Sesquiterpenoids hydrocarbons

The sesquiterpenoid hydrocarbons (5)-a-curcumene (59) and (5)-xanthorrhizol (60) were prepared by asymmetric conjugate addition of the appropriate aryllithium reagent to unsaturated oxazoline 56 to afford alcohols 57 (66% yield, 96% ee) and 58 (57% yield, 96% ee) upon hydrolysis and reduction. The chiral alcohols were subsequently converted to the desired natural products. ... 

Whereas sesquiterpenoid hydrocarbons, with few exceptions, have inferior characteristic organoleptic properties, the ethers of this series — as far as they are known — are distinguished by outstanding odor qualities. Once the general value of these compounds as aroma components is recognized, as it is the case with the monoterpenoid ethers, the importance of this group of compounds will rapidly grow. 

Smedman, L. A., E. Zavarin, and R. Teranishi Composition of Oxygenated Monoterpenoids and Sesquiterpenoid Hydrocarbons from the Cortical Oleoresin. of Abies Magnifica A. Murr. Phytochem. 8, 1457 (1969). 

Several examples of the monocyclic isothiocyano sesquiterpenoids having the bisabolane (83) skeleton are known. Along with the hydrocarbon theonellin (84), isothiocyanate 86 and formamide 87 were obtained from the Okinawan sponge Theonella cf. swinhoei. It seems remarkable, but not unusual, that not only was the amide the major constituent, but the isonitrile 85 was the missing member of the triad [57], Relative stereostructures were indicated by NMR analysis of theonellin formamide (87) and its transformation products. 

The result obtained by GC-MS, with the same SPME conditions, from the black thick balm of a crocodile mummy (sample 1400, Musee Guimet, Lyon, France) is presented in Figure 10.11. The composition of the extract is close to that of sample 1998 but phenolic compounds were not detected. The GC-MS chromatogram obtained with the same substance after acid methanolysis and silylation is presented in Figure 10.12. Except for the sesquiterpenoids eluted between 10 min and 22 min, the observed compounds originate from a beeswax. The biomarkers of this substance are hexadecanoic acids hydroxylated in position 14 or 15 and long chain hydrocarbons, acids and alcohols eluted between 50 min and 90 min. Diterpenoid or triterpenoid resin components are not observed. 

G.l.c. papers of interest include the classification of 22 acyclic monoterpenoid alcohols according to retention indexes, resolution of cyclic ketones [e.g. ( )-menthone, ( )-isomenthone] as diethyl (+)-tartrate acetals, and the use of lanthanide shift reagents to resolve non-terpenoid racemic epoxides.The occurrence and prevention of monoterpenoid hydrocarbon isomerization during silica gel chromatography has been examined and the separation of monoterpenoids and sesquiterpenoids by gel permeation chromatography is reported. Monoterpenoid hydrocarbons have been selectively extracted from essential oils using dimethylsilicone. ... 

A cell-free extract obtained from T. roseum has been shown to convert trans,trans-farnesyl pyrophosphate into trichodiene (87), the bicyclic hydrocarbon precursor of the trichothecane sesquiterpenoids.42 Related studies in this area have also been reported.43,44 Chemical and spectroscopic evidence has been reported which is consistent with the structure assigned to vetisporin (88), a new antibiotic isolated from Verticimonosporium diffractum.45... 

Formolysis of (264) produces the formate ester of (259) and (265) in 66% and 20% yield respectively the latter hydrocarbon is related to the pentalane class of sesquiterpenoids (see below). A study of this rearrangement, again using a deuteriated substrate, provided evidence for the pathway outlined in Scheme 38. Matsumoto et have also studied the mechanism of formation of the two tricyclic ethers (257) and (260) [with Hg(OAc)2] and the three tricyclic ethers [with Hg(N03)2] derived from humulene after NaBD4 work-up. Under these conditions the five deuteriated products are (266)—(270) respectively. The... 

The Ci5 terpenoids known as sesquiterpenoids are the most chemically diverse group of terpenoids known in nature. Like monoterpenoids, many sesquiterpenoids contribute to the flavor and fragrances of a variety of plant products. To date about 10,000 sesquiterpenoids are known (32), and in the plant kingdom they commonly occur as hydrocarbons, alcohols, aldehydes, ketones, carboxylic acids, lactones, and oxiranes. The acyclic sesquiterpene hydrocarbons a- and p-farnesenes (HI and H2, respectively) (Fig. 8) are constituents of the oils... 

In their synthesis of fukinone, Marshall and Cohen converted the known ene-ol (340) into (341) by acetylation, allylic oxidation, and conjugate methylation with dimethylcopperlithium. A Wolff-Kishner reduction of (341) followed by oxidation of the resultant alcohol and enol-acetylation yielded (342). The epoxide of (342) was thermolysed to give (343) which, on reaction with iso-propenyl-lithium and selective oxidation, gave the ketol (344) which was converted in two steps into fukinone (335). A number of sesquiterpenoids, e.g. fukinanolide (345), with the rearranged eremophilane skeleton viz. fukinane (346 R = Me) are known. Nay a and Kobayashi have now prepared this parent hydrocarbon by Raney nickel reduction of the thioacetal of fukinan-8-al (346 R = CHO). 

The mass spectra of a large number of sesquiterpenoids have been published. These consist mainly of hydrocarbons together with a limited number of alcohols and aldehydes. The mass spectra of some furanosesquiterpenoids have also been published. G.l.c. data have been collected for a number of sesquiterpene alcohols and furanosesquiterpenoids. ... 

C12 hydrocarbon (271)135 by a similar route but this compound is not identical to a tricyclic hydrocarbon isolated from East Indian sandalwood oil and reported to have this structure. (+)-Copacamphor (272) and (+)-copaborneol (273) have been isolated from Espeltiopsis guacharaca.136 The interesting sinularene derivative (274) and the acetoxycyclosinularane (275) have been isolated from the marine source, Clavularia inflata.137 These compounds, together with an aromadendrane derivative (see p. 181) are the first sesquiterpenoids from Octocorallia of the order Stolonifera. 

Apart from the n-alkanes discussed above, epicuticular wax hydrocarbons contain sesqui- and diterpenoids. These compounds are based on the structural skeletons of cadinane and abietane, respectively, which are shown in Fig. 7-24. The sesquiterpenoids recovered by Simoneit and Mazurek (1982) in the rural aerosol were calamenene, tetrahydrocadalane, and cadalene. These compounds presumably are degradation products of cadinane derivatives (various isomers of cadinenes and cadinols), which are ubiquitous in essential oils of many higher plants (Simonsen and Barton, 1961). The major diterpenoid hydrocarbons observed in the aerosol samples were dehy-droabietane, dehydroabietin, and retene. The main source of abietane derivatives are coniferous resins. The parent compounds dehydrate fairly rapidly to yield the more stable hydrocarbons found in the aerosols. These may then serve as markers for hydrocarbons arising from vegetation, in addition to the odd-to-even carbon number preference in the n-alkanes. 

Typically, the oil will contain 45-47% of the a-isomer and 20-30% of the (3-isomer. Both isomers contribute to the distinctive woody odour of the oil. The (3-isomer is more intense and also contributes to the slightly animalic, urinous character of the oil. It is interesting to note that the odours of sandalwood and urine are closely related. One of the commonest parosmias (where an odorant is perceived differently by different subjects) is that of sandalwood and urine. Similarly, when a secondary alcohol with a sandalwood character is oxidised to the corresponding ketone, there is a high probability that the ketone will smell urinous. There are many other components in sandalwood oil, particularly sesquiterpenoids alcohols, aldehydes and hydrocarbons. Some of these make important contributions to the overall odour effect. 

The continuing search for new marine natural products has led to the discovery of the farnesic acid glycerides (1)—(3) in the nudibranch Archidoris odhneri and the two hydrocarbons (4) and (5) from the gorgonian Plexaurella grisea Kunze. Other new farnesyl/nerolidyl sesquiterpenoids include (6)—(1and the interesting acetal eremoacetal (12) from Eremophila rotundifolia. ... 

Resin is used to refer to hydrocarbon secretions of many plants, particularly coniferous trees. The resins are complex lipid-soluble mixtures of both non-volatile and volatile compounds. The non-volatile fraction consists of diterpenoid and triterpenoid compounds, while the volatile fraction is mostly composed of mono- and sesquiterpenoids. Resins are valued for their chemical properties and associated uses, such as the production of varnishes, adhesives, and food-glazing agents. ... 

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