Structure–activity relationship studies on anti-HCV activity of ring-expanded (‘fat’) nucleobase analogues containing the imidazo[4,5-e][1,3]diazepine-4,8-dione ring system

In continuation of our structure–activity relationship studies on anti-HCV activity of the title imidazo[4,5-e][1,3]diazepine ring system, we report here the synthesis and effect on biological activity of introducing hydrophobic substituents at the 2-position of the heterocycle. Our results suggest that there is no particular advantage to that end as the observed antiviral activity of the test compounds was lower than that of the unmodified 2-bromo derivative used for comparison. The activity/toxicity profile of all target compounds, however, was still better than that of the reference compound ribavirin used in the antiviral assay, but not as good as that of interferon-α, the other reference compound used in the assay.