- Selective Ring-Opening of Di-Substituted Epoxides Catalysed by Halohydrin Dehalogenases
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Halohydrin dehalogenases (HHDHs) are valuable biocatalysts for the synthesis of β-substituted alcohols based on their epoxide ring-opening activity with a number of small anionic nucleophiles. In an attempt to further broaden the scope of substrates accepted by these enzymes, a panel of 22 HHDHs was investigated in the conversion of aliphatic and aromatic vicinally di-substituted trans-epoxides using azide as nucleophile. The majority of these HHDHs was able to convert aliphatic methyl-substituted epoxide substrates to the corresponding azidoalcohols, in some cases even with absolute regioselectivity. HheG from Ilumatobacter coccineus exhibited also high activity towards sterically more demanding di-substituted epoxides. This further expands the range of β-substituted alcohols that are accessible by HHDH catalysis.
- Calderini, Elia,Wessel, Julia,Süss, Philipp,Schrepfer, Patrick,Wardenga, Rainer,Schallmey, Anett
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p. 2099 - 2106
(2019/03/21)
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- Bioproduction of chiral epoxyalkanes using styrene monooxygenase from rhodococcus sp. ST-10 (RhSMO)
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We describe the enantioselective epoxidation of straight-chain aliphatic alkenes using a biocatalytic system containing styrene monooxygenase from Rhodococcus sp. ST-10 and alcohol dehydrogenase from Leifsonia sp. S749. The biocatalyzed enantiomeric epoxidation of 1-hexene to (S)-1,2-epoxyhexane (44.6 mM) using 2-propanol as the hydrogen donor was achieved under optimized conditions. The biocatalyst had broad substrate specificity for various aliphatic alkenes, including terminal, internal, unfunctionalized, and di- and tri-substituted alkenes. Here, we demonstrate that this biocatalytic system is suitable for the efficient production of enantioenriched (S)-epoxyalkanes.
- Toda, Hiroshi,Imae, Ryouta,Itoh, Nobuya
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p. 3443 - 3450
(2015/02/05)
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- Epoxidation of olefins with a silica-supported peracid
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Anhydrous [2-percarboxyethyl] functionalized silica (2a) is an advantageous oxidant for performing the epoxidation of olefins 1. Epoxides 3 do not undergo the ring-opening reactions catalyzed by the acidic silica surface, except for particularly activated cases such as styrene oxide. The hydrophilic and acidic character of the silica surface does not interfere with the directing effects exerted by allylic H-bond acceptor substituents. The alkenes 1 carrying hydroxyl groups react with silica-supported peracid 2a faster than unsubstituted alkenes, thus reversing the trend known for reactions with soluble peracids. These results are attributed to the H-bond interactions of substrate 1 with the silanol and carboxylic acid groups bonded to the silica surface.
- Mello, Rossella,Alcalde-Aragones, Ana,Gonzalez Nunez, Maria Elena,Asensio, Gregorio
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experimental part
p. 6409 - 6413
(2012/10/08)
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- Epoxidation of olefins with a silica-supported peracid in supercritical carbon dioxide under flow conditions
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Anhydrous 2-percarboxyethyl-functionalized silica (2b), a recyclable supported peracid, is a suitable reagent to perform the epoxidation of alkenes 1 in supercritical carbon dioxide at 250 bar and 40 °C under flow conditions. This procedure simplifies the isolation of the reaction products and uses only carbon dioxide as a solvent under mild conditions. The solid reagent 2b can be easily recycled by a reaction with 30% hydrogen peroxide in an acid medium.
- Mello, Rossella,Alcalde-Aragones, Ana,Olmos, Andrea,Gonzalez-Nunez, Maria Elena,Asensio, Gregorio
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experimental part
p. 4706 - 4710
(2012/07/28)
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- Molybdenum containing surface complex for olefin epoxidation
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Silica-supported molybdenum surface complexes were prepared by the reaction between (N≡)Mo(OtBu)3 and silica via displacement of the tert-butoxy ligands for siloxyls from the silica surface. The structure of the surface molybdenum complexes was well defined by in-situ FT-IR, elemental analysis, 1H NMR and 13C CP/MAS NMR techniques. The surface complexes could undergo alcoholysis reaction with CD3OD and CH3OH in the same way as free (N≡)Mo(OtBu)3 and they show high catalytic activity and selectivity in olefin epoxidation. Initial rates up to 24.9 mmol epoxide (mmol Mo)-1 min-1 were achieved in the epoxidation of cyclohexene using TBHP as oxidant.
- Yang, Qihua,Coperet, Christophe,Li, Can,Basset, Jean-Marie
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p. 319 - 323
(2007/10/03)
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- Deracemization of (±)-cis-dialkyl substituted oxides via enantioconvergent hydrolysis catalysed by microsomal epoxide hydrolase
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Both enantiomers of cis-(±)-2,3-epoxyheptane 1a, cis-3,4-epoxyheptane 1b, cis-3,4-epoxynonane 1c, cis-3,4-epoxynonane-1-ol 1d, and cis-1-methoxy-3,4-epoxynonane 1e undergo a highly stereoselective microsomal epoxide hydrolase catalysed hydration at the (S) carbon to give the corresponding threo (R,R)-diol at complete conversion. A total kinetic resolution of racemic epoxides is also obtained with 1a and 1e.
- Chiappe, Cinzia,Cordoni, Antonio,Lo Moro, Giacomo,Palese, Consiglia Doriana
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p. 341 - 350
(2007/10/03)
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- Deracemization of (±)-2,3-disubstituted oxiranes via biocatalytic hydrolysis using bacterial epoxide hydrolases: Kinetics of an enantioconvergent process
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Asymmetric biocatalytic hydrolysis of (±)-2,3-disubstituted oxiranes leading to the formation of vicinal diols in up to 97% ee at 100% conversion was accomplished by using the epoxide hydrolase activity of various bacterial strains. The mechanism of this deracemization was elucidated by 18OH2-labelling experiments using a partially purified epoxide hydrolase from Nocardia EH1. The reaction was shown to proceed in an enantioconvergent fashion by attack of OH- at the (S)-configured oxirane carbon atom with concomitant inversion of configuration. A mathematical model developed for the description of the kinetics was verified by the determination of the four relative rate constants governing the regio- and enantio-selectivity of the process.
- Kroutil, Wolfgang,Mischitz, Martin,Faber, Kurt
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p. 3629 - 3636
(2007/10/03)
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- Highly selective epoxidation of alkenes and styrenes with H2O2 and manganese complexes of the cyclic triamine 1,4,7-trimethyl-1,4,7-triazacyclononane
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In acetone and at subambient temperatures, manganese complexes of 1,4,7-trimethyl-1,4,7-triazacyclononane catalyse the selective oxidation of many alkenes and styrenes to epoxides with an efficient use of H2O2; the regio- and chemo-selectivity resemble those of manganese-porphyrin catalysts.
- De Vos, Dirk,Bein, Thomas
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p. 917 - 918
(2007/10/03)
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- Olefin Epoxidation Using Elemental Fluorine
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F2 reacts with water and CH3CN, apparently to produce the relatively stable complex HOF*CH3CN.This is probably the best known oxygen-transfer reagent and can epoxidize olefins quickly and efficiently.Various types of alkenes including aliphatic, benzylic, enones, dienones, maleates, and fumarates have been examined, and all react with the reagent to produce the corresponding mono- or diepoxides in good to excellent yields.This epoxidation is fully stereospecific, and the configuration of the starting olefin is fully retained in the resulting oxirane.In cases where exceptionally stable oxocarbocations can be formed as in 1,1-diphenylethene, the reaction produces vicinal glycols in good yields.Since the origin of the epoxides' oxygen is in the water, this method is very suitable for introducing the isotopes 17O and 18O in various molecules.
- Rozen, Shlomo,Kol, Moshe
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p. 5155 - 5159
(2007/10/02)
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- A SUPPORTED EPOXIDATION CATALYST FOR NUCLEOPHILIC OLEFINS
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A polystyrene-supported peptid-linked epoxidation catalyst is described and its utility for the discovery of new epoxidants is discussed.
- Okamoto, Yasushi,Still, W. Clark
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p. 971 - 974
(2007/10/02)
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- The Transition Metal Catalyzed Nucleophilic Epoxide Ring Opening Reaction
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The catalytic influence of MoO2(acac)2, Mo(CO)6, MoCl5, WCl6 and TaCl5 on the reaction of 1,2-epoxy-octane with ethanol at 100 deg C in dioxan or chlorobenzene as solvents is proved.Water and hydroperoxides react with a higher rate than alcohols.When changing from primary to secondary and tertiary alcohols a decrease of the reaction rate is observed. 2,3- and 3,4-Epoxyheptane and cis- and trans-4,5-epoxy-octane react more slowly than the corresponding 1,2-epoxides.Epichlorhydrin and methylglycidether react with a lower, cyclohexene oxide, styrene oxide and norbornene oxide react with a higher rate than 1,2-epoxyoctane.The reactivities of the two dicyclopentadiene monoepoxides correspond with the reactivities of the norbornene and cyclopentene oxides.In the molybdenum catalyzed epoxide ring opening reaction an isomer distribution appears in favour of the 1-hydroxy-2-ethoxy-alkane 2.A mechanism in the coordination sphere of the transition metal complex is proposed.
- Lauterbach, G.,Posselt, G.,Schaefer, R.,Schnurpfeil, D.
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p. 101 - 120
(2007/10/02)
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