Pheromones, unsaturated hydrocarbons

After excision of the transposon, the pheromone phenotype was reversed in 69 percent of the lines and the other excision lines showed generally decreased 7-unsaturated hydrocarbon levels (paralleled with similar increases in linear saturated hydrocarbons). These results clearly show the involvement of desatl in the biosynthesis of unsaturated hydrocarbons (Labeur et al., 2002). 

Fig. (5). Lepidopteran pheromone biosynthetic pathways utilize fatty acid synthesis, desatiindiun, specific chain-shortening enzymes, and/or functional modification of tlie carbony l carbon to produce species-apecific acetate ester, aldehyde, alcohol, or hydrocarbon pheromone blends. Unsaturated hydrocarbons can be further modified to epoxides (adapted from ref. [21]).

All the currently known indolizidine and quinolizidine alkaloids isolated from ants are illustrated in Fig. 6. (+ )-Monomorine I (427), the well-studied trail pheromone constituent of the Pharaoh ant Monomorium pharaonis), and the analogs 428-431 were described in the earlier volumes in this series. These five compounds are 3,5-disubstituted indolizidines bearing short saturated or mono-unsaturated hydrocarbon chains. The relative stereochemistry in monomorine VI (430) still remains unknown, while that of 431 was atypical for the class at the time of its isolation 380). The structural resemblance of fiiis group of alkaloids to the... 

CJundecane. Lithium didecylcuprate, prepared by reacting copper(I) iodide in ether with decyllithium in hexane, has been coupled with [ C]H3l. The above [ C]-labelled aliphatic and aromatic hydrocarbons have been used to study their effects on man, since they are common components in air pollutants. Aliphatic saturated and unsaturated hydrocarbons act also as pheromones and defensive secretions among some social insects such as ants and bees. The C-labelled compounds have been applied for in vivo studies" . ... 

Further chemistry of poly-unsaturated hydrocarbons is included in a review on the synthesis of the chiral component of insect pheromones/ and applications of the retro-Diels-Alder reaction in organic synthesis have been summarized/ ... 

By the radical pathway l, -diesters, -diketones, -dienes or -dihalides, chiral intermediates for synthesis, pheromones and unusual hydrocarbons or fatty acids are accessible in one to few steps. The addition of the intermediate radicals to double bonds affords additive dimers, whereby four units can be coupled in one step. By way of intramolecular addition unsaturated carboxyhc acids can be converted into five raembered hetero- or carbocyclic compounds. These radical reactions are attractive for synthesis because they can tolerate polar functional groups without protection. 

Insects make unsaturated as well as saturated hydrocarbons. The former as well as long-chain alcohols and their esters often form the volatile pheromones with which insects communicate. Thus, the female pink bollworm attracts a male with a sex pheromone consisting of a mixture of the cis,cis and cis,trans isomers of 7,11-hexadecadienyl acetate,13 and European corn borer males are attracted across the cornfields of Iowa by czs-ll-tetradecenyl acetate.14 Addition of a little of the trans isomer makes the latter sex attractant much more powerful. Since more than one species uses the same attractant, it is possible that the males can distinguish between different ratios of isomers or of mixtures of closely related substances. 

Chapter 19 by Bartelt is devoted to the pheromonal role of short-chain hydrocarbons, especially short i n etli y l/etli y I - branched and unsaturated components in beetles. The most abundant components in Carpophilus hemipterus (Coleoptera, Nitidulidae) have been identified as (2/ ,4/ ,6/ ,8/ )-3,5,7-(rimc(hyl-2,4,6,8-decatetracnc and (2E,4E,6E,SE)-3,5,7-trimethyl-2,4,6,8-undecatetraene (Bartelt et al., 1990). Later studies showed that male C. hemipterus emit nine all-E tetraene hydrocarbons and one all-E triene hydrocarbon in addition to the two previously reported pheromonally active tetraenes (Bartelt et al., 1992). In their review of biologically active compounds in beetles, Francke and Dettner (2005) fisted only a few dozen of those pheromonal compounds, most of which were identified by Bartelt. 

The majority of the known cuticular lipid constituents that function in chemical communication processes are hydrocarbons (Howard and Blomquist, 1982 Blomquist and Dillwith, 1985 Howard, 1993 Nelson and Blomquist, 1995). Most oxygenated lipids that function as pheromones are not part of the surface lipids but are secretory products of specialized glands (Tamaki, 1985 Am et al, 1986 Morgan and Mandava, 1988). Many of the compounds in pheromones are short-chain unsaturated aldehydes, ketones and acetate esters of short-chain (C10-C14) unsaturated alcohols. Those short-chain lipids (biological activity have been reviewed elsewhere (Blomquist and Dillwith, 1985 Tamaki, 1985 Lockey, 1988 Blomquist et al., 1993 Jurenka and Roelofs, 1993 Howard, 1993). 

One of the simplest methods of purification involves crystallization of synthetic intermediates (and sometimes of the pheromone itself) at low temperature. This technique has been extensively used in the purification of fatty acids, 9). Like unsaturated fatty acids, many of the related alcohols are very insoluble in hydrocarbon solvents at low temperature. 

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