Wittko Francke

University of Hamburg, Hamburg, Hamburg, Germany

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Publications (392)995.97 Total impact

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    ABSTRACT: How signal diversity evolves under stabilizing selection in a pheromone-based mate recognition system is a conundrum. Female moths produce two major types of sex pheromones, i.e., long-chain acetates, alcohols and aldehydes (Type I) and polyenic hydrocarbons and epoxides (Type II), along different biosynthetic pathways. Little is known on how male pheromone receptor (PR) genes evolved to perceive the different pheromones. We report the identification of the first PR tuned to Type II pheromones, namely ObruOR1 from the winter moth, Operophtera brumata (Geometridae). ObruOR1 clusters together with previously ligand-unknown orthologues in the PR subfamily for the ancestral Type I pheromones, suggesting that O. brumata did not evolve a new type of PR to match the novel Type II signal but recruited receptors within an existing PR subfamily. AsegOR3, the ObruOR1 orthologue previously cloned from the noctuid Agrotis segetum that has Type I acetate pheromone components, responded significantly to another Type II hydrocarbon, suggesting that a common ancestor with Type I pheromones had receptors for both types of pheromones, a preadaptation for detection of Type II sex pheromone.
    Full-text · Article · Jan 2016 · Scientific Reports
  • G. Bozsik · A. Tröger · W. Francke · G. Szőcs
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    ABSTRACT: Recently, the distribution of the Mediterranean cedar bark beetle, Phloeosinus aubei Perris (Coleoptera: Scolytidae), has expanded to Central Europe. Reported mostly on cypress in the Mediterranean area, potential host plants in the invaded range include other scale-leafed conifers, such as cultivars of arborvitae, Thuja occidentalis L. To reveal potential kairomonal cues for P. aubei, volatiles of T. occidentalis were collected and analysed by gas chromatography with electroantennographic detection (GC-EAD). Assignments of chemical structures of antennally active components were carried out by gas chromatography linked to mass spectrometry (GC-MS) using authentic reference samples. Antennal responses to synthetic samples of the identified compounds were studied by electroantennography (EAG), with antennae of female and male P. aubei. GC-EAD analysis of head space volatiles of T. occidentalis revealed 22 antennally active compounds, of which 21 were identified. The most abundant components were α- and β-thujone, fenchone, camphor, terpinen-4-ol, bornyl acetate and α-terpinyl acetate, all of which are oxygenated monoterpenes. When EAG activities of synthetic samples were compared, the most intensive responses from female antennae were elicited by a mixture of α- and β-thujone, followed by (-)-terpinen-4-ol, (+)-camphor, cis-4-thujanol, (+)-sabina ketone, (+)-terpinen-4-ol, isopulegone, (-)-fenchone, borneol, (3Z)-hexen-1-ol, (-)-1-octen-3-ol and (+)-sulcatol. Male antennae responded the most to (-)-terpinen-4-ol and cis-4-thujanol followed by the mixture of α- and β-thujone. The next highest responses were elicited by (+)-camphor, borneol, (+)-terpinen-4-ol, (+)-sulcatol and (+)-sabina ketone. Striking differences were found between responses to the enantiomers of fenchone, sulcatol and 1-octen-3-ol, whereas responses to the enantiomers of terpinen-4-ol did not differ significantly from each other. Several antennally active volatiles of T. occidentalis have also been reported from cypress and various other members of the Cupressaceae, suggesting that the sensory apparatus of P. aubei may recognize the shared components, which may enable rapid adaptation to new hosts in the invaded areas.
    No preview · Article · Oct 2015
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    ABSTRACT: Ceropegia species (Apocynaceae) have deceptive pitfall flowers and exploit small flies as pollinators, supposedly by chemical mimicry. Only preliminary data on the composition of flower scents are available for a single species so far, and the mimicry system is not yet understood in any species. We collected data on basic pollination aspects of C. dolichophylla, analyzed floral scent by gas chromatography linked to mass spectrometry (GC/MS), identified electrophysiologically active scent components by gas chromatography coupled with electroantennographic detection (GC/EAD), and determined compounds responsible for pollinator attraction in bioassays. We found that flowers of C. dolichophylla are visited by small flies of several taxa. Only Milichiidae and Chloropidae carried pollinaria and are, thus, pollinators. The pollen transfer efficiency (PTE) at two different sites was 2% and 4%, respectively. The floral scent was dominated by spiroacetals, mainly (2S,6R,8S)-8-methyl-2-propyl-1,7-dioxaspiro[5.5]undecane, n-tridecane, and N-(3-methylbutyl)acetamide. This spiroacetal and the acetamide elicited the most intense electrophysiological responses in fly antennae, and bioassays confirmed the capability of the spiroacetal in eliciting behavioral responses in pollinators. Most flies, determined as pollinators of C. dolichophylla, are kleptoparasites. They exploit insect prey of predatory arthropods as food source to which they are attracted by volatiles. 8-Methyl-2-propyl-1,7-dioxaspiro[5.5]undecane and N-(3-methylbutyl)acetamide have not been identified before as volatiles of other plants, however, they are known as insect volatiles. Both compounds occur in the venom glands of paper wasps, a potential food source for the pollinators of C. dolichophylla. We propose that C. dolichophylla shows a kleptomyiophilous pollination strategy. It mimics insect related odors to exploit the food-seeking behavior of its kleptoparasitic pollinators.
    Full-text · Article · Jul 2015
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    ABSTRACT: Male-specific volatile components, released by the dried bean beetle, Acanthoscelides obtectus, were identified as methyl (E,R)-2,4,5-tetradecatrienoate, methyl (2E,4Z,7Z)-2,4,7-decatrienoate, methyl (2E,4Z)-2,4-decadienoate, octadecanal and the sesquiterpenes (3Z,6E)- and (3E,6E)-α-farnesene. In olfactometer bioassays, pure methyl (E,R)-2,4,5-tetradecatrienoate was only weakly attractive to unmated females. However, a blend of the six identified compounds released in physiologically relevant ratios and doses proved to be as active as headspace odours collected from live males.
    Full-text · Article · May 2015 · European Journal of Organic Chemistry
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    ABSTRACT: The sex pheromone of the cloaked pug moth, Eupithecia abietaria G€otze, an important cone-feeding pest in spruce seed orchards in Europe, was investigated. Chemical and electrophysiological analyses of pheromone gland extracts of female moths and analogous analyses of synthetic hydrocarbons and epoxides of chain length C19 and C21 revealed (3Z,6Z,9Z)-3,6,9-nonadecatriene (3Z,6Z,9Z-19:H) and 3Z,6Z-cis-9,10- epoxynonadecadiene (3Z,6Z-cis-9,10-epoxy-19:H) as candidate pheromone components, which were found in a gland extract in a ratio of 95 : 5. In field trapping experiments, conspecific males were only attracted to a combination of 3Z,6Z,9Z-19:H and the (9S,10R)-enantiomer of 3Z,6Z-cis-9,10-epoxy-19:H. The (9R,10S)-enantiomer was not attractive, which is in agreement with studies on other Eupithecia species, for which males have only been attracted by the (9S,10R)-enantiomer of epoxides. Subsequent experiments showed that E. abietaria males were attracted to a wide range of ratios of the two active compounds and that trap catches increased with increasing dose of the binary blend. A twocomponent bait containing 300 lg 3Z,6Z,9Z-19:H and 33 lg of the (9S,10R)-enantiomer of 3Z,6Z-cis-9,10-epoxy-19:H was efficient for monitoring E. abietaria in spruce seed orchards in southern Sweden, where this species has probably been overlooked as an important pest in the past. With sex pheromones recently identified for two other moths that are major pests on spruce cones, the spruce seed moth, Cydia strobilella L., and the spruce coneworm, Dioryctria abietella Denis & Schifferm€uller, pheromone- based monitoring can now be achieved for the whole guild of conefeeding moths in European spruce seed orchards.
    Full-text · Article · May 2015 · Journal of Applied Entomology
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    ABSTRACT: Comparative GC/MS analysis of airborne volatiles produced by males and females of the guava weevil Conotrachelus psidii (Coleoptera: Curculionidae: Molytinae) showed the presence of a male-specific electroantennographically active compound identified as (1R,2S,6R)-2-hydroxymethyl-2,6-dimethyl-3-oxabicyclo[4.2.0]octane (papayanol). Release of this compound was dependent on the photoperiod, taking place primarily during the scotophase, with a maximum release between 2 and 6 h after the onset of the scotophase. Y-tube olfactometer bioassays revealed a strong attractiveness of the papayanol to male and female weevils considering the presence of the plant volatiles.
    No preview · Article · Apr 2015 · Journal of the Brazilian Chemical Society
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    ABSTRACT: Analysis of the pheromone gland extract of females of the click beetle Agriotes sordidus (Illiger), revealed the presence of geranyl hexanoate (GH) and (E,E)-farnesyl hexanoate (FH) in an approximate ratio of 1:1. In the female-released volatiles collected by headspace extraction, GH was a dominant component with FH present only in trace amounts. In field trapping tests GH on its own captured high numbers of A. sordidus adults, whereas the addition of FH in various proportions had no effect on captures. A closer scrutiny of adults caught in GH-baited traps revealed that 10–40 % of them were females. Significantly higher numbers of both female and male beetles were attracted to traps baited with GH as compared to unbaited controls showing a clear dose–response relationship with higher doses catching more beetles. In electroantennogram (EAG) tests responses of female and male antennae to a number of known click beetle pheromone components showed the same trend in both sexes, giving the highest answers to GH. This suggests that female and male antennae are similar with respect to the perception of pheromone components, and that GH shows some activity as an aggregation pheromone.
    Full-text · Article · Feb 2015 · Chemoecology

  • No preview · Conference Paper · Nov 2014
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    ABSTRACT: The sex pheromone of the cloaked pug moth, Eupithecia abietaria Götze, an important cone-feeding pest in spruce seed orchards in Europe, was investigated. Chemical and electrophysiological analyses of pheromone gland extracts of female moths and analogous analyses of synthetic hydrocarbons and epoxides of chain length C19 and C21 revealed (3Z,6Z,9Z)-3,6,9-nonadecatriene (3Z,6Z,9Z-19:H) and 3Z,6Z-cis-9,10-epoxynonadecadiene (3Z,6Z-cis-9,10-epoxy-19:H) as candidate pheromone components, which were found in a gland extract in a ratio of 95 : 5. In field trapping experiments, conspecific males were only attracted to a combination of 3Z,6Z,9Z-19:H and the (9S,10R)-enantiomer of 3Z,6Z-cis-9,10-epoxy-19:H. The (9R,10S)-enantiomer was not attractive, which is in agreement with studies on other Eupithecia species, for which males have only been attracted by the (9S,10R)-enantiomer of epoxides. Subsequent experiments showed that E. abietaria males were attracted to a wide range of ratios of the two active compounds and that trap catches increased with increasing dose of the binary blend. A two-component bait containing 300 μg 3Z,6Z,9Z-19:H and 33 μg of the (9S,10R)-enantiomer of 3Z,6Z-cis-9,10-epoxy-19:H was efficient for monitoring E. abietaria in spruce seed orchards in southern Sweden, where this species has probably been overlooked as an important pest in the past. With sex pheromones recently identified for two other moths that are major pests on spruce cones, the spruce seed moth, Cydia strobilella L., and the spruce coneworm, Dioryctria abietella Denis & Schiffermüller, pheromone-based monitoring can now be achieved for the whole guild of cone-feeding moths in European spruce seed orchards.
    Full-text · Article · Sep 2014 · Journal of Applied Entomology
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    ABSTRACT: Representatives of the highly speciose tropical butterfly genus Bicyclus (Lepidoptera: Nymphalidae) are characterized by morphological differences in the male androconia, a set of scales and hair pencils located on the surface of the wings. These androconia are assumed to be associated with the release of courtship pheromones. In the present study, we report the identification and biosynthetic pathways of several novel esters from the wings of male B. martius sanaos. We found that the volatile compounds in this male butterfly were similar to female-produced moth sex pheromones. Components associated with the male wing androconial areas were identified as ethyl, isobutyl and 2-phenylethyl hexadecanoates and (11Z)-11-hexadecenoates, among which the latter are novel natural products. By topical application of deuterium-labelled fatty acid and amino acid precursors, we found these pheromone candidates to be produced in patches located on the forewings of the males. Deuterium labels from hexadecanoic acid were incorporated into (11Z)-11-hexadecenoic acid, providing experimental evidence of a Δ11-desaturase being active in butterflies. This unusual desaturase was found previously to be involved in the biosynthesis of female-produced sex pheromones of moths. In the male butterflies, both hexadecanoic acid and (11Z)-11-hexadecenoic acid were then enzymatically esterified to form the ethyl, isobutyl and 2-phenylethyl esters, incorporating ethanol, isobutanol, and 2-phenylethanol, derived from the corresponding amino acids L-alanine, L-valine, and L-phenylalanine. Electronic supplementary material The online version of this article (doi:10.1007/s10886-014-0452-y) contains supplementary material, which is available to authorized users.
    Full-text · Article · Jun 2014 · Journal of Chemical Ecology
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    ABSTRACT: Females of the parasitoid wasp Trichogramma turkestanica produce the putative polydeoxypropionates (2E,4E,6S,8S,10S)-4,6,8,10-tetramethyltrideca-2,4-diene and (2E,4E,6S,8S,10S)-4,6,8,10-tetramethyltrideca-2,4-dien-1-ol or their enantiomers as sex specific volatiles. The structures were assigned on the basis of GC-MS investigations using synthetic reference compounds.
    Preview · Article · Apr 2014 · Beilstein Journal of Organic Chemistry
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    Full-text · Dataset · Mar 2014
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    John A. Byers · Göran Birgersson · Wittko Francke
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    ABSTRACT: The bark beetles Pityogenes bidentatus and Pityogenes quadridens (Coleoptera, Curculionidae, Scolytinae) are sibling species that feed and reproduce in bark areas on branches of Scotch pine, Pinus sylvestris. To identify aggregation pheromone components of both species, hindguts and head/thoraxes of males and females of both species feeding in hosts were extracted in pentane and analyzed by gas chromatography and mass spectrometry. Hindguts of male P. bidentatus contained grandisol as the major component along with small amounts of (4S)-cis-verbenol and other monoterpenes. Dose–response bioassays in the laboratory showed the components were attractive at 0.2 ng/min to walking beetles from a distance of ≥25 cm. In the field in southern Sweden, grandisol and (4S)-cis-verbenol were weakly attractive alone when released at rates of 0.05 and 0.5 mg/day, respectively, from a slow-rotating trap pair. Catch increased 3.6- to 13-fold when the two components were released together. The male proportion of the catch was 0.8 early in the flight period, declined to 0.5 on the peak flight day, and then declined further during the next 2 weeks to 0.2 on the last day of the flight period. Hindguts of male P. quadridens contained (2S,5R)- and (2S,5S)-chalcogran, as well as (E)-2-(3,3-dimethylcyclohexylidene)ethanol (E-grandlure 2) and E/Z-mixture of 2-(3,3-dimethylcyclohexylidene)acetaldehyde (grandlures 3 and 4), while female hindguts had only a trace amount of chalcogran. Laboratory studies proved E-grandlure 2 is an essential pheromone component for P. quadridens. Field bioassays with a slow-rotating trap pair in which the attractiveness of blends containing various candidate components were compared with that of less complete mixtures, showed that chalcogran and E-grandlure 2 were synergistic aggregation pheromone components of P. quadridens. Field tests also showed that grandisol (from P. bidentatus) reduced attraction of P. quadridens to its aggregation pheromone, whereas E-grandlure 2 and chalcogran (from P. quadridens) reduced response of P. bidentatus to its aggregation pheromone. Our results suggest that aggregation pheromone components from males of each species not only attract conspecifics but also aid individuals in avoiding interspecific mating and competition for food and spatial resources within the bark phloem layer.
    Full-text · Article · Dec 2013 · Chemoecology
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    ABSTRACT: Many pollinators specialize on a few plants as food sources and rely on flower scents to recognize their hosts. However, the specific compounds mediating this recognition are mostly unknown. We investigated the chemical basis of host location/recognition in the Campanula-specialist bee Chelostoma rapunculi using chemical, electrophysiological, and behavioral approaches. Our findings show that Ca. trachelium flowers emit a weak scent consisting of both widespread and rare (i.e., spiroacetals) volatiles. In electroantennographic analyses, the antennae of bees responded to aliphatics, terpenes, aromatics, and spiroacetals; however, the bioassays revealed a more complex response picture. Spiroacetals attracted host-naive bees, whereas spiroacetals together with aliphatics and terpenes were used for host finding by host-experienced bees. On the intrafloral level, different flower parts of Ca. trachelium showed differences in the absolute and relative amounts of scent, including spiroacetals. Scent from pollen-presenting flower parts elicited more feeding responses in host-naive bees as compared to a scentless control, whereas host-experienced bees responded more to the nectar-presenting parts. Our study demonstrates the occurrence of learning (i.e., change in the bee's innate chemical search-image) after bees gain foraging experience on host flowers. We conclude that highly specific floral volatiles play a key role in host-flower recognition by this pollen-specialist bee, and discuss our findings into the broader context of host-recognition in oligolectic bees.
    Full-text · Article · Nov 2013 · Journal of Chemical Ecology
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    ABSTRACT: Illiberis (Primilliberis) pruni Dyer (Lepidoptera: Zygaenidae) is an orchard pest distributed in China, Korea, the Far East of Russia, Mongolia and Japan. Field investigations organized in Naruto, Tokushima, Japan in 2008-2010 showed an attraction of the males of this species to (2R)-butyl (7Z)-dodecenoate alone and a mixture containing this compound and (2R)-butyl (9Z)-tetradecenoate. A further, more precise test, organized in 2011 clearly showed that for I. pruni males the most active attractant was the mixture containing (2R)-butyl (7Z)-dodecenoate and (2R)-butyl (9Z)-tetradecenoate in a ratio of 100:10. The seasonal flight of I. pruni as registered by catches in the pheromone traps in 2008-2011 was found to take place in June.
    Full-text · Article · Oct 2013 · Acta Zoologica Bulgarica
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    ABSTRACT: Unanswered key questions in bark beetle-plant interactions concern host finding in species attacking angiosperms in tropical zones and whether management strategies based on chemical signaling used for their conifer-attacking temperate relatives may also be applied in the tropics. We hypothesized that there should be a common link in chemical signaling mediating host location by these Scolytids. Using laboratory behavioral assays and chemical analysis we demonstrate that the yellow-orange exocarp stage of coffee berries, which attracts the coffee berry borer, releases relatively high amounts of volatiles including conophthorin, chalcogran, frontalin and sulcatone that are typically associated with Scolytinae chemical ecology. The green stage of the berry produces a much less complex bouquet containing small amounts of conophthorin but no other compounds known as bark beetle semiochemicals. In behavioral assays, the coffee berry borer was attracted to the spiroacetals conophthorin and chalcogran, but avoided the monoterpenes verbenone and α-pinene, demonstrating that, as in their conifer-attacking relatives in temperate zones, the use of host and non-host volatiles is also critical in host finding by tropical species. We speculate that microorganisms formed a common basis for the establishment of crucial chemical signals comprising inter- and intraspecific communication systems in both temperate- and tropical-occurring bark beetles attacking gymnosperms and angiosperms.
    Full-text · Article · Sep 2013 · PLoS ONE
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    ABSTRACT: It is unresolved as to whether fungi that share a common skin habitat might in principal interact. In in vitro screening tests with Candida albicans, Trichophytum rubrum and other common dermatophytes, we found C. albicans releases volatile compounds that inhibit growth of the dermatophytes. By applying (enantioselective) gas chromatography combined with mass spectrometry we identified 8 compounds among which stereochemically pure (3R,6E)-2,3-dihydrofarnesol (R-DHF) and (2E,6E)-farnesol (F-ol) were the main components. Synthetic R-DHF and its enantiomer, (3S,6E)-2,3-dihydrofarnesol (S-DHF), as well as F-ol were tested for their capacity to inhibit growth of dermatophytes in microtiter-plate assays over 62 h. All three compounds showed significant and concentration-dependent, to a certain extent even species-specific, inhibitory effects on T. rubrum, T. mentagrophytes, Microsporum canis and Epidermophyton floccosum. In general, S-DHF and F-ol had a pronounced effect on the dermatophytes, similar to or even stronger than that of fluconazole. E. floccosum was completely suppressed by 12.5 μg/ml dihydrofarnesol, as was the inhibition caused by 50 μg/ml fluconazole. Similarly, S-DHF- was more active against T. rubrum than fluconazole. To the best of our knowledge, 2,3-dihydrofarnesol has not yet been described as a volatile generated by microorganisms, and its inhibitory effect on dermatophytes is new to science. However, the relevance of this compound in interfungal interference in situ is unknown. In contrast, farnesol is a well-known semiochemical of C. albicans with intraspecific effects and a clear impact on other microorganisms. Mutual intermicrobial communication based on fungal volatiles therefore appears to be an exciting field for future investigations.
    Preview · Article · Aug 2013 · Medical mycology: official publication of the International Society for Human and Animal Mycology
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    ABSTRACT: Specificity in biological signalling systems is often important to keep information private. Foragers of several species of stingless bees deposit chemical marking signals to guide nestmates to food sources. The markings show species-and colony-specific compositions and primarily attract a bee's nestmates. An interesting question is whether the bees innately recognize specific trail markings or learn their particular composition from nestmates. To investigate this question, we tested whether Scaptotrigona pectoralis and Scaptotrigona subobscuripennis workers taken from their mother colonies and workers that emerged from combs transferred to foster colonies of the congeneric species are attracted to the marking compounds of workers from their natal colony or from the foster colony. A significant majority of workers were attracted to extracts prepared from foragers of the nest they inhabited, regardless of whether this was the original mother or the congeneric foster colony. Thus, the preference of stingless bee workers for specific food-marking scent mixtures is not innate, but is influenced by the odour they experience within their colony. Despite marked differences in the chemical composition of the scent marks in labial gland secretions of the two investigated species they also shared some main components. We hypothesize that recruitment trail information in stingless bees is composed of one or a few key pheromone compounds acting in conjunction with an additional signature mixture that is species and colony specific and must be learnt by recruited workers.
    Full-text · Article · Jan 2013 · Animal Behaviour
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    ABSTRACT: The native leafmining moth Tischeria ekebladella (Lepidoptera: Tischeriidae) feeds on oaks and recently has become a pest of silviculture and urban green areas in central Europe. The behavioral responses of male moths to hexane extracts of whole bodies of calling females or males were tested under laboratory conditions. Only extracts of females elicited responses from males. Analysis of extracts by coupled gas chromatography/electroantennographic detection revealed the presence of two electroantennogram-active peaks. Structure elucidation of these compounds, by gas-chromatography/mass spectrometry and independent synthesis revealed them to be (3Z,6Z,9Z)-tricosa-3,6,9-triene and (3Z,6Z,9Z,19Z)-tricosa-3,6,9,19-tetraene. While the triene was present in both sexes, the tetraene was female-specific. The latter is a new structure for a pheromone component of Lepidoptera and a novel natural product. Field trapping tests, carried out in a mixed oak forest near Budapest (Hungary), using synthetic compounds applied to rubber dispensers, showed that the tetraene per se elicited catches of males in large numbers. When the triene was added to the tetraene in a ratio of 1:1, there was no increase in trap catch; the triene alone did not elicit catches of males. For monitoring this insect, the tetraene, applied to rubber dispensers at a dose of 300 μg, is a potent sex attractant.
    Full-text · Article · Sep 2012 · Journal of Chemical Ecology
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    ABSTRACT: Following our earlier approach to the synthesis of dihydronepetalactones, all eight stereoisomers of trans-fused iridomyrmecins were synthesized starting from the enantiomers of limonene. Combined gas chromatography and mass spectrometry including enantioselective gas chromatography revealed that volatiles released by the endohyperparasitoid wasp Alloxysta victrix contain (4S,4aR,7S,7aR)-iridomyrmecin of 95-97% ee and stereochemically pure (4S,4aS,7R,7aS)-iridomyrmecin as a minor component.
    Full-text · Article · Aug 2012 · Beilstein Journal of Organic Chemistry

Publication Stats

10k Citations
995.97 Total Impact Points

Institutions

  • 1974-2016
    • University of Hamburg
      • Institute of Organic Chemistry
      Hamburg, Hamburg, Germany
  • 1991-2010
    • Cornell University
      Ithaca, New York, United States
    • Tulane University
      New Orleans, Louisiana, United States
  • 1987-2009
    • University of Freiburg
      • Institute of Forest Zoology
      Freiburg, Baden-Württemberg, Germany
  • 2002
    • Hungarian Academy of Sciences
      • Plant Protection Institute
      Budapeŝto, Budapest, Hungary
    • Simon Fraser University
      • Department of Biological Sciences
      Burnaby, British Columbia, Canada
  • 2001
    • Swedish University of Agricultural Sciences
      • Department of Plant Protection Biology
      Uppsala, Uppsala, Sweden
  • 2000
    • University of Greifswald
      • Institute for Microbiology
      Griefswald, Mecklenburg-Vorpommern, Germany
  • 1994
    • University of Queensland
      Brisbane, Queensland, Australia
  • 1992
    • Université Libre de Bruxelles
      Bruxelles, Brussels Capital Region, Belgium
    • University of Bayreuth
      • Chair of Organic Chemistry I
      Bayreuth, Bavaria, Germany
  • 1989
    • University of Santiago, Chile
      • Facultad de Ciencia
      Santiago, Region Metropolitana de Santiago, Chile