A β-L-nucleoside analog of thymidine that has antiviral activity; active against HBV in 2.2.15 cells (EC50 = 0.19 μM); selective for HBV over HIV-1, HSV-1, HSV-2, and influenza A and B (EC50s = >100 μM); reduces serum viral load in a woodchuck model of chronic HBV infection in a dose-dependent manner