Method for the treatment or prevention of flavivirus infections using nucleoside analogues

A method for the treatment of an hepatitis C infection in a host comprising administering a therapeutically effective amount of a compound having the formula Ib or a pharmaceutically acceptable salt thereof:

• wherein
• B is a nucleotide purine radical, a nucleotide pyrimidine radical or an analogue of a nucleotide purine radical or a nucleotide pyrimidine radical, wherein said analogue is derived by replacement of a CH moiety by a nitrogen atom in a nucleotide purine or pyrimidine radical, replacement of a nitrogen atom by a CH moiety in a nucleotide purine or pyrimidine radical, or both;
• or derived by removal of ring substituents of said nucleotide purine radical or pyrimidine radical;
• or combinations thereof;
• and said analogue is optionally substituted by halogen, hydroxyl, amino, or C1-6alkyl;
• Ra is H, monophosphate, diphosphate, triphosphate, carbonyl which is substituted by a straight, branched or cyclic alkyl having up to 6 C atoms wherein the alkyl is unsubstituted or substituted by halogen, nitro, CONH2, COOH, O—C1-6 alkyl, O—C2-6 alkenyl, O—C2-6 alkynyl, hydroxyl, amino, or COOQ, C2-6 alkenyl which is unsubstituted or substituted by halogen, nitro, CONH2, COOH, O—C1-6 alkyl, O—C2-6 alkenyl, O—C2-6 alkynyl, hydroxyl, amino, or COOQ, C2-6 alkynyl which is unsubstituted or substituted by halogen, nitro, CONH2, COOH, O—C1-6 alkyl, O—C2-6 alkenyl, O—C2-6 alkynyl, hydroxyl, amino, or COOQ, C6-10 aryl which is unsubstituted or mono- or di-substituted with OH, SH, amino, halogen or C1-6 alkyl, or
• Rc is, in each case independently, H, straight chain, branched chain or cyclic C1-6 alkyl which is unsubstituted or substituted by or substituted by halogen, nitro, CONH2, COOH, O—C1-6 alkyl, O—C2-6 alkenyl, O—C2-6 alkynyl, hydroxyl, amino, or COOQ, C2-6 alkenyl which is unsubstituted or substituted by or substituted by halogen, nitro, CONH2, COOH, O—C1-6 alkyl, O—C2-6 alkenyl, O—C2-6 alkynyl, hydroxyl, amino, or COOQ, C2-6 alkynyl which is unsubstituted or substituted by or substituted by halogen, nitro, CONH2, COOH, O—C1-6 alkyl, O—C2-6 alkenyl, O—C2-6 alkynyl, hydroxyl, amino, or COOQ, C6-10 aryl which is unsubstituted or mono- or di-substituted with OH, SH, amino, halogen or C1-6 alkyl, or a hydroxy projecting group;
• Q is C1-6 alkyl, C2-6 alkenyl, or C2-6 alkynyl;
• Z is ORb;
• Rb is H, straight chain, branched chain or cyclic C1-6 alkyl which is unsubstituted or substituted by or substituted by halogen, nitro, CONH2, COOH, O—C1-6 alkyl, O—C2-6 alkenyl, O—C2-6 alkynyl, hydroxyl, amino, or COOQ, C2-6 alkenyl which is unsubstituted or substituted by or substituted by halogen, nitro, CONH2, COOH, O—C1-6 alkyl, O—C2-6 alkenyl, O—C2-6 alkynyl, hydroxyl, amino, or COOQ, C2-6 alkynyl which is unsubstituted or substituted by or substituted by halogen, nitro, CONH2, COOH, O—C1-6 alkyl, O—C2-6 alkenyl, O—C2-6 alkynyl, hydroxyl, amino, or COOQ, C1-6 acyl, or a hydroxy protecting group;
• D1 and D2 are each independently N3, F or H, wherein D1 and D2 are not both H;
• or
• D1 and D2 together form ═CH2, —═CF2, or C3-cycloalkyl which is unsubstituted or substituted by or substituted by halogen, nitro, CONH2, COOH, O—C1-6 alkyl, O—C2-6 alkenyl, O—C2-6 alkynyl, hydroxyl, amino, or COOQ;
• with the proviso that:
• said method does not include administration of an interferon.