Of triterpenes

Chionochloa, known locally as snow tussock, consists of 22 species, 21 of which are native to New Zealand. The remaining species occurs in southeastern Australia and does not figure in the discussion. Studies of triterpene methyl ethers (TMEs) have revealed the existence of different chemodemes (Connor and Purdie, 1976, 1981). In some instances, it was shown that TMEs were present in populations of a given species in one part of its range but absent from others arundoin [57] (see Fig. 2.12 for structures 57-59) was identified from plants collected at Harpers... 

FIGURE 16.12 Structures of triterpenic pyrolysis products of olibanum resins. 

The structure-activity relation of triterpene QMs on the anti-inflammatory effect has been investigated with a series of analogues by comparing inhibition of the IL-1 (3 production in the LPS-induced monocytes.93-94 Clearly, the conjugated QM structure with alkenes is essential for the observed inhibition, and similar inhibitory effect was found with derivatives that are capable to form the conjugated QM through hydrolysis and/or oxidation.93-94 Also, the presence of the E ring in the triterpene QM structure is an additional contributor. 

Despite the broad medical potentials reported so far, the total synthesis of triterpene QMs is yet to be reported. On the contrary, the biosynthesis of triterpene QMs has recently been validated as from the oxidosqualene 88 (Scheme 8.16) in the plants including Maytenus aquifolium and Salacia campestris.10S With the assistance of HPLC analysis and isotopic labeling, it was found that triterpene QMs 90 were formed only in the root of these plants from friedelin 89 and similar cyclized intermediates, which were synthesized in the leaves from oxidosqualene by cyclase. 

Geetha T, Varalakshmi P. Anticomplement activity of triterpenes from Crataeva nur-vala stem bark in adjuvant arthritis in rats. Gen Pharmacol 1999 32 495-497. 

Kasture VS, Deshmukh VK, Chopde CT. Anticonvulsant and behavioral actions of triterpene isolated from Rubia cordifolia Linn. Indian J Exp Biol 2000 38 675-680. 

Figure 1.2 General molecular formulae of triterpenes present in triterpenoid resins...

P. Dietemann, M.J. Edelmann, C. Meisterhans, C. Pfeiffer, S. Zumbuhl, R. Knochenmuss, and R. Zenobi, Artificial Photoaging of Triterpenes Studied by Graphite assisted Laser Desorption/ Ionization Mass Spectrometry, Helv. Chim. Acta, 83, 1766 1777 (2000). 

Optically active (35)-form, 195, is a key intermediate in the biochemical synthesis of triterpenes and sterols in vertebrates, plants and fungi164. 

MORITA, M., SHIBUYA, M., KUSHIRO, T., MASUDA, K., EBIZUKA, Y., Molecular cloning and functional expression of triterpene synthases from pea (Pisum sativum), Eur. J. Biochem., 2000, 267, 3453-3460. 

The biomimetic cationic domino cyclization of an acyclic unsaturated substrate to give the tetracyclic scaffold of triterpenes and steroids is intensively described in the literature.1121 The concept has recently been used by Corey et al. to prepare enanti-opure (+)-dammarenediol II 18 in an exceptional short way.1131 The synthesis demonstrates the power of the combination of cation-olefin polyannulation with the aldol cyclization for tetraannulation (scheme 4). Successive treatment of the acylsilane 13 with 2-propenyllithium 14 and the iodoalkane 15 efficiently yidds the epoxytriene 16. The Lewis acid... 

Ring A diosterols.3 The ring A diosterols (3 and 4) of triterpenes can be prepared from the A2-alkene (1) by osmylation to form the two possible cis-diols (2), which on Swern oxidation give the a-diketone (3). The same diketone is also obtained by Swern oxidation of the 2(3,3a-diol, the product of peracid oxidation followed by acid cleavage. The diketone 3 rearranges to the more stable diosphenol (4) in the presence of base. 

Separation of triterpenoids from a crude extract of Ganoderma lucidum Separation of triterpenes... 

FIGURE 32. Constitution formula of triterpene-derived hydroperoxide 78 ... 

Black cohosh root doses vary widely, with up to 2000 mg/day of root being taken several times daily. Remifemin is the best-studied brand, and tablets containing 40 mg of black cohosh extract with 1 mg of triterpenes are given as one or two tablets twice daily. 

CS095 Itoh, O., T. Uetsuki, T. Tamura and A. Matsumoto. Characterization of triterpene alcohols of seed oils from some species of Theaaceae, Phytolac-caceae and Sapotaceae. Lipids 1980 ... 

In similar fashions, the core pathway up to C25 compounds (five isoprene units) is formed by sequential addition of C5 moieties derived from IPP to a starter unit derived from DMAPP. Thus, sesquiterpenes are formed form the precursor 2E, hS-farnesyl pyrophosphate (FPP), and diterpenes from 2E, 6E, IO -geranylgeranyl pyrophosphate (GGPP). The parents of triterpenes and tetraterpenes are formed by reductive coupling of two FPPs or GGPPs, respectively. Rubbers and other polyisoprenoids are produced from repeated additions of C5 units to the starter unit GGPP. 

Fujita, M., H. Itokawa, and Y. Kumekawa. 1974. The study on the constituents of Clematis and Akebia spp. I. Distribution of triterpenes and other components. Yakugaka Zasshi 94 189-191. 

Esterification with a fatty acid or with ferulic acid at C-3 of triterpene alcohols exerted almost no influence on the activity as has been observed with lupane- (264/265) and cycloartane- (66/67, 72/73) type compounds and a C-3 monohydroxy triterpenoid (264/266). However, esterification at C-3 with a fatty acid reduced the inhibitory activity of some dihydroxy triterpenoids (138/139,140 202/203, 204 230/231 232/233, 234). 

Concerning the metabolism of triterpenes and steroids, quite a number of P450 catalyzed transformations are very important, namely the 14a-demethyla-tion of lanosterol [50], the side-chain cleavage of cholesterol [51]and pregnenes [52], and the desaturation of ring A of androgens with concomitant oxidative removal of C(19) [53]. The latter reaction is catalyzed by human placental aromatase, associated with a NADPH-dependent reductase, and requires three moles of oxygen and three moles of NADPH in order to oxidize andro-stenedione 45 to formic acid and estrone 46, Fig. 10. 

Daphniphyllum macropodum contains a great variety of related alkaloids whose structures are quite complex and novel (Section II). It is structurally evident that these alkaloids with an isopropyl or a potential isopropyl group are regarded as a terpene alkaloid. Bio-genetieally, these Daphniphyllum alkaloids, particularly C22 alkaloids, have been proposed to be derived from four molecules of mevalonic acid (MVA) and one acetate unit (15, 39). However, the recent tracer experiments showed that these alkaloids could be biosynthesized from six MVA molecules through a squalene-like intermediate. Accordingly, they should be included in a group of triterpene alkaloid. 

The dammarenyl cation (21) represents the first branch point from which numerous mechanistic pathways of triterpene synthesis diverge. A detailed and interesting study of molecular modelling and conformational analysis indicates that the formation and... 

On the other hand, it was sufficiently large for many individual steps of the linking reactions to be avoided. The latter consideration was particularly important for the synthesis of triterpenes and tetraterpenes, such as apocarotenals and carotenoids, the industrial production of which was included in the concept from the beginning. 

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