We report the application of our phosphoramidate ProTide technology to the ribonucleoside analogue 4'-azidouridine to generate novel antiviral agents for the inhibition of hepatitis C virus (HCV). 4'-Azidouridine did not inhibit HCV, although 4'-azidocytidine was a potent inhibitor of HCV replication under similar assay conditions. However 4'-azidouridine triphosphate was a potent inhibitor of RNA synthesis by HCV polymerase, raising the question as to whether our phosphoramidate ProTide approach could effectively deliver 4'-azidouridine monophosphate to HCV replicon cells and unleash the antiviral potential of the triphosphate. Twenty-two phosphoramidates were prepared, including variations in the aryl, ester, and amino acid regions. A number of compounds showed sub-micromolar inhibition of HCV in cell culture without detectable cytotoxicity. These results confirm that phosphoramidate ProTides can deliver monophosphates of ribonucleoside analogues and suggest a potential path to the generation of novel antiviral agents against HCV infection. The generic message is that ProTide synthesis from inactive parent nucleosides may be a warranted drug discovery strategy.

We report on the synthesis of the anti hepatitis C virus (HCV) agent 4'-azidoadenosine (1) and the application of the phosphoramidate ProTide technology to this nucleoside. The synthesis of 1 was achieved through an epoxide intermediate followed by regio- and stereoselective ring opening by azidotrimethylsilane in the presence of a Lewis acid. Compound 1 did not inhibit HCV replication in cell culture at concentrations up to 0.1 mM. However, a submicromolar active agent could be derived from 1 by the application of the ProTide technology. All the phosphoramidates prepared were L-alanine derivatives with variations in the aryl moiety and in the ester part of the amino acid. The benzyl ester and the l-naphthyl phosphate (18) had the best activity in replicon assay. Phosphoramidates (18-21) achieved a significant improvement in antiviral potency over the parent nucleoside (1) with no increase in cytotoxicity.

No abstract

No abstract

No abstract