Allosteric Inhibitors of Hepatitis C Polymerase:  Discovery of Potent and Orally Bioavailable Carbon-Linked Dihydropyrones

The discovery and optimization of a novel class of carbon-linked dihydropyrones as allosteric HCV NS5B polymerase inhibitors are presented. Replacement of the sulfur linker atom with carbon reduced compound acidity and greatly increased cell permeation. Further structure−activity relationship (SAR) studies led to the identification of compounds, exemplified by 23 and 24, with significantly improved antiviral activities in the cell-based replicon assay and favorable pharmacokinetic profiles.