- Proton Switch in the Secondary Coordination Sphere to Control Catalytic Events at the Metal Center: Biomimetic Oxo Transfer Chemistry of Nickel Amidate Complex
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High-valent metal-oxo species are key intermediates for the oxygen atom transfer step in the catalytic cycles of many metalloenzymes. While the redox-active metal centers of such enzymes are typically supported by anionic amino acid side chains or porphyrin rings, peptide backbones might function as strong electron-donating ligands to stabilize high oxidation states. To test the feasibility of this idea in synthetic settings, we have prepared a nickel(II) complex of new amido multidentate ligand. The mononuclear nickel complex of this N5 ligand catalyzes epoxidation reactions of a wide range of olefins by using mCPBA as a terminal oxidant. Notably, a remarkably high catalytic efficiency and selectivity were observed for terminal olefin substrates. We found that protonation of the secondary coordination sphere serves as the entry point to the catalytic cycle, in which high-valent nickel species is subsequently formed to carry out oxo-transfer reactions. A conceptually parallel process might allow metalloenzymes to control the catalytic cycle in the primary coordination sphere by using proton switch in the secondary coordination sphere.
- Kim, Soohyung,Jeong, Ha Young,Kim, Seonghan,Kim, Hongsik,Lee, Sojeong,Cho, Jaeheung,Kim, Cheal,Lee, Dongwhan
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supporting information
p. 4700 - 4708
(2021/02/12)
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- Enantioselective organocatalysis-based synthesis of 3-hydroxy fatty acids and fatty γ-lactones
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3-Hydroxy fatty acids have attracted the interest of researchers, since some of them may interact with free fatty acid receptors more effectively than their non-hydroxylated counterparts and their determination in plasma provides diagnostic information regarding mitochondrial deficiency. We present here the development of a convenient and general methodology for the asymmetric synthesis of 3-hydroxy fatty acids. The enantioselective organocatalytic synthesis of terminal epoxides, starting from long chain aldehydes, is the key-step of our methodology, followed by ring opening with vinylmagnesium bromide. Ozonolysis and subsequent oxidation leads to the target products. MacMillan’s third generation imidazolidinone organocatalyst has been employed for the epoxide formation, ensuring products in high enantiomeric purity. Furthermore, a route for the incorporation of deuterium on the carbon atom carrying the hydroxy group was developed allowing the synthesis of deuterated derivatives, which may be useful in biological studies and in mass spectrometry studies. In addition, the synthesis of fatty γ-lactones, corresponding to 4-hydroxy fatty acids, was also explored.
- Bourboula, Asimina,Limnios, Dimitris,Kokotou, Maroula G.,Mountanea, Olga G.,Kokotos, George
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- Dinuclear Iron(III) and Nickel(II) Complexes Containing N-(2-Pyridylmethyl)-N′-(2-hydroxyethyl)ethylenediamine: Catalytic Oxidation and Magnetic Properties
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Dinuclear FeIII and NiII complexes, [(phenO)Fe(N3)]2(NO3)2 (1) and [(phenOH)Ni(N3)2]2 (2), were prepared by treating Fe(NO3)3?9 H2O and Ni(NO3)2?6 H2O in methanol, respectively, with phenOH (=N-(2-pyridylmethyl)-N′-(2-hydroxyethyl)ethylenediamine) and NaN3; both 1 and 2 were characterized by elemental analysis, IR spectroscopy, X-ray diffraction, and magnetic susceptibility measurements. Two ethoxo-bridged FeIII and two azido-bridged NiII were observed in 1 and 2, respectively; corresponding antiferromagnetic interaction via the bridged ethoxo groups and strong ferromagnetic coupling via the bridged end-on azido ligands within the dimeric unit were observed. Complex 1 did not exhibit any catalytic activity, while 2 exhibited excellent catalytic activities for the epoxidation of aliphatic, aromatic, and terminal olefins.
- Jeong, Ah Rim,Shin, Jong Won,Jeong, Jong Hwa,Bok, Kwon Hee,Kim, Cheal,Jeong, Donghyun,Cho, Jaeheung,Hayami, Shinya,Min, Kil Sik
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p. 3023 - 3033
(2017/03/13)
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- Trinuclear nickel and cobalt complexes containing unsymmetrical tripodal tetradentate ligands: Syntheses, structural, magnetic, and catalytic properties
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The coordination chemistries of the tetradentate N2O2-type ligands N-(2-pyridylmethyl)iminodiethanol (H2pmide) and N-(2-pyridylmethyl)iminodiisopropanol (H2pmidip) have been investigated with nickel(ii) and cobalt(ii/iii) ions. Three novel complexes prepared and characterized are [(Hpmide)2Ni3(CH3COO)4] (1), [(Hpmide)2Co3(CH3COO)4] (2), and [(pmidip)2Co3(CH3COO)4] (3). In 1 and 2, two terminal nickel(ii)/cobalt(ii) units are coordinated to one Hpmide- and two CH3CO2-. The terminal units are each connected to a central nickel(ii)/cobalt(ii) cation through one oxygen atom of Hpmide- and two oxygen atoms of acetate ions, giving rise to nickel(ii) and cobalt(ii) trinuclear complexes, respectively. Trinuclear complexes 1 and 2 are isomorphous. In 3, two terminal cobalt(iii) units are coordinated to pmidip2- and two CH3CO2-. The terminal units are each linked to a central cobalt(ii) cation through two oxygen atoms of pmidip2- and one oxygen atom of a bidentate acetate ion, resulting in a linear trinuclear mixed-valence cobalt complex. 1 shows a weak ferromagnetic interaction with the ethoxo and acetato groups between the nickel(ii) ions (g = 2.24, J = 2.35 cm-1). However, 2 indicates a weak antiferromagnetic coupling with the ethoxo and acetato groups between the cobalt(ii) ions (g = 2.37, J = -0.5 cm-1). Additionally, 3 behaves as a paramagnetic cobalt(ii) monomer, due to the diamagnetic cobalt(iii) ions in the terminal units (g = 2.53, =D= = 36.0 cm-1). No catalytic activity was observed in 1. However, 2 and 3 showed significant catalytic activities toward various olefins with modest to good yields. 3 was slightly less efficient toward olefin epoxidation reaction than 2. Also 2 was used for terminal olefin oxidation reaction and was oxidised to the corresponding epoxides in moderate yields (34-75%) with conversions ranging from 47-100%. The cobalt complexes 2 and 3 promoted the O-O bond cleavage to ~75% heterolysis and ~25% homolysis.
- Shin, Jong Won,Jeong, Ah Rim,Lee, Sun Young,Kim, Cheal,Hayami, Shinya,Min, Kil Sik
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p. 14089 - 14100
(2016/11/06)
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- A discrete {Co4(μ3-OH)4}4+ cluster with an oxygen-rich coordination environment as a catalyst for the epoxidation of various olefins
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Using the sterically hindered terphenyl-based carboxylate, the tetrameric Co(ii) complex [Co4(μ3-OH)4(μ-O2CAr4F-Ph)2(μ-OTf)2(Py)4] (1) with an asymmetric cubane-type core has been synthesized and fully characterized by X-ray diffraction, UV-vis spectroscopy, and electron paramagnetic resonance spectroscopy. Interestingly, the cubane-type cobalt cluster 1 with 3-chloroperoxybenzoic acid as the oxidant was found to be very effective in the epoxidation of a variety of olefins, including terminal olefins which are more challenging targeting substrates. Moreover, this catalytic system showed a fast reaction rate and high epoxide yields under mild conditions. Based on product analysis and Hammett studies, the use of peroxyphenylacetic acid as a mechanistic probe, H218O-exchange experiments, and EPR studies, it has been proposed that multiple reactive cobalt-oxo species CoVO and CoIVO were involved in the olefin epoxidation.
- Lee, Sun Young,Kim, Namseok,Lee, Myoung Mi,Jo, Young Dan,Bae, Jeong Mi,Hyun, Min Young,Yoon, Sungho,Kim, Cheal
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p. 1727 - 1736
(2016/01/30)
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- Terminal and internal olefin epoxidation with cobalt(II) as the catalyst: Evidence for an active oxidant CoII-acylperoxo species
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A simple catalytic system that uses commercially available cobalt(II) perchlorate as the catalyst and 3-chloroperoxybenzoic acid as the oxidant was found to be very effective in the epoxidation of a variety of olefins with high product selectivity under mild experimental conditions. More challenging targets such as terminal aliphatic olefins were also efficiently and selectively oxidized to the corresponding epoxides. This catalytic system features a nearly nonradical-type and highly stereospecific epoxidation of aliphatic olefin, fast conversion, and high yields. Olefin epoxidation by this catalytic system is proposed to involve a new reactive CoII-OOC(O)R species, based on evidence from H218O-exchange experiments, the use of peroxyphenylacetic acid as a mechanistic probe, reactivity and Hammett studies, EPR, and ESI-mass spectrometric investigation. However, the O-O bond of a CoII-acylperoxo intermediate (CoII-OOC(O)R) was found to be cleaved both heterolytically and homolytically if there is no substrate.
- Hyun, Min Young,Kim, Soo Hyun,Song, Young Joo,Lee, Hong Gyu,Jo, Young Dan,Kim, Jin Hoon,Hwang, In Hong,Noh, Jin Young,Kang, Juhye,Kim, Cheal
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p. 7307 - 7312
(2012/11/07)
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- Shell cross-linked micelle-based nanoreactors for the substrate-selective hydrolytic kinetic resolution of epoxides
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Shell cross-linked micelles (SCMs) containing Co(III)-salen cores were prepared from amphiphilic poly(2-oxazoline) triblock copolymers. The catalytic activity of these nanoreactors for the hydrolytic kinetic resolution of various terminal epoxides was investigated. The SCM catalysts showed high catalytic efficiency and, more significantly, substrate selectivity based on the hydrophobic nature of the epoxide. Moreover, because of the nanoscale particle size and the high stability, the catalyst could be recovered easily by ultrafiltration and reused with high activity for eight cycles.
- Liu, Yu,Wang, Yu,Wang, Yufeng,Lu, Jie,Pinon, Victor,Weck, Marcus
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supporting information; experimental part
p. 14260 - 14263
(2011/11/05)
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- "click" tetradentate ligands
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A series of triazole-based N4 tetradenate ligands 1a-d are efficiently synthesized using CuI-catalyzed azide-alkyne "click" strategy and are readily coordinated to many metal ions (e.g. MnII, NiII, ZnII and FeII). The X-ray structures of the resultant metal-complexes (4a-d, 5a, 6a and 7a) reveal an octahedral mononuclear structure with two co-ligands bonded in cis sites and the two triazoles as nitrogen donors to the metal center. The MnII-complexes (4a-d) show efficient catalytic activities in the epoxidation of various aliphatic terminal olefins with peracetic acid, and feature with low catalyst loading, fast conversion and high yields. The Royal Society of Chemistry 2010.
- Hao, Erhong,Wang, Zhaoyun,Jiao, Lijuan,Wang, Shaowu
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experimental part
p. 2660 - 2666
(2010/06/13)
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- A simple and effective catalytic system for epoxidation of aliphatic terminal alkenes with manganese(II) as the catalyst
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A simple catalytic system that uses commercially available manganese(II) Perchlorate as the catalyst and peracetic acid as the oxidant is found to be very effective in the epoxidation of aliphatic terminal alkenes with high product selectivity at ambient temperature. Many terminal alkenes are epoxidised efficiently on a gram scale in less than an hour to give excellent yields of isolated product (>90%) of epoxides in high purity. Kinetic studies with some C9-alkenes show that the catalytic system is more efficient in epoxidising terminal alkenes than internal alkenes, which is contrary to most commonly known epoxidation systems. The reaction rate for epoxidation decreases in the order: 1-nonene>cis-3-nonene> trans-3-nonene. ESI-MS and EPR spectroscopic studies suggest that the active form of the catalyst is a high-valent oligonuclear manganese species, which probably functions as the oxygen atomtransfer agent in the epoxidation reaction.
- Ho, Kam-Piu,Wong, Wing-Leung,Lam, Kin-Ming,Lai, Cheuk-Piu,Chan, Tak Hang,Wong, Kwok-Yin
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experimental part
p. 7988 - 7996
(2009/11/30)
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- A concise synthesis of (-)-deoxoprosopinine
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A simple and highly efficient approach to (-)-deoxoprosopinine from racemic epoxide as a starting material is described employing a Jacobsen's hydrolytic kinetic resolution (HKR) and Sharpless asymmetric dihydroxylation (AD) as key steps. Georg Thieme Verlag Stuttgart.
- Pandey, Satyendra Kumar,Kumar, Pradeep
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p. 2894 - 2896
(2008/02/12)
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- Stereochemistry of Δ4 dehydrogenation catalyzed by an ivy (Hedera helix) Δ9 desaturase homolog
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The stereochemistry of palmitoyl-ACP Δ4 desaturase-mediated dehydrogenation has been examined by tracking the fate of deuterium atoms located on stereospecifically monodeuterated substrates-(4S)- and (4R)-[4-2H1]-palmitoyl-ACP and (5S)- and (5R)-[5- 2H1]-palmitoyl-ACP. It was found that the introduction of the (Z)-double bond between C-4 and C-5 of a palmitoyl substrate occurs with pro-R enantioselectivity - a result which matches that obtained for a closely related homolog-castor stearoyl-ACP Δ9 desaturase. These data show that despite the difference in regioselectivity between the two enzymes, the stereochemistry of hydrogen removal is conserved. The Royal Society of Chemistry.
- Tremblay, Amy E.,Whittle, Edward,Buist, Peter H.,Shanklin, John
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p. 1270 - 1275
(2008/02/02)
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- Task-specific ionic liquids as efficient, green and recyclable reagents and solvents for oxidation of olefins
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Two kinds of task-specific ionic liquids (IIs) composed of imidazolinium or pyridinium cations with a carboxy group and Hydrogensulfate as counterion have been synthesised and their application in oxidation of olefins has been studied. The carbonyl compounds were obtained from the oxidation of chain olefins, and 1,2-cycloalkandiols were obtained from cycloalkenes in the novel oxidation systems which are easily manipulated. The products can be easily isolated from the reaction system and the ILs can readily be recovered and reused.
- Wang, Zhiming,Wang, Congna,Bao, Weiliang,Ying, Taokei
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p. 388 - 390
(2007/10/03)
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- The Structure of Metallomicelles
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The morphology of micelles formed by two novel metallosurfactants has been studied by small-angle neutron scattering (SANS) and small-angle-X-ray scattering (SAXS). The two surfactants both contain a dodecyl chain as the hydrophobic moiety, but differ in the structure of the head group. The surfactants are CuII complexes of monopendant alcohol derivatives of a) the face-capping macrocycle 1,4,7-triazacyclanonane (tacn), and b) an analogue based upon the tetraazamacrocycle 1,4,7,10-tetraazacyclododecane. Here, neutron scattering has been used to study the overall size and shape of the surfactant micelles, in conjunction with X-ray scattering to locate the metal ions. For the 1,4,7,10-tetraazacyclododecane-based surfactant, oblate micelles are observed, which are smaller to the prolate micelles formed by the 1,4,7-triazacyclononane analogue. The X-ray scattering analysis shows that the metal ions are distributed throughout the polar head-group region, rather than at a well-defined radius; this is in good agreement with the SANS-derived dimensions of the micelle. Indeed, the same model for micelle morphology can be used to fit both the SANS and SAXS data.
- Griffiths,Fallis,Willock,Paul,Barrie,Griffiths,Williams,King,Heenan,Goergl, Richard
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p. 2022 - 2028
(2007/10/03)
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- Synthesis of Cyclic Organic Carbonates from C3-C16 Epoxides
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Cyclic organic carbonates were prepared from epoxides (derivatives of C3-C16 olefins, C4 and C8 dienes, styrene; epichlorohydrin) in the presence of a catalytic system consisting of CoCl2 · 6H2O and dimethylformamide.
- Rybina,Srednev,Bobyleva
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p. 842 - 843
(2007/10/03)
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- Highly selective hydrolytic kinetic resolution of terminal epoxides catalyzed by chiral (salen)CoIII complexes. Practical synthesis of enantioenriched terminal epoxides and 1,2-diols
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The hydrolytic kinetic resolution (HKR) of terminal epoxides catalyzed by chiral (salen)CoIII complex 1·OAc affords both recovered unreacted epoxide and 1,2-diol product in highly enantioenriched form. As such, the HKR provides general access to useful, highly enantioenriched chiral building blocks that are otherwise difficult to access, from inexpensive racemic materials. The reaction has several appealing features from a practical standpoint, including the use of H2O as a reactant and low loadings (0.2-2.0 mol %) of a recyclable, commercially available catalyst. In addition, the HKR displays extraordinary scope, as a wide assortment of sterically and electronically varied epoxides can be resolved to ≥ 99% ee. The corresponding 1,2-diols were produced in good-to-high enantiomeric excess using 0.45 equiv of H2O. Useful and general protocols are provided for the isolation of highly enantioenriched epoxides and diols, as well as for catalyst recovery and recycling. Selectivity factors (krel) were determined for the HKR reactions by measuring the product ee at ca. 20% conversion. In nearly all cases, krel values for the HKR exceed 50, and in several cases are well in excess of 200.
- Schaus, Scott E.,Brandes, Bridget D.,Larrow, Jay F.,Tokunaga, Makoto,Hansen, Karl B.,Gould, Alexandra E.,Furrow, Michael E.,Jacobsen, Eric N.
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p. 1307 - 1315
(2007/10/03)
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- Synergistic sex pheromone components of white-spotted tussock moth, Orgyia thyellina
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In 1996, the exotic white-spotted tussock moth (WSTM), Orgyia thyellina (Lepidoptera: Lymantriidae), was discovered in Auckland, New Zealand. Because establishment of WSTM would threaten New Zealand's orchard industry and international trade, eradication of WSTM with microbial insecticide was initiated. To monitor and complement eradication of WSTM by capture of male moths in pheromone-baited traps, pheromone components of female WSTM needed to be identified. Coupled gas chromatographic-electroantennographic detection analysis of pheromone gland extract revealed several compounds that elicited responses from male moth antennae. Mass spectra of the two most EAD-active compounds suggested, and comparative GC-MS of authentic standards confirmed, that they were (Z)-6-heneicosen-11-one (Z6-11-one) and (Z)-6-heneicosen-9- one, the latter termed here 'thyellinone.' In field experiments in Japan, Z6- 11-one plus thyellinone at a 100:5 ratio attracted WSTM males, whereas either ketone alone failed to attract a single male moth. Addition of further candidate pheromone components did not enhance attractiveness of the binary blend. Through the 1997-1998 summer, 45,000 commercial trap lures baited with 2000 μg of Z6-11-one and 100 μg of thyellinone were deployed in Auckland towards eradication of the residual WSTM population.
- Gries, Gerhard,Clearwater, John,Gries, Regine,Khaskin, Grigori,King, Skip,Schaefer, Paul
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p. 1091 - 1104
(2007/10/03)
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- A new methodology for synthesis of 1,2-epoxy alkane with the linear aliphatic olefins in presence of molecular oxygen
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The linear aliphatic olefins, such as 1-octene, 1-decene, 1-dodecene and 1-tetradecene, were effectively epoxidized with molecular oxygen catalyzed by the amino acid Schiff base manganese complex (Sal-Phe-Mn). The products of the reaction was 1,2-epoxy alkane.
- Wang,Hao,Wang
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p. 1409 - 1414
(2007/10/03)
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- Chemoenzymatic epoxidation of alkenes by dimethyl carbonate and hydrogen peroxide
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(matrix presented) Monoperoxy carbonic acid methyl ester can be generated under neutral conditions by lipase-catalyzed perhydrolysis of dimethyl carbonate with hydrogen peroxide. It can be used in situ for the selective and efficient epoxidation of olefins; the unstable coproduct carbonic acid monomethylester decomposes to carbon dioxide and methanol. Thus, an "acid-free" Prileshajev epoxidation is realized, which is especially useful for the epoxidation of acid-sensitive substrates such as β-pinene.
- Rusch Gen Klaas, Mark,Warwel, Siegfried
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p. 1025 - 1026
(2008/02/09)
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- A convenient resolution of long-chain alkyl epoxides with Jacobsen's salen(Co)III(OAc) catalysts
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Non-racemic terminal long-chain alkyl epoxides are prepared from racemic epoxides and 1 mol% (R,R)- and (S,S)-salen(Co)III catalysts following a modified procedure for kinetic resolution. The ee's for all epoxides (C-10, C-12, C-14, C-16, C-18, C-20) exceed 95% and the chemical yields range from 85% to 95%.
- Savle, Prashant S.,Lamoreaux, Marika J.,Berry, John F.,Gandour, Richard D.
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p. 1843 - 1846
(2007/10/03)
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- Lipase catalyzed synthesis of peroxycarboxylic acids and lipase mediated oxidations
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Lipase catalyzed synthesis of long chain peroxycarboxylic acids from hydrogen peroxide and free carboxylic acid was investigated. A 51% yield of peroxytetradecanoic acid was achieved when using a two phase system of toluene and water. The peroxy acids thus formed were applied for in situ oxidation of alkenes, in general leading to high yields of the corresponding epoxide. For example, a quantitative yield of cyclohexene oxide and a 94% yield of 1-hexadecene oxide was achieved in a solvent-free process.
- Bjorkling,Frykman,Godtfredsen,Kirk
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p. 4587 - 4592
(2007/10/02)
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- Direct Epoxidation of Olefins Catalyzed by Nickel(II) Complexes with Molecular Oxygen and Aldehydes
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The presence of a bis(1,3-diketonato)nickel(II) complex, various olefins are directly monooxygenated into the corresponding epoxides on treatment with atmospheric pressure of oxygen or air and aldehydes.Especially, it is noted that bisnickel(II) behaves as an excellent catalyst in the present epoxidation.
- Yamada, Tohru,Takai, Toshihiro,Rhode, Oliver,Mukaiyama, Teruaki
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p. 2109 - 2117
(2007/10/02)
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- Fatty acid leukotriene synthesis inhibitors
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Fatty acid compounds of the formula (I): STR1 wherein R1, R2, R3, R4, R5, A, Y and k are as defined herein are novel and useful in the treatment of allergic and inflammatory disorders.
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- Selective Delivery of Cytotoxic Compounds to Cells by the LDL Pathway
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Cancer cells need cholesterol to make new membrane.They get it either by de novo synthesis or low-density lipoprotein (LDL), or both.Some types of cancer have very high LDL requirements.LDL particles, which circulate in the blood, contain a cholesteryl ester core surrounded by a phospholipid coat containing apoproteins that are recognized by LDL receptors on cell surfaces.After attachment to cells, LDL is endocytosed into lysosomes, where the core is exposed and hydrolyzed.A technique is known whereby LDL can be isolated, its core removed and replaced by a compatible lipophilic substance, and then reconstituted into intact LDL particles that are recognized and internalized by cells in the normal manner.A series of cytotoxic compounds has been synthesized, designed to be compatible with reconstituted LDL, and directed against cancers that copiously internalize LDL.They were evaluated by measuring the toxicity of reconstituted LDL toward test cells bearing LDL receptors.Selectivity was determined by comparison, either with mutant cells with few LDL receptors or with reconstituted methylated LDL (which is not recognized by LDL receptors) on normal cells.Two compounds, 19 and 25, were found that reconstitute well, kill or arrest the test cells at reasonably low concentrations, and are completely selective, suggesting that they are delivered to cells exclusively via the LDL pathway.
- Firestone, Raymond A.,Pisano, Judith M.,Falck, J. R.,McPhaul, Michael M.,Krieger, Monty
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p. 1037 - 1043
(2007/10/02)
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- The Catalyzed Liquid-Phase Oxidation of Normal Alk-1-enes
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The efficiencies of various homogeneous soluble transition metal compounds to increase epoxide yields in the autoxidation of alk-1-enes were studied.Combinations of typical autoxidation and typical epoxidation catalysts were also used.It was proved through balance experiments, that in no case yields of 50percent or more of the corresponding epoxides were obtained.The simple mechanism (epoxidation via allylic hydroperoxides) assumed only insufficiently reflects the reaction course.
- Barth, U.,Fiedler, H.,Gross, G.,Lauterbach, G.,Schnurpfeil, D.
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p. 887 - 901
(2007/10/02)
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