A-Famesene

Several natural products (Scheme 60) have been synthesized in vitro via singlet oxygen ene reactions. For example, clavukerin C was prepared202 in racemic form, in a biomimetic synthesis by Kim and Pak, whereas a-famesene hydroperoxide was obtained203 starting from geraniol. 

Composition Main constituent is zingiberene (>30%) followed by P-sesquiphelland-rene. (-H)-ar-curcumene, (E,E)-a-famesene and (-)-P-bisabolene are further important sesquiterpene hydrocarbons. a-Terpineol and citral (up to 9% in Australian ginger) result in the citrus note, whereas nerolidol is responsible for the woody-soapy taste [115]. Further constituents are camphene, limonene, phellandrene, bomeol, 1,8-cine-ole, linalool, a-bisabolene, oxygenated sesquiterpene hydrocarbons, etc. For recent analytical data see [116, 117, 118]. 

Z, 6 )-a-Famesene (204) has been prepared by Homer olefination of methyl vinyl ketone with the phosphine oxide (202) (Scheme 27). The nature of the base used has a large effect on the yield and the authors report that it is more efficient to carry out the elimination step directly with the mixture of diastereo-... 

R0STELIEN, T., BORG-KARLSON, A.-K., MUSTAPARTA, H., Selective receptor neurone responses to -P-ocimene, P-myrcene, , -a-famesene and /jo/wo-famesene in the moth Heliothis virescens, identified by gas chromatography linked to electrophysiology, y. Comp. Physiol. A, 2000,186, 833-847. 

Aside from the stoichiometric construction of steroidal side chains by the reaction of alkenylzirconium derivatives with steroidal 7r-allylpalladiums, a one-pot synthesis of a-famesene and its 6Z-isomer from generanyl and neryl chlorides, respectively, reported in 1981 appears to be the first example of natural product syntheses via Pd-catalyzed allylation (Scheme 21). 

Following a very satisfactory synthesis of a-famesene via alkenyl-aUyl cou-pling[i74] example of natural product syntheses of this class, some other... 

---