Date of Award

1987

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Abstract

Pheromones are highly active chemical messengers which are secreted by a member of an animal species and elicit a definite behavior in other members of the same species. The study of insect pheromones has recently attracted great attention because of their purely scientific interest and their favorable prospects for the control of pest insects. The study in this dissertation aims at the elucidation of some important aspects of the mechanism of perception of insect pheromones, which is based on the fact that the cyclic analogs of the natural pheromone have partially fixed conformations, whereas the straight-chain natural pheromone is more flexible and can adopt numerous conformations. The cyclic compound which best mimics the action of the natural pheromones presumably has a conformation similar to that which the pheromone adopts when bound to the receptor site. The project includes the following: (1) Syntheses of cyclic analogs of natural pheromones: (i) 4-ethyl-3-(5-acetoxypentyl)cyclopentene (20) and its cyclopentane (18). (ii) 4-methyl-3-(5-acetoxypentyl)cyclohexene (21) and its cyclohexane (19). (2) Structure elucidation including conformational analysis. (3) Results of conformational energies derived from MM2 calculations. Compound (20) was synthesized from the kinetic silyl enol ether of 2-(5-acetoxypentyl)-3-ethylcyclopentanone (37) which was treated with BH$\sb3$. THF, followed by acidification, to give (20). Compound (21) was also obtained using the same method from 2-(5-acetoxypentyl)-3-methyl-cyclohexan-one (63). Compound (37) was reacted with p-toluenesulfonylhydrazine in DMF-sulfolane having p-toluenesulfonic acid monohydrate as a catalyst, and followed by NaBH$\sb3$CN to give 2-(5-acetoxypentyl)ethylcyclopentane (18). In a similar manner, 2-(5-acetoxypentyl)methylcyclohexane (19) was obtained from (63). Several less successful routes to these disubstituted ring compounds were explored. The structures of (20), (18), (21), and (19) were assigned based on $\sp1$H NMR, $\sp{13}{\rm C}$-NMR, IR, and MS spectral data. Their stereochemical assignments have been made on the stereochemistry of analogs, their epimerization under alkaline conditions, or the coupling constants of the two hydrogen atoms on the two carbons bearing substituents. The most stable conformations of the 5- and 6-membered ring systems are in an envelope and a chair forms, respectively from MM2 calculations.

Pages

264

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