Terpene sesqui

From a chemical point of view, vegetable resins are a complex mixture of mono-, sesqui-, di- and triterpenes, which have, respectively, 10, 15, 20 and 30 carbon atoms per molecule. The mono- and sesquiterpenes are both present in most resins. The di- and triterpenes are rarely found together in the same resin, which means that terpenic resins can be divided into two main classes. Table 1.5 lists the botanical origin and the kind of terpenoid compounds of some natural resins. 

German for turpentine) and there are approximately 15000 terpenes. Terpenes are lipophilic, and the building blocks are five-carbon units with the branched carbon skeleton of isopentane. The basic units are sometimes called isoprene (F ig. 11.5fl), because heat decomposes terpenoids to isoprene. Depending on the number of C5 units fused, we distinguish mono- (Cio), sesqui- (C15), di- (C20), tri-(C30), tetra- (C40) and polyterpenoids [(Cs) , with n > 8]. Alpha-Pinene and bor-neol (Fig. 11.56) are examples of monoterpenes. 

Hendriks, H., T. M. Malingre, S. Batterman and R. Bos. Mono- and sesqui-terpene hydrocarbons of the essential oil of Cannabis sativa. Phytochemistry 1975 14 814—815. Thorbum, M. J. Jamaican bushes and human chromosomes. Jamaica J 1975 8(4) 18. 

Cyclization reactions of GGPP mediated by car-bocation formation, plus the potential for Wagner -Meerwein rearrangements, will allow many structural variants of diterpenoids to be produced. The toxic principle taxine from common yew (Taxus baccata Taxaceae) has been shown to be a mixture of at least eleven compounds based on the taxadiene skeleton which can be readily rationalized as in Figure 5.43, employing the same mechanistic principles as seen with mono- and sesqui-terpenes. 

Though terpenes are made from C5 units, they are classified in C10 units. The monoterpenes are the C10 compounds, the sesquiterpenes (sesqui is Latin for one-and-a-hatf) are the C15 compounds, the diterpenes are the C20 compounds, and so on. 

There have been a number of previous reviews on microbial oxidations of terpenes. - Monoter-penes are often degraded progressively after an initial hydroxylation step, but di-, tri- and sesqui-terpenes can be converted more selectively, to accumulate useful quantities of hydroxylated products. Less systematic woric on the microbial oxidation of terpenoids has been carried out than in the case of steroids, and therefore prediction of the regio- and stereo-chemistry is scarcely possible. 

Among the first synthetic achievements, based on the use of tricyclooctanones, are the following preparations of mono- and sesqui-terpenes. Four members of the monoterpene iridoid family have been obtained by a single approach (Scheme 17). The disadvantage of the stereo/io/iselective reduction of (21b), affording (82) and (83) in a 1 1 ratio, is compensated for by the benefit of simultaneous access to four natural products ( )-boschnialactone and the epimer (84), this being a suitable precursor to attain ( )-al-... 

THE SYNTHESIS OF SOME MONO-, SESQUI-, DI-, TRI- and TETRA-TERPENES... 

Af-Chlorosuccinimide is the most widely used reagent for the chlorination of P-ketophosphonates and l-(alkoxycarbonyl)methylphosphonates to give structures that are often incorporated into complex carbacyclins, - prostaglandins, or bicyclic sesqui- and di terpenes. The reaction takes place in the presence of NaH (2 eq) in DME or I HL at room temperature, and the resulting chlorinated carbanions are allowed to react in situ with the appropriate carbonyl compounds to give the desired chloroolefins in 38-80% yields. ... 

The further development of 48 is interesting. Conjugate addition of McjOuhi creates a quaternary centre 49 and acid hydrolysis of the furan releases the triketone 50 used to make sesqui terpene lactones. The yields in these three steps are amazingly good. 

This section covers alkaloids which have piperidine or pyridine rings as the distinguishing skeletal features, including those which are related to mono- or sesqui-terpenes. 

As a general rule, natural products derived from isoprenoid units arise from head-to-tail reactions of that synthon. The majority of the structures of such products built up by condensation of IPP will as a result display a branched methyl on every fifth atom in the chain. Thus, reaction of IPP (1-5) with the isomer with the internal double bond (1-6) proceeds by head-to-tail coupling with expulsion of a pyrophosphate ion. The free alcohol from the product 2-1 (Scheme 2.2) is the fragrant terpene geraniol. Reaction of 2-1 with a second isoprene unit in this case again takes place by head-to-tail reaction to afford 2-2. The free alcohol from this 15-carbon triene is known as farnesol and is generally classed as a sesquiterpene (Latin sesqui-, one and a half). The molecule is displayed in the unlikely conformation 2-2b, in anticipation of the next reaction. 

Our recent research suggests organ-, tissue-, and cell-specific localization of constitutive and induced terpenoid defense pathways in conifers. For example, linalool synthase (PaTPS-Lin) seems to be preferentially expressed in needles of Norway spruce and Sitka spruce with little or no expression in sterns. ft is also likely that expression of PaTPS-Lin in spruce needles is not associated with resin ducts but could reside in other cells involved with induced terpenoid emission. In contrast, we can speculate that most other mono-TPS and di-TPS are associated with epithelial cells of constitutive and induced resin ducts. The possible localization of conifer sesqui-TPS is difficult to predict. Furthermore, the exact spatial and temporal patterns of terpenoid pathway gene expression associated with traumatic resin duct development in the cambium zone and outer xylem remain to be studied at the tissue and cell level. In situ hybridization and immuno-localization of TPS will address these open questions. These methods have worked well in identifying cell type specific gene and protein expression of alkaloid formation in opium poppy Papaver somniferum) As the biochemistry of induced terpene defenses and the development of traumatic resin ducts have been well described in spruce, this system is ideal for future studies of tissue- and cell-specific localization of transcripts and proteins associated with oleoresin defense and induced volatile emissions in conifers. In addition, the advent of laser dissection microscopy techniques presents a fascinating means by which to further address RNA and protein analysis in a tissue-and cell-specific manner. These techniques, when applied to the cambium zone, xylem mother cells, and the epithelial cells that surround traumatic resin ducts, and will allow a temporal and spatial analysis of cellular functions occurring in the traumatic resin response. 

Perlplanones. The P. A-D are germacranoid sesqui-terpene pheromones of females of the American cockroach Periplaneta americana. ... 

The occurrence of terpenes is ubiquitous. Natural terpenes are found in plants and animals in minute amounts. Especially in higher plants, terpenes characterize the type of plant (chemotaxonomy) mono- and sesquiterpenes in essential oils, sesqui-, di-, triterpenes in balsams and resins, tetraterpenes in pigments and polyterpenes in latexes.Therefore, terpenes are often emitted from natural products such as citrus fruits or trees, e.g. conifers. 

The differences in structure and the physical and chemical properties of the terpene- and phenylpropane derivatives encountered in essential oils, have been described in the standard works of Gdldemeister-Hoffmann [72], Guenther [82], SmoNSBN [240], deMayo [160], W. Karrer [117] and Moritz [173]. Haaqen-Smit[86] has dealt with sesqui- and diterpenes. Both Steiner and Holtzem [721] and Jones and Hals all [109] have compiled comprehensive articles on triterpenes. 

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