A mixture of 2-(ethoxymethyl)-1-({1-[2-(methylsulfonyl)ethoxy]cyclobutyl}methyl)-1H-imidazo[4,5-c]quinolin-4-amine (prepared as described in Example 26, 0.500 g, 1.16 mmol) and platinum(IV) oxide (0.5 g) in trifluoroacetic acid (5 mL) was hydrogenated on a Parr apparatus at 50 psi (3.5×105 Pa) hydrogen pressure for 1 day. The mixture was filtered through CELITE filter agent, which was washed afterwards with dichloromethane. The filtrate was concentrated under reduced pressure to afford an oil that was suspended in water (20 mL) and adjusted to pH 13 with 50% aqueous sodium hydroxide. A white solid formed that was isolated by filtration, washed with water, and recrystallized from acetonitrile. The crystals were isolated and dried under vacuum at 65° C. to afford 0.35 g of 2-(ethoxymethyl)-1-({1-[2-(methylsulfonyl)ethoxy]cyclobutyl}methyl)-6,7,8,9-tetrahydro-1H-imidazo[4,5-c]quinolin-4-amine as a white powder, mp 186-188° C.
