Under a nitrogen atmosphere, chloropropylsulfonyl chloride (0.05 ml, 0.46 mmol) was added dropwise to a solution of 1-[2-(2-aminoethoxy)ethyl]-2-butyl-1H-imidazo[4,5-c]quinolin-4-amine (0.12 g, 0.37 mmol) and triethylamine (0.065 ml, 0.46 mmol) in dichloromethane (5 ml). The reaction was stirred for 20 hours followed by removal of the solvent in vacuo. The resulting off-white solid was dissolved in N,N-dimethylformamide (5 mL) and 1,8-diazabicyclo[5.4.0]undec-7-ene (0.087 ml, 0.58 mmol) was added. The reaction was stirred for 18 hours under an atmosphere of nitrogen and then quenched with water and extracted with dichloromethane (2×). The organic fractions were combined, washed with water followed by brine, dried (Na2SO4), filtered, and concentrated in vacuo to provide an off-white solid. Recrystallization from ethyl acetate yielded 0.068 g of 2-butyl-1-{2-[2-(1,1-dioxidoisothiazolidin-2-yl)ethoxy]ethyl}-1H-imidazo[4,5-c]quinolin-4-amine as off-white crystals, m.p. 152–154° C.
