A-Bisabolene

Nezara antennata males produce similar volatile compounds, including Z-a-bisabolene, trans-Z-BAE, czs-Z-BAE, and E-nerolidol, as do males of four Acrosternum species [17,72]. In three of these species (A. aseadum, A. hilare, and A. marginatum), the transxis ratio strongly favors cz s-BAE, whereas in A. pennsylvanicum, the ratio is about equal. For all species except A. hilare, the absolute configurations of the compounds and their biological roles remain unknown. 

The bisabolanes, of which eight have been reported in these studies, also deserve special mention. Again, Z,E-farnesyl pyrophosphate is the putative progenitor. One study (13) reported 3-bisabolol (199) to be about 34% of the volatile alcohol fraction, making it about 5% of the total essential oil. a-Bisabolene (193) is representative of the hydrocarbons of this group. 

Bisabolene-type sesquiterpenes, e.g. a-bisabolene 74 (Structure 4.20), are widely distributed in nature. This sesquiterpene hydrocarbon is a constituent of bergamot, myrrh and a wide variety of essential oils. Its oxygenated derivatives a-bisabolol [6-methyl-2-(4-methyl-3-cyclohexen-l-yl)-5-hepten-2-ol] 75 and -bisabolol [4-methyl-l-(6-methylhept-5-en-2-yl)cyclohex-3-enol] 76 are found abundantly in chamomile. 

Opopanax Commiphora guidottii /3-Ocimene (82), (S,Z)-a-bisabolene (76), a-santalene (83) 109... 

Bohlmann, J., Crock, J., Jetter, R. and Croteau, R. (1998a) Terpenoid-based defenses in conifers cDNA cloning, characterization and functional expression of wound-inducible (E)-a-bisabolene synthase from grand fir (Abies grandis). Proc. Natl. Acad. Sci. USA, 95, 6756-61. 

To date over 30 plant terpenoid synthases have been cloned as cDNAs, and many of these were found to encode enzymes of secondary metabolism (43). Isolation and analysis of six genomic clones encoding monoterpene ((—)-pinene and (—)-limonene), sesquiterpene ((E)-a-bisabolene and S-selinene) and diterpene (abietadiene) synthases from Abies grandis, and a diterpene (taxadiene) synthase from Taxus brevifolia have been reported (44). Overexpression of a cotton farnesyl diphosphate synthase (EPPS) in transgenic Artemesia annua has resulted in 3- to 4-fold increase in the yield of the sesquiterpenoid anti-malarial drug, artemisinin, in hairy roots (45). 

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]. 

The previously reported biogenetic-type cyclization of nerol and geraniol to limonene using 2-fluoropyridinium salts has been extended to the sesquiter-penoid area. Thus treatment of cw,rran5-farnesol (77) with 2-fluoropyridinium (74), 2-fluorobenzothiazolium (75), or 2-chlorobenzothiazolium (76) salts resulted in the formation of a-bisabolene (78) and y-bisabolene (79) in 55—75% yield. 

Ag f-a-bisabolene syn Pa isopimara-7,15-diene syn Pa levopimaradiene/abietadiene syn Ag abietadiene syn Gb levopimatadiene syn... 

Owens, T.D., Souers, A.J. and Ellman, J.A. (2003) The preparation and utility of bis(sulfinyl) imidoamidine ligands for the copper-catalysed Diels-Alder reaction. The Journal of Organic Chemistry, 68, 3-10 Kochi, T. and Ellman, J.A. (2004) Asymmetric a-alkylation of N -tert-butanesulfinyl amidines. Application to the total synthesis of (6R,75)-7-amino-7,8-dihydro-a-bisabolene. Journal of the American Chemical Society, 126, 15652-15653. 

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