N6-[(Hetero)aryl/(cyclo)alkyl-carbamoyi-methoxy-phenyl]-(2chloro)-5′-N-ethylearboxamido-adenosines:: The first example of adenosine-related structures with potent agonist activity at the human A2B adenosine receptor

A new series of N-6-[(hetero)aryl/(cyclo)alkyl-carbamoyl-methoxy-phenyl]-(2-chloro)-5'-N-ethylcarboxamido-adenosines (24-43) has been synthesised and tested in binding assays at hA(1), hA(2A) and hA(3) adenosine receptors, and in a functional assay at the hA(2B) subtype. The examined compounds displayed high potency in activating A(2B) receptors with good selectivity versus A(2A) subtypes. The introduction of an unsubstituted 4-[(phenylcarbamoyl)-methoxyl-phenyI chain at the N-6 position of 5'-N-ethylcarboxamido -adenosine led us to the recognition of compound 24 as a full agonist displaying the highest efficacy of the series (EC50 hA(2B) = 7.3 nM). These compounds represent the first report about adenosine-related structures capable of activating hA2B subtype in the low nanomolar range. (c) 2007 Elsevier Ltd. All rights reserved.