Halophenyl furanopyrimidines as potent and selective anti-VZV agents

Bicyclic furano pyrimidines have been previously reported by us to be highly potent and selective inhibitors of varicella zoster virus (VZV). p-Alkyl phenyl analogues are particularly potent with EC50 values below 1 nM. In this article we report the synthesis and anti-VZV activity of a series of halophenyl analogues, with variation in the nature (F, Cl, Br) and location (o, m, p) of the halogen substituent. The compounds show a range of activities from ca. 10 nM to > 50 microM. In most cases, ortho substitution leads to greatest activity, meta substitution is in general poor, and the effect of p-substitution shows a marked dependence on the halogen atom. The p-fluorophenyl compound is unique amongst compounds of this class in being inactive as an antiviral. The possible origins of these marked SARs are discussed.