A mixture of 3-(3,5-dimethoxy-phenyl)-1-ethyl-7-methanesulfinyl-3,4-dihydro-pyrimido[4,5-d]pyrimidin-2(1H)-one (0.5 g, 1.33 mmol), 4-diethylaminobutylamine (0.38 g, 2.66 mmol,) and trifluoroacetic acid (0.31 g, 2.66 mmol) in acetonitrile (6 mL) was heated in a sealed tube at 90° C. for 18 hours. The solvent was removed under reduced pressure and the residue taken up in 1N HCl. The solution was made basic with 50% NaOH and extracted twice with dichloromethane. The combined organic layers were dried over magnesium sulfate, filtered, and evaporated. The residue was purified by radial chromatography eluting with a solvent mixture of ethyl acetate/methanol/ethyl (89:10:1 v/v/v) to give 0.34 g (56%) of the titled compound: mp 83-85° C. Mass Spectrum (APCI, 80/20 CH3CN/H2O, Probe=450° C.) (m+1)/z 458.2
