BACKGROUND: Nucleoside analogues always require phosphorylation to be active. This appears to be a particular limitation for uridine-based nucleosides. Our ProTide method allows the direct use of masked membrane-soluble preformed nucleoside phosphates, bypassing the need for the initial phosphorylation step. We herein applied it to some novel 5-trimethylsilyl arabinosyl uridines. METHODS: 5-Trimethylsilyl-1-beta-D-(arabinofuranosyl)uracil was prepared in six steps starting from uridine, and five phosphoramidate ProTide derivatives were synthesized. These compounds were investigated for activity against a range of DNA and RNA viruses, including herpes simplex virus type-1 and type-2, vaccinia virus and HIV. RESULTS: Overall, these compounds did not show significant antiviral activity against any of the viruses tested. CONCLUSIONS: The inactivity of the ProTides of this nucleoside could correspond with poor ProTide activation in vitro, poor onward metabolism or low activity of the putative monophosphate metabolite.