Insecticidal activity of some oxime carbamates

Abstract

The insecticidal activity of representatives of a new group, the aldoxime carbamates, has been assessed and compared with that of known carbamate insecticides. Structure/activity relations have first been studied in terms of overall insecticidal activity and ability to inhibit housefly head acetylcholinesterase. Within the aldoxime carbamates, the thio- series are particularly active against caterpillars and the oxy- series against the housefly. Compounds of this group can exist in two geometrical forms, and of these the syn-configuration has been shown to be the more active against the enzyme and against whole insects. Systematic variation of the alkyl substituents has revealed that changes that increase PI50 do not necessarily give higher insecticidal activity. Two further factors, metabolism (inferred from tests with synergists) and partition co-efficient (as measured by Rm value) have therefore been considered. Certain anomalies of PI50 and toxicity can be explained on the basis of the degree to which compounds can be synergised in the whole housefly. In particular, members of the thio- series are more strongly synergised than those of the oxy- series. It also emerges that PI50 and Rm are directly related within a homologous series, but that there is an optimum Rm value for activity against the housefly.