The phosphoramidate ProTide approach greatly enhances the activity of beta-2'-C-methylguanosine against hepatitis C virus.

Beta-2'-C-methyl purines (1, 2) are known inhibitors of hepatitis C virus (HCV). We herein report the synthesis, biological and enzymatic evaluation of their 5'-phosphoramidate ProTides. Described herein are seven l-alanine phosphoramidate derivatives with variations to the amino acid ester. The 1-naphthyl phosphoramidate of beta-2'-methylguanosine containing the benzyl ester (20) was the most active at 0.12microM, an 84-fold of increase in activity compared to the parent nucleoside (2) with no increase of cytotoxicity. The carboxypeptidase mediated hydrolysis of several ProTides showed a predictive correlation with their activity versus HCV in replicon.