CHEMICAL SIGNALS FOR MANAGING INSECTS
Title: Improved synthesis of (3E,6E,9Z)-1,3,6,9-nonadecatetraene, inhibitor of attraction of bruce spanworm, operophtera bruceata, to pheromone traps for monitoring winter moth, operophtera brumata
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 14, 2009
Publication Date: January 3, 2010
Citation: Khrimian, A., Lance, D.R., Mastro, V.C., Elkinton, J.S. 2010. Improved synthesis of (3E,6E,9Z)-1,3,6,9-nonadecatetraene, inhibitor of attraction of bruce spanworm, Operophtera bruceata, to pheromone traps for monitoring winter moth, Operophtera brumata. Journal of Agricultural and Food Chemistry. 58(3):1828-1833.
Interpretive Summary: Insect pests cause a significant damage to crops and forest, and monitoring their populations aids greatly to reducing the pesticide use and biological control. Pheromones, or chemicals that trigger a natural behavioral response in another member of the same species, are commonly used as baits for sampling inset populations. The winter moth is an invasive species that attacks a wide variety of hardwoods and conifers. The insect is native to Europe but has become established in at least three areas of North America including southeastern New England. The pheromone of the winter moth is known but it also attracts closely related species, Bruce spanworm, which is not considered a pest and is visually indistinguishable from winter moth, thus complicating analysis of pheromone-baited traps. Hence, a trapping method that is specific for winter moth is highly desirable. A chemical (structurally related to winter moth pheromone) that inhibits the attraction of Bruce spanworm but does not affect winter moth catches has been reported in literature. However, the synthesis of this chemical has not been optimized, not has the trapping using both pheromone and the inhibitor.
We report now on two new and efficient syntheses of the inhibitor of Bruce spanworm attraction, thus making it available for field trails for monitoring winter moth. The results of this study are of interest to other chemists and entomologist involved in the research of potential pest control compounds, and to State and Federal agencies involved in monitoring and controlling insect pests of agriculture and forest.
The winter moth, Operophtera brumata (Lepidoptera: Geometridae), is an early-season defoliator that attacks a wide variety of hardwoods and, in some cases, conifers. The insect is native to Europe but has become established in at least three areas of North America including southeastern New England. The female-produced sex attractant pheromone of the winter moth was identified as (3Z,6Z,9Z)-1,3,6,9-nonadecatetraene (1), which also attracts a native congener, the Bruce spanworm, Operophtera bruceata. Dissection, or (for certainty) a DNA molecular testing is required to differentiate between males of the two species. Thus, a trapping method that is selective for winter moth would be desirable. A geometric isomer of the pheromone, (3E,6Z,9Z)-1,3,6,9-nonadecatetraene (2), can reportedly inhibit attraction of Bruce spanworm to traps without affecting winter moth catch, but use of the pheromone and inhibitor together has not been optimized, nor has the synthesis of the inhibitor. We present two new syntheses of (3E,6Z,9Z)-1,3,6,9-nonadecatetraene based on the intermediate (3Z,6Z)-3,6-hexadecadien-1-ol (3), which has also been utilized in the synthesis of the pheromone. The syntheses combine traditional acetylenic chemistry and Wittig olefination techniques. In one approach, we synthesized 2 of 80% purity (20% being pheromone 1), and in the second, tetraene 2 of 96% purity (and free of 1) was produced in overall 25 % yield from dienol 3. The last method benefited from a refined TEMPO-mediated PhI(OAc)2 oxidation of 3 and a two-carbon homologation of the corresponding alhedyde 4.