- A new clade of styrene monooxygenases for (R)-selective epoxidation
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Styrene monooxygenases (SMOs) are excellent enzymes for the production of (S)-enantiopure epoxides, but so far, only one (R)-selective SMO has been identified with a narrow substrate spectrum. Mining the NCBI non-redundant protein sequences returned a new distinct clade of (R)-selective SMOs. Among them,SeStyA fromStreptomyces exfoliatus,AaStyA fromAmycolatopsis albispora, andPbStyA fromPseudonocardiaceaewere carefully characterized and found to convert a spectrum of styrene analogues into the corresponding (R)-epoxides with up to >99% ee. Moreover, site 46 (AaStyA numbering) was identified as a critical residue that affects the enantioselectivity of SMOs. Phenylalanine at site 46 was required for the (R)-selective SMO to endow excellent enantioselectivity. The identification of new (R)-selective SMOs would add a valuable green alternative to the synthetic tool box for the synthesis of enantiopure (R)-epoxides.
- Xiao, Hu,Dong, Shuang,Liu, Yan,Pei, Xiao-Qiong,Lin, Hui,Wu, Zhong-Liu
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p. 2195 - 2201
(2021/04/12)
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- Scalable Regioselective and Stereoselective Synthesis of Functionalized (E)-4-Iodobut-3-en-1-ols: Gram-Scale Total Synthesis of Fungal Decanolides and Derivatives
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A reliable protocol to synthesize both racemic and chiral (E)-4-iodobut-3-en-1-ols from aldehydes or epoxides, respectively, containing various aromatic and aliphatic substitutions has been established. The utility of these compounds was then demonstrated
- Sherwood, Alexander M.,Williamson, Samuel E.,Johnson, Stephanie N.,Yilmaz, Anil,Day, Victor W.,Prisinzano, Thomas E.
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p. 980 - 992
(2018/01/27)
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- The Activation of Carboxylic Acids via Self-Assembly Asymmetric Organocatalysis: A Combined Experimental and Computational Investigation
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The heterodimerizing self-assembly between a phosphoric acid catalyst and a carboxylic acid has recently been established as a new activation mode in Br?nsted acid catalysis. In this article, we present a comprehensive mechanistic investigation on this activation principle, which eventually led to its elucidation. Detailed studies are reported, including computational investigations on the supramolecular heterodimer, kinetic studies on the catalytic cycle, and a thorough analysis of transition states by DFT calculations for the rationalization of the catalyst structure-selectivity relationship. On the basis of these investigations, we developed a kinetic resolution of racemic epoxides, which proceeds with high selectivity (up to s = 93), giving the unreacted epoxides and the corresponding protected 1,2-diols in high enantiopurity. Moreover, this approach could be advanced to an unprecedented stereodivergent resolution of racemic α-chiral carboxylic acids, thus providing access to a variety of enantiopure nonsteroidal anti-inflammatory drugs and to α-amino acid derivatives.
- Monaco, Mattia Riccardo,Fazzi, Daniele,Tsuji, Nobuya,Leutzsch, Markus,Liao, Saihu,Thiel, Walter,List, Benjamin
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supporting information
p. 14740 - 14749
(2016/11/18)
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- Catalytic Enantioselective Conversion of Epoxides to Thiiranes
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A highly efficient and enantioselective Br?nsted acid catalyzed conversion of epoxides to thiiranes has been developed. The reaction proceeds in a kinetic resolution, furnishing both epoxide and thiirane in high yields and enantiomeric purity. Heterodimer formation between the catalyst and sulfur donor affords an effective way to prevent catalyst decomposition and enables catalyst loadings as low as 0.01 mol %.
- Liao, Saihu,Leutzsch, Markus,Monaco, Mattia Riccardo,List, Benjamin
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supporting information
p. 5230 - 5233
(2016/05/19)
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- Exploring substrate scope of Shi-type epoxidations
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Enantioselective epoxidations of alkenes (12 examples) were achieved using a Shi-type carbohydrate-derived hydrate and Oxone. The chiral platform provided by the catalyst tolerates a wide range of substituents providing high yields and enantioselectivities (80-95.5% ee). However, styrene derivatives were only converted with poor selectivities (11-26% ee). Georg Thieme Verlag Stuttgart.
- Nieto, Natalia,Munslow, Ian J.,Fernández-Pérez, Héctor,Vidal-Ferran, Anton
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experimental part
p. 2856 - 2858
(2009/05/07)
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- Dynamic kinetic resolution of racemic β-haloalcohols: Direct access to enantioenriched epoxides
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The direct chemo-enzymatic DKR of racemic β-haloalcohols is reported, yielding the corresponding optically active epoxides in a single step. The mutant haloalcohol dehalogenase HheC Cys153Ser Trp249Phe is used for the asymmetric ring closure, whereas racemization of the remaining enantiomer of the haloalcohol is achieved using the new iridacycle 3, one of the most effective racemization catalysts to date for β-haloalcohols. Copyright
- Haak, Robert M.,Berthiol, Florian,Jerphagnon, Thomas,Gayet, Arnaud J. A.,Tarabiono, Chiara,Postema, Christiaan P.,Ritleng, Vincent,Pfeffer, Michel,Janssen, Dick B.,Minnaard, Adriaan J.,Feringa, Ben L.,De Vries, Johannes G.
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supporting information; scheme or table
p. 13508 - 13509
(2009/02/06)
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- Chiral styrene oxides from α-haloacetophenones using NaBH4 and TarB-NO2, a chiral Lewis acid
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High enantioselectivities are obtained for the preparation of chiral styrene oxides through reduction of α-haloacetophenones using TarB-NO 2 reagent and the inexpensive and mild reducing agent NaBH 4. The epoxides are easily obtained in up to 95% ee through routine acid-base workup of the product alcohols. Either the (R) or (S) epoxide can be obtained by using the appropriate l- or d-tartaric acid starting material in the TarB-NO2 reagent.
- Cordes, David B.,Kwong, Tracey J.,Morgan, Kellie A.,Singaram, Bakthan
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p. 349 - 351
(2007/10/03)
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- Bacterial monooxygenase mediated preparation of nonracemic chiral oxiranes: Study of the effects of substituent nature and position
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Monooxygenation of styrene derivatives using recombinant E. coli biocatalyst is an efficient way to prepare the corresponding oxiranes. The electronic and geometric effects of the ring substituents are described and show the relaxed specificity of the enzyme and its high stereoselectivity.
- Bernasconi, Silvana,Orsini, Fulvia,Sello, Guido,Di Gennaro, Patrizia
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p. 1603 - 1606
(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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- Asymmetric Epoxidation of Simple Olefins by Chiral Bitetralin-Linked "Twin-Coronet" Porphyrin Catalysts
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Catalytic and asymmetric epoxidation of styrenes and related aryl substituted olefins with the iron complexes of chiral bitetralin (Bitet)-linked "twin-coronet" porphyrins was performed with iodosylbenzene as an oxidant.Among two topological isomers of the catalyst, the eclipsed one (5b) showed higher enentioselectivity than the staggered (6b).With 5b, the resulting epoxides, except for the olefins bearing an electron-donating substituent, were obtained in good to excellent enantioselectivity (54-96percent ee), especially for the styrenes with electron-withdrawing substituent(s).Being different from other porphyrin-based chiral catalysts, the catalyst 5b is robust enough under the applied oxidation conditions to exhibit chiral epoxidation with the same ee and the same rate as those of the initial period of the reaction even after about 500 turnovers.The Bitet catalyst is superior in the epoxide enantioselectivity than the corresponding chiral binaphthalene (Binap)-linked catalyst (3b).In the reactions with the catalysts 3b and 5b, good correlation in epoxide ees was observed.Increase of the epoxide ee in the reaction with the Bitet catalyst was elucidated by the shape and size of the reaction cavities of the Bitet were tighter than those of the latter.The observed ees of the substituted styrene oxides showed good correlation with Σ?+ values of their substituent(s).In the reaction with the electron-deficient olefins, ?-?* interaction between the HOMO of the electron-rich Bitet auxiliary ring and the LUMO of the electron-deficient aryl ring of the substrate are pointed out as the key for the realization of high ees.Some nitrostyrenes, however, gave rather lower ees in spite of rather higher degree of their electron deficiency.This deviation was elucidated by the mismatching of their frontier orbitals.
- Naruta, Yoshinori,Ishihara, Nobuo,Tani, Fumito,Maruyama, Kazuhiro
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p. 158 - 166
(2007/10/02)
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- Synthesis of Chiral Bitetralin-strapped "Twin Coronet" Porphyrins. Catalytic and Asymmetric Epoxidation of Styrene Derivatives
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"Twin-coronet" porphyrins bearing optically active 1,1'-bitetrahydronaphthalene derivatives on the both faces of the porphyrin were prepared as enantioselective oxidation catalysts modeling on cytochrome P-450s.The eclipsed isomer of the corresponding iron(III) porphyrins catalyzed epoxidation of styrenes substituted with electron-withdrawing groups in high e.e. (61-89 percent) and high product selectivity.
- Naruta, Yoshinori,Ishihara, Nobuo,Tani, Fumito,Maruyama, Kazuhiro
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p. 1933 - 1936
(2007/10/02)
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