To a round-bottomed flask containing 1-(4-aminobutyl)-2-methoxymethyl-1H-imidazo[4,5-c]quinolin-4-amine (10.0 g, 33.4 mmol) was added methanol (160 mL) followed by acetic acid (40 mL). The reaction was stirred for 5 minutes and pyridine 3-carboxaldehyde (5.4 g, 50.1 mmol) was added and the reaction was stirred overnight at ambient temperature. Sodium cyanoborohydride (1 M in THF, 33.4 mL, 33.4 mmol) was added to the resultant imine in portions over 10 minutes. After 45 minutes the solvent was evaporated to afford an oil. To the oil was added saturated aqueous sodium bicarbonate (200 mL) and the aqueous layer was washed with ethyl acetate (200 mL) and dichloromethane (200 mL). The product was extracted from the aqueous with 20% methanol (2×100 mL) in dichloromethane. The organic layers were combined and the solvent evaporated to afford crude 2-methoxymethyl-1-{4-[(pyridin-3-ylmethyl)amino]butyl}-1H-imidazo[4,5-c]quinolin-4-amine (about 2 g). The aqueous layer was again extracted with 20% dimethylformamide (2×100 mL) in dichloromethane. The organic layers were combined and the solvent evaporated to afford crude 2-methoxymethyl-1-{4-[(pyridin-3-ylmethyl)amino]butyl}-1H-imidazo[4,5-c]quinolin-4-amine (about 2 g).
