Insecticidal Activities of Phenoxy Analogues of Dihydropipercide

The Piperaceae Amides (Part 7)

Abstract

In this series of communications, we have reported the isolation of an unsaturated amide, namely dihydropipercide [N-isobutyl-11-(3, 4-methylenedioxyphenyl)-(2E, 4E)-2, 4-undecadienamide] as well as two structually related amides as insecticidal principles from fruits of Piper nigrum L. This communication describes the structure-insecticidal activity relation-ships of the phenoxy analogues of dihydropipercide. As a result, N-isobutyl-12-(3-Br, 3-Cl or 3-CF₃ phenoxy)-(2E, 4E)-2, 4-dodecadienamides were selected as the most toxic compounds against Callosobruchus chinensis (adzuki bean weevil, about ten times as toxic as dihydropipercide). These selected amides revealed noticeable toxicities against Chilo suppressalis (rice stem borer), Musca domestica (housefly) and Spodoptera litura (tobacco cutworm). Electro-physiological study of the 3-CF₃ phenoxy derivative indicated that it acts on the central nerve cord as a neurotoxic principle. The amide caused Periplaneta americana (American cockroach) to knockdown by injection while the amide did not reveal knockdown effect when the same dosage was applied topically.