- Asymmetric Synthesis of Oxygenated Monoterpenoids of Importance for Bark Beetle Ecology
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Herein we report the asymmetric syntheses of a number of oxygenated terpenoids that are of importance in the chemical ecology of bark beetles. These are pinocamphones, isopinocamphones, pinocarvones, and 4-thujanols (= sabinene hydrates). The camphones were synthesized from isopinocampheol, the pinocarvones from β-pinene, and the thujanols from sabinene. The NMR spectroscopic data, specific rotations, and elution orders of their stereoisomers on a chiral GC-phase (β-cyclodextrin) are also reported. This enables facile synthesis of pure compounds for biological activity studies and identification of stereoisomers in mixed natural samples.
- Ganji, Suresh,Svensson, Fredric G.,Unelius, C. Rikard
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p. 3332 - 3337
(2020/11/30)
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- Nanosized sulfated zinc ferrite as catalyst for the synthesis of nopol and other fine chemicals
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A nanosized highly ordered mesoporous zinc ferrite (ZnFe2O 4; ZF) was synthesized via co-precipitation method, further sulfated with ammonium sulfate solution to obtain sulfated ZF (SZF) and have been used for the synthesis of nopol by Prins condensation of β-pinene and paraformaldehyde. The NH3-TPD and pyridine sorption DRIFT-IR studies revealed the significant enhancement in Lewis acidic sites of the zinc ferrite on sulfatation. The influence of various reaction parameters such as reaction temperature, effect of substrate stoichiometry and catalyst loading has been investigated. It gave 70% conversion of β-pinene with 88% selectivity to nopol. The spent catalyst was regenerated and reused successfully up to four cycles with slight loss in catalytic activity. The nanosized SZF catalyst was found to be highly active towards several other commercially important acid catalyzed reactions such as isomerization, acetalization and aldol condensation.
- Jadhav, Sumit V.,Jinka, Krishna Mohan,Bajaj, Hari C.
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- Peculiarities of β-pinene autoxidation
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The thermal oxidation of the renewable olefin β-pinene with molecular oxygen was experimentally and computationally investigated. Peroxyl radicals abstract weakly bonded allylic hydrogen atoms from the substrate, yielding allylic hydroperoxides (i.e., myrtenyl and pinocarvyl hydroperoxide). In addition, peroxyl radicals add to the C=C bond of the substrate to form an epoxide. It was found that a relatively high peroxyl radical concentration, together with the high rate of peroxyl cross-reactions, make radical-radical reactions surprisingly important for this particular substrate. Approximately 60% of these peroxyl cross-reactions lead to termination (radical destruction), keeping a radical chain length of approximately 4 at 10% conversion. Numerical simulation of the reaction-based on the proposed reaction mechanism and known or predicted rate constants-demonstrate the importance of peroxyl cross-reactions for the formation of alkoxyl radicals, which are the precursor of alcohol and ketone products. Copyright
- Neuenschwander, Ulrich,Meier, Emanuel,Hermans, Ive
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experimental part
p. 1613 - 1621
(2012/03/11)
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- TERPENOIDS FROM THE FRENCH LIVERWORT TARGIONIA HYPOPHYLLA
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Key Word Index - Targionia hypophylla; Targioniaceae; Hepaticae; cis- and trans-pinocarveyl acetates; mono-, sesqui- and diterpenoids.Two monoterpene acetates, cis- and trans-pinocarveyl acetates, which make up the characteristic aroma of the thalloid liverwort Targionia hypophylla were isolated, together with the previously known sesquiterpene alcohol, drimenol.
- Asakawa, Yoshinori,Toyota, Masao,Cheminat, Annie
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p. 2555 - 2556
(2007/10/02)
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- Hydroxylation by Cytochrome P-450 and Metalloporphyrin Models. Evidence for Allylic Rearrangement
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The allylic hydroxylation of 3,3,6,6-tetradeuteriocyclohexene, methylenecyclohexane, and β-pinene has been examined with phenobarbital-induced liver microsomal cytochrome P-450 (P-450LM2) and with iron porphyrin and chromium porphyrin model systems.Aerobic and peroxide dependent enzymic regimes were investigated with purified P-450LM2 and with microsomal suspensions.Epoxidation and allylic hydroxylation were primary reactions with all substrates.With 3,3,6,6-tetradeuteriocyclohexene, the major hydroxylation product (60-80percent) was the result of hydroxylation at the deuterated allylic site.In all cases, a significant amount (20-40percent) of hydroxylation occurred with allylic rearrangement.The iron porphyrin/iodosylbenzene model system also showed preferential hydroxylation of the deuterated allylic site (70percent) with significant allylic rearrangement (30percent).By contrast, the chromium porphyrin/iodosylbenzene model system showed complete scrambling of the allylic system.Extensive rearrangement accompanied the hydroxylation of methylenecyclohexane and β-pinene by both the enzymic and metalloporphyrin systems whereas the selenium dioxide oxidation of these substrates gave selective allylic hydroxylation without rearrangement.A mechanism is suggested for allylic hydroxylation by cytochrome P-450 and by the metalloporhyrin model systems involving initial hydrogen atom abstraction from the allylic site and geminate, cage recombination of the incipient, allylic free radical.
- Groves, John T.,Subramanian, Durga V.
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p. 2177 - 2181
(2007/10/02)
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