P-Famesene

The Rh/tppts catalysed C-C coupling reaction (Figure 17) has a broad scope and numerous conjugated dienes e.g. isoprene and P-famesene can be used as starting materials with other active methylene compounds e.g. acetylacetone and barbituric acid.506 Figure 18 depicts the Rh/tppts/Na2C03-catalysed isopreny-lation of barbituric acid which proceeds at room temperature in an H20/MeOH (75/25) solvent mixture.506... 

Some aphid species depend on ants (they are myrmecophilous) while others do not (nonmyrmecophilous aphids). The latter are better at defending themselves They move faster and defend themselves chemically. When attacked by ladybird beetles, they release the alarm pheromone (fj-P-famesene. In response to the pheromone other aphids walk around or drop from the plant. Pea aphids even may grow wings in response to alarm pheromone, allowing them to fly from the host plant. Ants also prey on other herbivorous insects, thus lowering their impact on the host plant. 

Composition a-Pinene and P-pinene, daucene, E-P-famesene, caryophyllene, gera-niol, geranyl acetate, daucol and as main constituent carotol. For latest literature see [44]. 

Aphid Alarm Pheromone. The alarm pheromone of aphids in the subfamily Aphidinae is ( )-P-famesene. The pheromone can be synthesized easily, but it is unstable under field conditions and therefore has limited potential for application. Although many plants produce this volatile chemical constitutively in their essential oil, aphids can differentiate between plant-produced material and aphid-produced material by the presence of other plant-derived terpenes, particularly ( )-caryophyllene, in the volatile blend. 

Figure 1 Transgenic signaling Arabidopsis thaliana emitting (E)-P-famesene...

Regioselective tail-to-tail coupling of p-famesene (19) was achieved using a modified palladium catalyst consisting of palladium nitrate, triphenylphos-phine, and sodium o-methoxyphenoxide. Catalytic hydrogenation gave squalene 20 in 85% yield. 

Figure 3. Total ion chromatogram of the ether extract of MUP from male mice. L 6-hydroxy-6-methyl-3-hep-tanone or its equilibrium lactol form shows as the large peak, the small peaks designated with the same letter are its degradation products, dihydrofurans DB 3,4-dehydro- xo-brevicomin BT 2-5ec-butyl-4,5-dihydrothiazole G geraniol p p-famesene a a-famesene. The unlabeled trace peaks are contaminants from distilled water and buffers.

Laboratory mice have been used as the model rodent to demonstrate the potential of aversive social odors to manage populations. Chemical constituents in the urine of dominant male mice have been shown to inhibit the exploratory behaviour of subordinate mice in laboratory-based arena studies. Two constituents, a and P-famesene, have been patented as mouse repellents (Novotny, Harvey Jemiolo, 1993). However, we do not know what effect these chemicals have on free-living rodent populations, where dominance hierarchies may not always exist. The scent marks left by dominant male rats within family groups appear to act not so much as warning signals for strange rats, but as aids to orientation (Lund, 1975). In the context of controlling rat populations, social odors are unlikely to produce the immediate reduction in numbers required to control a troublesome rat... 

The alarm pheromones of aphids often are sesquiterpenes such as ( )-3-famesene (71) and germacrene A (72) (Bowers, 1985). Upon release of these compounds, aphids drop from the plant on which they have been feeding. The compounds are very labile and break down in only a few minutes. This is important to prevent the aphids from being in a constant state of alarm (Bowers, 1985). Although this sesquiterpene elicits response in many species of aphids, the turnip aphid Lipaphis (Hyadaphis) erysimi responds only weakly. Addition of plant-derived isothiocyanates to p-famesene has a synergistic effect and greatly enhances the effect of P-famesene (71) (Dawson et al., 1987 Harbome, 1989). 

The famesenes are branched hydrocarbons with four double bonds (Fig. 96.9). E.E-a-famesene and E-p-famesene are widespread in essential oils, whereas E,Z-a-famesene and Z,Z-ot-famesene are not reported to occur in nature. Z, -a-famesene is a constituent of the trail pheromone of the red fire ant. The oxidation products, famesols as primary alcohols, as well as E- and Z-nerolidol as tertiary alcohol are occasional essential oil constituents. 

---