6-Hydrazinopurine 2′-methyl ribonucleosides and their 5′-monophosphate prodrugs as potent hepatitis C virus inhibitors

A series of 6-hydrazinopurine 2′-methyl ribonucleosides was synthesized and tested for its inhibitory activity against the hepatitis C virus (HCV). The lack of antiviral activity of these nucleosides was associated with a poor affinity for adenosine kinase, which prompted us to synthesize several of their 5′-monophosphate prodrugs. Some of these prodrugs exhibited more than 1000-fold improvement in anti-HCV activity when compared to their parent nucleosides (EC50 of 24 nM vs 92 μM for the parent).