Trienoic acids

Synthesis of 12-(5)-10-hydroxy-/ra/is-ll,12-epoxyeicosa-5,9,14-(Z)-trienoic acids, position isomers of hepoxylins isolated from blood platelets (Ref. 2) ... 

This remarkably selective internal epoxidation of peroxyarachidonic acid to form 14,15-oxido-arachidonic acid occurs as shown because of unusually favorable stereoelectronics. The corresponding reaction sequence with eicosa-(E)-8,ll,14-trienoic acid affords the Ai4,i5 epoxide in 94% isolated yield and >95% purity. 

The biosynthetic precursor of PGEi is cA,( ,( -icosa-8,ll,14-trienoic acid. 

Essential fatty acid deficiency Deficiency of linoleic acid, linolenic acid, and/or arachidonic acid, characterized by hair loss, thinning of skin, and skin desquamation. Long-chain fatty acids include trienes (containing three double-bonds [e.g., 5,8,11-eicosatrienoic acid, or Mead acid trienoic acids) and tetraenes (containing four doublebonds [e.g., arachidonic acid]). Biochemical evidence of essential fatty acid deficiency includes a trieneitetraene ratio greater than 0.4 and low linoleic or arachidonic acid plasma concentrations. 

Nomura and Ogata provided the first evidence that tunicates can produce PGs [17]. Using a rat stomach fundus bioassay, Halocynthia roretzi tissues were shown to possess low levels of PGs. The testes showed higher levels (9 ngg-1 wet tissue) than ovary and muscle tissue. The sea-squirt Styela clava did not show PGs by this method. No structures were determined in this work. Reexamination of the ability of H, roretzi to produce PGs was carried out by Ogata and coworkers [19]. Incubation of selected tissues with 14C-labeled eicosa-8,11,14-trienoic acid and subsequent isolation of PGE and PGF fractions after addition of carrier showed the branchial tissue to have the highest conversion levels. Quantitation was done by LSC. Using a TLC radioscanner, the authors determined that fractions with metabolites similar to PGE and PGF... 

Unsaturated fatty acids are probably the most abundant oxidizable endogenous substrates. In the past it was erroneously believed that unsaturated fatty acids are just products of lipid peroxidation. Now, it has been shown that they have dietary origin. Family of unsaturated fatty acids includes linoleic (Ci8), arachidonic (C2o), docosahexaenoic (C22), and other fatty acids containing two, three, four, five, or six double bonds. Some acids can be in vivo converted into others for example, linoleic acid can be metabolized to linolenic and eicosa-trienoic acids [78]. 

A convenient way of six-carbon homologation of aldehydes and ketones is the nucleophilic addition of the dianion generated from sorbic acid, (2 ,4 )-hexa-2,4-dienoic acid and subsequent dehydration to form the corresponding trienoic acid (equation 43)81. The 3-methyl analogue of sorbic acid has been used in a similar fashion for a short synthesis of vitamin A carboxylic acid (equation 44)82. 

FIGURE 2 Biosynthesis of ectocarpene in the higher plant S. isatideus (Aster-aceae). ro3 fatty acids and their degradation products (/3-oxidation) comprise the structural elements for the biosynthesis of ectocarpene in the higher plant S. isatideus. The structurally related trideca-3,6,9-trienoic acid is metabolized by analogy into the C 2 homoectocarpene. 

Interestingly, the first biosynthetic experiments with [3H]linolenic add and the terrestrial plant Senecio isatideus (Asteraceae) as a model system for the biosynthesis of algal pheromones were unsuccessful. If, however, labeled dodeca-3,6,9-trienoic add is administered, a rapid transformation into ectocarpene takes place (36). Nevertheless, the C12 add ultimately derives from linolenic acid via three /3-oxidations, since labeled tetradeca-5,8,11-trienoic acid, which requires only one /3-oxidation, is converted into labeled ectocarpene albeit with very low effidency (37). 

Mechanistic insight into this process was obtained by administration of labeled trideca- or undeca-3,6,9-trienoic acid instead of the natural C12 precursor (Figure 2). In this case, the artificial 2H metabolites can be analyzed by mass spectrometry without interference from the plants own 1H metabolites, since a homo- or norectocarpene is formed. The sequence of the oxidative decarboxylation/cyclization reaction proceeds without loss of 2H atoms from the double bonds but with loss of a single 2H atom from certain methylene groups of the precursor acids (Figure 3). If C(l) and a 2H atom from C(5) of the labeled precursor is lost, finavarrene is the product of the reaction channel. If the methylene group... 

FIGURE 3 Cn hydrocarbons from dodeca-3,6,9-trienoic acid. Loss of C(l) and a single hydrogen from C(5) yield the acyclic hydrocarbon finavarrene. Decarboxylation and loss of a single hydrogen from C(8) results in (6S)-ectocarpene. No other hydrogen atoms are lost during the biosynthetic sequence. 

FIGURE 5 Biosynthesis of Cla hydrocarbons in higher and lower plants. The similar pattern of functionalization of dodeca-3,6,9-trienoic acid and 9-HPEPE is shown. 

T etracyclo[5.5.1.13-11.15,9]hexasiloxanes nomenclature, X, 25 n-Tetradeca-frans-2,4,5-trienoic acid methyl ester synthesis, X, 429 Tetralactones ifiacrocyclic synthesis, 7, 749... 

In contrast, the hemolymph of females of the arctiid moth Spilosoma imparilis were found to contain significant levels of the polyunsaturated hydrocarbons corresponding to the epoxide pheromone components produced by this species (Wei el al., 2003). In a biosynthetic study with the arctiid Syntomoides imaon, the pheromone of which consists of a blend of 3Z,6Z,9Z-21 H and 1,3Z,6Z,9Z-21 H (Matsuoka el al., 2008), the lipids extracted from oenocytes and peripheral fat bodies associated with the abdominal integument contained both (llZ,14Z,17Z)-eicosa-ll,14,17-trienoic acid and (13Z,16Z,19Z)-docosa-13,16,19-trienoic acid, the intermediates predicted by elongation of linolenic acid by one or two cycles of 2-carbon chain extension (Ando et al., 2008). The latter acid is likely to be the direct biosynthetic precursor to 3Z,6Z,9Z-21 H (Ando et al., 2008). 

In the final installment of this story to date, Matsuoka et al. (2008) determined that female A. selenaria cretacea contained (llZ,14Z,17Z)-eicosa-ll,14,17-trienoic acid but not the longer-chain (13Z,16Z,19Z)-docosa-13,16,19-trienoic acid, in line with the fact that the pheromone of this species consists of 3Z,6Z,9Z-19 H and a corresponding monoepoxide (Matsuoka et al., 2008). That is, this geometrid only requires a C20 fatty acid precursor to decarboxylate to its C19 pheromone compounds. In contrast, as mentioned above, the arctiid species Syntomoides imaon, which produces C2i triene and tetraene pheromone components, was found to contain both (llZ,14Z,17Z)-eicosa-ll,14,17-trienoic acid and the longer-chain (13Z,16Z,19Z)-docosa-13,16,19-trienoic acid (Matsuoka et al., 2008). That is, the arctiid species requires the C22 precursor in order to produce its C21 pheromone components by decarboxylation, whereas the geometrid species only requires the C20 precursor, because its pheromone is composed of the shorter-chain C19 compounds. These data suggest that the chain elongation of linolenic acid and related precursors is under precise control. 

Matsuoka, K., Yamamoto, M., Yamakawa, R., Muramatsu, M., Naka, H., Kondo, Y. and Ando, T. (2008). Identification of novel C20 and C22 trienoic acids from arctiid and geometrid female moths that produce polyenyl type II pheromone components. 

Polyunsaturated fatty acids can also be prepared by Wittig reactions. Thus, Bergel-son and Shemyakin synthesized a-eleostearic acid [(9Z, 11ZT, 13 )-9,11,13-octadeca-trienoic acid 42] from (2 ,4 )-2,4-nonadienal 40 and phosphorane 4149). The intro-... 

For the study of the physical and chemical properties of triply unsaturated fatty acids and for the comparison with y-linolenoic acid [6Z,9Z.12Z)-6,9,l2-octadeca-trienoic acid] coworkers of the Unilever Research Centre in Vlaardingen (Netherlands) synthesized some methyl esters of ( ,Z,Z)-trisunsaturated fatty acids 73). For the preparation of the esters of (2E,9Z, 12Z)-2,9,12-octadecatrienoic acid and of (2 ,11Z,14Z)-2,11,14-eicosatrienoic acid (68 a and b) they used the Wittig reaction to introduce the ( )-2-double bond into the starting diunsaturated aldehyde. Reduction of the acid chlorides of (7Z,10Z)-7,10-hexadecadienoie acid and of linolenoic acid (65a and b) with lithium tri-tert-butoxyaluminium hydride affords the corresponding aldehydes 66 a and b which can be olefinated with the stable ylide 67 to methyl ( ,Z,Z)-alkatrienoates 68a, b with a (Z)-2-isomer content of 4.6%73) (Scheme 13). 

---