Method for the treatment or prevention of viral infection using nucleoside analogues

A method for treating a viral infection selected from the group consisting of herpes simplex virus, varicella zoster virus, respiratory syncytial virus and cytomegalovirus in a host, said method comprising administering to said host a therapeutically effective amount of a compound having the formula I:

• wherein
• Y is N or C—X;
• X is selected from the group consisting of H, halogen, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, CN, CF3, N3, NO2, C6-10 aryl, C6-10 heteroaryl and CORb;
• Rb is selected from the group consisting of H, OH, SH, C1-6 alkyl, C1-6 aminoalkyl, C1-6 alkoxy and C1-6 thioalkyl;
• Ra is selected from the group consisting of H, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C6-10 aryl,
• monophosphate, diphosphate, triphosphate, carbonyl substituted with a C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C6-10 aryl, and
• Rc in each case is independently selected from the group comprising H, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl and an hydroxy protecting group;
• and
• R1 is selected from the group consisting of H, a C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C6-10 aryl, and carbonyl substituted with a C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, or C6-10 aryl;
• or
• a pharmaceutically acceptable salt thereof wherein said compound is in the form of a single enantiomer or a mixture of enantiomers.