Insect sex pheromone precursors

In Vivo Synthesis in Yeast of Insect Sex Pheromone Precursors An Alternative Synthetic Route for the Production of Environmentally Benign Insect Control Agents... 

The presence of pyrrolizidine alkaloids in arctiid moths that had been reared on Senecio and Crotalaria species has been established by Rothschild et al.4S These alkaloids are stored in the moths, and serve as a deterrent to vertebrate predators and as precursors for insect sex pheromones. A pyrrolizidine alkaloid metabolite from the Cinnabar moth (Tyria jacobaea L.), named callimorphine, has been shown to have the structure (49) on the basis of mass-spectral and degradative evidence.46 The structure (49) was confirmed by synthesis of callimorphine and a diastereo-isomer by treatment of 9-chlororetronecine with the sodium salt of ( )-2-acetoxy-2-methylbutanoic acid. 

Via stereoselective ethenolysis of 1,5-cyclooctadiene (COD), Bykov et al. [25] prepared l,d5-5,9-decatriene, a precursor for the synthesis of many ds-isomeric insect sex pheromone compounds. In the presence of the MoCl5/Si02/Me4Sn catalyst system, at 20 °C and an ethene pressure of 25 bar, a 80 % conversion of COD was obtained with a selectivity of 68.4% for l,ds-5,9-decatriene. From this triene, many long-chain (CiQ-Cig) unsaturated acetates, alcohols and aldehydes can be obtained with the required biologically active cis conformation. Cross-metathesis of cyclooctene with a-olefins in the presence of the same catalyst gave... 

We have used cometathesis of cycloolefins with a-olefins (Scheme 1) as a general approach to biologically active natural compounds [26-30], primarily for preparation of l,A-dienes precursors of monoenic insect sex pheromone components having a double bond in 6-11 positions. The size of starting cycloolefin defines the internal double bond position in the target diene. The length of the latter is defined by total number of C -atoms in the cycloolefin and a-olefin. 

Thompson A. C. and Mitlin N. (1979) Biosynthesis of the sex pheromone of the male boll weevil from monoterpene precursors. Insect Biochem. 9, 293-294. 

Morse D. and Meighen E. A. (1987a) Biosynthesis of the acetate ester precursors of the spruce budworm sex pheromone by an acetyl CoA fatty alcohol acetyltransferase. Insect Biochem. 17, 53-59. 

The CM of fatty acids and derived compounds also has been used for the production of fine chemicals that are difficult to obtain by other synthetic approaches. Some examples include the synthesis of a plant growth stimulant, an insect pheromone precursor, the sex pheromone of the peach twig borer moth, and others [28]. Furthermore, the conjugation of fatty acid derivatives, sugars, and amino acids via CM was shown by Vemall and Abell [41]. C4 with a catalyst loading of 20 mol% was used to perform the CM of either Ai-Boc-L-ly sine or N-Boc-L-cysteine bearing a 10-undecenoic chain with methyl 10-undecenoate or a sugar olefin. 

Matsuoka, K Tabunoki, H., Kawai, T., Ishikawa, S., Yamamoto, M Sato, R. and Ando, T. (2006). Transport of a hydrophobic biosynthetic precursor by lipophorin in the hemolymph of a geometrid female moth which secretes an epoxyalkenyl sex pheromone. Insect Biochem. Mol. Biol., 36, 576-583. 

Wei, W., Yamamoto, M., Asato, T., Fujii, T., Pu, G. Q. and Ando, T. (2004). Selectivity and neuroendocrine regulation of the precursor uptake by pheromone glands from hemolymph in geometrid female moths, which secrete epoxyalkenyl sex pheromones. Insect Biochem. Mol. Biol., 34, 1215-1224. 

Some insects use hydrocarbons as sex pheromones. For example, the housefly, Musca domestica, uses a mixture including (Z) -9-tricosene, the corresponding epoxide and ketone, and several methyl alkanes (2iI). The tricosene is derived by chain elongation of oleic acid, and the epoxide and ketone are made from it. The methyl alkanes are made de novo from acetate and propionate, with one propionate unit per molecule supplying the branch carbon. Propionate can arise from the degradation of valine or isoleucine, but not from succinate, although succinate may serve as an acetate precursor. 

Host plants play a key role in the production and use of sex pheromones by herbivorous insects through larval or adult sequestration of chemically active compounds and pheromone precursors [210]. One of the best examples of sequestration of plant chemicals by larvae and their subsequent use by adult males in sex attraction or courtship interactions is shown in Utetheisa ornatrix (Arctiidae), whose courtship pheromone derives from pyrrolizidine alkaloids (PAs) ingested at the larval stage from the host plant Crotalaria spectabilis [211]. U. omatrix larvae sequester PAs (e.g. monocrotaline) and retain the alkaloids through metamorphosis into the adult stage to provide egg protection for the next generation. 

Another example of organic synthesis via cross-metathesis is the synthesis of biologically active compounds such as insect pheromones. Use of such pheromones offers an effective and selective pest control method. Thus, cross-metathesis of ethyl oleate with 5-decene results in a cis-trans mixture of ethyl 9-tetradecenoate, an insect pheromone precursor [15]. Cross-metathesis of methyl d.y-5-eicosenoate (obtained from meadowfoam oil) with excess 5-decene gives methyl tm 5-decenoate, which can be transformed into a 83 17 mixture of trani -5-decenylacetate and tran.y-5-decenol (in total 90% trans), the sex pheromone of the Peach Twig Borer moth, a major pest in Northern Hemisphere fruit orchards. The isomeric mixture was active in mating disruption [16]. Other examples of organic synthesis via cross-metathesis are summarised elsewhere [17 18]. 

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