Terpenes tetra- 335

Processes of this kind are important in the biosynthesis of steroids and tetra- and pentacyclic terpenes. For example, squalene 2,3-oxide is converted by enzymatic catalysis to dammaradienol. 

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. 

Kostiainen (1995) identified more than 200 individual VOCs indoors in 26 houses. In addition, they compared the VOC concentrations in normal houses to those where complaints of odors or illness had been registered. A number of different VOCs were present at increased concentrations in the houses with complaints compared to the normal houses these included a variety of aromatic hydrocarbons, methylcyclohexane, n-propylcyclohexane, terpenes, and chlorinated compounds such as 1,1,1-trichloroethane and tetra-chlorethene. 

Oligomerization of isoprenoids under elimination of pyrophosphate affords the precursors for the biosynthesis of monoterpenes, sesquiterpenes, diterpenes, triterpenes, and tetra-terpenes (93). Long-chain oligomer pyrophosphates also supply the side chains of vitamin E (99, a-tocopherol. Fig. 11), heme a (18), chlorophyll (17, Fig. 2), and the quinone type cofactors, including vitamin K (menaquinone, 98) and coenzyme QIO (ubiquinone, 97). The quinone moieties are derived from hydroxybenzoate that is synthesized from tyrosine in animals or from chorismate in microorganisms (53, 54). 

Further investigatkms with palladium-myrcene complexes show that, in acetic acid, a mixture of acetates [linalyl (24), neryl (9), geranyl (10), (25), and (26)] is formed, while a cyclic complex (27) is formed in methanol. Analogous complexes of ocimene have been studied, and found to yield geranyl methyl ether with methanol, and a dimer of limonene with acetone. An interesting method proposed for the removal of myrcene from a terpene mixture is selective clathra-tion with nickel tetra-(4-methylpyridine)dithiocyanate. ... 

The tetra-hydro cymene containing one double bond or ethylene group is known as menthene or a terpene, while the di-hydro cymene containing two double bonds is named mentha-di-ene, a terpa-di-ene. The terminology and its significance will be recognized as exactly the same as used in the naming of the unsaturated aliphatic hydrocarbons... 

Derivatives of Menthene.— The most important alcohols and ketones derived from the menthene unsaturated group of terpenes are terpineol, di-hydro carveol, di-hydro carvone and pulegone. The first one, the alcohol terpineol, occurs in its dextro form in cardamon oil and marjoram oil, in its leoo form in neroU oil and in its inactive form in cajeput oil. The constitution is proven by Perkin s synthesis from As-tetra-hydro para-toluic acid by means of the Grignard reaction. 

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

Chiral alkoxy-l,3-cyclohexadienes 1 add to 1,4-naphthoquinone (2) yielding 3 with moderate to very high diastereomcric ratios. The best results (d.r. 97.5 2.5) are achieved for dienes le and lf(l,2 5,6 -di-O-isopropylidene-a-D-glucopyranoside as an auxiliary). Diene Id (2.3,4,6-tetra-0-methyl-/(-D-glucopyranoside as auxiliary) gives a d.r. of only 58.5 41.5. Terpene derivatives as auxiliary alcohols do not work much better d.r. 63 27, 53 47, 64 36 are obtained for la [(-)-borneol], lb [( — )-menthol] and lc [(—)isopinocampheol], respectively18. 

Polyterpenes (polyterpenoids). Natural products made up of n C lo units (= 2 n isoprene building blocks) with n>4, the biogenesis of which generally obeys the isoprene rule. The most important P. are the tetra-terpenes (n=4) including carotinoids, ficaprenols, natural rubber, balata, and gutta-percha. The name is also used for hydrocarbon resins (terpene resins) prepared synthetically by polymerization of monoter-penes. 

QuassMoids). A group of structurally complex tri-terpenes with various tetra- and pentacyclic C -, C -, C20-, and C25-skeleton. The C2o picra ane system is the most widely distributed. Q. occur principally in the wood of the tree Quassia amara indigenous to Brazil and Surinam as well as the Caribbean Picrasma ex-celsa (Simaroubaceae). They have antifeedant effects on insects and taste very bitter. The most important representative of the Q. is quassia (2,12-dimethoxy-picrasa-2,12-diene-1,11,16-trione, nigakilactone D) C22H28O6, Mr 388.46, mp. 221-222 °C, [aJo +34.5° (CHCI3) - a partially hydrogenated phenanthiene derivative. 

The structures of terpenes or terpenoids varies widely and are classified according to various aspects, e.g. number of isoprene units (Cio monoterpenes, C15 sesquiterpenes, C20 diterpenes, C25 sesterterpenes, C30 triterpenes, C40 tetraterpenes) or division in acyclic, mono-, hi-, tri-, tetra-, pentacyclic terpenes. Often terpenes are named by their trivial names, e.g. d-limonene. 

The pyrophosphate ester of G. is an important intermediate in the biosynthesis of Terpenes (see). Head-to-tail coupling of two molecules produces ger-anylgeranylpyrophosphate, the precursor of the tetra-terpenes. 

Triteipenes an extensive group of terpenes biosynthesized from six isoprene units Apart from squa-lene, which is acyclic, most of this group are tetra- or pentacyclic hydroaromatic compounds based on the patent hydrocarbon, sterane, i.e. they are steroids Included with T. are those terpenoid natural products with fewer than 30 C-atoms, which are biosynthesized via a C30 intermediate, but with subsequent loss of one or more C atoms Addition of extra C atoms and incorporation of heteroatoms are also possible, e.g. 

The term terpene has been given its widest interpretation here, and modified terpene types such as furanoterpenes and norterpenes (including steroids) are included. The arrangement of material is basically in order of increasing molecular weight, i.e. from mono- to tetra-terpenes, and within each subdivision the simple types, as far as practicable, precede the more complex. 

Another access to the enzymes responsible for monoterpene synthesis is provided by dimethylaminoethyl diphosphate, an analogon of dimethylallyl diphosphate which inhibits the iso-pentenyl diphosphate A-isomerase at very low concentrations (Muhlbacher and Poulter 1985). This inhibitor was tested for its influence on monoterpene biosynthesis using radioactively labeled IPP and nonlabeled dimethylallyl diphosphate as substrates and optimized monoterpene conditions as mentioned above, Monoterpene synthesis was inhibited up to 50at an inhibitor concentration of 2 pM whereas the synthesis of di- and tetra-terpenes and geranylgerany 1 diphosphate was not impaired (Fig. 3). 

Examples of monoterenes include the linear aldehyde citral which is found in many essential oils, and the (cis) alcohol geraniol—a major component of oil of geranium. Cyclic mono-terpenes include limonene, menthol pinene, camphor, and carvone—major components of lemon oil, mint oil, turpentine, camphor oil, and caraway oil, respectively. Sesquiterpenes include/arneso/, a component of rose oil, and bisabolene, a component of Bisabol myrrh. The diterpenes include phytol a component of chlorophyll, and vitamin A, which is one-half of the tetraterpene jS-carotene. The triterenes include squalene, a precursor of cholesterol. Examples of tetra-... 

A classification of the terpenes found in Dendroceratida and Dictyoceratida was given by Bergqttist and Wells, and there is no need to expand on this topic because the scheme shown in Figure 19.96 is clear and logical (Bergqttist and Wells, 1983). In this scheme there are six classes (A-F) the first three (A-C) consist of furanoterpenes, the next two (D and E) are tetra- and tricyclic diterpenes, and the... 

Tartaric Acid acide tartrique Taxonomy taxonomie Teaseed thd Terpenes terp nes Tetracycline tetracyclines Tetrahydrofuran tetrahydrofurane Tetrahydrofurfuryl Alcohol alcool tetra-hydrofurfurylique... 

Tenside agents tensioactifs, surfactants Terpene terpfenes Terpentinol essence de t r benthine Tetracycline tetracyclines Tetrahydrofiiran tetrahydrofurane Tetrahydrofinfurylalkohol alcool tetra-hydrofurfurylique... 

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