Submitted to: European Journal of Organic Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/15/2004
Publication Date: 3/1/2004
Citation: Mori, K., Ohtaki, T., Ohrui, H., Berkebile, D.R., Carlson, D.A. 2004. Synthesis of the four stereoisomers of 6-acetoxy-19-methylnonacosane, the most potent component of the female sex pheromone of the new world screwworm fly, with special emphasis on partial racemization in the...hydrogenation. European Journal of Organic Chemistry. pp. 1089-1096. Interpretive Summary: The New World Screwworm fly remains a destructive pest of cattle and other mammals in several Caribbean nations and in all of South America, despite its eradication by USDA and IAEA sterile male release projects in North and Central America. A study of synthetic sex pheromone candidates was made using bioassays of synthetic chemicals in tests against colonized male New World Screwworm flies. A scientist at the Center for Medical, Agricultural and Veterinary Entomology, Gainesville Florida and another at the Midwest Livestock Insect Research Unit, Lincoln, Nebraska conducted bioassays with these flies. The tests show excellent biological activity including mating attempts using specially synthesized optically-active isomers of 6-acetoxy-19-methylnonacosane when tested at 0.5 ug or more against fertile males of 3 colonized strains. The compounds had been synthesized by Dr. K. Mori, Fuji Flavors Company, Japan for this important international effort. Research efforts continue in the search for attractive chemicals that can be used against these destructive insects using traps.
Technical Abstract: Starting from the enantiomers of citronellal and 1-octyn-3-o1, all four stereoisomers of 6-acetoxy-19-methylnonacosane were synthesized with sufficiently high stereochemical purities (more than 90% ee at C-6; about 97% ee at C-19) for biological testing as the female sex pheromone of the screwworm fly (Cochliomyia hominivorax).. All four isomers showed strong pheromone activity even at 1 /lg. and no significant difference was observed in their potency. Adams' platinum oxide was found to cause partial racemization of enantiomerically pure secondary propargylic alcohols in the course of their catalytic hydrogenation to saturated and secondary alcohols, while palladium-charcoal was less potent in causing partial racemization. A new HPLC-based discrimination of chiral and secondary alcohols proved to be useful in following such a subtle partial racemization.