E-cadinene

Using methylene-triphenylphosphorane 205, in many cases carbonyl functions have been converted into exomethylene groups in cyclic terpene chemistry. This technique was used, among others in the preparation of (+)-steviol methyl ether 244), dihydro-5,6-norcaryophyllene 245), ( )-nootkatone 246 (-)-phyllodadene 247), and (+)-e-cadinene 248). In the synthesis of the latter the trans-decalin derivative 462 was formed from the cis-decalone 461 the epimerization of which proceeded via the enol form during the methylenation 248 (Scheme 80). 

The dihydroxy-ketal (240), previously prepared from ( —)-santonin, has been used to synthesize a number of related sesquiterpenoids. Thus the diacetate of (240) was converted in six steps into (241), which was then treated with iso-propenyl acetate-sulphuric acid the derived enol-acetate was cleaved to the triol (242) by ozonolysis and lithium aluminium hydride reduction. The triol (242) was then converted into the di-iodo acetate (243) in a number of steps and thence to shyobunone (244) by dehydroiodination, reduction, and oxidation. Thermolysis of shyobunone at 160—180 °C gave preisocalamendiol (245) in about 30% yield. More recently, Iguchi et al. have shown that preisocalamendiol (245) can be cyclized to isocalamendiol (246) in aqueous acetic acid no trace of calamendiol (247) was found. A number of other interesting acid-catalysed cyclizations have been observed in this area, e.g. the formation of (248 R = OH) and (248 R = OAc) from (249) and the formation of (250) from (251). Finally, e-cadinene (252) has been obtained from (253), the lithium aluminium hydride product of preisocalamendiol (245). 

Alkene positional isomerism is a problem that arises from time to time. It is conceptually related to regiochemistry and is presented here. Careful synthetic planning is usually required to solve this problem, as illustrated by the Burk-Soffer synthesis of e-cadinene (53) and V2-cadinene (54). 9 Conversion of 52 first to the ketone, then to the tertiary alcohol, and finally to the tertiary chloride allows E2 elimination to give 53. Conversely, Wittig olefination (sec. 8.8.A) of the ketone gave the exo methylene derivative, 54. It is important to note that formation of the C2-C3 C=C unit is favored for trans decalin derivatives over the C3-C4 unit. 

With Rh(I)/PF-PPh2, reactions of Z-allylic alcohols generally afford higher enantios-electivity than the corresponding E-isomers. We applied this process to formal total syntheses of (-)-7-hydroxycalamenene and (-)-7-hydroxycalamenenal [8], two naturally occurring sesquiterpenes in the cadinene family (Eq. 7). 

Cadinene is a trivial name of a number of isomers which occur in a wide variety of essential oils e.g. cubeb oil. Actually, it is derived from the Cade juniper Juniperus oxycedrus L.). The cadalane (4-isopropyl-1,6-dimethyldecahydro-naphthalene) carbon skeleton is the base. Prominent stereochemical isomers are a-cadinene 79, y-cadinene 80 and d-cadinene 81 (Structure 4.23). This group is also known as naphthalene-type sesquiterpenes. 

Se8qulterpenold semlochemlcals. The aphid-repellent effect of Type B trichomes of S. berthaultii (25) appears to be due to the presence of sesquiterpenes (22). Three major components, identified by GC-MS, were B-caryophyllene, B -cubebene and A-cadinene. E-B-farnesene was also identified, but was a minor component. GC-MS of the other major components in Type B trichome exudate indicated sesquiterpenold structures, but these have not been identified. 

Woody higher plants can also exude resins. For example, dammar resin from certain angiosperms (e.g. dipterocarps) contains a polycadinene (Fig. 2.26), based on a A5-cadinene monomer (van Aarssen et al. 1990). Gymnosperm resin polymers are based on labdatriene (diterpenoid) monomers such as communic acid (Fig. 2.26 Mills et al. 1984/5 Hatcher Clifford 1997), and some angiosperm resins also contain these polymers. In contrast to polycadinene formation, polymerization of labdatrienes is thought to occur after exudation. 

All samples are characterized by a prominent brown ester zone at R, 0.75 due to bornyl and/or terpinyl acetate and the violet zone.s of terpcne.s (e.g. cadinene) at the solvent front. The pattern and amount of blue and violet-blue zones in the R, range 0.4-0.6 and the zones of terpene alcohols (e.g. borneol T2, terpineol) in the R, range 0.25-0.4 varies in the commercial oil samples 1 --5. 

Class I terpene synthases are highly a-helical proteins containing conserved aspartate-rich motifs. These motifs bind divalent metal ions (Mg " ) via salt bridges to form a trinuclear metal cluster that complexes the polyisoprenoid for diphosphate abstraction. Like ( )-selective prenyltransferases, type I terpene synthases exhibit one conserved aspartate-rich DDXX(D,E) motif, but instead of a second DDXXD on the opposite side of the active center, a consensus sequence of (N,D)D(L,I,V)X (S,T)XXXE (also termed NSE/DTE triad) is found here. One exception is the (-l-)-5-cadinene synthase from Gossypium arboreum that like prenyltransferases contains two DDXXE motifs [195]. 

Of the above four types, cadinanes are most common and are fairly widely distributed in nature (396). Several of these compounds have been found in woody parts of plants. Examples are T cadinol (294) and the hydroxy ketone 295 from the wood of Taiwania cryptomerioides (92, 255), (4-)-5-cadinene (296) from trunk wood of Cedrela toona (291), and (-)-y-cadinene (286), khusinol (297) and several related compounds from vetiver oil of North Indian origin (222, 394). Muurolenes (e.g., e-muurolene, 298) were first characterized in 1966, and were isolated from wood of Firms sylvestris (413). Cedrela toona wood (291). The other two types have not... 

The chemistry of this oil is in need of further elucidation, as it is -clear that thei-e are several constituents present which have, so far, escaped identification. The terpene dipentene is present, and probably small quantities of pinene or camphene cadinene is present, as well as a second sesquiterpene not yet identified. There is also present, especially in the oil distilled from old fruit, which has doubtless become partially oxidised, a small amount of the so-called cubeb-camphor. This b y, C H gOH, appears to be a crystalline sesquiterpene alcohol derived from the sesquiterpenes (or one of them) by oxidation. From a mixture of ether and alcohol it crystallises in rhombs, melting at 65 and is laevo-rotatory. It boils at 248 , with decomposition. The nature of the blue oil found in the higher fractions is unknown. 

Amyrol cannot be esterified with phthalic acid anhydride quantitative acetylation is equally impossible. Amyrol is probably a sesquiterpene alcohol, CijHggO. In addition to this body. West Indian aandal-wood oil contours a sesquiterpene, whose nature has been investigated by E. Deussen. He introduced hydrochloric acid gas up to saturation into the oil dissolved in dry ether, and obtained crystals of cadinene dihydrochloride. The corresponding compounds of hydrogen bromide and iodide, of which the constants are given below, were produced in a similar manner —... 

Contains about 2% volatile oil resins C25, C27, and C29 -alkanes salicin and populin phenolic acids (e.g., caffeic) chalcones and others. Compounds reportedly present in the volatile oil include (/-cadinene, cineole, ar-curcumene, bisabolene, farnesene, /-a-bisa-bolol, 3-phenethyl alcohol, acetophenone (karrer), andhumulene (a-caryophyllene) (cLAus FURiA AND bellanca youngken). 

Dwarf pine needle oil has been reported to contain mostly monoterpene hydrocarbons (ca. 70%), including bomyl acetate and other esters aldehydes (e.g., hexanal, cuminaldehyde, and anisaldehyde) r/-ciyp-tone small amounts of sesquiterpenes (e.g., cadinene) and alcohols among others (list and horhammer martindale merck remington). 

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