Piperidine (0.22 ml, 0.0022 mol) was added to a stirred suspension of 5-(5-bromoacetyl-2-ethoxyphenyl)-1-methyl-3-n-propyl-1,6-dihydro-7H-pyrazolo [4,3-d]pyrimidin-7-one (preparation 8, 0.95 g, 0.0022 mol) and anhydrous potassium carbonate (0.6 g, 0.0044 mol) in acetonitrile (50 ml) at room temperature. After 18 hours the mixture was evaporated under vacuum, the residue dissolved in water (50 ml) and the solution extracted with ethyl acetate (3×30 ml). The organic extracts were combined, washed with brine (3×20 ml), dried (Na2SO4) and evaporated under vacuum. The resulting yellow solid was chromatographed in silica gel (12 g), using a methanol in dichloromethane elution gradient (0-2% methanol), to give an off-white solid. Crystallisation from ethyl acetate-hexane gave the title compound as an off-white powder (0.27 g, 28%), m.p. 149°-151° C. Found C,66.13; H,6.90; N,15.95. C24H31N5O5 requires C, 65.88; H,7.14; N,16.01%
