Synthesis and cardiovascular activity of new 8-alkylamino-1,3-dimethyl-7-(2-hydroxy-3-piperazinopropyl)-3,7-dihydro-1H-purine-2,6-diones

7-{2-Hydroxy-3-[4-(2-phenoxyethyl)-piperazinyl-1-yl]-propyl}-1,3-dimethyl-3,7-dihydro-1H-purine-2,6-dione dihydrochloride (2), and several of its 8-alkylamino substituted derivatives (11-17) were synthesized and tested for electrocardiographic, antiarrhythmic and hypotensive activity. Also their alpha(1)- and alpha(2)-adrenoreceptor affinities were determined. It was found that compound 2, and its analogue 15 with 8-(2-morpholin-4-yl-ethylamino) substituent displayed a strong prophylactic antiarrhythmic activity in experimentally induced arrhythmia. (LD50/ED50 = 54.9 and 55.0, respectively). The hypotensive activity was observed for 8-benzylamino (11) or 8-(pyridin-2-yl-methylamino) (12) analogues. All the new derivatives (11-17) and 2 showed a weak affinity for alpha(1)-(K-i = 0.225-1.400 muM) and alpha(2)-(K-i = 0.152-4.299 muM) receptors.