Modified 2′ and 3′-nucleoside prodrugs for treating Flaviviridae infections

A method for the treatment of a host infected with a hepatitis C virus, comprising administering to the host infected with a hepatitis C virus an effective amount of a compound having the formula:

• or a pharmaceutically acceptable salt thereof, wherein:
• R1 is H;
• mono-, di- or triphosphate;
• acyl;
• an amino acid ester;
• a carbohydrate;
• a peptide;
• or a pharmaceutically acceptable leaving group which when administered in vivo provides a compound wherein R1 is H or phosphate;
• R2 is H;
• acyl;
• an amino acid ester;
• a carbohydrate;
• a peptide;
• or a pharmaceutically acceptable leaving group which when administered in vivo provides a compound wherein R2 is H;
• Base* is selected from the group consisting of adenine, N6-alkylpurine, N6-acylpurine, N6-benzylpurine, N6-halopurine, N6-vinylpurine, N6-acetylenic purine, N6-acyl purine, N6-hydroxyalkyl purine, N6-alkylaminopurine, N6-thioalkyl purine, N2-alkylpurine, N2-alkyl-6-thiopurine, thymine, cytosine, 5-fluorocytosine, 5-methylcytosine, 6-azapyrimidine, 6-azacytosine, 2- and/or 4-mercaptopyrimidine, uracil, 5-halouracil, 5-fluorouracil, C5-alkylpyrimidine, C5-benzylpyrimidine, C5-halopyrimidine, C5-vinylpyrimidine, C5-acetylenic pyrimidine, C5-acyl pyrimidine, C5-hydroxyalkyl purine, C5-amidopyrimidine, C5-cyanopyrimidine, C5-iodopyrimidine, C6-iodo-pyrimidine, C5-Br-vinyl pyrimidine, C6-Br-vinyl pyrimidine, C5-nitropyrimidine, C6-amino-pyrimidine, N2-alkylpurine, N2-alkyl-6-thiopurine, 5-azacytidinyl, 5-azauracilyl, triazolopyridinyl, imidazolopyridinyl, pyrrolopyrimidinyl, pyrazolopyrimidinyl, guanine, hypoxanthine, 2,6-diaminopurine, and 6-choropurine;
• R12 is C(Y3)3;
• and
• Y3 is independently H or F.