Terpenoid number

Type of terpenoids Number of carbon atoms Number of isoprene units Example... 

Implicit ia the base names are the absolute configurations at carbons 8 and 12 and the iadicated numbering systems. Derivatives of these parent stmctures are named according to terpene and steroid nomenclature rules (see Steroids Terpenoids). The lengthy and awkward nature of the chemical abstract systematic nomenclature (12) for these compounds has resulted ia the development (13) and use of simplified nomenclature based on common names. 

Terpenes (and terpenoids) are further classified according to the number of 5-carbon units they contain. Thus, monoterpenes are 10-carbon substances biosynthesized from two isoprene units, sesquiterpenes are 15-carbon molecules from three isoprene units, diterpenes are 20-carbon substances from four isoprene units, and so on. Monoterpenes and sesquiterpenes are found primarily in plants, but the higher terpenoids occur in both plants and animals, and many have important biological roles. The triterpenoid lanosterol, for example, is the precursor from which all steroid hormones are made. 

Indicate by asterisks the chirality centers present in each of the terpenoids shown in Problem 27.24. What is the maximum possible number of stereoisomers for each ... 

Compds of the general formula R2C=N—N02. The first compd of this kind was prepd in 1895 by Angeli et al upon treating camphoroxime with nitrous acid. Similar compds were obtained from a number of terpenoid ketones. Angeli called the resulting substances perni-troso derivatives and assigned to them structures of either R2C=N—O—NO or R2C=(NO)2 (Refs 1 2)... 

We are concerned here with systems that have been studied using secondary products—flavonoids and terpenoids in particular— but other information, including micro- and macrofossils, and occasionally chromosome numbers, will be included in the discussions when snch information is available. The majority of current research on postglacial reestablishment of plant distribution patterns is based on DNA seqnence information. In a few instances below, reference will be made to such information, but this in not the place for a detailed review of that literature. 

Hydroxylation and Baeyer-Villiger reactions carried out by monooxygenation are important in the degradation of a range of terpenoids and steroids. The aerobic degradation of limonene can take place by a number of reactions several of which involve hydroxylation at allylic positions... 

Terpenoids are susceptible to a number of alterations mediated by oxidation and reduction reactions. For example, the most abundant molecule in aged Pinus samples is dehydroabietic acid [Structure 7.10], a monoaromatic diterpenoid based on the abietane skeleton which occurs in fresh (bleed) resins only as a minor component. This molecule forms during the oxidative dehydrogenation of abietic acid, which predominates in rosins. Further atmospheric oxidation (autoxidation) leads to 7-oxodehydroabietic acid [Structure 7.11]. This molecule has been identified in many aged coniferous resins such as those used to line transport vessels in the Roman period (Heron and Pollard, 1988 Beck et al., 1989), in thinly spread resins used in paint media (Mills and White, 1994 172-174) and as a component of resin recovered from Egyptian mummy wrappings (Proefke and Rinehart, 1992). 

Adults of some species also produce 4-oxo-( )-2-alkenals. Other types of simple compounds that have been found in the defensive secretions of true bugs include common terpenoids such as a- and (3-pinenes, limonene, linalool, and Z, -oc-farnesene, and simple aromatic compounds such as benzyl alcohol, ben-zaldehyde,p-hydroxybenzaldehyde, methyl p-hydroxybenzoate,phenylethanol, and guaicol. In general, although a number of species may share particular components, each species does appear to produce its own particular blend. In at least one species, the blend of defensive compounds is reported to vary with season and/or diet [36]. 

In addition, the idea of the terpenoid side chain of 10 essentially assisting in anchoring the coenzyme in the cytoplasmic membrane without having any impact on the redox potential was to be explored. To this end, a number of phenazine ethers 44a-g were synthesized by Williamson ether synthesis and then investigated by electrochemical methods. And indeed, we were able to identify a good match between the redox potentials of the various phenazine ethers, which turned out to be independent of the side chain structure. 

The terpenes are simple lipids whose base unit is isoprene. Oxygen-containing ter-penes are called terpenoids, and terpenes with hydroxyl groups are called terpenols. Terpenes are further classified based on the number of isoprene imits in the molecule as shown in Table 22.6. Examples of terpene molecular structures are presented in Figure 22.18. 

Many thousands of secondary plant compounds have been identified and 400000 are suspected to exist. These numbers provide a great incentive for chemical prospecting (Eisner, 1989). The most prevalent, broad classes of plant secondary compound are phenolics, alkaloids, and terpenoids (Table 11.1). 

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. 

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