601486 Disclosed is the use of azido and purine or pyrimidine substituted tetrahydrofurans in the manufacture of a medicament for treating hepatitis B virus (HBV). Examples of the compounds are: 9-((2R,3S,4S,5R)-5-azido-3-ethyl-4-hydroxy-5-(hydroxymethyl)tetrahydrofuran-2-yl)-9H-purin-6-ol 4-amino-1-((2R,3S,4S,5R)-5-azido-4-hydroxy-5-(hydroxymethyl)-3-methyltetrahydrofuran-2-yl)pyrimidin-2(1H)-one and 9-((2R,3S,4S,5R)-5-azido-4-hydroxy-5-(hydroxymethyl)-3-(trifluoromethyl)tetrahydrofuran-2-yl)-9Hpurin-6-ol.