Synthesis and SAR optimization of diketo acid pharmacophore for HCV NS5B polymerase inhibition

Hepatitis C virus (HCV) NS5B polymerase is a key target for anti-HCV therapeutics development. Here we report the synthesis and biological evaluation of a new series of alpha,gamma-diketo acids (DKAs) as NS5B polymerase inhibitors. We initiated structure-activity relationship (SAR) optimization around the furan moiety of compound 1a [IC50 = 21.8 mu M] to achieve more active NS5B inhibitors. This yielded compound 3a [IC50 = 8.2 mu M] bearing the 5-bromobenzofuran-2-yl moiety, the first promising lead compound of the series. Varying the furan moiety with thiophene, thiazole and indazole moieties resulted in compound 11a [IC50 = 7.5 mu M] bearing 3-methylthiophen-2-yl moiety. Finally replacement of the thiophene ring with a bioisosteric phenyl ring further improved the inhibitory activity as seen in compounds 21a [IC50 = 5.2 mu M] and 24a [IC50 = 2.4 mu M]. Binding mode of compound 24a using glide docking within the active site of NS5B polymerase will form the basis for future SAR optimization. (C) 2011 Elsevier Masson SAS. All rights reserved.