Sesquiterpene oxides

Table 23. hjtf-values and colour reactions of some terpene- and sesquiterpene oxides, epoxides and peroxides cm silica gel layers ... 

Essential Oils. Volatile oils from plants are referred to as essential oils. The oils can be obtained through steam distillation, solvent extraction, or separation of the oils from pressed fmit. They consist of oxygenated compounds, terpenes, and sesquiterpenes. The primary flavor components of essential oils are oxygenated compounds. Terpenes contain some flavors but are often removed from the essential oil because they are easily oxidized (causiag off-flavors or odors) and are iasoluble. Essential oils are prepared from fmits, herbs, roots, and spices. 

Sponge sesquiterpenes H NMR, 4, 560 Squalene synthesis, 1, 469 Squalene oxide occurrence, 7, 119 Squamalone... 

A study of the oxidation products and nitroso-derivatives of caryophyllene, leads Deussen to consider that this sesquiterpene is a naphthalene derivative of the formula—... 

They have also carried out the oxidation of selinene by means of ozone and potassium permanganate and have thus been able to establish that the regenerated selinene is not absolutely identical with the natural selinene. They are the first to record the existence of a hemi-cyclic-sesquiterpene this compound is termed pseudo-()3)-selinene. By passing a current of ozone into a solution of natural selinene (pseudo-( 8)-selinene). in acetic acid, there is obtained a diketone, CjjHogOj, which is purified by treatment with permanganate in acetone solution. Its properties are as. follows —... 

It yields on reduction dihydrocopaene, a compound boiling at 118° to 121° at 12 mm. By oxidation hy ozone or hy permanganate of potassium it yields a ketonic acid of the formula CijH Oj, which forms a semicarbazone melting at 221°. These derivatives characterise copaene AS a new sesquiterpene. Its characters, however, have only heen very slightly investigated at present. 

Costol is a diolefinic bicyclic sesquiterpene alcohol, which, on oxidation by chromio acid in acetic acid yields an aldehyde, CjgH jO, which jrields a semi-carbazone, melting at 217° to 218°. This aldehyde, which U triolefinic has the following characters —... 

Eudesmol is a sesquiterpene alcohol, isolated from several species of eucalyptus oil by Baker and Smith, who regarded it as an oxide of the formula C gO. Semmler and Tobias have, however, shown that it is a tricyclic, unsaturated alcohol. It has the following characters —... 

The chemical composition of C. sativa is very complex and about 500 compounds in this plant are known. A complete list can be found in [81] with some additional supplementations [2,82]. The complex mixture of about 120 mono- and sesquiterpenes is responsible for the characteristic smell of C. sativa. One of these terpenoic compounds, carophyllene oxide, is used as leading substance for hashish detection dogs to find C. sativa material [83]. It is a widespread error that dogs that are addicted to drugs are employed for drug detection. A9-THC is an odorless substance and cannot be sniffed by dogs. 

Kim EJ, Hye KJ, Yong KK, et al. Suppression by a sesquiterpene lactone from Carpe-sium divaricatum of inducible nitric oxide synthase by inhibiting nuclear factor-KB activation. Biochem Pharmacol 2001 61 903-910. 

Matsuda H, Tadashi K, Iwao T, Hiroki U, Toshio M, Masayuki Y. Inhibitory effects of sesquiterpenes from bay leaf on nitric oxide production in lipopolysaccharide-activated... 

Wilson, C. W. et al., J. Agric. Food Chem., 1978, 26, 1430-1432 Oxidation of the sesquiterpene valencene to the 4-en-3-one proceeds explosively when at sub-ambient temperatures [1], A safer alternative oxidation procedure is detailed [2],... 

Figure 10.4 Temperature profiles for three classes of analytes monoterpenes (limonene) sesquiterpenes [(3 caryophyllene, caryophyllene oxide (caryo. oxide)] and diterpenes [cem brene A, isoincensole acetate (iso. acetate)]. PDMS fibre, sampling time 40 min. Reproduced from S. Hamm, E. Lesellier, J. Bleton, A. Tchapla, J. Chromatogr., A, 1018, 73 83. Copyright 2003 Elsevier Limited...

The behaviour of sesquiterpenes, which are less volatile (fi-caryophyllene bp760 262°C), is quite different. Initially their migration from the matrix to the gaseous phase is predominant but beyond a certain temperature, which depends on the boiling point, the migration from the fibre to the gaseous phase predominates. For example, the optimal trapping temperature is lower (40°C) for fi-caryophyllene than for its oxide derivative (60°C). 

Sampling time 60 min extraction temperature 80°C. Monoterpenes a-pinene, p-myrcene, a-phellandreneand limonene sesquiterpenes a-cubebene, a-copaene, p-elemene, p-caryophyllene, a-humulene, y-muurolene, p-eudesmene and caryophyllene oxide diterpenes cembrene A and isoincensole acetate. 

The first observation is the similarity between the chemical compositions of both the Boswellia carteri and Boswellia sacra. For these three olibanum samples, a-pinene (2), (3-myrcene (8) and limonene (14) are the predominant monoterpenes. p-Caryophyllene (73) is the major sesquiterpene besides a-copaene (65), a-humulene (also called a-caryophyllene) (78) and caryophyllene oxide (95). The characteristic olibanum compounds isoincensole and isoincensole acetate (128) together with cembrene A (120) are the main diterpenes. 

Boswellia serrata olibanum has a chemical composition close to that of both the B. carteri and of B. sacra, but contains compounds that are absent in those from other Boswellia and could be used as markers methylchavicol (38), p-anisaldehyde (47), methyleugenol (70), isocaryophyllene (82), sesquiterpene 91, elemicin (92) and an unidentified diterpene (124) eluting between cembrene C (123) and verticilla-4(20),7,ll-triene (125). It is devoid of (5-caryophyllene (73), a-humulene (78), caryophyllene oxide (95) and bornyl acetate (50). 

The chemical composition of B. papyrifera olibanum is markedly different from that of other Boswellia, with small amounts of monoterpenes and sesquiterpenes, large amounts of w-octanol (18) and -octy I acetate (40), with the latter being the major compound, and the presence of particular diterpenes [incensole (127), incen-sole acetate (129), incensole oxide (130) and incensole oxide acetate (131)] and the absence of both isoincensole and isoincensole acetate (128). Linear carboxylic acids from hexanoic acid (10) to lauric acid (93) were also identified in B. papyrifera olibanum exclusively. 

Eight olibanum samples of unknown botanical origin have been analysed [26]. The chemical compositions are summarized in Table 10.3 for three of them. Both the olibanum coming from Somalia and that from a market in Ta izz (Yemen) have been attributed to Boswellia carteri or sacra on the basis of the occurrence of the characteristic diterpenes isoincensole and isoincensole acetate (128) together with diterpene 126. The absence of methylchavicol (38), oxygenated sesquiterpene 91 and diterpene 124 and the presence in relatively large amount of (3-caryophyllene (73), ot-humulene (78) and caryophyllene oxide (95) excluded the hypothesis of a B. serrata sample. 

A total synthesis of the sesquiterpene ( )-illudin C 420 has been described. The tricyclic ring system of the natural product is readily quickly assembled from cyclopropane and cyclopentene precursors via a novel oxime dianion coupling reaction and a subsequent intramolecular nitrile oxide—olefin cycloaddition (463). 

About 20 years ago, Bohlmann and co-workers examined South American plants of the widespread Vemonia species and found the first and (until now) only naturally occurring endocydic allenes (Scheme 18.32) [97]. These are the bicyclic sesquiterpene lactones 100-102 bearing a 10-membered ring [98], in which the E-double bond of the larger ring can also be present in its oxidized form (101, 102). As in other cases, these fasdnating natural products have not been synthesized until now. 

There is little information on the stability of the sesquiterpene lactones. However, one report [21] states that a chloroform solution of parthenolide stored at room temperature was found to contain costunolide diepoxide (29) after a few days, probably formed by aerial oxidation. The literature also suggests that parthenolide can polymerize on prolonged storage [22]. 

A different cychzation reaction of 460, by treatment with iodine and silver oxide, gave l,6-dioxaspiro[3.4]octanes 469 (Scheme 130). This heterocychc core present in a series of sesquiterpenic lactones has interesting biological activity and is isolated as secondary metabolites from species of the Compositae family . 

Under the Ritter reaction conditions above described, the sesquiterpene (—)-cariophyllene oxide undergoes an interesting rearrangement, originating an A-acyl amino clovane-type compound, in 33% yield, after purification by flash chromatography (Scheme 21) [92]. 

By using betulin as substrate, some mechanistic studies were performed and it was demonstrated that these reactions are catalyzed by Brpnsted acid species generated in situ from the hydrolysis of Bi(0Tf)3-.vH20. This process was also applied to other terpenic compounds. The sesquiterpene ( )-caryophyllene oxide originated clov-2-en-9a-ol by a cariophyllene-clovane rearrangement (Scheme 41) whereas 3-oxo- l 8a-olean-28- l 3(3-olide was obtained from oleanonic acid (Scheme 42). With this triterpene derivative, only 28,13(3-lactonization occurred, with inversion of the configuration of the stereocenter at C18 [133],... 

Natural sesquiterpene pyridine alkaloid formation needs two precursors, one for the pyridinium moiety and another for the sesquiterpene moiety. The a for formation of the pyridinium moiety is nicotinic acid, which reacts with isoleucine and, by oxidative reaction, produces evoninic acid, wilfordic acid or edulinic acids, a for the sesquiterpene moiety is still open to question, but E, E-famesyl cation has been suggested as one possibility and hedycarylol as a second. This moiety is dihydroagarofuran. Therefore, a for the sesquiterpene pyridine alkaloids is nicotinic acid and E, E-famesyl cation and, controversially, hedycaryol. The /3 is amacrocycling ring formation substance (two moieties), from which the alkaloid forms (Figure 62). 

R)- and (S)-LBA 52 were also applied to the diastereoselective cychzafion of optically acttve hydroxypolyprenoid 53 to afford after several steps the natural bicyclic sesquiterpene ethers (-)-caparrapi oxide and (-i-)-8-epicaparrapi oxide, respectively (Scheme 5.69) [130]. Notably, LBAs 52 and ent-52 were able to... 

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