2,5-Diketopiperazine Derivatives as Potential Anti-Influenza (H5N2) Agents: Synthesis, Biological Evaluation, and Molecular Docking Study.

2,5-Diketopiperazine derivatives, consisting of benzylidene and alkylidene substituents at 3 and 6 positions, have been considered as a core structure for their antiviral activities. Herein, the novel -substituted 2,5-Diketopiperazine derivatives were successfully prepared and their antiviral activities against influenza virus were evaluated by monitoring viral propagation in embryonated chicken eggs. It was found that (3,6)-3-benzylidene-6-(2-methyl propylidene)-4-substituted-2,5-Diketopiperazines (), (3,6)-3-benzylidene-6-(2-methylpropyli dene)-1-(1-ethyl pyrrolidine)-2,5-Diketopiperazine (), and Lansai-C exhibited negative results in influenza virus propagation at a concentration of 25 µg/mL.