The present invention discloses compounds of formula (I), or its β-L enantiomer, or a pharmaceutically acceptable salt, ester, stereoisomer, tautomer, solvate, prodrug, or combination thereof: which inhibit, preventing or treating abnormal cellular proliferation and/or a viral infection, particularly by HIV, HCV or HBV. Consequently, the compounds of the present invention interfere with the replication cycle of a virus and are also useful as antiviral agents, or interfere with host cellular biochemical process and are also useful as antiproliferative agents. The present invention further relates to pharmaceutical compositions comprising the aforementioned compounds for administration to a subject suffering from viral infection and/or cell proliferation. The invention also relates to methods of treating a viral infection and/or cell proliferation in a subject by administering a pharmaceutical composition comprising the compounds of the present invention. The present invention relates to novel antiviral/anti-proliferative compounds represented herein above, pharmaceutical compositions comprising such compounds, and methods for the treatment or prophylaxis of viral infection in a subject in need of such therapy with said compounds.