Trans-farnesene

Nickel-catalysed trimerization of isoprene has been shown to provide a mixture of natural /S-trans-farnesene (8) (cf. Vol. 1, p. 82) and the isomeric compound (9). ... 

Edwards, L. J., J. B. Siddall, L. L. Dunham, P. Uden, and C. J. Kislow trans- -Farnesene, Alarm Pheromone of the Green Peach Aphid, Myzus persicae (Sulzer). Nature 241, 126 (1973). 

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. 

Artemisia lactiflora Wallich Tian Cai (whole plant) Flavonoid glycoside, coumarin, lactiflorenol, spathulenol, s-guaiazulene, beta-guaienen, trans-(3-farnesene, frans-caryophyllene, limonene, elemene, copaene, myrcene.57 Diuretic, regulate menstruation, treat headache, high blood pressure. 

D-Bornyl acetate (= Borneol acetate) (monoterpene) Cardenolides (triterpene glycosides aglycones) see Table 4.1 for cardenolide Na+, K+-ATPase inhibitors Citral (= mixture of a-Citral (Geranial) (3-Citral (Neral) = trans-St av-3,7-Dimethyl-2,6-octadienal) (monoterpene) Citronellal (= 3,7-Dimethyloct-6-enal) (monoterpene) a-Farnesene (sesquiterpene)... 

Aphid Alarm Pheromones. When aphids are attacked by predators they produce droplets of secretion from their cornicles whose odor initiates escape behavior in nearby siblings. The first alarm pheromone was identified by Bowers et al. (2A) for the rose, pea, greenbug, and cotton aphids as trans-0-farnesene. The macrocyclic hydrocarbon germacrene A was subsequently identified as the alarm pheromone of the sweetclover and spotted alfalfa aphids (Figure 6) (25., 25.). 

This isomerization reaction was also found to provide the most useful route, short of total synthesis, to the relatively rare trans,trans-a-f mesene (7).4 Rhodium trichloride catalyzed isomerization of the relatively abundant trans-p-farnesene (6) gave the desired a-farnesene (7) in 57% yield. Products having a... 

Palladium-catalysed reaction of trans-j8-farnesene, formed by catalytic tri-merization of isoprene, resulted in regioselective head-to-head coupling to a dimer which yielded squalene on hydrogenation. A detailed n.m.r. study of functionalized squalane derivatives and model compounds suggests the presence of precoiled conformations. ... 

According to the TNO compilation (18) Bartlett pear aroma contains very low levels of butyl acetate (0.16 ppm), hexyl acetate (0.09 ppm), methyl trans-2-cis-4-decadienoate (0.05 ppm), ethyl trans-2-cis-4-decadienoate (0.04 ppm) and a-farnesene (0.04 ppm). The concentrations of the other compounds identified in Fig. 13 were not reported in the reference. 

---