Compounds having the formula I wherein R1 is as herein defined are Hepatitis C virus NS5b polymerase inhibitors. Also disclosed are compositions and methods for inhibiting hepatitis replication, and processes for making the compounds of formula I本發明係關於具有式I之化合物,其中R1如本文定義,其為C型肝炎病毒NS5b聚合酶抑制劑。本發明亦揭示抑制肝炎複製之組合物及方法,以及製造式I之化合物之方法