Synthesis and Insect Growth Regulatory Activity of Alkoxy-Substituted Benzaldoxime Ethers

Alkoxy-substituted benzaldoxime ethers, namely (i) 3-methoxy-4-ethoxybenzaldoxime N-O-alkyl ethers, (ii) 3,4-dimethoxybenzaldoxime N-O-alkyl ethers, and (iii) 3,4-methylenedioxybenzaldoxime N-O-alkyl ethers, have been synthesized and evaluated for their insect growth regulatory activity against fifth-instar nymphs of the desert locust Schistocerca gregaria F. When injected into insect hemolymph at the lowest dose level of 3 µg/nymph, 3,4-methylenedioxybenzaldoxime N-O-methyl ether and 3,4-methylenedioxybenzaldoxime N-O-isopropyl ether showed 40 and 50% growth deformities respectively. On topical application (at 20 µg/nymph) 3-methoxy-4-ethoxybenzaldoxime N-O-methyl ether inflicted 100% abnormalties in insect growth. Structure-activity relationship studies revealed that maximum activity was associated with compounds having three carbons in the oxime ether moiety.