Pheromones geometric isomers

Miiller-Schwarze D., Silverstein R., Mtfller-Schwarze C., Singer A., et al. (1976). Response to a mamalian pheromone and its geometric isomer. J Chem Ecol 2, 389-398. 

A good example of applying the hydrazone method is the preparation of the optically active pheromone 34 (Scheme 2-22).38 Further study of the crude product prepared from SAMP-hydrazone and 3-pentanone 33 shows that, among the four possible stereoisomers, (Z,S, S )-isomer 35 predominates along with the minor (E,S,S)-isomer, the geometric isomer of 35. The final product 34 was obtained with over 97% enantiomeric excess (ee). 

The female sex pheromone of the currant shoot borer, Lampronia capitella Clerck (Lepidoptera Prodoxidae), was identified as a mixture of (Z, Z )-9,11-tetradecadienol and its corresponding acetate and aldehyde. The EAG-activity of all the four geometric isomers was studied, and the respective (Z, Z)-isomers were found to be the most active in all cases. Aldehydes elicited the highest response followed by the alcohol the ester was the least active compound. ... 

Analytical Properties Separation of positional isomers of aromatic compounds and geometrical isomers of sex pheromones Reference 7... 

Klun J. A., Chapman O. L., Mattes K. C., Wojtkowski P. W., Beroza M. and Sonnet P. E. (1973) Insect sex pheromones minor amounts of opposite geometrical isomer critical to sex attraction. Science 162, 661-663. 

The ability of male moths to perceive mixtures of geometric isomers with extraordinary acuity was further documented in an investigation of the responses of males of the redbanded leaf-roller and two populations of the European cornborer to isomers of 11-tetradecenyl acetate (21). Redbanded leafroller males were essentially unresponsive to pure preparations of their reported sex pheromone, (Z)-11-tetradecenyl acetate, but were strongly attracted to lures containing up to 8% of the (E)-isomer. Similarly, European cornborer males from Iowa responded maximally when 4% of the (E)-isomer was added to the (Z)-isomer, whereas the New York population was attracted to an isomeric mixture containing about 4% of the (Z )-isomer. Enhanced attraction by a small proportion of the opposite geometric isomer was also demonstrated with males of the oriental fruit moth,... 

The olfactory basis for the great discriminatory abilities of male moths vis-a-vis geometric isomers is unknown, but its presence provides an elegant mechanism for developing a highly specific sex pheromonal blend. 

Having determined that the high polarity cyano phase and the liquid crystal phase provide the best separation of the compounds likely to be found as components of the pheromone blend of H. virescens and H. subflexa, we analyzed a complex mixture of positional and geometrical isomers of 16 carbon aldehydes, alcohols, and acetates on these two columns (Figure 7). As noted earlier, the elution order of Z- and JE-isomers is opposite on the two phases. Aldehydes elute first on both phases. The alcohols are retained more than the acetates on the high polarity cyano phase, but the elution order of alcohols and acetates is reversed on the liquid crystal phase. While neither phase separated all of the synthetic mixture, the combination of separations obtained on both columns enabled us to pursue the... 

The chemical and stereochemical purities of synthetic pheromones are often of critical importance for their use in survey and monitoring traps (2,5). The problems associated with inhibitors requires, in general, that the synthetic products have high chemical purity. The fact that a precise mixture of geometrical isomers is usually essential if the synthetic material is to be an effective attractant in the field requires that the synthetic route give a product of reproducible and predictable stereochemical composition. 

Figure 18. The 4 geometrical isomers of 11,13-hexadecadienal (Z,Z-isomer is the navel orangeworm pheromone). Conditions 30M, LFV — 17 cm/s, 159°C, 50 =...

Like many other insects, moths attract mates by long-distance pheromones. Females produce these pheromones in specialized abdominal glands. Chemically, they are acetates, often active in precise mixtures of geometric isomers. Males fly upwind, following the females pheromone plume to the somce, and mating ensues. In a typical experiment, a female moth, or just the pheromone, serves as odor source. An air current from that source helps to attract males who fly upwind to the pheromone source and attempt to mate. With this technique, we can compare the effects of known pheromones from different, related species on one species (species specificity). We can also test the attractiveness of different compounds that are stracturally similar to a known pheromone. In the laboratory, a wind tunnel, where available, is ideal, for this experience. 

From 1976 to 1978, tremendous efforts were spent on the isolation of a major component (in a pure form) of the sex pheromone of the female cockroach, Periplaneta americana. The potency of the compound isolated, periplanone B, was truly amazing (threshold limits of 10 pg). It was considered to be a promising agent to control this pest. However, only trace amounts were isolated from natural sources (a total of 0.2 mg isolated from 75 000 specimens). Even the use of modern methods of instrumental analysis did not lead to the elucidation of its complete structure. With the help of these methods it was possible only to ascertain the basic structural features, as shown in formula 59a (Scheme 1.16). The problem of its stereochemistry remained unanswered. This most difficult part of the problem was finally solved only after a total synthesis of three of four possible geometrical isomers of periplanone Comparison of the spectral parameters of synthetic samples with those of the natural periplanone B determined the stereochemistry as shown in structure 59b. A minor component of the same pheromone, periplanone A, was available in even... 

Selected Applications in Synthesis 4.1 Carotenoids, Retenoids and Pheromones.- Classical Wittig methods involving the ylide (146) and the dialdehyde (147) have been used to synthesize (148), a diastereoisomer of decaprenoxanthin.88 The retinonitrile (150) has been prepared as a mixture of four geometric isomers by phosphonate-based olefination of the 1-cis, 9-cis-Ci5-aldehyde (149). It was possible to separate the four isomers of (150) and reduce each of them to the corresponding retinal. 

Bombykol is a well-known pheromone, first isolated from Bombyx mori L. Bombykol the three related isomers were synthesized by cross-coupling reaction. Three alkenylboronates or boronic acids (35 and 36) required for the coupling are prepared by starting from two alkynes. The stereoselective syntheses of ( )- and (Z)-l-alkenylboronic acids or esters have been discussed in Section 2.2.1. Halogenation of alkenylboronic acid 34 with either iodine or bromine provides ( )- and (Z)-haloalkenes [71]. The palladium-and base-assisted coupling of the Cj-boronate 32 or 33 with the C,-halide 35 or 36 stereoselectively provides bombykol and its three geometrical isomers (Scheme 2-29) [72]. 

When we first introduced the concept of enantiomers and chirality in Chapter 16, we stressed that any imbalance in enantiomers always derives ultimately from nature. A laboratory synthesis, unless it involves an enantiomerically pure starting material or reagent, will always give a mixture of enantiomers. Here is just such a synthesis of the Japanese beetle pheromone you have just met. You can see the Z-selective Lindlar reduction in use—only one geometrical isomer of the double bond is formed— but, of course, the product is necessarily racemic and therefore useless as beetle bait, because in the original addition of the lithiated alkyne to the aldehyde there can be no control over stereochemistry. If all the starting materials and reagents are achiral, the product must be... 

A single geometrical isomer of an insect pheromone was prepared in the following way. Which isomer is formed and why ... 

The agreement of mass spectra does not infer equivalence of double bond configurations because the geometrical isomers of these tetraenes, in our experience, have virtually identical spectra. However, the GC retentions of 6 and the pheromone were identical, and GC retention is very sensitive to double bond configuration. In addition, the samples had identical retentions on the AgNO column and UV spectra. Thus, from all available chemical evidence, compound... 

Muller-Schwartze, D., R.M. Silverstein, C. Muller-Schwartze, A.G. Singer, and N.J. Volkman Response to a Mammalian Pheromone and its Geometrical Isomers. J. Chem. Ecol. 2, 389-398 (1976). 

However, no cells in the males were keyed to the third compound (- )-cubebene which is produced by the host tree. Both sexes of 5. scolytus possess a majority of receptor cells keyed to either of the two male-produced compounds, (-)-threo-4-methyl-3-heptanol and the (-)-erythro-stereo-isomer, and in this species some cells were keyed also to (- )- -multistriatin (Wadhams et al., 1982). The relative sensitivities and specificities of these cells were determined in the same way as described for Ips species. Each cell was minimally activated by pheromone components other than its own key substance. The functional types of olfactory receptor cells discussed here for Scolytus, as with the cells of Ips, apparently are all keyed to the specific isomer of the pheromone compounds. The cells specialized to (- )-a-multistriatin are 1000 times less sensitive to the geometrical isomer d-multistriatin. However, the discrimination of the optical form of multistriatin seemed to be less pronounced. The substantially lower effect of the (-l-)-stereo-isomer (optical purity 99.5%), cannot be solely ascribed to contamination with the (- )-enantiomer. It implies that these cells in fact may also respond to (-l- )-multistriatin, although to a lesser extent. The cells keyed to methyl-heptanol are, however, highly optically specific in both species. 

Den Otter, C. T. (1977) Single sensillum responses in the male moth Adoxophyes orana (F.v.R.) to female sex pheromone components and their geometrical Isomers. J. comp. Physiol., 121, 205-22. 

It is also interesting to note that for all nine of these mealybug and diaspidid scale species, the male insects are readily attracted to mixtures of the pheromone component(s) with other stereoisomers. This is in distinct contrast to the pheromone-mediated behavior of insects in other orders, such as moths and beetles, in which the males are frequently acutely sensitive to trace amounts of stereoisomers of the pheromone conq)onents, including both geometric isomers and enantiomers. The reason for this is that insects such as moths and beetles usually make use of a limited number of pheromone components, with species-... 

Geometric Isomers in Nature Males of the Iowa strain of the European corn borer respond most strongly to mixtures of the female sex attractant pheromone that are 96% c/s isomer. But males of the New York strain respond most strongly to mixtures containing 97% trans isomer. 

Sesquiterpenic alcohols Examples of sesquiterpenic alicyclic alcohols (8-24) are farnesol and nerolidol (also known as peruviol). Both alcohols, smelling of flowers, are components of many essential oils used in perfumery. Of the four possible geometric isomers, the (2 ,6B)-isomer of farnesol, is the most common in nature and occurs, for example, in basil oil and ambrette (Abelmoschus moschatus Malvaceae) seed oil. The (2Z,6 )-isomer occurs in the petit grain oil bigarade, which is derived from the bitter orange tree leaves (Citrus aurantiumvai. amara, Rutaceae). Farnesol is a natural pesticide for mites and a pheromone for several species of insects. Nerolidol with a double bond at C-6 occurs in the form of (Z)- and ( )-isomers, each of which can exist as an enantiomeric pair (chiral carbon C-3). The individual enantiomers and their mixtures are found in many essential oils. For example, the essential oil known as cabreuva oil that is used in perfumery is obtained from the bark of the South American tree Myrocarpus frondosus (Fabaceae) and contains the (-F)-(E)-isomer of nerolidol (3S,6 )-nerolidol. 

Disparlure, the sex attractant pheromone of the female gypsy moth, has the following general structure. Are geometric isomers possible for this molecule ... 

Determine the cis-trans geometry around the double bonds in the following compound, a trail pheromone of termites. (The chain is numbered starting from the carbon atom with the hydroxyl group.) How many geometric isomers are possible for the structure ... 

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