Albans, Keith Richard (1981) The inhibition of insect response by parapheromones. University of Southampton, Doctoral Thesis.
Abstract
The synthesis of twenty six esters and ketones which are structurally related to the major component of the sex pheromone of the Tobacco Budworm, Heliothis virescens, (Z)-1l-hexadecenal, is described. The compounds were screened in a laboratory bioassay experiment for parapheromonal activity associated with inhibition of the response of males to their natural pheromone. (Z)-9-Tetradecenyltrifluroacetate, (Z)-9-tetradecenyl trichloroacetate, N-methyl-(Z)-9-tetradecenyl carbamate and (Z)-l2-heptadecen-2-one were shown to be significantly active. In three cases the inhibition was shown to be reversible, but the carbamate had a lasting effect on the insects. The distance between the point of unsaturation and the carbonyl group was shown to be a critical parameter in the activity of these parapheromones. (Z)-12-lleptadecen-2-one was also shown to be active in blocking the response of the Cotton Leafworni Sp odoptera littoralis, to its own pheromone, as was the carbamate eater derived from a 9:1 mixture of (Z,E)-9, 11-tetradecadienol and (Z)-9-tetradecenul. However, the corresponding trifluroacetate ester was shown to be inactive. The response of H. virescens males to the seven individual components of their sex pheromone was studied by EAG. A minor component, (Z)-9-tetradecenal, was shown to be the most active. EAG was also used to study the response of H. virescens males to six parapheromones, only three of which are behaviourally active. No correlation between EAG response and parapheromonal activity was found.The effect of pre-exposure to an active parapheromone on the EAG response of insects to the primary pheromone components was studied. The response was significantly reduced initially, but increased with time, indicating that parapheromonal inhibition is at least partly associated with interaction with the antennae. The synthesis of five aldehydes which may adopt the same spatial conformation as the two primary pheromone components of ll. virescens is described. The response of the insect to these compounds was assayed by EAG but the results were inconclusive. The identification of the major component of the sex pheromone of the Tomato Moth, Laconobia oleracea, as (Z)-11-hexadecenyl acetate is described.
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