Natural products-based insecticidal agents 7. Semisynthesis and insecticidal activity of novel 4alpha-alkyloxy-2-chloropodophyllotoxin derivatives against Mythimna separata Walker in vivo.

In continuation of our program aimed at the discovery and development of natural products-based insecticidal agents, 16 novel 4alpha-alkyloxy-2-chloropodophyllotoxin derivatives were semisynthesized from podophyllotoxin, and preliminarily evaluated for their insecticidal activity against the pre-third-instar larvae of Mythimna separata Walker in vivo. Among all the tested derivatives, especially compounds 4b, 4e, 4g, and 4p exhibited more promising and pronounced insecticidal activity than toosendanin, a commercial insecticide derived from Melia azedarach. Generally, it was obviously demonstrated that the length of straight-chain or branched-chain alkyloxy, and heteroatom-containing cycloalkyloxy at the C-4 position of 2-chloropodophyllotoxin were very important for the insecticidal activity.