Ketones long-chain, unsaturated

By changing the groups the process has increased the versatility of Claisen rearrangements and has made it a powerful synthetic tool. Thus long chain unsaturated ketones can be prepared in good yields by the following reaction. 

While these functionalized ethers maybe long range signals,long chain unsaturated ketones, isolated from the elytra of females of the related species Anoplophora malasiaca, act as contact pheromones. The mixture of 10-hepta-cosanone, (Z)-18-heptacosen-10-one, (18Z,21Z) -18,21 -heptacosadien-10-one and (18Z,21Z,24Z)-18,21,24-heptacosatrien-10-one 188 proved to show pronounced biological activity [349]. 

Alkenones Long-chain, unsaturated ketones that are synthesized exclusively by certain haptophyte microalgae (e.g., Emiliania huxleyi). 

Sicre, M.-A., R. B. Gagosian, and E. T. Peltzer, Evaluation of the Atmospheric Transport of Marine-Derived Particles Using Long-Chain Unsaturated Ketones, J. Geophys. Res., 95, 1789-1795 (1990a). 

Cranwell P. A. (1985) Long-chain unsaturated ketones in recent lacustrine sediments. Geochim. Cosmochim. Acta 49, 1545-1551. 

Marlowe I. T., Brassell S. C., Eglinton G., and Green J. C. (1984b) Long chain unsaturated ketones and esters in hving algae and marine sediments. Org. Geochem. 6, 135-141. 

Self-metathesis describes the reachon of an unsaturated fatty acid with itself. For example, methyl oleate gives a mixture of starting material (50%), unsaturated hydrocarbon (25%), and long-chain unsaturated diester (25%), aU as a mixture of T-and trani-isomers. (Figure 18). The diester can be converted to the musk component civetone, but a more efficient route is through self metathesis of the ketone oleon derived from methyl oleate by Claisen condensation (104) (Figure 18). 

Prahl, F.G., and S.G. Wakeham. 1987. Calibration of unsaturation patterns in long-chain ketone compositions for paleotemperature assessment. Nature 320 367-369. 

Each turn of the P-oxidation spiral splits off a molecule of acetyl-CoA. The process involves four enzymes catalysing, in turn, an oxidation (to form a double bond), a hydration, another oxidation (forming a ketone from a secondary alcohol) and the transfer of an acetyl group to coenzyme A (Figure 7.12). The process of P-oxidation operates as a multienzyme complex in which the intermediates are passed from one enzyme to the next, i.e. there are no free intermediates. The number of molecules of ATP generated from the oxidation of one molecule of the long-chain fatty acid pal-mitate (C18) is given in Table 7.4. Unsaturated fatty acids are also oxidised by the P-oxidation process but require modification before they enter the process (Appendix 7.3). 

Paleotemperature might be reconstructed in ancient sediments through biomarker signals if cold-adapted and warm-adapted organisms produced distinctive lipids. The best-known example of such a signal is the long-chain ketones produced by haptophytes that carry patterns of unsaturation determined by sea-surface temperature (Brassell et al., 1986). 

Multiple intramolecular ring closures of aryl-substituted unsaturated long chain alcohols, acids, acid chlorides and ethers in the presence of Friedel-Crafts catalysts have been extensively employed to synthesize polynuclear hydroaromatic hydrocarbons and polycyclic ketones. This is illustrated by two examples shown in equations (112) and (113). The application of stereospecific cycloalkylations in approaching the synthesis of complex organic molecules has been reviewed by Barclay. ... 

Very long chain di- and tri-unsaturated methyl and ethyl ketones. 

Although the ratio of 180 160 in carbonate tests of marine invertebrates can be used to examine sea surface temperatures, the extent of continental glaciation, the balance between precipitation and evaporation, the carbonate compensation depth and the diagenetic alteration of carbonate all influence whether an estimation can be made and its accuracy (Boxes 5.6, 5.7 Marshall 1992). There is also a reliable organic geochemical palaeothermometer based on the distributions of long-chain (C37-C39) unsaturated ketones (Brassell et al. 

The degree of unsaturation of long-chain ketones in Emiliania huxleyi can be evaluated from the concentrations of the dominant di- and triunsaturated C37 components (C37.2 and C37.3 respectively see Fig. 5.1) ... 

Hydrolysis revealed mainly fatty acids, fatty alcohols and long chain n-am ides accompanied by unsaturated and branched isomers. In addition, steroid alcohols appeared in high amounts, but noteworthy the oxidized analogeous, the steroid ketones (e.g. cholestanone or coprostanone) were not present. Therefore a covalent association of the hydroxylated isomers by ester bondings is evident. 

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