Synthesis of new N(6)-substituted 2-phenyl-8-azaadenosines. Their affinity for adenosine A1 and A2 receptors. A comparison with the corresponding 2-phenyl-9-benzyl-8-azaadenines. VI.

Comparison of the affinity towards adenosine receptors of 2-phenyl-8-azaadenosines, bearing a lipophilic substituent on N(6), with the corresponding 2-phenyl-8-azaadenines was carried out. The compounds have good A1 affinity and high A1 selectivity. The obtained Ki(rib)/Ki(benz) ratios for A1 receptors, which showed variable values depending on the structure of the N(6) substituent, confirmed that 2-phenyl-8-azaadenines are characterized by greater freedom inside A1 receptors. This situation may be a favourable test of the hypothesized double disposition of these exogenous molecules within A1 receptors.