Natural products-based insecticidal agents 13. Semisynthesis and insecticidal activity of novel phenazine derivatives of 4β-acyloxypodophyllotoxin modified in the E-ring against Mythimna separata Walker in vivo

In continuation of our program aimed at the discovery and development of natural products-based insecticidal agents, a series of novel phenazine derivatives of 4β-acyloxypodophyllotoxin modified in the E-ring were synthesized, and preliminarily evaluated for their insecticidal activity against the pre-third-instar larvae of Mythimna separata Walker in vivo. Among all the derivatives, compounds 7b, 7g, 7h and 7j exhibited more pronounced insecticidal activity than or comparable to toosendanin. Especially compounds 7h and 7j displayed the best promising insecticidal activity. Meanwhile, the relationships between their structures and the insecticidal activity were also described.

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► A series of novel phenazine derivatives of 4β-acyloxypodophyllotoxin modified in the E-ring were prepared.
► Two compounds displayed more pronounced insecticidal activity.
► The interesting structure–activity relationship was observed.
► It will pave the way for further design and synthesis of new podophyllotoxins.