Synthesis and Evaluation of a New Series of 8-(2-Nitroaryl)Xanthines as Adenosine Receptor Ligands

Preclinical Research A new series of 1,3-dimethylxanthine derivatives bearing 8-(2-nitroaryl) residue was synthesized and evaluated for affinity for recombinant human adenosine receptors subtypes. Nitrate esters of 7-substituted-1,3-dimethyl-8-phenylxanthines were also synthesized and tested. Introducing a nitro substituent at the 2-position of the 8-substituted phenyl ring resulted in generally low affinity for adenosine receptors (ARs), selectivity toward the A2A subtype was enhanced in some of the compounds. 8-(4-Cyclopentyloxy-5-methoxy-2-nitrophenyl)-1,3-dimethylxanthine (9e) proved to be a potent compound among the 2-nitrophenyl substituted xanthines exhibiting a Ki  = 1 μM at human A2A ARs with at least 30 fold selectivity versus human A1 and A2B ARs. Replacement of 8-chloropropoxy phenyl with 8-nitrooxypropoxy phenyl resulted in a negligible change in binding affinity of the 8-substituted xanthines for various AR subtypes. Drug Dev Res 77 : 241-250, 2016. © 2016 Wiley Periodicals, Inc.