- Transformations of isocaryophyllene diepoxide under conditions of homogeneous and heterogeneous acid catalysis
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Transformations of isocaryophyllene diepoxide (an isomer of widely spread natural sesquiterpene) were studied in various acidic media under conditions of homogeneous and heterogeneous catalysis. A number of previously unknown compounds were thus obtained. The experimental data were compared with the results of molecular-mechanics and quantum-chemical simulation of the most probable transformation paths.
- Salomatina,Yarovaya,Korchagina,Gatilov,Polovinka,Barkhash
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- Electron transfer-initiated epoxidation and isomerization chain reactions of β-caryophyllene
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The abundant sesquiterpene b-caryophyllene can be epoxidized by molecular oxygen in the absence of any catalyst. In polar aprotic solvents, the reaction proceeds smoothly with epoxide selectivities exceeding 70%. A mechanistic study has been performed and the possible involvement of free radical, spin inversion, and electron transfer mechanisms is evaluated using experimental and computational methods. The experimental data-including a detailed reaction product analysis, studies on reaction parameters, solvent effects, additives and an electrochemical investigation-all support that the spontaneous epoxidation of b-caryophyllene constitutes a rare case of unsensitized electron transfer from an olefin to triplet oxygen under mild conditions (80 8C, 1 bar O2). As initiation of the oxygenation reaction, the formation of a caryophyllene-derived radical cation via electron transfer is proposed. This radical cation reacts with triplet oxygen to a dioxetane via a chain mechanism with chain lengths exceeding 100 under optimized conditions. The dioxetane then acts as an in situ-formed epoxidizing agent. Under nitrogen atmosphere, the presence of a one-electron acceptor leads to the selective isomerization of b -caryophyllene to isocaryophyllene. Observations indicate that this isomerization reaction is a novel and elegant synthetic pathway to isocaryophyllene.
- Steenackers, Bart,Campagnol, Nicol,Fransaer, Jan,Hermans, Ive,De Vos, Dirk
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p. 2146 - 2156
(2015/01/30)
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- Transannular cyclization of epoxycaryophyllenes catalyzed by Ti III: An efficient synthesis of tricyclo[6.3.0.02,5] undecanes
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The transannular cyclization of epoxycaryophyllenes 2-7 catalyzed by TiIII has been investigated. This cyclization led to alcohols 8-15, all of them possessing a tricyclo[6.3.0.02,5]undecane skeleton. All of these compounds present pleasant aromatic properties. The cyclization takes place with high yields (> 80 %) and via the αα or ββ conformation of the intermediate radical I. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Barrero, Alejandro F.,Herrador, M. Mar,Quilez Del Moral, Jose F.,Arteaga, Pilar,Sanchez, Elena M.,Arteaga, Jesus F.,Piedra, Maria
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p. 3434 - 3441
(2007/10/03)
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- Betulenols from Betula species
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The essential oils from buds of five Betula species growing in Turkey were investigated by GC-MS. A major component in the essential oils was shown to be 14-hydroxy-β-caryophyllene (6). The structure of β-betulenal (12) which was isolated from Betula essential oils was also confirmed by synthesis. Chemical reactions yielded 14-acetoxy-β-aryophyllene (15), 14- hydroxy-isocaryophyllene (10) and its acetate (14), giving evidence to the natural occurrence in Betula species of the formerly known α-betulenol acetate (3), β-betulenol (2) and β-betulenol acetate (4), respectively. Compounds 6, 9, 10, 12, and 15 were evaluated for antimicrobial activity.
- Demirci, Betuel,Huesnue Can Baser,Oezek, Temel,Demirci, Fatih
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p. 490 - 493
(2007/10/03)
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- Rearrangement of (-)-β-caryophyllene. A product analysis and force field study
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The rearrangement of (-)-β-caryophyllene (1) with sulfuric acid in ether has been reinvestigated. In the early stage, a multitude of products is formed. Of these, fourteen hydrocarbons (3, 4, 6-17) and four alcohols (5, 18-20) were obtained pure. From the very beginning, the tricycloundecenes 15-17 assumulate quickly. This indicates that a previously unknown rearrangement of 1 by protonation of the exocyclic double bond followed by transannular ring closure is a main reaction, and that the conformation βα is involved. Three hydrocarbons (3, 4, 8) and three alcohols (5, 18, 19) proved to be stable. They are the main components in the late stage. A complete rearrangement scheme followed from a force field analysis using MMP2. First, all conformations up to 4 kcal above the global minimum of each product and each carbenium ion necessary for its formation were detected automatically using the search program HUNTER. Second, the conformation favoring a specific transformation was searched for. For transannular cyclizations, the conformation with the shortest distance between the atoms to be bound and, for ring openings and 1,2-shifts, the conformation with the smallest dihedral angle between the empty p-orbital and the bond to be broken were selected. In all cases, the selection criteria proved valid: The stereochemistry of the conformations selected matched the stereochemistry of the products observed. On the basis of the results presented, a fully automated search program for favorable rearrangement paths may be developed.
- Fitjer, Lutz,Malich, Andreas,Paschke, Carola,Kluge, Sabine,Gerke, Ralf,Rissom, Beate,Weiser, J?rg,Noltemeyer, Mathias
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p. 9180 - 9189
(2007/10/03)
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- Stereochemistry of 14-hydroxy-β-caryophyllene and related compounds
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The isomerization of β-caryophyllene (3), under treatment with SeO2, is described. Chemical correlations, between 3 and 14-hydroxy-β-caryophyllene (6) from Juniperus oxycedrus, are established. High resolution 1H NMR spectra and analysis by molecular mechanics of 3, 6 and 14-acetoxy-β-caryophyllene (7) indicate the existence of two conformational isomers, βα and ββ, in each compound. At 25°C, the βα conformer predominates in 3 and 7 but the ββ conformer predominates in 6. The higher percentage of 6ββ possibly derives from an intramolecular hydrogen bond. The treatment of 3, 6 and 7 with m-CPBA generates, in each case, two diastereomeric 4,5-epoxi-derivatives. The epoxides obtained from 6 have been isolated and analysed separately.
- Barrero,Molina,Oltra,Altarejos,Barragan,Lara,Segura
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p. 3813 - 3822
(2007/10/02)
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- Thermoconversion of caryophyllene- to farnesene-type sesquiterpenes. Short access to the enantiomers of (6RS,7RS)- and (6RS,7SR)-6,7-epoxy-6,7-dihydro-β-farnesenes
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Flash-vacuum thermolysis of the four diastereoisomeric 5,6-epoxy-5,6-dihydro-caryophyllenes 1-4 at 500-550°/0.1-0.7 Torr leads to the hitherto unreported enantiomers of (6RS,7RS)- and (6RS,7SR)-6,7-epoxy-6,7-dihydro-β-farnesenes ((±)-5 and (±)-6, resp.). In particular, (+)-5 is formed in 45% yield (ca. 90% ee) and is, thus, an attractive chiral building block for natural-product synthesis.
- Giersch,Boschung,Snowden,Schulte-Elte
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- SYNTHESIS AND TRANSFORMATIONS OF SOME DIENES WITH CARYOPHYLLANE SKELETON IN ACIDIC MEDIA
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Three new dienes with caryophyllane skeleton were synthesized by hydrochlorination-dehydrochlorination of caryophyllene.The mechanism of their intramolecular rearrangements was investigated in media with various acidities.
- Khomenko, T. M.,Korchagina, D. V.,Gatilov, Yu. V.,Bagryanskaya, Yu. I.,Tkachev, A. V.,et al.
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p. 1839 - 1852
(2007/10/02)
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- EIGHT NEW XENIA DITERPENOIDS FROM THREE SOFT CORALS OF THE RED SEA
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Investigation of the terpenoid content of three soft corals from the Gulf of Eilat (THe Red Sea), Xenia macrospiculata, X. obscuronata and X. lilielae resulted in the isolation of 8 new diterpens.Two of the new compounds belong to the xeniolides (xenialactol-D (10a) and xeniolide-E (13)) and the other six (4,14-diepoxyxeniaphyllene (15), 4,5-epoxyxeniaphyllan-14,15-diol (17), 4,14-diepoxy-xeniaphyllenol-A (21a), xeniaphyllenol-B (23a), xeniaphyllenol-C (24a) and xeniaphyllantriol (25) are new xeniaphyllanes (prenylated caryophyllanes).The structure determination of the various compounds is based on chemical transformations as well as on the 1H and 13C NMR spectra.Several known caryophyllene derivatives have been synthesised for 13C NMR spectra and chemical comparisons.The 13C NMR has proven to be an excellent probe for structural and stereochemical determinations.
- Groweiss, Amiram,Kashman, Yoel
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p. 3385 - 3396
(2007/10/02)
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