3'-Deoxy-3'-C-CF3, 2',3'-dideoxy-3'-C-CF3 and 2',3'-unsaturated-3'-C-CF3 nucleoside derivatives of adenosine and cytidine have been synthesized. All these derivatives were prepared by glycosylation of adenine and uracil with a suitable peracylated 3-trifluoromethyl sugar precursor. The resulting protected nucleosides were subject to appropriate chemical modifications to afford the target nucleoside derivatives. Additionally, the chemical stability in acidic and neutral media of the 2',3'-dideoxy-3'-C-CF3 and 2',3'-unsaturated-3'-C-CF3 nucleoside derivatives of adenosine was compared to that of their parent nucleosides 2',3'-dideoxyadenosine (ddA) and 2',3'-dideoxy-2',3'-didehydroadenosine (d(4)A). Our results confirm that addition of a trifluoromethyl group at C-3' on such nucleoside derivatives appears to confer increased chemical stability toward acid-catalyzed cleavage of the glycosidic bond comparatively to their parent counterparts. When evaluated for their antiviral activity in cell culture experiments, two compounds, namely, 2',3'-dideoxy-3'-C-CF3-adenosine and 2',3'-dideoxy-2',3'-didehydro-3'-C-CF3-cytidine exhibited moderate anti-HBV activity with EC50 values of 10 and 5 microM, respectively.