Pheromones terpene derived

Structurally, beetle pheromones are difficult to classify. They are often fatty acid or oxygen-containing terpene derivatives, occasionally with a complex polycyclic structure. 

The studies on the synthesis of the terpene-derived pheromones have led to the hypothesis that these compounds are waste products from the detoxification of host terpenes that, as a consequence of the timing and conditions of their production and release, have secondarily been utilized as chemical messengers. The nature of these oxidations, the large quantities of products formed, and the formation of the same products by other insects such as house flies when exposed to the terpenes led to the suggestion that the mixed-function oxidase system in the insect may well be involved. ... 

The special potential for constructing double bonds stereoselectively, often necessary in natural material syntheses, makes the Wittig reaction a valuable alternative compared to partial hydrogenation of acetylenes. It is used in the synthesis of carotenoids, fragrance and aroma compounds, terpenes, steroides, hormones, prostaglandins, pheromones, fatty acid derivatives, plant substances, and a variety of other olefinic naturally occurring compounds. Because of the considerable volume of this topic we would like to consider only selected paths of the synthesis of natural compounds in the following sections and to restrict it to reactions of phosphoranes (ylides) only. 

Aphid Alarm Pheromone. The alarm pheromone of aphids in the subfamily Aphidinae is ( )-P-famesene. The pheromone can be synthesized easily, but it is unstable under field conditions and therefore has limited potential for application. Although many plants produce this volatile chemical constitutively in their essential oil, aphids can differentiate between plant-produced material and aphid-produced material by the presence of other plant-derived terpenes, particularly ( )-caryophyllene, in the volatile blend. 

Silver ion chromatography is used primarily in liquid [213,215-218], thin-layer [212,213,216,219], and supercritical fluid chromatography [220-222] for the separation of fatty acid derivatives and triacylglycerols, and to a lesser extent, terpenes, sterols, carotenoids, and pheromones. Silver ion chromatography is widely used on its own, or as a preliminary simplification step, to elucidate the stmctures of fats, oils and lipids [213]. It is possible to fractionate animal or fish oils into fractions with zero to six double bonds. Species with the same total number of double bonds can be separated based on the difference in the number of double bonds in individual acyl residues. 

Terpenes are known to play important ecological roles not only in the defense of the tree, but also in bark beetle chemical ecology. Two chapters in this volume (see chapters by Raffa, et al, and Tittiger, et al.) review aspects of terpenoids as chemicals in conifer-bark beetle interactions and isoprenoid formation in bark beetle chemical ecology. While some species of bark beetles may be able to produce monoterpene pheromones de novo, bark beetles can also use host-derived monoterpenes as precursors to their own sex and aggregation pheromones. Bark beetle monoterpene pheromones are often used in a stereospecific manner such that often only one enantiomer is able to serve as a sex or aggregation pheromone. Since both enantiomeric host-derived monoterpene precursors are accepted and chemically modified by the beetle, the exact monoterpene enantiomeric mixture of conifer resin is important to both the beetle s ability to produce the correct pheromone and to the trees ability to escape an attack. ... 

Successful attempts to engineer mutants for selective oxidation of cheap terpenes to expensive oxidized derivatives have also been accomplished. Rational mutants of P450cam exhibited activity toward the sesquiterpene (+ )-valencene (48) and produced > 85% of (-F )-frans-nootkatol and (+ )-nootkatone [201]. The monoterpene (+ )-a-pinene (49) was oxidized by P450cam mutants to 86% (+ )-as-verbenol or to a mixture of (+ )-verbenone and (+ )-cis-verbenol (Figure 12.3) [202]. Verbenol and verbenone are active pheromones against various beede species. 

A large number of insect pheromone compounds are either simple terpenes or are derived from them. The few examples of monoterpenes given in Figure 6.4 illustrates the variety of structures that can be made from geranyl pyrophosphate or linalyl pyrophosphate without much further reaction. Both the Coleoptera and the Hymenoptera make frequent use of terpenes as secretory substances. Bark beetles have particularly employed monoterpenes in their aggregation pheromones. 

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