Synthesis of 4,6-disubstituted- and 4,5,6-trisubstituted-2-phenyl-pyrimidines and their affinity towards A(1) adenosine receptors

Synthesis and assay of title compounds are reported. The results can support our hypothesis about the possibility that molecules characterized by great flexibility, as the title 2-phenyl-4,5,6-triaminopyrimidines, can better interact with the receptor sites compared with rigid molecules as 2,6,9-trisubstituted 8-azaadenines. Relatively low activity shown by pyrimidine derivatives demonstrated the importance of the bicyclic aromatic system in 8-azaadenines and adenines to give a favourable interaction between a hexogenous molecule and the A(?)1 adenosine receptors.