Natural products in pest control

The utilization of natural products in pest control may be considered from a number of standpoints. First, the variety of structural types provides a rich source of compounds or models for conventional screening programmes. Second, consideration of the known biological activity of a natural product may lead to its application in pest management, either directly or after structural modification. Third, the recognition and understanding of the function of a chemical in nature may reveal potential approaches to pest management. 

Exposure to methyl bromide may occur in its production, in pest control and in fumigation of soil. Methyl bromide is naturally produced in oceans. It is commonly detected in ambient air and at low levels in water. 

Application of natural products to pest control is subject to similar considerations to those that affect synthetic compounds. Elucidation of structure may be a relatively routine matter, but synthesis may present difficulties, particularly where there are several stereochemical possibilities. There are often great differences in biological activity among different stereoisomers and the presence of Inactive Isomers in a product may be undesirable. However, such technical problems can be overcome as in the case of the synthetic pyrethroids where specific stereoisomers of high purity are now produced on a commercial scale. 

Biochemical Mechanisms. The role of natural products in the control of pests has increased in recent decades as the chemist has acquired more sophisticated tools with which to elucidate complex structures. This in turn has led to explosive growth in the understanding of biochemical processes. Knowledge of metabolism biosynthetic processes neurochemistry regulatory mechanisms and many other aspects of plant animal and Insect biochemistry has provided a more complete basis for understanding the mechanisms of plant resistance. 

McChesney, J.D., After discovery the issue of supply strategies in the development of natural products, in Bioregulators for Crop Protection and Pest Control, ACS Symposium Series No. 557, American Chemical Society, Washington, D.C., 1994. 

The rapidly expanding growth of knowledge of natural product structures now provide clearer understanding of biochemical mechanisms. This has made possible "biorational" approaches to the design of pest control agents. Natural products may be of potential value in pest control in several ways. 

Projects relating to the use of bioproducts have been conducted in our laboratory at the Federal University of Sao Carlos in Brazil. Three main projects can be mentioned. The first involves studies on the potential of certain plant species to produce natural products for the control of leaf-cutting ants. The second is on the theme of phytochemistry and chemical ecology, and concerns the search for model eompounds for the development of new insecticides, fungicides and bactericides to control plant pests. And the third concerns a search for antiparasitic natural products. 

Nordlund, DA. (1981) in Semiochemi-cals Their Role in Pest Control (eds D.A. Nordlund, R.L (ones, and W.J. Lewis), John Wiley Sons, Inc., New York, pp. 13-28 and references cited therein. Mori, K. (1992) in The Total Synthesis of Natural Products, Vol. 9 (ed. ). ApSimon), Wiley-Interscience, New York, pp. 1-534. 

In an article dealing with applications of olefin CM to a series of commercial products [138], solvent-free CM between ( )-3-hexene (produced by homocoupling of 1-butene) and 11-eicosenyl acetate 303 (produced from jojoba oil) was used to produce acetate 304 (Scheme 59), which is - as a natural 82 18 (EIZ) mixture - the pheromone of omnivorous leafroller, and serves as an environment-friendly pest controlling agent. The CM reaction was performed without solvent at 5 °C with a 4 1 mixture of ( )-3-hexene and 303, in the presence of only 0.2 mol% catalyst C, and furnished after 20 h coupling product 304 ( Z=83 17) in 50% yield. 

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