Synthesis and A1-adenosine receptors affinities of purino[7,8-c]quinazoline-8,10(9H,11H)-diones as rigid analogues of 8-arylxanthines.

Title compounds were prepared by a cyclocondensation reaction between 8-(2-aminophenyl)xanthines and trialkyl orthoesters. Some of them showed activities as A1-adenosine receptor antagonists with binding values in the micromolar range. Results are discussed with reference to 1,3-dialkyl-8-arylxanthines. Considerations on the role played by both electronic and conformational factors are also reported.