Farnesenic acid

In order to establish the primary character of farnesol, farnesenic acid was prepared from farnesal oxime and the corresponding nitrile. Saponification of the farnesene-nitrile with caustic soda solution yields farnesenic acid and acetic acid, and also a ketone which was identified as a dihydropsewdoionone. The semi-carbazone melts between 95° and 96°. The dihydropmtdoionone from farnesene nitrile proved to be... 

Experiments have been described94 in which small amounts of tracer have been incorporated into juvenile hormones from amino-acid precursors under conditions where the intracellular pool size of these precursors may be determined by routine methods, and an assay procedure has been developed95 by which the esterification of farnesenic acid with the methyl group from methionine, and the 10,11-epoxidation of the resultant ester to yield JH-III, can be measured in corpora allata of the adult female Schistocerca gregaria. 

The action of precocenes on the molecular level is not understood. Pratt and Bowers (1977) demonstrated the inhibition of the final steps in juvenile hormone biosynthesis, including epoxidation of farnesenic acid, following administration of precocene II to the test insects. Based on their experimental findings, members of the Bristol research group hypothesised that precocene and its derivatives are epoxidised to 3,4-epoxides having alkylating properties. The formation of these epoxides competes with the epoxidation step in JH biosynthesis, thus destroying the ability of corpora allata to synthesise JH. 

Dienic carboxylic acids. Prater has described a method for addition of an isoprene unit to an allylic alcohol. The method is iUustrated for the conversion of the ester (1) of geraniol into farnesenic acid (3). The ester is treated with lithium N-isopropylcyclohexylamide (LilCA, 4, 306-309) and then with trimethylchlorosilane. The resulting trimethylsilylketene acetal (a) undergoes... 

Farnesenic acid. Farnesic acid. Farnesylic acid [7548-13-2]... 

Ethyl propionate, in P-00078 14-Ethyltetradecanolide, in H-00275 Ethyl tridecyl ketone, see H-00178 Ethyl undecyl ketone, see T-00039 Ethynedicarboxylic acid, see B-00042 EU-4906, in S-00008 7,24-Euphadien-3j3-ol, see B-00043 Exaltolide, in H-00386 Exorcarpic acid, in 0-00148 Fagarol, in S-00001 Falcarindiol, in H-00031 Falcarinol, in H-00035 Falcarinone, in H-00040 a-Farnesene, F-OOOOl /3-Farnesene, F-00002 Farnesenic acid, see T-00205 Farnesic acid, see T-00205... 

Farnesenic Acid (2 6 lO-Trimethyl-undeca-1 5 9-triene carboxylic acid, or 2 6 l0-[Pg.62]

The flavour of distillates from apple and pear is characterised by typical aroma compounds from these fruits formed by enzymatic degradation of fatty acids to C6-fragments like hexanol, trans-2-hexenol, as well as ethyl esters and acetates of hexanoic acid. In distillates of pears, especially of the variety Bartlett pear, the characteristic pear flavour is mainly dominated by the ethyl and methyl esters of frans-2-czs-4-decadienoic acid and trans-2-trans-A-decadienoic acid [27-29], The biogenesis of these monounsaturated, diunsaturated, and triunsaturated esters may be explained by -oxidation of unsaturated linoleic and linolenic acid in the fruits. The sesquiterpene compound a-farnesene, which is formed during postharvest ripening and storage of Bartlett pears [28], shows that quality and intensity of distilled pear spirits is mainly influenced by the quality and degree of ripeness of the fruits. 

Fig. 5.1. A sample of floral scent compounds. (1) Substituted methyl esters of benzoic acid. The ester smells unpleasantly sweet when R = H (methyl benzoate), of wintergreen when R = OH (methyl salicylate), and of concord grape when R = NH2 (methyl anthranylate). Odorants with unusual origins and biological functions include the homoterpene 4,8-dimethyl-1,3,7-nonatriene (2) and the wet-earth compound geosmin (3). Some ubiquitous fragrance compounds are ben-zaldehyde (4), benzyl alcohol (5), indole (6), (S)-linalool (7), ( )-/ -ocimene (8), and of-farnesene (9).

Higher oxygenated terpenes include the sesquiterpene alcohol, famesol, which has a lily-of-the-valley odor and occurs in ambrette-seed oil. On acid dehydration it gives a-farnesene (Table 30-1) under some conditions, and bis-abolene (a component of oil of bergamot) under others ... 

The Ci5 terpenoids known as sesquiterpenoids are the most chemically diverse group of terpenoids known in nature. Like monoterpenoids, many sesquiterpenoids contribute to the flavor and fragrances of a variety of plant products. To date about 10,000 sesquiterpenoids are known (32), and in the plant kingdom they commonly occur as hydrocarbons, alcohols, aldehydes, ketones, carboxylic acids, lactones, and oxiranes. The acyclic sesquiterpene hydrocarbons a- and p-farnesenes (HI and H2, respectively) (Fig. 8) are constituents of the oils... 

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