Nucleosides and nucleotides. 107. 2-(cycloalkylalkynyl)adenosines: Adenosine A2 receptor agonists with potent antihypertensive effects

Article abstract of DOI:10.1021/jm00090a017

Adenosine receptor-binding profiles in rat brain tissues and antihypertensive effects in spontaneously hypertensive rats (SHR) of a series of 2-(cycloalkylalkynyl)adenosine (2-CAAs) and their congeners are described. The structure-activity relationship of this series of compounds is discussed, focusing on the length of the alkynyl side chain and bulkiness of the terminal cycloalkyl substituents in terms of binding activity and cardiovascular effects. All the 2-CAAs had a preferential affinity for A₂ receptors. Of these derivatives, 2-(3-cyclopentyl-1-propyn-1-yl)adenosine (10b) exhibited the most selective affinity for A₂ receptors (K(i) ratio: A₁/A₂ = 70) on the basis of receptor binding. In the C-2 binding region of adenosine, compounds often have potent and/or selective A₂ activity from introduction of an acetylenic group at the C-2 position followed by one methylene residue further followed by a hydrophobic substituent such as a cycloalkyl ring at the terminal position of the alkynyl side chain. Intravenous injection of 10b up to 100 μg/kg had a potent hypotensive effect without a marked decrease in heart rate in anesthetized SHR. Compounds 10j-s, with a hydroxyl group in the C-3 position of the alkynyl side chain, had a potent affinity for both A₁ and A₂ receptors, but they were not highly selective for A₂ receptors. These compounds caused a marked bradycardia upon intravenous administration in anesthetized SHR. Oral administration of 10b (0.1-1 mg/kg) had a potent and long-lasting antihypertensive effect in conscious SHR.