A modification on the methods described in Parts A-H of Example 2 were used to prepare 2-(2-methoxyethyl)-1-propyl-1H-imidazo[4,5-c]quinolin-7-ol, with 3-benzyloxyaniline and 3-methoxypropanoyl chloride used in lieu of 4-benzyloxyaniline and ethoxyacetyl chloride, respectively. A solution of diisopropyl azodicarboxylate (6.28 mL, 31.9 mmol) in tetrahydrofuran (25.5 mL) was added dropwise to a mixture of 2-(2-methoxyethyl)-1-propyl-1H-imidazo[4,5-c]quinolin-7-ol (7.28 g, 25.5 mmol), triphenylphosphine (8.36 g, 31.9 mmol), and t-butyl 4-hydroxypiperidine-1-carboxylate (6.42 g, 31.9 mmol) in tetrahydrofuran (191 mL) at 5° C. The mixture was allowed to warm to room temperature. After 2 days, the solvent was removed under reduced pressure and the residue was purified by flash chromatography (silica gel, gradient elution with 1.5-4% methanol in dichloromethane) to yield 9.77 g of tert-butyl 4-{[2-(2-methoxyethyl)-1-propyl-1H-imidazo[4,5-c]quinolin-7-yl]oxy}piperidine-1-carboxylate as a gray amorphous solid.
