A series of novel acyclic thymine nucleoside analogues were prepared by the Mitsunobu reaction from appropriately protected chiral triols. The enantiomeric triols were obtained from substituted gamma-lactone acids, prepared by asymmetric oxidation of 3-substituted-1,2-cyclopentanediones. The cytotoxic activity of new analogues was evaluated on MCF-7 human breast cancer and HeLa cells, and antiviral activities on human immunodeficiency virus type 1 and hepatitis C virus models. The synthesized compounds revealed specific anti-retroviral activity and no cytotoxic side effects.