8-Benzyloxy-2-ethoxymethyl-1-propyl-1H-imidazo[4,5-c]quinoline (2.0 g, 5.3 mmol) was dissolved in chloroform (20 mL). 3-Chloroperoxybenzoic acid (60% pure, 1.53 g, 5.3 mmol) was added in one portion and the mixture was stirred for 25 minutes. Ammonium hydroxide (20 mL) was added and the biphasic mixture was stirred for 10 minutes. p-Toluenesulfonyl chloride (1.0 g, 5.3 mmol) was added in one portion and the reaction was stirred for an additional 1 hour. The layers were separated and the aqueous fraction was extracted with dichloromethane. The organic fractions were combined and washed successively with 5% aqueous sodium carbonate, water and saturated aqueous sodium chloride. The organic fraction was dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residue was purified by flash column chromatography. The purification was carried out eluting with chloroform:CMA in a gradient from 99:1 to 93:7 to provide a red-brown solid. The solid was recrystallized from acetonitrile to yield 1.1 g of 8-benzyloxy-2-ethoxymethyl-1-propyl-1H-imidazo[4,5-c]quinolin-4-amine as red brown crystals, mp 152.5-154.0° C.
