Reaction Steps
Under a nitrogen atmosphere, a suspension of 1-[2-(4-amino-2-ethoxymethyl-1H-imidazo[4,5-c]quinolin-1-yl)-1,1-dimethylethyl]-3-(1-methylethyl)urea (1.19 g, 2.99 mmol) in dichloromethane (30 mL) was chilled in an ice bath. Boron tribromide (7.47 mL of 1 M in dichloromethane) was added. The reaction mixture was allowed to warm slowly to ambient temperature and then stirred for 18 hours. Additional boron tribromide (2 eq) was added. After 2 hours the reaction mixture was diluted with acetonitrile (10 mL) and the reaction mixture was stirred overnight. The reaction mixture was diluted with dichloromethane (10 mL) and acetonitrile (10 mL), stirred for an additional 16 hours, quenched with methanol (25 mL), and then concentrated under reduced pressure to provide an orange foam. The foam was dissolved in hydrochloric acid (25 mL of 6 N) and heated at 50° C. for 2 hours. The solution was neutralized with 50% sodium hydroxide. The resulting gummy precipitate was extracted with chloroform (3×15 mL). The combined organics were washed with brine (15 mL), dried over magnesium sulfate, filtered, and then concentrated under reduced pressure to provide an off white solid. This material was purified by prep HPLC (HORIZON HPFC system, eluting with a gradient of 15-50% CMA in chloroform) and then recrystallized from acetonitrile to provide 335 g of 1-[2-(4-amino-2-hydroxymethyl-1H-imidazo[4,5-c]quinolin-1-yl)-1,1-dimethylethyl]-3-(1-methylethyl)urea as a white crystalline solid, mp 196-199° C.; 1H NMR (300 MHz, DMSO-d6) δ 8.38 (d, J=8.0 Hz, 1H), 7.59 (d, J=7.5 Hz, 1H), 7.43-7.38 (m, 1H), 7.24-7.19 (m, 1H), 6.54 (s, 2H), 5.72 (s, 1H), 5.63 (d, J=7.6 Hz, 1H), 5.46 (t, J=5.7 Hz, 1H), 5.01 (s, 2H), 4.78 (s, 2H), 3.78-3.67 (m, 1H), 1.17 (bs, 6H), 1.05 (d, J=6.9 Hz, 6H); 13C NMR (75 MHz, DMSO-d6) δ 157.2, 154.2, 152.3, 145.6, 134.3, 126.8, 126.7, 121.5, 120.9, 115.8, 56.5, 54.2, 52.1, 26.4, 23.6; MS (APCI) m/z 371 (M+H)+; Anal. Calcd for C19H26N6O2.0.3H2O: % C, 60.72; % H, 7.13; % N, 22.36. Found: % C, 60.44; % H, 7.42; % N, 22.52.
