Nucleoside derivatives as inhibitors of viral RNA-dependent RNA polymerase.

A compound of structural formula I: or a pharmaceutically acceptable salt thereof; wherein R1 is C2-4 alkenyl, C2-4 alkynyl or C1-4 alkyl, wherein alkyl is unsubstituted or substituted with hydroxy, amino, C1-4 alkoxy, C1-4 alkylthio, or one to three fluorines; R2 is hydrogen, fluorine, hydroxy, mercapto, C1-4 alkoxy or C1-4 alkyl; or R1 and R2 together with the carbon atom to which they are attached form a saturated monocyclic ring system of 3 to 6 members, optionally containing one heteroatom selected from O, S and N-alkyl (C0-4); R3 and R4 each independently from the group consisting of hydrogen, cyano, azido, halogen, hydroxy, mercapto, amino, C1-4alkoxy are selected, C2-4alkenyl, C2-4alkynyl and C1-4 alkyl, wherein alkyl is unsubstituted or substituted with hydroxy, amino, C1-4alkoxy, C1-4alkylthio or one to three fluorines; R5 is hydrogen, alkyl (C1-10) alkylcarbonyl, P3O9H4, P2O6H3, or P (O) R13R14; R6 and R7 are each formaindependiente hydrogen, methyl, hydroxymethyl or fluoromethyl; R8 is hydrogen, C1-4 alkyl, C2-4 alkynyl, halogen, cyano, carboxy, (1-4C) alkoxycarbonyl, azido, amino, (1-4C) alkylamino, di (C1-4 alkyl) - amino, hydroxy, C1-6 alkoxy, C1-6 alkylthio, C1-6 alkylsulfonyl, (C1-4 alkyl) 0-2 aminomethyl or cycloheteroalkyl-C4-6, unsubstituted or substituted with one to two groups selected independently from halogen, hydroxy, amino, C1-4 alkyl, C1-4 alkoxy; R9 is hydrogen, cyano, nitro, C1-3 alkyl, NHCONH2, CONR12R12, CSNR12R12, COOR 12, C (= NH) NH2, hydroxy, C1-3alkoxy, amino, (1-4C) alkylamino, di (C1 -4) alkylamino, halogen, (1, 3-oxazol-2-yl), (1, 3-thiazol-2-yl), or (imidazol-2-yl); where the alkyl is unsubstituted or substituted with one to three groups independently selected from halogen, amino, hydroxy, carboxy and C1-3 alkoxy; R10 and R11 are each independently, hydrogen, hydroxy, halogen, C1-4 alkoxy, amino, (1-4C) alkylamino, di (C1-4 alkyl) amino, (3-6C) alkylamino, di (C3-6) alkylamino, C4-6 cycloheteroalkyl or, unsubstituted or substituted with one to two groups independently selected from halogen, hydroxy, amino, C1-4 alkyl, C1-4 alkoxy; each R12 is independently hydrogen or C1-6 alkyl; and R13 and R14 are each independently hydroxy, OCH2CH2SC (= O) (C1-4) alkyl, OCH2O (C = O) (C1-4) alkyl, NHCHMeCO2Me, OCH (C1-4 alkyl) O (C = O) (1-4C) alkyl,