Phosphodiesterase 4 Isoenzyme Inhibitory Activity of 3-Phenylxanthines and 4-Phenyl[i]condensed-purines.

On the basis of our study on the structure-activity relationships of 1,3,7-alkylxanthines and condensed-purines on cAMP-phosphodiesterase 4 (PDE 4) isoenzyme inhibitor, we investigated the synthesis and the inhibitory activity of 3-phenylxanthine and 4-phenyl[i]condensed-purine derivatives. Xanthines and condensed-purines with the phenyl group exhibited potent and selective PDE 4 inhibitory activity.