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1.
Hakryul Kim Harold W. Gardner Ching T. Hou 《Journal of the American Oil Chemists' Society》2000,77(1):95-99
The new microbial isolate Pseudomonas aeruginosa (PR3) has been reported to produce from oleic acid a new compound, 7,10-dihydroxy-8(E)-octadecenoic acid (DOD), with 10-hydroxy-8-octadecenoic acid (HOD) being a probable intermediate. The production of DOD
involves the introduction of two hydroxyl groups at carbon numbers 7 and 10, and a rearrangement of the double bond from carbons
9–10 to 8–9. It has been shown that the 8–9 unsaturation of HOD was possibly in the cis configuration. Now we report that the rearranged double bond of HOD is trans rather than cis, as determined by spectral data. Also, it was found that the 10-hydroxyl was in the S-configuration as determined by gas chromatographic separation of R- and S-isomers after preparation of the (−)-menthoxycarbonyl derivative of the hydroxyl group followed by oxidative cleavage of
the double bond and methyl esterification. This latter result coincides with our recent finding that the main final product,
DOD, is in the 7(S),10(S)-dihydroxy configuration. In addition, a minor isomer of HOD (about 3%) with the 10(R)-hydroxyl configuration was also detected. From the data obtained herein, we concluded that 10(S)-hydroxy-8(E)-octadecenoic acid is the probable intermediate in the bioconversion of oleic acid to 7(S),10(S)-dihydroxy-8(E)-octadecenoic acid by PR3. 相似文献
2.
13-[18O] Hydroperoxylinolenic acid was permitted to react with an extract of flaxseed acetone powder containing hydroperoxide cyclase
activity. The resulting product, 12-oxo-cis-10,cis-15-phytodienoic acid (12-oxo-PDA), contained18O in the carbonyl oxygen at carbon 12, suggesting that an epoxide was an intermediate in the hyderoperoxide cyclase reaction.
A substrate specificity study showed that acis double bond β,γ to the conjugated hydroperoxide group was essential for the substrate to be converted to a cyclic product
by hydroperoxide cyclase. 相似文献
3.
[1-14C]Linoleic acid was incubated with a whole homogenate preparation of potato leaves (Solanum tuberosum 1., var. Bintje). The methyl-esterified product was subjected to straight-phase high-performance liquid chromatography and
was found to contain four major radioactive oxidation products, i.e., the epoxy alcohols methyl 10(S), 11(S)-epoxy-9(S)-hydroxy-12(Z)-octadecenoate (14% of the recovered radioactivity) and methyl 12(R), 13(S)-epoxy-9(S)-hydroxy-10(E)-octadecenoate (14%), and the trihydroxy derivatives methyl 9(S), 10(S), 11(R)-trihydroxy-12(Z)-octadecenoate (18%) and methyl 9(S), 12(S), 13(S)-trihydroxy-10(E)-octadecenoate (30%). The structures and stereochemical configurations of these oxylipins were determined by chemical and
spectral methods using the authentic compounds as references. Incubations performed in the presence of glutathione peroxidase
revealed that lipoxygenase activity of potato leaves generated the 9- and 13-hydroperoxides of linoleic acid in a ratio of
95∶5. Separate incubations of these hydroperoxides showed that linoleic acid 9(S)-hydroperoxide was metabolized into epoxy alcohols by particle-bound epoxy alcohol synthase activity, whereas the 13-hydroperoxide
was metabolized into α- and γ-ketols by a particle-bound allene oxide synthase. It was concluded that the main pathway of
linoleic acid metabolism in potato leaves involved 9-lipoxygenase-catalyzed oxygenation into linoleic acid 9(S)-hydroperoxide followed by rapid conversion of this hydroperoxide into epoxy alcohols and a slower, epoxide hydrolase-catalyzed
conversion of the epoxy alcohols into trihydroxyoctadecenoates. Trihydroxy derivatives of linoleic and linolenic acids have
previously been reported to be growth-inhibitory to plant-pathogenic fungi, and a role of the new pathway of linoleic acid
oxidation in defense reactions against pathogens is conceivable. 相似文献
4.
The reaction of methyl 11, 12-E-epoxy-9Z-octadecenoate (1) with boron trifluoride etherate furnished a mixture of methyl 12-oxo-10E-octadecenoate (3a) and methyl 11-oxo-9E-octadecenoate (3b) in 66% yield. Methyl 9, 10-Z-epoxy-11 E-octadecenoate (2) with boron trifluoride etherate furnished a mixture of methyl 9-oxo-10 E-octadecenoate (4a, 45%) and methyl 10-oxo-11 E-octadecenoate (4b, 19%). A plausible mechanism is proposed for these reactions, which involves the attack on the epoxy ring system by BF3, followed by deprotonation, oxo formation, and double bond migration to give a mixture of two positional α,β-unsaturated
C18 enone ester derivatives (3a/3b, 4a/4b). The structures of these C18 enone ester derivatives (3a/3b, 4a/4b) were identified by a combination of NMR spectroscopic and mass spectrometric analyses. 相似文献
5.
Oat seeds are a rich source of peroxygenase, an iron heme enzyme that participates in oxylipin metabolism in plants. An isomer
of CLA, 9(Z), 11(F)-octadecadienoic acid (1), believed to have anticarcinogenic activity, was used as a substrate for peroxygenase in an aqueous medium using t-butyl hydroperoxide as the oxidant. After acidification of the reaction medium, the products were extracted with ethyl ether,
converted to their methyl esters, and characterized using HPLC. Major products after reaction for 24 h showed resonances from
1H NMR spectroscopy that were further downfield than the expected epoxides and were thought to be diol hydrolysis products.
However, analyses by HPLC with atmospheric pressure chemical ionization MS (APCI-MS) of the putative allylic diols or their
bis-trimethylsilyl ether derivatives gave incorrect M.W. The M.W. of the diols could be obtained by APCI-MS after removal
of unsaturation by hydrogenation or by EI-MS after conversion of unsaturation by hydrogenation or by EI-MS after conversion
of the allylic 1,2-diols to cyclic methyl boronic esters. Data from MS in conjunction with analyses using 1H and 13C NMR showed that the methylated products from 1 were methyl 9,10(threo)-dihydroxy- 11(E)-octadecenoate, methyl 9,10(erythro)-dihydroxy-11(E)-octadecenoate, methyl 9,12(threo)-dihydroxy-10(E)-octadecenoate. Solid-phase extraction without prior acidification and conversion of the products to methyl esters allowed
identification of the following epoxides: methyl 9,10(Z)-epoxy-11(E)-octadecenoate (6M), methyl 9,10(E)-epoxy-11(E)-octadecenoate, and methyl 11,12(E)-epoxy-9(Z)-octadecenoate. At times of up to at least 6h, 6M accounted for approximately 90% of the epoxide product. Product analysis after the hydrolysis of isolated epoxide 6M showed that hydrolysis of epoxide 6 could largely account for the diol products obtained from the acidified reaction mixtures. 相似文献
6.
The effect of pulegone chiral center configuration on its antifeedant activity to Myzus persicae was examined. Biological consequences of structural modifications of (R)-(+)- and (S)-(−)-pulegone, the lactonization, iodolactonization, and incorporation of hydroxyl and carbonyl groups were studied, as well.
The most active compounds were (R)-(+)-pulegone (1a) and δ-hydroxy-γ-spirolactones (5S,6R,8S)-(−)-6-hydroxy-4,4,8-trimethyl-1-oxaspiro[4.5]decan-2-one (5b) and (5R,6S,8S)-6-hydroxy-4,4,8-trimethyl-1-oxaspiro[4.5]decan-2-one (6b) derived from (S)-(−)-pulegone (1b). The compounds deterred aphid probing and feeding at preingestional, ingestional, and postingestional phases of feeding.
The preingestional effect of (R)-(+)-pulegone (1a) was manifested as difficulty in finding and reaching the phloem (i.e., prolonged time preceding the first contact with phloem
vessels), a high proportion of probes not reaching beyond the mesophyll layer before first phloem phase, and/or failure to
find sieve elements by 20% of aphids during the 8-hr experiment. The ingestional activity of (R)-(+)-pulegone (1a) and hydroxylactones 5b and 6b resulted in a decrease in duration of phloem sap ingestion, a decrease in the proportion of aphids with sustained sap ingestion,
and an increase in the proportion of aphid salivation in phloem. δ-Keto-γ-spirolactone (5R,8S)-(−)-4,4,8-trimethyl-1-oxaspiro[4.5]decan-2,6-dione (8b) produced a weak ingestional effect (shortened phloem phase). The postingestional deterrence of (R)-(+)-pulegone (1a) and δ-hydroxy-γ-spirolactones (5R,6S,8R)-(+)-6-hydroxy-4,4,8-trimethyl-1-oxaspiro[4.5]-decan-2-one (5a), 5b, (5S,6R,8R)-6-hydroxy-4,4,8-trimethyl-1-oxaspiro[4.5]decan-2-one (6a), 6b, and δ-keto-γ-spirolactone 8b prevented aphids from settling on treated leaves. The trans position of methyl group CH3–8 and the bond C5–O1 in lactone 6b appeared to weaken the deterrent activity in relation to the cis diastereoisomer (5b). 相似文献
7.
George J. Piazza Thomas A. Foglia Alberto Nuñez 《Journal of the American Oil Chemists' Society》2001,78(6):589-592
Peroxygenase is a plant enzyme that catalyzes the oxidation of a double bond to an epoxide in a stereospecific and enantiofacially
selective manner. A microsomal fraction containing peroxygenase was prepared from oat (Avena sativa) seeds and the enzyme immobilized onto a hydrophobic membrane. The enzymatic activity of the immobilized preparation was
assayed in 1 h by measuring epoxidation of sodium oleate (5 mg) in buffer-surfactant mixtures. The pH optimum of the reaction
was 7.5 when t-butyl hydroperoxide was the oxidant and 5.5 when hydrogen peroxide was the oxidant. With t-butyl hydroperoxide as oxidant the immobilized enzyme showed increasing activity to 65°C. The temperature profile with hydrogen
peroxide was flatter, although activity was also retained to 65°C. In 1 h reactions at 25°C at their respective optimal pH
values, t-butyl hydroperoxide and hydrogen peroxide promoted epoxide formation at the same rate. Larger-scale reactions were conducted
using a 20-fold increase in sodium oleate (to 100 mg). Reaction time was lengthened to 24 h. At optimized levels of t-butyl hydroperoxide 80% conversion to epoxide was achieved. With hydrogen peroxide only a 33% yield of epoxide was obtained,
which indicates that hydrogen peroxide may deactivate peroxygenase. 相似文献
8.
Prior work has shown that oat (Avena sativa) seeds are a rich source of peroxygenase, an enzyme that promotes the oxidation of carbon-carbon double bonds to form epoxides.
Ground and defatted oat seeds were used as a low-cost source of peroxygenase. A systematic study of the epoxidation of i-butyl amides from linseed oil was conducted. Hexane was used as the primary component of the reaction media to eliminate
the need for extraction. We found that the addition of a small amount of buffered water containing Tween 20 enhanced the epoxidation
activity when using t-butyl hydroperoxide and cumene hydroperoxide as oxidants. This activity could be further enhanced by the addition of isopropyl
ether. Conditions for larger-scale reactions were developed and applied to amides prepared from linseed, soybean, and canola
oils. Because of enzymatic selectivity, the epoxidation of adjacent double bonds was low, and monoepoxides from the amides
of oleate and linoleate predominated; the diepoxide, N-i-butyl-9,10–15,16-diepoxy-12(Z)-octadecenamide, was obtained from the amide of linolenate. The enzymatically epoxidized amides from the oils were hydrolyzed
in dilute acid, and the distribution of the various classes of polyols was determined. Reflecting the high proportion of starting
monoepoxides, saturated diols and diols with one double bond were the major polyols obtained from soybean and canola oils.
Because linseed oil contains a high proportion of linolenate, polyols obtained from the epoxides of this oil had a major amount
of the tetrol, N-i-butyl-9,10,15,16-tetrahydroxy-12(Z)-octadecenamide. In contrast, the components of polyols obtained from the hydrolysis of commercial epoxide preparations of
soybean and linseed methyl esters followed by amide formation were primarily saturated diols and furan derivatives resulting
from the presence of adjacent epoxide groups in these preparations. 相似文献
9.
Winfried Beil Markus Gres Frank Nerenz Ekkehard Winterfeldt 《Advanced Synthesis \u0026amp; Catalysis》1999,341(4):384-390
We have previously described an enantioselective total synthesis of the tumor inhibiting didemnenones 1a , b and 2 . Our investigations reported here shed light on the structure–activity relationships of these natural products. The significantly lower activity found for (3aS*, 6aS*)-3 [(E)-allyliden]-2-oxo-6a-(-hydroxymethyl)-2,3,3a,6a-tetrahydro-4H-cyclo-penta[b]furan]2(3H)-one ( 4 ) supported the hypothesis that the oxonium intermediate 3 is the active species. The strategy of the synthesis of the natural products was used to prepare acceptor substituted analogues (3aS*, 6aS*) [(E)-[3-(4-oxo-pent-2-(E)-enylidene]-6a-(4-hydroxymethyl)-2-methoxy-2,3,3a, 6a-tetrahydro[4H-cyclopenta[b]furan]-4-one ( 18 ) and (3aS*, 6aS*) [(E)-[3-(4-oxo-pent-2-(E)-enylidene]-6a-(4-hydroxymethyl)-2,3,3a,6a-tetrahydro-[4H-cyclopenta[b]furan]-2-(3H)-one ( 20 ). Although there were only moderate structural changes some of the key transformations differed remarkably in yield and general performance from those employed in the former synthesis. Optimization of the synthesis rewardingly led to compounds with increased biological activity against human gastric carcinoma cell-lines. 相似文献
10.
A previously established method was utilized to determine the stereoconfiguration of 7,10-dihydroxy-8(E)-octadecenoic acid (DHOE) from bioconversion of oleic acid by Pseudomonas aeruginosa NRRL strain B-18602 (PR3). The method involved formation of the (−)-menthoxycarbonyl (MCO) derivative of the two hydroxyls,
oxidative cleavage of the double bond, and gas chromatography (GC) analysis of the two methyl-esterified diastereomeric fragments,
methyl 2-MCO-decanoate and dimethyl 2-MCO-octanedioate. As described by previous workers, the 2(S)-MCO derivatives elute at earlier times by GC than the 2(R)-MCO derivatives. By comparing the GC analysis of the 2-MCO derivatives obtained from DHOE with that obtained from a partially
racemized sample, DHOE was determined to be 7(S),10(S)-dihydroxy-8(E)-octadecenoic acid. 相似文献
11.
The linoleate 9-lipoxygenase product 9(S)-hydroperoxy-10(E),12(Z)-octadecadienoic acid was stirred with a crude enzyme preparation from the beetroot (Beta vulgaris ssp. vulgaris var. vulgaris) to afford a product consisting of 95% of 9(S),12(S),13(S)-trihydroxy-10(E)-octadecenoic acid (pinellic acid). The linolenic acid-derived hydroperoxide 9(S)-hydroperoxy-10(E),12(Z),15(Z)-octadecatrienoic acid was converted in an analogous way into 9(S),12(S),13(S)-trihydroxy-10(E),15(Z)-octadecadienoic acid (fulgidic acid). On the other hand, the 13-lipoxygenase-generated hydroperoxides of linoleic or linolenic
acids failed to produce significant amounts of trihydroxy acids. Short-time incubation of 9(S)-hydroperoxy-10(E),12(Z)-octadecadienoic acid afforded the epoxy alcohol 12(R),13(S)-epoxy-9(S)-hydroxy-10(E)-octadecenoic acid as the main product indicating the sequence 9-hydroperoxide → epoxy alcohol → trihydroxy acid catalyzed
by epoxy alcohol synthase and epoxide hydrolase activities, respectively. The high capacity of the enzyme system detected
in beetroot combined with a simple isolation protocol made possible by the low amounts of endogenous lipids in the enzyme
preparation offered an easy access to pinellic and fulgidic acids for use in biological and medical studies. 相似文献
12.
The effects of oxygen pressure, substrate concentration and solvent on the rate and products of oxidation of methyl linoleate
were studied at 50 C with azobisisobutyronitrile as a radical initiator. The absolute and quantitative numbers for oxygen
uptake, substrate disappearance, and formation of conjugated diene and hydroperoxides were measured. Under the present conditions,
4 conjugated diene hydroperoxides, 13-hydroperoxy-9-cis, 11-trans-(2a), 13-hydroperoxy-9-trans, 11-trans-(3a), 9-hydroperoxy-10-trans, 12-cis-(4a), and 9-hydroperoxy-10-trans, 12-trans-(5a) octadecadienoic acid methyl esters, were formed almost quantitatively. The rate of oxidation decreased with decreasing oxygen
pressure. However, the ratio ofcis,trans totrans,trans hydroperoxides, (2a+4a)/(3a+5a), was independent of oxygen pressure, and this ratio increased with increasing methyl linoleate concentration, as found recently
by Porter. Further, the rate of oxidation and the ratio ofcis,trans/trans,trans hydroperoxides were dependent on solvent and increased with an increase in dielectric constant of solvent. A mechanism of
methyl linoleate oxidation consistent with these results is discussed.
Presented at the 15th Symposium on Oxidation Reactions, Nagoya, October 1981. 相似文献
13.
Linoleic acid was efficiently converted into the two major components of conjugated linoleic acid, 9Z,11E-octadecadienoic (1a) and 10E,12Z-octadecadienoic acid (1b) using either the superbase (n-butyllithium/potassium tert-butoxide) or by simply refluxing with KOH in 1-butanol. In turn, 1a and 1b were separated from each other using the lipase from Aspergillus niger via stereoselective esterification in 1-butanol. This enzyme has a preference for the 9Z,11E isomer, 1a, and has excellent selectivity. This method has allowed the ready preparation of gram quantities of 1a and 1b in their highly purified forms, which are not readily accessible by current methods. 相似文献
14.
Mats Hamberg 《Lipids》1989,24(4):249-255
The major part (80%) of the fatty acid hydroperoxide isomerase activity present in homogenates of the fungus,Saprolegnia parasitica, was localized in the particle fraction sedimenting at 105,000×g.
13(S)-Hydroperoxy-9(Z),11(E)-octadecadienoic acid and 9(S)-hydroperoxy-10(E),12(Z)-octadecadienoic acid were both good substrates for the particle-bound hydroperoxide isomerase. The products formed from
the 13(S)-hydroperoxide were identified as an α,β- and a γ,δ-epoxy alcohol, i.e., 11(R),12(R)-epoxy-13(S)-hydroxy-9(Z)-octadecenoic acid and 9(S),10(R)-epoxy-13(S)-hydroxy-11(E)-octadecenoic acid, respectively. The 9(S)-hydroperoxide was converted in an analogous way into an α,β-epoxy alcohol, 10(R),11(R)-epoxy-9(S)-hydroxy-12(Z)-octadecenoic acid and a γ,δ-epoxy alcohol, 12(R),13(S)-epoxy-9(S)-hydroxy-10(E)-octadecenoic acid.
9(R,S)-Hydroperoxy-10(E),12(E)-octadecadienoic acid and 13(R,S)-hydroperoxy-9(E),11(E)-octadecadienoic acid were poor substrates for theS. parasitica hydroperoxide isomerase. Experiments with 13(R,S)-hydroperoxy-9(Z),11(E)-octadecadienoic acid showed that the 13(R)-hydroperoxy enantiomer was slowly isomerized by the enzyme. The major product was identified as α,β-epoxy alcohol 11(R),12(R)-epoxy-13(R)-hydroxy-9(Z)-octadecenoic acid. 相似文献
15.
(±)-5-Hydroxy-1,7-bis-(4-hydroxyphenyl)-3-heptanone (2a), (±)-5-hydroxyl-1-(4-hydroxyphenyl)-7-phenyl-3-heptanone (2b), (±)-5-hydroxy-7-(4-hydroxyphenyl)-1-phenyl-3-heptanone (2c), and (±)-5-hydroxy-1,7-bis-(phenyl)-3-heptanone (2d) have been synthesized to study the structure–activity relationship regarding digestibility inhibition in vitro in cow rumen fluid. The activities were compared with the activity of chiral (S)-2a and its glucoside platyphylloside (1), isolated from Betula pendula. Compound 2a was slightly less active, 2b and 2c were more active, and 2d was less active than (S)-2a and platyphylloside. 相似文献
16.
Moghis U. Ahmad M. Shamim Ahmad S. M. Osman 《Journal of the American Oil Chemists' Society》1978,55(5):491-495
Methyltrans-2-hexadecenoate (1b) on allylic bromination with N-bromosuccinimide (NBS) (0.5 mole) yielded methyl 4-bromo-trans-2-hexadecenoate (2b) in 50% yield. Reaction with 2.0 moles of NBS afforded the allylic bromide (2b, δ 80%) as well as the dibromide (3b). Alkaline hydrolysis of the bromo ester (2b) yielded 4-hydroxy-trans-2-hexadecenoic acid (4a, δ 70%) and an unexpected product, 4-oxo-hexadecanoic acid (5a, δ 30%). A mechanism involving rearrangement is proposed to account for this unusual product. The effect of the ester carbonyl
adjacent to the double bond in2b was found to suppress dehydrobromination (elimination) reaction and favors only substitution (SN2), unlike the allylically brominated derivatives of internal olefinic compounds. The CrO3-pyridine oxidation of4b yielded the corresponding unsaturated ketone (7b). The structures of individual reaction products were established by elemental analyses as well as by spectral studies. 相似文献
17.
Treatment of isomeric methyl linoleate hydroperoxides with a Lewis acid, BF3, in anhydrous ether led to a carbon-to-oxygen rearrangement that caused cleavage into shorter-chain aldehydes. Methyl (9Z,11E)-13-hydroperoxy-9,11-octadecadienoate afforded mainly hexanal and methyl (E)-12-oxo-10-dodecenoate, whereas methyl (10E,12Z)-9-hydroperoxy-10,12-octadecadienoate cleaved into 2-nonenal and methyl 9-oxononanoate. The 2 aldehydes obtained from each
hydroperoxide isomer were uncharacteristic of the complex volatile profile usually obtained by β-scission of oxy radicals
derived from homolysis of the hydroperoxide group. Rather, the reaction resembled the one catalyzed by the plant enzyme, hydroperoxide
lyase.
Presented in part at the American Oil Chemists' Society Meeting, Chicago, Illinois, May 8–12, 1983.
The mention of firm names or trade products does not imply that they are endorsed or recommended by the USDA over other firms
or similar products not mentioned. 相似文献
18.
12-Oxo-10,15(Z)-phytodienoic acid biosynthesized from 13(S)-hydroperoxy-9(Z),11(E),15(Z)-octadecatrienoic acid using a preparation of corn (Zea mays L) hydroperoxide dehydrase recently was found to be a mixture of enantiomers in a ratio of 82∶18 (Hamberg, M., and Hughes,
M.A. (1988)Lipids 23, 469–475). In this work, 12-oxophytodienoic acid and (+)-7-iso-jasmonic acid were converted into a common derivative, methyl
3-hydroxy-2-pentyl-cyclopentane-1-octanoate. From gas liquid chromatographic analysis of the (−)-menthoxycarbonyl derivative
of methyl 3-hydroxy-2-pentyl-cyclopentane-1-octanoates prepared from 12-oxophytodienoic acid and (+)-7-iso-jasmonic acid,
it could be deduced that the major enantiomer of 12-oxophytodienoic acid had the 9(S),13(S) configuration. Therefore, in the major enantiomer of 12-oxophytodienoic acid, the configurations of the side chainbearing
carbons are identical to the configurations of the corresponding carbons of (+)-7-iso-jasmonic acid, thus giving support to
previous studies indicating that 12-oxophytodienoic acid serves as the precursor of (+)-7-iso-jasmonic acid in plant tissue.
When absolute configurations of C-9 and C-13 are not specifically indicated, phytonoic acid is used to denote 2-pentyl-cyclopentane-1-octanoic
acid in which the two side chains have thecis relationship, whereas phytonoic acid (trans isomer) denotes 2-pentyl-cyclopentane-1-octanoic acid in which the two side chains have thetrans relationship. 相似文献
19.
George J. Piazza Thomas A. Foglia Alberto Nuñez 《Journal of the American Oil Chemists' Society》1997,74(11):1385-1390
Methyl 11(R), 12(R)-epoxy-13(S)-hydroxy-9(Z)-octadecenoate (threo isomer) was generated from linoleic acid by the sequential action of an enzyme and two chemical reagents. Linoleic acid was
treated with lipoxygenase to yield its corresponding hydroperoxide [13(S)-hydroperoxy-9(Z), 11(E)-octadecadienoic acid]. After methylation with CH2N2, the hydroperoxide was treated with titanium (IV) isopropoxide [Ti(O-i-Pr)4] at 5°C for 1 h. The products were separated by normal-phase high-performance liquid chromatography and characterized with
gas chromatography-mass spectrometry, infrared spectroscopy, and nuclear magnetic resonance spectroscopy. Approximately 30%
of the product was methyl 13(S)-hydroxy-9(Z), 11(E)-octadecadienoate. Over 60% of the isolated product was methyl 11(R), 12(R)-epoxy-13(S)-hydroxy-9(Z)-octadecenoate. After quenching Ti(O-i-Pr)4 with water, the spent catalyst could be removed from the fatty products by partitioning between CH2Cl2 and water. These results demonstrate that Ti(O-i-Pr)4 selectively promotes the formation of an α-epoxide with the threo configuration. It was critically important to start with dry methyl 13(S)-hydroperoxy-9(Z),11(E)-octadecadienoate because the presence of small amounts of water in the reaction medium resulted in the complete hydrolysis
of epoxy alcohol to trihydroxy products. 相似文献
20.
Tae Seok Seo Dae Sik Hong Dong Wook Jung Hyun Yong Cho Seong Ihl Woo 《Korean Journal of Chemical Engineering》2002,19(4):622-626
Symmetric and asymmetric Ni(II) diimine complexes such as 2-[(2,6-diisopropylphenylimino)methyl]pyridine nickel(II) dibromide
(a), 2-[1-(2,6-diisopropylphenylimino)ethyl]pyridine nickel(II) dibromide (b) and [1,2-bis(2,6-diisopropylphenylimino)] acenaphthene nickel(II) dibromide (c) were synthesized. For olefin homopolymerization, asymmetric Ni(II) diimine complexes [(a) & (b)] were compared with symmetric system (c). Asymmetric Ni(II) diimine complexes exhibited less catalytic activity and thermal stability as well as more b-hydride elimination
than a symmetric diimine complex (c). The activity of (a) was larger than that of (b), which indicates that methyl group has a contribution to the instability of catalyst by s bond vibration rather than the
stabilization of the active site by electron releasing property.
This paper is dedicated to Professor Wha Young Lee on the occasion of his retirement from Seoul National University. 相似文献