Insect Chemistry and Chirality PATRICIA Y. HAYES, 1 MARY T. FLETCHER, 1 SHARON CHOW, 1 MATTHEW J. McGRATH, 1 YONG Q. TU, 1 HESHENG ZHANG, 1 NATASHA L. HUNGERFORD, 1 CHRISTOPHER S.P. McERLEAN, 1 JEANNETTE E. STOK, 1 CHRISTOPHER J. MOORE, 2 JAMES J. DeVOSS, 1 AND WILLIAM KITCHING 1 * 1 Department of Chemistry, The University of Queensland, Brisbane, Australia 2 Department of Primary Industries, Yeerongpilly, Queensland, Australia ABSTRACT Examination of the chemistry of a number of Australian insect species provided examples of unusual structures and encouraged determinations of their abso- lute stereochemistry by stereocontrolled syntheses and chromatographic comparisons. Inter alia, studies with the fruit-spotting bug (Amblypelta nitida), certain parasitic wasps (Biosteres sp.), the aposematic shield bug (Cantao parentum), and various species of scarab grubs are summarized. The determination of enantiomeric excesses (ee’s) for component epoxides, lactones, spiroacetals, and allenes are described. Stereochemical and related aspects of the biosynthesis of spiroacetals in certain fruit-fly species (Bac- trocerae sp.) are also presented. Chirality 15:S116–S127, 2003. © 2003 Wiley-Liss, Inc. KEY WORDS: insect; synthesis; enantioselective; chromatography; epoxide; lactone; spiroacetal; allene; monooxygenase; biohydroxylation; stereoselectivity The characterization, synthesis, and demonstration of the biological role of insect-derived organic molecules con- stitute a fertile and interactive field for analytical and syn- thetic organic chemists, biochemists, and entomologists. Since Butenandt’s pioneering work with the silkworm moth and the role of (10E;12Z)-hexadeca-10,12-dienol (bombykol), 1 the progress in this general field has been phenomenal and the result of the productive intersection of the above disciplines. “Pheromone science” 2 has conse- quently emerged as a fascinating, interdisciplinary area of endeavor, and is driven to some degree by commercial and ecological considerations with respect to species-specific, “cleaner and greener” control measures for pest species. Not all insect components are “pheromonal,” but rigor- ous study of the overall chemical profile is justified, par- ticularly for chemo-taxonomic reasons. Studies of nonpest species are also worthwhile so that a panoramic under- standing of the chemistry and biochemistry, characterizing the various stages of the life-cycle, may be developed. In addition, insect chemistry provides some novel structures, which imply unusual and versatile biosynthetic capability. This latter aspect is beginning to receive more sustained attention. Component availability per individual insect is generally low (micro-nanogram amounts) and most are liquids of varying but significant volatility, and these characteristics posed earlier difficulties for structure elucidation. It is therefore no surprise that the great progress in this area has coincided with the advances in analytical organic chemistry, particularly various forms of chromatography and mass spectrometry. However, final and unambiguous determination of structure, and particularly chirality, where applicable, require synthesis of the suspected com- pound by routes that deliver particular stereoisomers, in- cluding enantiomers. The great advances in stereocon- trolled organic syntheses are well recognized and “phero- mone science” has provided some of the stimulation in this general field. Enantiomer availability permits determina- tion of the natural absolute stereochemistry by chromato- graphic, spectroscopic, and chiroptical methods and bioas- says, and the larger amounts furnished by synthesis permit more extensive assessments of attractancy, reception, etc. Many aspects of component identification, synthesis, re- ception, and biosynthesis have been dealt with else- where. 3,4 The purpose of this report is to describe some recent results from our laboratory, which emphasize structural diversity, stereocontrolled syntheses, and determinations of absolute stereochemistry of components from a range of insect species and in biosynthetic steps leading to spiro- acetals in fruit-fly species. RESULTS AND DISCUSSION (3R;5E)-2,6-Dimethyl-2,3-epoxyocta-5,7-diene: The Major Volatile Component From Male Fruit-Spotting Bugs, Amblypelta nitida Most fruit and nut crops in tropical and subtropical Aus- tralia are affected adversely by the fruit-spotting bug, Am- blypelta nitida (Heteroptera; Coreidae) and the banana spotting bug, A. lutescens. Neither appears to have signifi- cant natural enemies. Control is based largely on prophy- lactic use of endosulfan, but a “biocontrol” approach was Contract grant sponsor: the Australian Research Council. *Correspondence to: Professor William Kitching, Department of Chemis- try, The University of Queensland, Brisbane 4072, Australia. E-mail: kitching@chemistry.uq.edu.au Received for publication 16 December 2002; Accepted 1 April 2003 CHIRALITY 15:S116–S127 (2003) © 2003 Wiley-Liss, Inc.