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This research was carried out to study the pharmacological activity of a newly synthesized series of 2-alkoxy-[1,2,4]triazolo[1,5-a]quinazolin-5-ones as adenosine receptor antagonists. These compounds have been tested in radioligand binding assays on cloned Chinese hamster ovary (CHO) cells transfected with A(1), A(2A), A(2B) and A(3) receptors. In particular, among the triazoloquinazolines (1-11), the dialkoxy derivative (7b) was found to have the highest affinity at A(1) subtype receptor, and its radioligand binding activity together with 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) was studied. Finally, the structure-activity relationship (SAR) studies on the titled compounds provide some new insights about steric hindrance and lipophilic requirements for anchoring to the adenosine receptors recognition site.

All compounds (I)-(IV) are tested for their affinity at the adenosine receptor subtypes A1, A2A, and A2B.

Reaction of primary anthranilamide (I) with oxalyl chloride in the presence of imidazole gives selectively the title benzodiazepine (III) or benzoxazolodiazepine derivatives (IV) depending on the molar ratio of the reactants.

The ultrasound-promoted cyclocondensation of guanidines (I) with 2-amino-2-thioxoacetate (II) leads to the novel title triazinones (III) (7 examples).