Sesquiterpenoid

Figure 5 Proposed mechanism for biosynthetie introduetion of bromine and ehlorine atoms into the Lcmrencia sesquiterpenoid nidifieine (24)...

The organization of Part Two is according to structural type. The first section, Chapter Seven, is concerned with the synthesis of macrocyclic compounds. Syntheses of a number of heterocyclic target structures appear in Chapter Eight. Sesquiterpenoids and polycyclic higher isoprenoids are dealt with in Chapters Nine and Ten, respectively. The remainder of Part Two describes syntheses of prostanoids (Chapter Eleven) and biologically active acyclic polyenes including leukotrienes and other eicosanoids (Chapter Twelve). 

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. ... 

Heterocycles in synthesis of drimane sesquiterpenoids from labdane diterpenoids 97IZV896. 

Synthesis of germacrane sesquiterpenoid lactones and related compounds 99T2115. 

Synthetic studies on sesquiterpenoids from D-glucose, total syntheses of (-H)-eremantholide A and (—)-verrucarol 98YGK1026. 

A modern variant is the intramolecular magnesium-ene reaction, e.g. the reaction of the alkene-allylic-Grignard compound 9 to give the five-membered ring product 10. This reaction proceeds regio- and stereoselectively, and is a key step in a synthesis of the sesquiterpenoid 6-protoilludene ... 

Terpenoids are classified according to the number of five-carbon multiples they contain. Monoterpenoids contain 10 carbons and are derived from two isopentenyl diphosphates, sesquiterpenoids contain 15 carbons and are derived from three isopentenyl diphosphates, diterpenoids contain 20 carbons and are derived from four isopentenyl diphosphates, and so on, up to triterpenoids (C30) and tetraterpenoids (C40). Monoterpenoids and sesquiterpenoids are found primarily in plants, bacteria, and fungi, but the higher terpenoids occur in both plants and animals. The triterpenoid lanosterol, for example, is the precursor from which steroid hormones are made, and the tetraterpenoid /3-carotene is a dietary source of vitamin A (Figure 27.6). 

The terpenoid precursor isopentenyl diphosphate, formerly called isopentenyl pyrophosphate and abbreviated IPP, is biosynthesized by two different pathways depending on the organism and the structure of the final product. In animals and higher plants, sesquiterpenoids and triterpenoids arise primarily from the mevalonate pathway, whereas monoterpenoids, diterpenoids, and tetraterpenoids are biosynthesized by the 1-deoxyxylulose 5-phosphate (DXP) pathway. In bacteria,... 

Sesquiterpenoid. 203, 1071 Sex hormone, 1082-1083 Sharpless, K. Barry. 734 Sharpless epoxidation, 735 Shell (electron), 5 capacity of, 5 Shielding (NMR). 442 Si prochirality, 315-316 Sialic acid. 997 Side chain (amino acid), 1020 Sigma (cr) bond, 11 symmetry of, 11 Sigmatropic rearrangement, 1191-1195... 

The functional groups of abscisin II could easily arise from a precursor like violaxanthin (M), a carotenoid of widespread occurrence (see 11). Whatever the genesis of abscisin II, it is clear that it must be different from that of the bis-sesquiterpenoid, gossypol (N), which also occurs in the cotton plant and has received considerable attention. 

The next example involves a recent study of essential oil polymorphism in Thymus praecox Opiz subsp. arcticus (E. Durand) Jalas (syn. T. drucei Ronn.) on the British Isles (Schmidt et al., 2004). More than 700 specimens of the plant were collected in Ireland, Scotland, and southern England and subjected to gas chromatographic analysis (coupled with mass spectroscopy). Sixty-nine constituents were identified, the majority of which were mono- and sesquiterpenoids. Analysis of the data revealed a highly polymorphic assemblage with 13 chemotypes in Scotland, 11 in Ireland, and 17 in the south of England. Polymorphism seems to... 

Hashimoto, T., Tori, M. and Asakawa, Y. 1989. Drimane-type sesquiterpenoids from the liverwort Makinoa crispata. Phytochemistry 28 3377-3381. 

Itoh, T., Matsuo, Y. and Suzuki, M. 1997b. Sesquiterpenoids of Laurencia majuscula... 

He, X.G. et al, Liquid chromatography-electrospray mass spectrometric analysis of curcuminoids and sesquiterpenoids in turmeric Curcuma longa), J. Chromatogr. A, 818, 127, 1998. 

Hu L, Zhongliang CH. Sesquiterpenoid alcohols from Chrysanthemum morifolium. Phytochemistry 1997 44 1287-1290. 

Hernandez V, del Carmen Recio M, Manez S, Prieto JM, Giner RM, Rios JL. A mechanistic approach to the in vivo anti-inflammatory activity of sesquiterpenoid compounds isolated from Inula viscosa. Planta Med 2001 67 726—731. 

Maier, W., K. Hammer et al. (1997). Accumulation of sesquiterpenoid cyclohexenone derivatives induced by an arbuscular mycorrhizal fungus in members of the Poaceae. Planta 202(1) 36—42. 

Maier, W., B. Schneider et al. (1998). Biosynthesis of sesquiterpenoid cyclohexenone derivatives in mycorrhizal barley roots proceeds via the glyceraldehyde 3-phosphate/pyruvate pathway. Tetrahedron Lett. 39(7) 521-524. 

Meinwald, J., K. Erickson, M. Hartshorn, Y. C. Meinwald, and T. Eisner (1968). Defensive mechanisms of arthropods. XXIII. Anallenic sesquiterpenoid from the grasshopper Romalea microptera. Tetrahedron Lett. 25 2959-2962. 

We have used the Kupchan scheme successfully in the separation of the multifunctional diterpenoid kalihinols from various Acanthella species (cf. Sect. 4.2.2). These compounds were distributed between the carbon tetrachloride and chloroform layers [19, 25], No isocyanosesquiterpenes were present in the hexane layer. By contrast, separate experiments with the Australian A. klethra revealed that sesquiterpenoid isonitriles were found exclusively in the hexane extract. No kalihinols were present in the carbon tetrachloride or chloroform extracts [26],... 

The antipodal relationship appears secure despite differences in the magnitude of the rotation values ([a]D 32, —63° 43, +100°), both of which were measured in CC14. Of particular interest is the isothiocyanato-alcohol 46, which is the first example of an oxygenated marine sesquiterpenoid possessing a function unrelated to the -NC/-NCS/-NHCHO triad. 

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