& Biochemistry (2R,5S)-Theaspirane Identified as the Kairomone for the Banana Weevil, Cosmopolites sordidus, from Attractive Senesced Leaves of the Host Banana, Musa spp. Samson A. Abagale, [a, b] Christine M. Woodcock, [c] Antony M. Hooper, [d] John C. Caulfield, [c] David Withall, [c] Keith Chamberlain, [c] Samuel O. Acquaah, [b] Helmut Van Emden, [e] Haruna Braimah,* [a] John A. Pickett, [f] and Michael A. Birkett* [c] Abstract: The principal active component produced by highly attractive senesced host banana leaves, Musa spp., for the banana weevil, Cosmopolites sordidus, is shown by coupled gas chromatography-electroantennography (GC- EAG), coupled GC-mass spectrometry (GC-MS), chemical synthesis and coupled enantioselective (chiral) GC-EAG to be (2R,5S)-theaspirane. In laboratory behaviour tests, the synthetic compound is as attractive as natural host leaf material and presents a new opportunity for pest control. The banana weevil, Cosmopolites sordidus Germar (Coleoptera, Curculionidae), is the most important insect pest of bananas and plantains, Musa spp. [1–3] throughout the world. Feeding damage is caused by larvae of C. sordidus which are protected within the plant tissue, and so management strategies target adult weevils. Pheromones and other semiochemicals (natural- ly occurring behaviour- or development-modifying chemicals) constitute important tools for monitoring and detecting insect populations. A male-produced aggregation pheromone, (1S,3R,5R,7S)-sordidin, has been identified for C. sordidus. [4] For smallholder farmers in Ghana, for whom banana and plantain provide staple food, (1S,3R,5R,7S)-sordidin is deemed to be too expensive, and alternative semiochemical-based tools are ur- gently sought. Previous studies have shown that host plant lo- cation by adult C. sordidus is influenced by a highly attractive volatile kairomone from senesced banana leaves, [5, 6] which, if identified, could provide an effective and affordable alternative lure for management of C. sordidus on smallholder farms. The purpose of this work was to identify the active component(s) from volatile material collected from senesced leaves, using coupled gas chromatography-electroantennography (GC-EAG) recordings from the antennae of adult female C. sordidus, and confirm the attractiveness of the identified compound(s), thereby providing the quality assurance for using senesced banana leaves as an ethnobotanically based locally produced material in C. sordidus management. Coupled GC-EAG analysis (see the Supporting Information) with natural volatile material collected from senesced banana leaf material confirmed that the attractiveness of the material was caused by a very minor component with highly significant EAG activity (Figure 1). The 70 eV EI mass spectrum of the un- known EAG-active component (Figure 2) showed a base peak at m/z 138, an additional diagnostic fragment at m/z 179 and a molecular ion at m/z 194. Comparison of this spectrum with the literature [7, 8] suggested a theaspirane isomer 1, the base peak being rationalised by loss formally of isobutene (C 4 H 8 ) via a retro Diels–Alder rearrangement (Figure 2 inset). The pres- ence of two stereocentres (at the 2- and 5-positions) gives four possible stereoisomers, produced initially as the mixture, by chemoenzymatic synthesis from dihydro-b-ionone 2 (Scheme 1). To approach resolution of the natural EAG active isomer, initial reduction of 2 with sodium borohydride in a non-stereospecific manner gave a mixture of the (R) and (S)- isomers of dihydro-b-ionol in overall 100 % yield. The mixture of ionol isomers was resolved chemoenzymatically using lipase-mediated acetylation (Pseudomonas cepaciae lipase Amano PS-C, vinyl acetate, 99.2 % ee R, 94.8 % ee S). By adjust- ing incubation time, it was possible to obtain 99.1 % ee S. Fol- lowing separation of the (R)-ionol acetate and the (S)-ionol by silica gel liquid chromatography, the ionol then underwent in- [a] Dr. S. A. Abagale, Dr. H. Braimah Crops Research Institute, Council for Scientific and Industrial Research P.O. Box 3785, Fumesua-Kumasi (Ghana) E-mail : braimah_haruna@yahoo.co.uk [b] Dr. S. A. Abagale, Prof. S. O. Acquaah Department of Chemistry, Kwame Nkrumah University of Science and Technology, PMB, Kumasi (Ghana) [c] C. M. Woodcock, Dr. J. C. Caulfield, Dr. D. Withall, Dr. K. Chamberlain, Dr. M. A. Birkett Department of Biointeractions and Crop Protection, Rothamsted Research Harpenden, Hertfordshire, AL5 2JQ (UK) E-mail : mike.birkett@rothamsted.ac.uk [d] Dr. A. M. Hooper School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS (UK) [e] Prof. H. Van Emden School of Agriculture, Policy and Development The University of Reading, Earley Gate P.O. Box 237, Reading, Berkshire, RG6 6AR (UK) [f] Prof. J. A. Pickett School of Chemistry, Cardiff University,Cardiff, Wales CF10 3AT (UK) Supporting information and the ORCID identification number(s) for the au- thor(s) of this article can be found under: https://doi.org/10.1002/chem.201800315. # 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons At- tribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Chem. Eur. J. 2018, 24, 9217 – 9219 # 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 9217 Communication DOI: 10.1002/chem.201800315