4′-Substituted nucleoside derivatives as inhibitors of HCV RNA replication

A method of treating a hepatitis C virus (HCV) infection comprising administering to a patient in need thereof an effective amount of a compound of formula I

• wherein the compound of formula I is in the D configuration, and;
• R is hydrogen;
• R1 is alkyl, alkenyl, alkynyl, haloalkyl, alkylcarbonyl, hydroxyalkyl, alkoxyalkyl, alkoxy, cyano, azido, hydroxyiminomethyl, alkoxyiminomethyl, halogen, alkylcarbonylamino, alkylaminocarbonyl, or aminomethyl, alkylaminomethyl, dialkylaminomethyl or heterocyclyl;
• R2 is hydrogen, hydroxy, alkyl, hydroxyalkyl, alkoxy, halogen or cyano;
• R3 and R4 (i) independently are hydrogen, hydroxy, alkoxy, halogen or hydroxyalkyl, provided that at least one of R3 and R4 is hydrogen;
• or
• (ii) together represent ═CH2 or ═N—OH, or
• (iii) both represent fluorine;
• R5 is hydrogen, hydroxy, alkyl, alkoxy, alkylthio, NHR8, halogen or SH;
• R6 is hydroxy, NHR8, NHOR9, NHNR8, —NHC(O)OR9′ or SH;
• R7 is hydrogen, hydroxy, alkyl, alkoxy, alkylthio, NHR8, halogen, SH or cyano;
• R8 is hydrogen, alkyl, hydroxyalkyl, arylcarbonyl or alkylcarbonyl;
• R9 is hydrogen or alkyl;
• R9′ is alkyl;
• and pharmaceutically acceptable salts thereof.