Guanine, Pyrazolo[3,4-d]pyrimidine, and Triazolo[4,5-d]pyrimidine (8-Azaguanine) Phosphonate Acyclic Derivatives as Inhibitors of Purine Nucleoside Phosphorylase

Abstract
Phosphonate acyclic derivatives of guanines, pyrazolo[3,4-d]pyrimidines, and triazolo[4,5-d]pyrimidines (8-azaguanines) are inhibitors of the enzyme purine nucleoside phosphorylase (PNPase) with Ki‘ values ranging from 0.05 to 1.6 μM. These compounds are enzymatically stable congeners of the potent PNPase inhibitor acyclovir diphosphate (53).