Beetle pheromone

The third component of the elm bark beetle pheromone (p T 4) is a-cubebene (34) which the beetle takes from the tree. Simple disconnections lead to ketone (35). What disconnection would you suggest next ... 

Coleoptera comprise the largest order of insects and accordingly pheromone structures and biochemical pathways are diverse [98, 99]. Beetle pheromone biosynthesis involves fatty acid, amino acid, or isoprenoid types of pathways. In some cases dietary host compounds can be converted to pheromones, but it is becoming apparent that most beetle pheromones are synthesized de novo. 

Macrolide aggregation pheromones produced by male cucujid beetles are derived from fatty acids. Feeding experiments with labeled oleic, linoleic, and palmitic acids indicate incorporation into the macrolide pheromone component [ 117 ]. The biosynthesis of another group of beetle pheromones, the lactones, involves fatty acid biosynthetic pathways. Japonilure and buibuilactone biosynthesized by the female scarab, Anomalajaponica, involves A9 desaturation of 16 and 18 carbon fatty acids to produce Z9-16 CoA and Z9-18 CoA,hydroxylation at carbon 8 followed by two rounds of limited chain shortening and cyclization to the lactone [118]. The hydroxylation step appears to be stereospecific [118]. 

It appears that, in beetles, pheromone production is regulated by JH III, despite the variations in biosynthetic pathways. JH apparently regulates pheromone production in beetles that utilize both fatty acid and isoprenoid biosynthetic pathways [8,98]. Environmental and physiological factors will in turn regulate production of JH. The endocrine regulation of pheromone production in the beetles has been best studied with regard to the bark beetles. 

Structure elucidation of semiochemicals by modern NMR-techniques (including HPLC/NMR) is often hampered by the very small amounts of available material and problems in the isolation of pure compounds from the complex mixtures they are embedded in. Thus, the combination of gas chromatography and mass spectrometry, GC/MS, is frequently the method of choice. Determination of the molecular mass of the target compound (by chemical ionisation) and its atomic composition (by high resolution mass spectrometry) as well as a careful use of MS-Ubraries (mass spectra of beetle pheromones and their fragmentation pattern have been described [27]) and gas chromatographic retention indices will certainly facihtate the identification procedure. In addition, the combination of gas chromatography with Fourier-transform infrared spec-... 

The biosynthesis and endocrine regulation of pheromone production in beetles has been reviewed [33, 34]. Nevertheless, some more general pathways will be briefly discussed here. As corresponding structures are widespread among insects [2], the examples shown here are selected mostly from taxa other than beetles. Structures representing beetle pheromones will be shown in the context of the discussion of the corresponding species. 

The biosyntheses of the sap beetle pheromones has been carefully investigated by Bartelt and his co-workers [47,48]. The typical methyl-branching of the compounds originates from propanoate (or methylmalonate) units that form the principal structures (see Fig. 2). Replacement of propanoate by butyrate during chain elongation yields ethyl-branching. In about half of the compounds (125-128,133-136,138-140, and 144) the structures suggest acetate to act as a starter while in 133 and 147 the starter should be butyrate. The chains... 

An enantioselective approach to both enantiomers of a-alkyl-a-methoxyarylacetic acid derivatives has been described from L-(- -)-tartaric acid. Key steps include stereoselective addition of Grignard reagents to 1,4-diketones derived from tartaric acid. This methodology has been applied in synthesizing the pine beetle pheromone frontalin. 

Regiospecific Mono-Hydroxyalkylation of Dilithiated Lsopropenyiacetylene with Isovaleraldehyde (Preparation of a Precursor of a Bark-Beetle Pheromone)... 

Asymmetric reduction of Myny ketones. The (Reform of the complex (1) reduces alkynyl ketones to optically active propargylic alcohols (usually R) in 65-85% chemical yield and in 85-95% optical yield use of the (S)-form of 1, as expected, results in the epimeric alcohol. This reduction was used in a synthesis of the natural Japanese beetle pheromone (2, equation I).1... 

Bicyelic endoperoxides. The novel bicyclic [3.2.1]endoperoxide 2 has been prepared in high yield by oxidation of the ketone 1 with 90% H202 in the presence of BF3 etherale. The mechanism of this oxidation is not clear. Benzo-phenone-sensitized ultraviolet irradiation converts 2 into the pine beetle pheromone frontnlin (3) in i)uanlitntive yield. In the absence of the sensitizer the epoxide 4 is... 

The elm bark beetle pheromone contains three compounds multistriatin, the alcohol 12 and a-cubebene 13. At first we shall consider simple molecules like 12 but by the end of the book we shall have thought about molecules at least as complex as multistriatin and cubebene. 

This is the first of four General Strategy chapters in which we discuss important points that apply to the whole of synthetic design rather than one particular area. This chapter concerns general principles to help you choose one C-C disconnection rather than another. Even a simple molecule like the alcohol 1, introduced in chapter 1 as a component of the elm bark beetle pheromone, can be disconnected at any of the five marked bonds. 

Brand J. M., Bracke J. W., Britton L. N., Markovetz A. J. and Barras S. J. (1976) Bark beetle pheromones Production of verbenone by a mycangial fungus of Dendroctonus frontalis. J. Chem. Ecol. 2, 195-199. 

Leal W. S. (1998a) Biosynthesis of scarab beetle pheromones and neuropeptide regulation. Presented at Annu. Meet. Ent. Soc. Am., Las Vegas. 

Leal W. S., Zarbin P. H. G., Wojtasek H. and Ferreira J. T. (1999) Biosynthesis of scarab beetle pheromones enantioselective 8-hydroxylation of fatty acids. Eur. J. Biochem. 259, 175-180. 

Seybold S. J., Bohlmann J. and Raffa K. F. (2000) The biosynthesis of coniferophagous bark beetle pheromones and conifer isoprenoids evolutionary perspective and synthesis. Can. Entomol. 132, 697-753. 

White R. A., Jr, Agosin M., Franklin R. T. and Webb J. W. (1980) Bark beetle pheromones evidence for physiological synthesis mechanisms and their ecological implications. Z angew. Entomol. 90, 255-274. 

Molecular biology of bark beetle pheromone production and endocrine regulation... 

Some early and obvious questions about bark beetle pheromone components concerned their origins are they synthesized de novo from acetate or derived from plant precursor molecules And are the biochemical reactions performed by insect tissues or symbiotic bacteria Ipsdienol and ipsenol are clearly monoterpenoid alcohols. Since de novo monoterpenoid biosynthesis was unprecedented in the Metazoa before 1995, and monoterpenes are produced by host trees, it seemed logical that monoterpenoid pheromone components were derived from ingested plant precursor molecules (reviewed in Vanderwel and... 

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