Aromatic triterpene

Gotsypol an aromatic triterpene from cotton seed (Gossypum hirsiuum). M, 518.54, m.p. 184°C from ether, 199"C from chloroform, 214°C from light petroleum. G. is biosynthesized from mevalonic acid via neryl pyrophosphate and cisjcis-famesyl pyrophosphate. It is somewhat poisonous, and has been suggested for use as an insecticide. 

Isoprene metabolism in plants is very complex. Plants can synthesize many types of aromatic substances and volatile oils from isoprenoids. Examples include menthol (1= 2 ), camphor (1 = 2), and citronellal (1 = 2). These Cio compounds are also called monoterpenes. Similarly, compounds consisting of three isoprene units (1 = 3) are termed sesquiterpenes, and the steroids (1 = 6) are called triterpenes. 

As part of the total synthesis of the triterpene (+)-a-onocerin, one of the first total syntheses in which RuO played a key role, a diphenylethyleneacetoxyketone was oxidised to the corresponding acetoxyketoacid by RuO /aq. Na(10yacetone. Aromatic ring oxidation was also involved (cf. 3.3.1 below) [219]. An oxidative cyclisation of a 1,5-diene to a diol by RuCl3/Na(10 )/wet SiO /THF formed part of the synthesis of the antitumour agent cw-solamin [220]. 

Schaeffer, P. Trendel, J.-M. Albrecht, P. (1995) Stmcture and origin of two triterpene-da ived aromatic hydrocarbons in Messel shale. J. Chan. Soc., Chem. Commun., 1275-6. 

In addition to these solvent peaks, we can count 26 peaks in the spectrum. Because there are 27 carbons in the cholesterol molecule (three are lost in the biosythesis from a triterpene precursor), there must be one peak that accounts for two carbons. The tallest peak (labeled 1, m ) in fact corresponds to two different carbons with nearly identical chemical shifts. The most downfield peaks ( aa and z ) are in the olefin/aromatic region of the 13 C spectrum (120-140 ppm), so they must correspond to C-5 andC-6. Peak aa is less intense ( shorter ) than all of the other peaks because of slow relaxation it must be a quaternary carbon. We will see that the proximity of protons is the primary means of relaxation of 13 C nuclei, so carbons lacking a proton relax much more slowly and give less intense peaks, especially if... 

Although previous workers have suggested bacterial synthesis as a possible source of biogenic PAHs in modem sediments, Hase and Hites (1976) have shown that bacteria more likely only bioaccumulate them from the growth medium. Anaerobic aromatization of tetracyclic triterpenes appeared to have been demonstrated by Lohmann et aL (1990) by incubating radiolabeled j8-amyrin. 

Hydrocarbons. Both even- and odd-chain w-paraffins, including branched-chain (iso and anteiso) compounds, which are minor components of the hydrocarbon fraction, are present in virgin olive oil. The polyunsaturated triterpenic hydrocarbon squalene, and biochemical precursor of sterols, is the main component of the hydro carbon fraction. The squalene content of olive oil ranges from 150 to 700 mg per 100 g (27-30). p-Carotene is also present in olive oil as are aromatic hydrocarbons, including benzenoid, napthalenic, and more complex aromatic hydrocarbons (30-37). 

Similar procedures are also successful in the construction of cyclobutane rings in other stereochemical environments, including the formation of bicyclo[3.1.1]heptane (67)and bridged tricyclic systems such as (68), (69) ° and (70). ° A variety of annelated cyclobutanes have been prepared by the photochemical procedure as above, yields are sometimes poor or only moderate. Examples include bicy-clo[2.1.0]pentanes (71), °° bicyclo[2.2.0]hexanes (72)"° and cyclobuteno aromatics (e.g, 73), " o-nor-steroids e.g. 74)," A-bisnorsteroids" and triterpenes" as well as the highly strained tricyclo[4.2.0.0 ]octane system (75)," and the [4.4.4.5]fenestrane (76)." ... 

Lupane triterpenes are very common in the Celastraceae family. Esters of lupane triterpenes with aromatic acids have been isolated from others sources but in Celastraceae 0-caffeoyl esters are the most frequently found. C-3 position is the most common compromised with esterification and the stereochemistry of the ester moiety is usually p. 

Dimers are a class of compounds isolated from only seven species of Celastraceae family [8,88]. These triterpene dimers were found to be composed of one quinoid type and one aromatic type of triterpene derived from pristimerin, tingenone and / or their congeners joined together by two ether linkages formed between the two A rings or between the A and B rings. From the methylene chloride soluble portion of a methanolic extract of Maytenus chuchuhuasca, four dimeric compounds were isolated by Shirota et al. [88]. 

Compound (90) showed a molecular formula of C60H80O9, determined by HRFAB-MS. The H and 13C NMR spectra of (90) showed that two pristimerin-type triterpene units composed it, one in the quinoid form and the other in the aromatic form. The units were different that those from scutidin aA [89] and xuxuarine Ep [90]. From the spectroscopic data, it... 

Compounds (91), (92) and (93) had an identical molecular formula C58H74O8, which was established by HRFAB-MS. The NMR spectral data, which were similar to those of cangorosin B [7], suggested that each consisted of two different types of triterpene units, tingenone and pristimerin, one in the quinoid form and the other in the aromatic form. The stereochemistry was confirmed by means of ROES Y and CD spectral studies. The FAB-MS data enabled to determine whether the pristimerin and the tingenone type triterpene were in the quinoid form or in the aromatic form. Considering the spectroscopic evidences, the structures of (91), (92) and (93) were assigned to xuxuarines Fp, Ga and Gp respectively, Fig. (49). 

Compound (94) has a molecular formula CeoHgoOg, based on HRFASMS analysis and its 13C-NMR spectrum. According to the data obtained from its H and 13C-NMR spectra suggested that (94) was a triterpene dimer composed of two pristimerin-type triterpenes with one subunit in the quinoid form and the other in the aromatic form. Confirmation of the structure was made by analysis of the 2D NMR spectroscopic data. The absolute configuration was determined from its CD spectrum. According to the above data, the authors concluded that (94) was a regioisomer of scutionin aA [89], and it was called scutionin aB, Fig. (50). 

Leopold Ruzicka s structural studies of hydrocarbons, also in collaboration with the perfume industry (see chapter 3), took Wallach s terpene studies to a new level. He smdied the dehydrogenation of monoterpenes (to formp-cymene) as well as the dehydrogenation, using selenium (Diels reaction), of sesquiterpenes (C15), diterpenes (C20), and triterpenes (C30), and dehydrogenated them (via the Diels reaction, to form aromatics derivatives of naphthalene, anthracene, chrysene, and others). During the 1920s Ruzicka postulated that steroids are derived from terpenes and, in... 

At present mainly terpenes and aromatic compounds have been isolated and identified as components of resins with diterpenes (less frequently sesquiterpenes and triterpenes) and phenylpropane derivatives usually dominating. 

Alkaloids can be divided into different t q3es according their pure chemical structures pointing first at the alkaloid base, a basic chemical nucleus. The following are basic types of alkaloids acridones, aromatics, carbo-lines, ephedras, ergots, imidazoles, indoles, bisindoles, indolizidines, manza-mines, oxindoles, quinolines, quinozolines. quinolizidines, phenylisoquinolines, phenylethylamines, piperidines, purines, pyrolidines, pyrrolizidines, pyrro-loindoles, pyrydines, sesquiterpenes, simple tetrahydroisoquinolines, stereoids, tropanes, terpenoids, diterpenes, and triterpenes. 

Unsaturated and hydroxylated triterpenes and steroids give colored products with aromatic aldehydes in strong mineral acids, with acetic anhydride in sulfuric acid, and with inorganic salts (cerium(IV) sulfate and antimony(III) chloride, for example) in an acidic solution. These reactions have been used as the basis for determination of saponins. The analysis of Ginseng radix (Panax ginseng, Araliaceae) in Pharmacopoeia Helvetica VII, for example, relies on reaction with glacial acetic acid/sulfuric acid and spectrophotometric determination at 520 nm of the red product. The jS-aescine component of horse chestnut (Aesculus hippocastanum, Hippocastan-aceae) saponin can be determined spectrophoto-metrically after treatment with a mixture of iron(III) chloride, acetic acid, and sulfuric acid. 

An idenhcal approach was followed for the preparahon of combinatorial libraries from ursohc acid, betulinic add, and lupeol (Figure 11.50). In the case of betuhnic acid (105) and ursohc acid, the triterpene scaffold was immobilized onto a prederivatized amino acid on 2-chlorotrityl or Sieber amide resin, and treated with a variety of ahphahc, aromatic, and amino acids, to generate a library of C-3 and C-28 derivatives 106.In another series, C-3 oxime esters 107 were prepared from... 

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