Synthesis and evaluation of adenosine derivatives as A, A, A and A adenosine receptor ligands containing boron clusters as phenyl isosteres and selective A agonists.

A series of adenosine and 2'-deoxyadenosine pairs modified with a 1,12-dicarba-closo-dodecaborane cluster or alternatively with a phenyl group at the same position was synthesized, and their affinity was determined at A, A, A and A adenosine receptors (ARs). While AR affinity differences were noted, a general tendency to preferentially bind A AR over other ARs was observed for most tested ligands. In particular, 5'-ethylcarbamoyl-N-(3-phenylpropyl)adenosine (18), N-(3-phenylpropyl)-2-chloroadenosine (24) and N-(3-phenylpropyl)adenosine (40) showed nanomolar A affinity (K 4.