B-ring modified aurones as promising allosteric inhibitors of hepatitis C virus RNA-dependent RNA polymerase

• Various B-ring substituted aurones were synthetized.
• Aurones derivatives are allosteric inhibitors of HCV NS5B polymerase.
• Thumb pocket I of NS5B is the binding site for aurones analogues.
• Aurones bearing an indolyl as B-ring have the highest inhibitory effect (SAR study).
• Aurones analogues could be considered as potential hepatitis C antivirals.

Following our recent report showing the potential of naturally occurring aurones (2-benzylidenebenzofuran-3(2H)-ones) as anti-hepatitis C virus (HCV) agents, efforts were continued in order to refine the structural requirements for the inhibitory effect on HCV RNA-dependent RNA polymerase (RdRp). In this study, we targeted the B-ring moiety of aurones with the aim to improve structural features associated with higher inhibition of the targeted polymerase. In vitro evaluation of the RdRp inhibitory activity of the 37 newly synthesized compounds pointed out that the replacement of the B-ring with an N-substituted indole moiety induced the highest inhibitory effect. Of these, compounds 31, 40 and 41 were found to be the most active (IC50 = 2.3–2.4 μM). Docking experiments performed with the most active compounds revealed that the allosteric thumb pocket I of RdRp is the binding pocket for aurone analogues.

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