Synthesis and biological evaluation of 2-oxo-pyrazine-3-carboxamide-yl nucleoside analogues and their epimers as inhibitors of influenza A viruses.

Novel 2-oxo-pyrazine-3-carboxamide-yl nucleoside analogues and their epimers were designed, synthesized and evaluated for their activities against influenza A viruses H1N1 and H3N2 in Madin-Darby canine kidney cells. All the compounds showed low cytotoxicities in these anti-influenza tests. One of the epimers, 4-[(1S, 3R, 4R, 7R)-7-hydroxy-1-(hydroxymethyl)-2,5-dioxabicyclo[2.2.1]heptan-3-yl]-3-oxo-3,4-dihydropyrazine-2-carboxamide 8a, with high antiviral activities (IC50 = 7.41, 5.63 μm for H3N2 and H1N1, respectively) and remarkable low cytotoxicity (TC50 > 200 μm), has great potential for further development as a novel anti-influenza A agent. Molecular docking of compound 8a with RNA-dependent RNA polymerase was performed to understand the binding mode between these inhibitors and the active site of RdRp and to rationalize some SARs.