4′-substituted nucleoside derivatives as inhibitors of HCV RNA replication.

The method of treating an HCV infection comprising administering to a patient in need thereof a therapeutically effective amount of a the compound of formula I

• wherein
• R1 is alkenyl, alkynyl, haloalkyl, alkylcarbonyl, alkoxy, hydroxymethyl, cyano, azido, alkoxyiminomethyl, alkylcarbonylamino, alkylaminomethyl or dialkylaminomethyl;
• R2 R2 is hydrogen, hydroxy, alkoxy, or halogen;
• R3 and R4 are hydrogen, hydroxy, alkoxy, halogen or hydroxyalkyl, provided that at least one of R3 and R4 is hydrogen;
• or
• R3 and R4 represent fluorine;
• R11 is hydrogen and pharmaceutically acceptable salts thereof.