it was placed in a separatory funnel. The mixture was then extracted twice with ethyl acetate, washed twice with water, washed twice with brine, concentrated de vacuo and then purified via column chromatography (5% methanol/95% dichloromethane) to provide tert-butyl 2-amino-4-(5-phenylpentyl)-1H-imidazole-1-carboxylate as a hygroscopic light yellow solid (0.77 g, 63% yield), 1H NMR (300 MHz, CDCl3) δ 7.31 (m, 2H), δ 7.26 (m, 3H), δ 6.66 (s, 2H), δ 6.51 (s, 1H), δ 2.63 (t, J=7.5 Hz, 2H), δ 2.39 (t, J=7.5 Hz, 2H), δ 1.67 (m, 4H), δ 1.53 (s, 9H), δ 1.40 (m, 2H) ppm; 13C NMR (75 MHz, CDCl3) δ 151.1, 149.8, 143.0, 130.3, 128.7, 128.5, 125.8, 106.2, 84.5, 36.1, 31.6, 29.2, 28.5, 28.4, 28.2 ppm; IR νmax (cm−1) 3433, 2098, 1639, 1454, 1204; HRMS (ESI) calcd for C19H27N3O2 (M+) 329.2103, found 329.2109. Then, tert-butyl 2-amino-4-(5-phenylpentyl)-1H-imidazole-1-carboxylate was dissolved in a 1:4 mixture of trifluoroacetic acid/dichloromethane and allowed to stir for five hours and then concentrated de vacuo. The sample was then dissolved with a dilute HCl/methanol (5 drops HCl/50 mL of methanol) and then concentrated de vacuo to provide 4-(5phenylpentyl)-1H)-imidazol-2-amine hydrochloride as a hygroscopic light yellow solid (0.62 g, 63% overall yield). 1H NMR (300 MHz, CD3OD) δ 7.20 (t, J=7.2 Hz, 2H), δ 7.12 (d, J=7.2 Hz, 3H), δ 6.37 (s, 1H), δ 2.56 (t, J=7.5 Hz, 2H), δ 2.41 (t, J=7.5 Hz, 2H), δ 1.57 (m, 4H), δ 1.34 (m, 2H) ppm; 13C NMR (75 MHz, CDCl3) δ 147.3, 142.5, 128.3, 128.1, 127.7, 125.6, 108.2, 35.5, 31.1, 28.3, 27.0, 24.2 ppm; IR νmax (cm−1) 3385, 2933, 2857, 1679, 1536, 1495, 1453, 1335, 1172, 748, 700; HRMS (ESI) calcd for C14H19N3(M+) 229.1578, found 229.1571.
