Phenyl‐substituted N6‐phenyladenosines and N6‐phenyl‐5′‐N‐ethylcarboxamidoadenosines with high activity at human adenosine A2B receptors

A series of phenyl‐substituted N⁶‐phenyladenosines and N⁶‐phenyl‐5′‐N‐ethylcarboxamidoadenosines were synthesized and tested at adenosine receptor subtypes. EC₅₀ values were determined for cyclic AMP production in CHO cells expressing human A_2B receptors. Binding affinities were determined for rat A₁ and A_2A receptors and human A₃ receptors. N⁶‐phenyladenosine displayed an EC₅₀ value at A_2B receptors of 6.3 μM. Several N⁶‐phenyladenosine derivatives were more active than N⁶‐phenyladenosine, while two analogs were also more potent than 5′‐N‐ethylcarboxamidoadenosine (NECA, 0.76 μM), i.e., the 4‐iodophenyl ( 10 , 0.37 μM) and the 4‐aminosulfonylphenyl ( 20 , 0.44 μM) derivatives. N⁶‐phenyl‐NECA derivatives were as active as their analogous adenosine derivatives. Drug Dev. Res. 49:85–93, 2000. © 2000 Wiley‐Liss, Inc.