HCV polymerase inhibitors

A compound represented by formula:

• wherein:
• B is a nucleobase selected from the groups (a) to (d):
• wherein Y is N or —C(R19)—;
• R3 is OH, C1-C6alkoxy, C3-C7cycloalkoxy, C3-C7cycloalkylC1-C3alkoxy, benzyloxy, O—(C1-C6alkylene)-T-R21 or NHC(R15)(R15′)C(═O)R16;
• R4, R5, R7 and R8 are each independently H, C1-C6alkyl, C1-C6haloalkyl, C1-C6hydroxyalkyl, halo, —OR18, —SR18 or —N(R18)2;
• R6, R9, R10, R11 are each independently selected from H, C1-C6alkyl, C2-C6alkenyl, C2-C6alkynyl, C3-C7cycloalkyl, C1-C6haloalkyl, C1-C6hydroxyalkyl, halo, OR18, SR18, N(R18)2, —NHC(O)OR18, —NHC(O)N(R18)2, —CN, —NO2, —C(O)R18, —C(O)OR18, —C(O)N(R18)2 and —NHC(O)R18, wherein said C2-C6alkenyl group and said C2-C6alkynyl group can be optionally substituted with halo or C3-C5cycloalkyl;
• R16 is H, C1-C10alkyl, C2-C10alkenyl, C3-C7cycloalkyl, C3-C7cycloalkylC1-C3alkyl, benzyl, phenyl or adamantyl, any of which is optionally substituted with 1, 2 or 3 groups, each independently selected from halo, OR18 and N(R18)2;
• each R18 is independently H, C1-C6alkyl, C1-C6haloalkyl or C3-C7cycloalkyl;
• each R21 is independently H, C1-C24alkyl, C1-C6haloalkyl, C1-C6hydroxyalkyl, C2-C6alkenyl, C2-C6alkynyl, C3-C7cycloalkyl or C3-C7cycloalkenyl;
• U is O or S;
• each T is independently —S—, —O—, —SC(O)—, —C(O)S—, —SC(S)—, —C(S)S—, —OC(O)—, —C(O)O— and —OC(O)O—;
• or a pharmaceutically acceptable salt and/or solvate thereof.