The synthesis of 9-alkyl substituted adenine derivatives presenting aromatic groups and cycloalkyl rings in 8- and N6-position, respectively, is reported. The compounds were tested with radioligand binding studies showing, in some cases, a low nanomolar A1 adenosine receptor affinity and a very good selectivity versus the other adenosine receptor subtypes. Functional assays at human adenosine receptors and at a mouse ileum tissue preparation clearly demonstrate the antagonist profile of these molecules, with inhibitory potency at nanomolar level. A molecular modeling study, consisting in docking analysis at the recently reported A1 adenosine receptor crystal structure, was performed for the interpretation of the obtained pharmacological results. The N6-cyclopentyl-9-methyl-8-phenyladenine (17), resulting the most active derivative of the series (Ki = 2.8 nM and IC50 = 14 nM), was also very efficacious in counteracting the effect of the agonist CCPA on mouse ileum contractility. This new compound represents a tool for the development of new agents for the treatment of intestinal diseases as constipation and postoperative ileus.
Keywords: A(1) adenosine receptor; Adenosine; Adenosine receptor antagonists; Adenosine receptors; Mouse ileum; Purinergic receptors.
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