Fig. 1.

Anti-influenza virus activity of 15a and synthesis of its derivatives. (A) Chemical structure of the hit compound 15a. (B) Inhibition of influenza virus-induced cytopathic effects by 15a. MDCK cells were mock-infected (no virus) or infected with three different types of influenza viruses, such as A/Puerto Rico/8/34 (H1N1), A/Hong Kong/8/68 (H3N2), and B/Lee/40, and then treated with serially diluted 15a in cell culture media. On day 3 p.i., the cell viability was measured using the MTT assay. The viability of uninfected, DMSO-treated cells was set to 100%, while that of cells infected with each virus was only set to 0%. The data shown are the means ± standard deviations (S.D.) of two samples from three independent experiments. n.d., not detected. (C) Synthesis scheme of the chemicals 15a–x. Me, methyl; Ph, phenyl.