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Olfaction in Insects: A Look at the Chemistry and Biology of Insect Sex Pheromones

Olfaction in Insects: A Look at the Chemistry and Biology of Insect Sex Pheromones. Jennifer N. Slaughter. Outline. Background Bombykol Chemical Characterization Synthesis 1. Lineatin 2. (+)-Grandisol 3. Brazilian Stink Bug Pheromone 4. Epianastrephin Conclusions. Introduction.

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Olfaction in Insects: A Look at the Chemistry and Biology of Insect Sex Pheromones

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  1. Olfaction in Insects: A Lookat the Chemistry and Biology of Insect Sex Pheromones Jennifer N. Slaughter

  2. Outline • Background • Bombykol • Chemical Characterization • Synthesis • 1. Lineatin • 2. (+)-Grandisol • 3. Brazilian Stink Bug Pheromone • 4. Epianastrephin • Conclusions

  3. Introduction semiochemicals pheromones allelochemicals semiochemicals (Gk. semeon, meaning mark or signal) pheromones (Gk. pherin, to carry and hormon, to excite) Allelochemicals (Gk. allelon, of one another) do Nascimento, R. R.; Morgan, E. D.Quim. Nova1996, 19, 156-65.

  4. Applications • Biochemist: ideal models • Agricultural community: insect control (beetles) • 1. monitoring • 2. direct insect control • 3. in conjugation with microorganisms • 4. enhancing beneficial activity • Synthetic chemist: challenging targets Krieger J; Breer, H. Science 1999, 286, 720-23. Pheromones of Non-Lepidopteran Insects Associated with Agricultural Plants; Hardie, J. and Minks, A. K., Eds.; 1999.

  5. Pheromones • Insects largely perceive the world through molecular interactions. • As a result, their olfactory systems have evolved • to an acute level of sensitivity and selectivity. • Moths with feathery antenna exhibit • detection on molecular level. • >1600 insect species resulted • in >300 unique chemical structures. A newly hatched male gum emperor moth. Roelofs, W. L. PNAS1995, 92, 44-49

  6. Stereochemistry and Activity 1. A single enantiomer is bioactive. • roughly 10 categories • each combination represented 2. A bioactive pheromone is inhibited by the enantiomer 3. A bioactive pheromone is inhibited by the diastereomer Mori, K. Chirality1998, 10, 578-86.

  7. Stereochemistry and Activity 4. Stereoisomers of the natural pheromone are also active • The natural pheromone is an enantiomeric mixture; both are • separately active 6. Different stereoisomers are employed by different species Mori, K. Chirality1998, 10, 578-86.

  8. Stereochemistry and Activity • Both enantiomers are necessary for bioactivity; neither is separately active 8. One enantiomer is more active than the other • One enantiomer is active on males, while the other is active on females Mori, K. Chirality1998, 10, 578-86.

  9. Insect Olfactory Receptor System male silkworm moth

  10. How Do Pheromones Get from the Environment to the Receptor Cell?

  11. Pheromone Transport • Pheromones are hydrophobic. • Water soluble PBPs pheromones at pore surfaces. • Elucidation of PBP-bombykol complex crystal structure

  12. Bombykol • produced by the female silkworm moth Bombyx mori • structure elucidation by Butendant and co-workers in 1959 Techniques in Pheromone Research; Hummel, H. E. and Miller, T. A., Ed.; Springer-Verlag: New York, 1984.

  13. Crystal Structure of PBP-bombykol The 15.9 kDa PBP has approximate dimensions of 40 x 35 x 30 Å. X-ray diffraction at 1.8Å resolution. Sandler, B. H.; Nikonova, L.; Leal, W. S.; Clardy, J. Chemistry & Biology2000, 7, 143-51.

  14. BmPBP Binding Pocket • Bombykol is found in a large flask-shaped cavity with a tiny • opening at the surface. • The only part of bombykol that is not surrounded by a-helices is • the hydroxyl end. Sandler, B. H.; Nikonova, L.; Leal, W. S.; Clardy, J. Chemistry & Biology2000, 7, 143-51.

  15. Bombykol Binding and Release • BmPBP undergoes a pH-dependent conformational transition. • BmPBP dos not bind ligands below pH 5. • BmPBP undergoes a conformational change when mixed • with model proteins. Briand, L.; Nespoulous, C.; Huet, J.; Takahshi, M.; Pernollet, J. Eur. J. Biochem 2001, 268, 752-60. Horst, R.; Damberger, F.; Luginbuhl, P.; Guntert, P.; Peng, G.;Nikonova, L.; Leal, W. S.; Wuthrich, K. PNAS2001, 98, 14374-79. Wojtaesk, H.; Leal, W. S. J. Bio. Chem. 1999, 274, 30950-56.

  16. Structure of BmPBP at Low pH • The most pronounced difference • between the BmPBP complex and • BmPBPA is the appearance of • helix a-7. 1H frequency of 750 MHz at 20ºC and pH 4.5. For comparison, the X-ray crystals were grown at pH 8.2. Horst, R.; Damberger, F.; Luginbuhl, P.; Guntert, P.; Peng, G.; Nikonova, L.; Leal, W. S.; Wuthrich, K.PNAS2001, 98, 14374-79.

  17. Representations of the BmPBP Binding Pocket BmPBP complex (pH 8.2) BmPBP in solution (pH 4.5) Horst, R.; Damberger, F.; Luginbuhl, P.; Guntert, P.; Peng, G.; Nikonova, L.; Leal, W. S.; Wuthrich, K.PNAS2001, 98, 14374-79.

  18. Isolation and Characterization • Pheromones are obtained in small quantities as volatile oils. • The first step is the separation of insect parts. • In earlier years of pheromone research, three techniques were • widely used in the initial isolation of pheromones. • These have been replaced due to large volumes of solvent and • massive amount of insect material required. • GC, GC-MS, IR, GC-FTIR do Nascimento, R. R.; Morgan, E. D.Quim. Nova1996, 19, 156-65.

  19. Determination of Stereochemistry • Stereochemical assignment by conventional analysis is • not possible. • Enantioselective synthesis of a target pheromone • Compare chiroptical properties to natural pheromone • Mori and co-workers have demonstrated the utility • this approach. Mori, K. Chirality1998, 10, 578-86.

  20. (+)-Acoradiene: Determination of Absolute Configuration 1R, 4R, 5S • The structure above was proposed on the basis of NMR studies. • It is a major component of the aggregation pheromone of the • broad-horned flour beetle. • unique spiro-sesquiterpene structure Kurosawa, S.; Bando, M.; Mori, K.Eur. J. Org. Chem.2001, 4395-99.

  21. Retrosynthetic Strategy Kurosawa, S.; Bando, M.; Mori, K.Eur. J. Org. Chem.2001, 4395-99.

  22. (+)-Acoradiene Kurosawa, S.; Bando, M.; Mori, K.Eur. J. Org. Chem.2001, 4395-99.

  23. Absolute Configuration • The X-ray structure reflects the major isomer from the • cyclization (1R, 4S, 5R, 10S). • The synthetic and natural pheromones are different. Kurosawa, S.; Bando, M.; Mori, K.Eur. J. Org. Chem.2001, 4395-99.

  24. Syntheses of Pheromones with Interesting Carbon Skeletons

  25. Lineatin striped ambrosia beetle 1R, 4S, 5R, 7R (+) • Aggregation pheromone of female ambrosia beetle • (+)-enantiomer is the naturally occurring pheromone • a member of the first class Baeckstrom, P.; Li, L.; Polec, I.; Unelius, C. R.; Wimalasiri, W. R.J. Org. Chem. 1991, 56, 3358-62.

  26. Retrosynthetic Strategy Key step in the synthesis of lineatin is the [2 + 2] cycloadditions to form cyclobutane ring Baeckstrom, P.; Li, L.; Polec, I.; Unelius, C. R.; Wimalasiri, W. R.J. Org. Chem. 1991, 56, 3358-62.

  27. Lineatin Baeckstrom, P.; Li, L.; Polec, I.; Unelius, C. R.; Wimalasiri, W. R.J. Org. Chem. 1991, 56, 3358-62.

  28. (+)-Grandisol • sex pheromone of male cotton boll weevils. • alkylation and [2 + 2] cycloaddition.

  29. Retrosynthetic Strategy • based on work done with C2-symmetric bis(a,b-butenolides) • asymmetric induction during the photoaddition process. de March, P.; Figuerdo, M.; Font, J.; Raya, J. Org. Lett. 2000, 2, 163-65.

  30. (+)-Grandisol Figuerdo, M.; Font, J.; Virgill, A. Tetrahedron 1987, 43, 1881-86. de March, P.; Figuerdo, M.; Font, J.; Raya, J. Org. Lett. 2000, 2, 163-65.

  31. Retrosynthetic Strategy Monteiro, H. J.; Zuckerman-Schpector, J. Tetrahedron1996, 52, 3879-88.

  32. (+)-Grandisol Monteiro, H. J.; Zuckerman-Schpector, J. Tetrahedron1996, 52, 3879-88.

  33. Brazilian Stink Bug Pheromone • structure was confirmed by synthesizing the racemic mixture • enantiomers were synthesized and separated Kuwahara, S.; Hamade, S.; Leal, W. S.; Ishikawa, J.; Kodama, O. Tetrahedron2000, 56, 8111-17.

  34. Retrosynthetic Strategy Kuwahara, S.; Ishikawa, J.; Leal, W. S.; Hamade, S.; Kodama, O.Synthesis2000, 1930-35.

  35. Brazilian Stink Bug Kuwahara, S.; Ishikawa, J.; Leal, W. S.; Hamade, S.; Kodama, O.Synthesis2000, 1930-35.

  36. Brazilian Stink Bug Kuwahara, S.; Hamade, S.; Leal, W. S.; Ishikawa, J.; Kodama, O. Tetrahedron2000, 56, 8111-17. Kuwahara, S.; Ishikawa, J.; Leal, W. S.; Hamade, S.; Kodama, O.Synthesis2000, 1930-35.

  37. Epianastrephin • sex pheromone mixture of the male Caribbean fruit fly • natural pheromone contains 55:45 mixture of enantiomers • a member of class five • relative stereochemistry determined by crystallographic studies • absolute stereochemistry established by chemical synthesis Schultz, A. G.; Kirincich, S. J. J. Org. Chem. 1996, 61, 5626-30.

  38. (-)-Epianastrephin: Retrosynthesis Tadano, K.; Isshiki, Y.; Minami, M.; Seiichiro, O. J. Org. Chem. 1993, 58, 6266-79.

  39. (-)-Epianastrephin Tadano, K.; Isshiki, Y.; Minami, M.; Seiichiro, O. J. Org. Chem. 1993, 58, 6266-79.

  40. (-)-Epianastrephin Tadano, K.; Isshiki, Y.; Minami, M.; Seiichiro, O. J. Org. Chem. 1993, 58, 6266-79.

  41. (+)-Epianastrephin: Retrosynthesis Schultz, A. G.; Kirincich, S. J. J. Org. Chem. 1996, 61, 5626-30. Schultz, A. G.; Kirincich, S. J. J. Org. Chem. 1996, 61, 5631-34.

  42. (+)-Epianastrephin Schultz, A. G.; Kirincich, S. J. J. Org. Chem. 1996, 61, 5626-30.

  43. Conclusions • insect olfactory system • pheromone transport (BmPBP) • isolation and characterization • synthetic challenges

  44. Acknowledgements • Members of the Mecozzi Group: • Sandro • Khanh • Oana • Peers: • Whitney Erwin Valerie Keller • Jason Pontrello Margaret Biddle • Lisa Jungbauer John Campbell • Erik Puffer Scott Petersen • Matthias Brewer Nero Shah • Konstantin Levitsky

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