Two new series of BTD derivatives have been synthesised allowing to explore the steric requirements for their biological activity. The N3-alkylBTD compounds have shown antiviral activity in the same order or lower than previously prepared compounds. However, the cytotoxicity values observed prevent this new series of BTD derivatives from its potential therapeutic application. Concerning BTD derivatives with the modified linker attached to N1 position, we have obtained new non-nucleoside anti-HCMV derivatives. The activity against HCMV is shown at concentrations that were 10-fold lower than the concentration that was toxic for the host cells, which confirm that these derivatives show a specific antiviral effect against HCMV. SAR conclusions derived from these last compounds have provided new knowledge about the structural requirements of BTD showing certain positions that could be modified for enhancing the anti-HCMV action.