Tricosene synthesis

The endocrine regulation of sex pheromone production in a laboratory strain of the housefly has been summarized (Blomquist, 2003). Because housefly sex pheromone production was correlated with ovarian development, it was possible that both oogenesis and (Z)-9-tricosene synthesis were regulated by a common hormone. Such a common factor was found in cockroaches and beetles, where juvenile hormone (JH) induces both vitellogenesis and sex pheromone production. 

The role of hemolymph in transporting hydrocarbons and hydrocarbon pheromones has only recently become fully appreciated. Older models of hydrocarbon formation showed epidermal-related cells (oenocytes) synthesizing and transporting hydrocarbons directly to the surface of the insect (Hadley, 1984). In the housefly, the role of hemolymph is most clearly seen when (Z)-9-tricosene production is initiated. (Z)-9-Tricosene first accumulates in the hemolymph, and then after a number of hours, is observed on the surface of the insect. Modeling of the process (Mpuru el al., 2001) showed that the delay is surprisingly long, more than 24 h are necessary for transportation from site of synthesis to deposition on the surface of the insect. 

Since a number of insect pheromones are nonfiinctionalized alkenes, they are potential target molecules for synthesis from petrochemicals by the metathesis reaction. Cross metathesis between unsymme-trical internal alkenes can lead to a complex mixture of products however, in some cases, this reaction provides the easiest method for production of such alkenes. For example, the pheromone for Musca do-mestica, tricosene, has been prepared from 2-hexadecene and 9-octadecene (equation 6). Both of these alkenes are readily available. 

Interesting results have been obtained in the synthesis of biologically active compounds such as insect pheromones. Conventional synthetic routes to these pheromones are often multistep sequences, which make many pheromones too expensive for widespread use [23]. Metathesis offers a shorter, alternative route to pheromone synthesis, generating these compounds in a few steps only. The use of insect sex pheromones is an environmentally friendly, effective, and selective method of pest control. Kiipper and Streck [24] synthesized insect sex pheromones by cross-metathesis reactions between linear olefins. In the presence of the catalyst Re207/Al203, 9-tricosene was synthesized by cross-metathesis of the readily available aUcenes 2-hexadecene and 9-octadecene (Eq. 8). 

Muscalure, cis-9-tricosene, is the sex-attractant insect pheromone of the common housefly. Give a practical synthesis of this compound from acetylene and straight chain alcohols. 

Dithiins act as alkene precursors, the desulfurisation being both fast and stereospecific as illustrated by a synthesis of muscalure, Z-9-tricosene, in 69% yield from decanal (94T7265). 

Muscalure, the sex attractant of the common housefly, is cis-9-tricosene. Most syntheses of alkenes give the more stable trans isomer as the major product. Devise a synthesis of muscalure from acetylene and other compounds of your choice. Your synthesis must give specifically the cis isomer of muscalure. 

Propose a synthesis for (Z)-9-tricosene (muscalure), the sex pheromone for the common housefly (Musca domestica), starting with acetylene and haloaUcanes as sources of carbon atoms. 

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