Synthesis of some ester derivatives of 4′-demethoxyepipodophyllotoxin/2′-chloro-4′-demethoxyepipodophyllotoxin as insecticidal agents against oriental armyworm, Mythimna separata Walker

Abstract

Podophyllotoxin is a naturally occurring non-alkaloid toxin isolated from the roots and rhizomes of Podophyllum peltatum and P. hexandrum. In continuation of our program aimed at the discovery and development of natural product-based insecticides, two series of ester derivatives of 4′-demethoxyepipodophyllotoxin/2′-chloro-4′-demethoxyepipodophyllotoxin were prepared. The structures of the target compounds were well characterized by 1H NMR, IR, optical rotation and mp. The precise three-dimensional structural information of 8j was further determined by single-crystal X-ray diffraction. Their insecticidal activity was tested against Mythimna separata Walker. These compounds showed delayed insecticidal activity. Among all derivatives, some compounds showed more potent insecticidal activity than toosendanin against M. separata; especially compounds 8k and 9k exhibited the most potent activity with the final mortality rates of 71.4%. Their structure–activity relationships were discussed.