- Structure-Guided Regulation in the Enantioselectivity of an Epoxide Hydrolase to Produce Enantiomeric Monosubstituted Epoxides and Vicinal Diols via Kinetic Resolution
-
Structure-guided microtuning of an Aspergillus usamii epoxide hydrolase was executed. One mutant, A214C/A250I, displayed a 12.6-fold enhanced enantiomeric ratio (E = 202) toward rac-styrene oxide, achieving its nearly perfect kinetic resolution at 0.8 M in pure water or 1.6 M in n-hexanol/water. Several other beneficial mutants also displayed significantly improved E values, offering promising biocatalysts to access 19 structurally diverse chiral monosubstituted epoxides (97.1 - ≥ 99% ees) and vicinal diols (56.2-98.0% eep) with high yields.
- Hou, Xiao-Dong,Hu, Bo-Chun,Hu, Die,Lei, Yu-Qing,Rao, Yi-Jian,Wu, Min-Chen,Zhang, Dong
-
supporting information
p. 1757 - 1761
(2022/03/16)
-
- Are Highly Stable Covalent Organic Frameworks the Key to Universal Chiral Stationary Phases for Liquid and Gas Chromatographic Separations?
-
High-performance liquid chromatography (HPLC) and gas chromatography (GC) over chiral stationary phases (CSPs) represent the most popular and highly applicable technology in the field of chiral separation, but there are currently no CSPs that can be used for both liquid and gas chromatography simultaneously. We demonstrate here that two olefin-linked covalent organic frameworks (COFs) featuring chiral crown ether groups can be general CSPs for extensive separation not only in GC but also in normal-phase and reversed-phase HPLC. Both COFs have the same 2D layered porous structure but channels of different sizes and display high stability under different chemical environments including water, organic solvents, acids, and bases. Chiral crown ethers are periodically aligned within the COF channels, allowing for enantioselective recognition of guest molecules through intermolecular interactions. The COF-packed HPLC and GC columns show excellent complementarity and each affords high resolution, selectivity, and durability for the separation of a wide range of racemic compounds, including amino acids, esters, lactones, amides, alcohols, aldehydes, ketones, and drugs. The resolution performances are comparable to and the versatility is superior to those of the most widely used commercial chiral columns, showing promises for practical applications. This work thus advances COFs with high stability as potential universal CSPs for chromatography that are otherwise hard or impossible to produce.
- Cui, Yong,Jia, Wenyan,Li, Yanan,Yu, Ziyun,Yuan, Chen,Yuan, Li-Ming,Zi, Min
-
p. 891 - 900
(2022/02/03)
-
- Asymmetric Epoxidation of Olefins Catalyzed by Substituted Aminobenzimidazole Manganese Complexes Derived from L-Proline
-
A family of manganese complexes [Mn(Rpeb)(OTf)2] (peb=1-(1-ethyl-1H-benzo[d]imidazol-2-yl)-N-((1-((1-ethyl-1H-benzo[d]imidazol-2-yl)methyl) pyrrolidin-2-yl)methyl)-N-methylmethanamine)) derived from L-proline has been synthesized and characterized, where R refers to the group at the diamine backbone. X-ray crystallographic analyses indicate that all the manganese complexes [Mn(Rpeb)(OTf)2] exhibit cis-α topology. These types of complexes are shown to catalyze the asymmetric epoxidation of olefins employing H2O2 as a terminal oxidant with up to 96% ee. Obviously, the R group of the diamine backbone can influence the catalytic activity and enantioselectivity in the asymmetric epoxidation of olefins. In particular, Mn(i-Prpeb)(OTf)2 bearing an isopropyl arm, cannot catalyze the epoxidation reaction with H2O2 as the oxidant. However, when PhI(OAc)2 is used as the oxidant instead, all the manganese complexes including Mn(i-Prpeb)(OTf)2 can promote the epoxidation reactions efficiently. Taken together, these results indicate that isopropyl substitution on the Rpeb ligand inhibits the formation of active Mn(V)-oxo species in the H2O2/carboxylic acid system via an acid-assisted pathway.
- Lin, Jin,Sun, Wei,Tian, Jing,Xia, Chungu,Zhang, Jisheng
-
supporting information
(2021/11/16)
-
- Chirally-Modified Graphite Oxide as Chirality Inducing Support for Asymmetric Epoxidation of Olefins with Grafted Manganese Porphyrin
-
Abstract: A chirality inducer was prepared by graphite oxide (GO) functionalization with enantiopure l-tartrate (GO*) and used as asymmetric support for a covalently-linked manganese porphyrine complex [Mn(TPyP)OAc]. The thereby obtained heterogeneous catalyst, GO*-[Mn(TPyP)OAc], showed excellent performance and ee-values of 92–99% for the asymmetric epoxidation of prochiral olefins with O2 as oxidant and isobutyraldehyde as co-reductant in acetonitrile; linear terminal olefins with 54–76% conversion and quantitative conversion of aromatic olefins. The GO*-[Mn(TPyP)OAc] catalyst is highly active, recyclable, and at the same time simple and inexpensive to prepare with a chiral inducer from the chiral pool. The structure of the catalyst was elucidated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET analysis,?FT-IR, Raman, and photoluminescence spectroscopic methods. Graphic Abstract: Graphite oxide functionalized with an enantiopure group was used as a chirality inducer and asymmetric support for a Mn-porphyrine complex. The thereby obtained heterogeneous catalyst is an excellent enantioselective catalyst for the epoxidation of prochiral olefins.[Figure not available: see fulltext.].
- Ahadi, Elahe,Hosseini-Monfared, Hassan,Schlüsener, Carsten,Janiak, Christoph,Farokhi, Afsaneh
-
p. 861 - 873
(2019/11/03)
-
- Chiral salen Mn (III) immobilized on ZnPS-PVPA through alkoxyl-triazole for superior performance catalyst in asymmetric epoxidation of unfunctionalized olefins
-
Chiral salen Mn (III) catalysts anchored onto ZnPS-PVPA via click chemistry are prepared and applied in asymmetric epoxidations of unfunctionalized olefins. Superior catalytic performances (conv%, up to >99; ee%, up to >99) are achieved in the epoxidations of α-methylstyrene, styrene, indene and 1-octene. According to 6-cyano-2,2-dimethylchromene and 6-nitro-2,2-dimethylchromene, configuration of epoxides are reversed. And then the catalysts are selective in not only oxidative systems, but also substrates. Moreover, superior reusability (yield, 82%; ee, 86%) after recycling for nine times could also be obtained, which provide the potential application in industry.
- Huang, Jing,Liu, Sirui,Ma, Yan,Cai, Jiali
-
-
- Olefins oxidation with molecular O2 in the presence of chiral Mn (III) salen complex supported on magnetic CoFe2O4@SiO2@CPTMS
-
In the present study, CoFe2O4@SiO2@CPTMS nanocomposite was synthesized and the homogeneous chiral Mn-salen complex was anchored covalently onto the surface of CoFe2O4@SiO2@CPTMS nanocomposite. The heterogeneous Mn-salen magnetic nanocatalyst (CoFe2O4@SiO2@CPTMS@ chiral Mn (III) Complex) was characterized by different techniques including transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), vibrating sample magnetometer (VSM), scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Then, the aerobic enantioselective oxidation of olefins to the corresponding epoxide was investigated in the presence of magnetic chiral CoFe2O4@SiO2@Mn (III) complex at ambient conditions within 90?min. The results showed the corresponding products were synthesized with excellent yields and selectivity. In addition, the heterogeneous CoFe2O4@SiO2@ CPTMS@ chiral Mn (III) complex has benefits such as high selectivity and comparable catalytic reactivity with its homogeneous analog as well as mild reaction condition, facile recovery, and recycling of the heterogeneous catalyst.
- Hemmat, Kaveh,Nasseri, Mohammad A.,Allahresani, Ali
-
-
- Asymmetric epoxidation of unfunctionalized olefins catalyzed by chiral salen-Mn (III) immobilized on alkoxyl-modified ZnPS-PVPA
-
Novel layered heterogeneous chiral salen Mn (III) catalysts anchored onto ZnPS-PVPA by means of click chemistry are synthesized and employed in asymmetric epoxidations of unfunctionalized olefins. The catalysts manifest superior catalytic performances (conv%, up to >99; ee%, up to >99) according to the epoxidations of α-methylstyrene, styrene, indene and 1-octene. But for 6-cyano- 2,2-dimethylchromene and 6-nitro-2,2-dimethylchromene, configuration of epoxides are reversed. Moreover, the catalysts could still indicate comparable properties (yield, 82%; ee, 86%) after recycling for nine times and excellent functions in large-scale reactions, which paves the way for the application in industry.
- Huang, Jing,Xie, Junjie,Cai, Jiali
-
-
- Manganes-Porphyrin as Efficient Enantioselective Catalyst for Aerobic Epoxidation of Olefins
-
A chiral manganese porphyrin, [Mn(TCPP-Ind)Cl], was synthesized using cis-1-amino-2-indanol substituent. It showed remarkable catalytic activity and enantioselectivity in the epoxidation of olefins with O2/RCHO. Terminal olefins and styrene derivatives were successfully oxidized (> 99% ee). TON of 73,000 was achieved in the epoxidation of α-methylstyrene after five times recycling. Graphical Abstract: [Figure not available: see fulltext.].
- Farokhi, Afsaneh,Berijani, Kayhaneh,Hosseini-Monfared, Hassan
-
p. 2608 - 2618
(2018/06/14)
-
- Collaborative effect of Mn-porphyrin and mesoporous SBA-15 in the enantioselective epoxidation of olefins with oxygen
-
The rational design of heterogeneous, low cost transition metal complexes that can catalyze olefin with high enantioselectivity and activity has been a challenging goal for the synthetic chemist. In this study a chiral ion pair strategy was used for the synthesis of a biomimetic efficient manganese-tetrapyridylporphyrin (H2TPyP) catalyst for the asymmetric epoxidation of olefins with O2. Complex Mn-TPyP was covalently linked to mesoporous SBA-15 in heme-type environments and its counter ion was replaced by L-tartrate anion (SBA15-[Mn(TPyP)TA]). Chiral and achiral homogeneous analogous of Mn-TPyP were also prepared. The Mn-porphyrin confined in nanoreactors of SBA-15 exhibited enhanced activity (TOF = 652 h?1) and enantiomeric excess (ee 93%) compared with the value obtained when the same chiral catalyst functioned in homogeneous solution (TOF 97 h?1 and ee 83%) in the oxidation of 1-decene with O2/isobutyraldehyde. The high specific surface area, uniformly sized pore channels and site isolated active centers of the catalyst may contribute to the high activity and enantioselectivity. SBA15-[Mn(TPyP)TA] was structurally stable and could be recycled for repeated use. Total turnover number in the oxidation of styrene after five cycles was 47,400 with 86% epoxide selectivity and ee 86%.
- Berijani, Kayhaneh,Hosseini-Monfared, Hassan
-
p. 113 - 120
(2017/11/10)
-
- Enhanced enantioselective oxidation of olefins catalyzed by Mn-porphyrin immobilized on graphene oxide
-
An efficient enantioselective heterogeneous catalyst, GO-[Mn(TPyP)tart], was prepared by covalent attachment of Mn(III) complex of H2TPyP via the propyl linkage to graphene oxide (GO) nanosheet and using chiral tartrate counter ion. The catalyst was characterized by Fourier transform infrared (FT-IR), diffuse reflectance ultraviolet–visible (DR UV–Vis) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman and thermogravimetric analysis (TGA). The graphene-supported Mn-porphyrin showed higher activity for the enantioselective epoxidation of unfunctionalized olefins with molecular oxygen in the presence of isobutyraldehyde. It could be recovered easily and reused in asymmetric oxidation of styrene precursor in a five-step sequence without any considerable loss of its catalytic activity and selectivity. The obtained optically epoxide selectivities were achieved in 86% to 100%.
- Berijani, Kayhaneh,Farokhi, Afsaneh,Hosseini-Monfared, Hassan,Janiak, Christoph
-
p. 2202 - 2210
(2018/04/02)
-
- A novel chiral manganese-tetraamide macrocycle complex covalently attached to magnetite as recyclable catalyst for aerobic asymmetric epoxidation of olefins
-
A novel Mn complex containing N4-tetradentate tetraamide macrocyclic ligand (L) derived from chiral diethyl-2,3-benzylidene-L-tartrate and polyamidoamine dendrimer on Fe3O4@SiO2 surface was synthesized. The nanocomposite particles were investigated by SEM, XRD, VSM, EPR and FTIR. The nanocomposite showed high catalytic activity and selectivity for the epoxidation of linear terminal, cyclic and most of the aromatic olefins by O2 in the presence of isobutyraldehyde under mild conditions; epoxide selectivity 87–100%, enantiomeric excess 53–100%. The catalyst could be separated and recovered from the reaction system by applying an external magnetic field and reused for four cycles without the loss of activity after each cycle. Total TON of 16957 was obtained after four cycles.
- Hadian-Dehkordi, Leila,Hosseini-Monfared, Hassan,Aleshkevych, Pavlo
-
p. 142 - 151
(2017/03/29)
-
- A heterogenized chiral imino indanol complex of manganese as an efficient catalyst for aerobic epoxidation of olefins
-
Herein, a new heterogenized chiral catalyst, GFC-[Mn(L)(OH)], was synthesized by grafting the complex [Mn(L)(OH)] on carbon-coated magnetic Fe3O4 nanoparticle-decorated reduced graphene oxide sheets (GFC) through an amine linkage (L = (1R,2S)-1-(N-salicylideneamino)-2-indanol). The catalyst was characterized via FT-IR, UV/vis, XRD, SEM, and vibrating sample magnetometer (VSM) techniques. It exhibited excellent activity and selectivity in the epoxidation of olefins with oxygen in the presence of isobutyraldehyde under mild conditions (conversion 38-98%; selectivity 65-98%; and enantioselectivity 58-100%, except for alpha-methylstyrene). Furthermore, the synergistic effect of the reduced graphene oxide support was observed on the increasing activity, epoxide selectivity, and enantioselectivity. The catalyst can be recovered via magnetic separation from the reaction mixture and recycled five times without any significant loss in its activity. The advantage of this development is the use of both the synergic effect of reduced graphene oxide and the magnetite nanoparticles to obtain an easily recyclable heterogeneous green catalyst. In addition, high asymmetric induction of a rigid indanol-based unit of the ligand results in high enantioselectivity.
- Abbasi, Vahideh,Hosseini-Monfared, Hassan,Hosseini, Seyed Majid
-
p. 9866 - 9874
(2017/09/18)
-
- Highly efficient asymmetric epoxidation of olefins with a chiral manganese-porphyrin covalently bound to mesoporous SBA-15: Support effect
-
A chiral MnIII-porphyrin complex covalently bonded with mesoporous SBA-15 (SBA15-[Mn(TCPP-R?)Cl]) was synthesized and fully characterized. The heterogeneous SBA15-[Mn(TCPP-R?)Cl] exhibited remarkable catalytic activity toward enantioselective olefin epoxidation using O2 as terminal oxidant in the presence of isobutyraldehyde. The catalyst showed higher enantioselectivity than its homogeneous counterpart in the oxidation of α-methylstyrene. SBA15-[Mn(TCPP-R?)Cl] catalyzed epoxidation of styrene was achieved within 8?h and optically active styrene oxide was obtained in 89% ee and 90% yield. Likewise, styrene derivatives (trans-β-methylstyrene, indene), conjugated cis- and trans-disubstituted olefins (e.g. cis- and tans-stilbene) and terminal olefins were converted effectively to their corresponding epoxides in 63–99%?ee under the Mn(III)-catalyzed conditions. The catalyst could be recycled five times without any significant loss in activity.
- Farokhi, Afsaneh,Hosseini Monfared, Hassan
-
p. 229 - 238
(2017/06/19)
-
- Asymmetric epoxidation of unfunctionalized olefins catalyzed by Jacobsen's catalyst on alkoxyl-modified zirconium poly (styrene-phenylvinylphosphonate)-phosphate (ZPS-PVPA)
-
New chiral Jacobsen's catalysts grafted onto alkoxyl-modified ZPS-PVPA are synthesized and applied in asymmetric epoxidations of unfunctionalized olefins. Specially, the supported catalysts indicate excellent catalytic activities (conv%, up to 96; sele%, up to 96; ee%, up to >99) in the absence of N-methylmorpholine N-oxide (NMO) by virtue of the special configurations of the catalysts. The superior stability (recycling for ten times) and the comfortable dispositions in large-scale reactions (such as 200 times) grant the potential application in industry to the heterogeneous catalysts.
- Huang, Jing,Luo, Yan,Cai, Jiali,Chen, Xiaohong
-
-
- Photocatalytic Asymmetric Epoxidation of Terminal Olefins Using Water as an Oxygen Source in the Presence of a Mononuclear Non-Heme Chiral Manganese Complex
-
Photocatalytic enantioselective epoxidation of terminal olefins using a mononuclear non-heme chiral manganese catalyst, [(R,R-BQCN)MnII]2+, and water as an oxygen source yields epoxides with relatively high enantioselectivities (e.g., up to 60% enantiomeric excess). A synthetic mononuclear non-heme chiral Mn(IV)-oxo complex, [(R,R-BQCN)MnIV(O)]2+, affords similar enantioselectivities in the epoxidation of terminal olefins under stoichiometric reaction conditions. Mechanistic details of each individual step of the photoinduced catalysis, including formation of the Mn(IV)-oxo intermediate, are discussed on the basis of combined results of laser flash photolysis and other spectroscopic methods.
- Shen, Duyi,Saracini, Claudio,Lee, Yong-Min,Sun, Wei,Fukuzumi, Shunichi,Nam, Wonwoo
-
supporting information
p. 15857 - 15860
(2016/12/23)
-
- Titanium cis-1,2-Diaminocyclohexane Salalen Catalysts of Outstanding Activity and Enantioselectivity for the Asymmetric Epoxidation of Nonconjugated Terminal Olefins with Hydrogen Peroxide
-
We report a new and readily accessible class of titanium salalen complexes derived from cis-1,2-diaminocyclohexane (cis-DACH) and fluorinated salicylic aldehyde derivatives. With aqueous hydrogen peroxide as the oxidant, these complexes catalyze the epoxidation of terminal, nonconjugated olefins in high yields with high enantioselectivities. We furthermore discovered that the addition of certain acidic or basic co-catalysts significantly accelerated the epoxidation. For example, in the presence of 1 mol % Ti catalyst and 1 mol % pentafluorobenzoic acid, 1-octene epoxidation (95 % ee) was completed at room temperature within 8 h. The catalytic process was compatible with many functional groups (e.g., ethers, esters, halides, nitriles, and nitro groups), whereas free hydroxy groups appeared to slow down the reaction to some extent. Catalyst recycling was possible.
- Lansing, Markus,Engler, Hauke,Leuther, Tobias M.,Neud?rfl, J?rg-M.,Berkessel, Albrecht
-
p. 3706 - 3709
(2016/12/24)
-
- The Activation of Carboxylic Acids via Self-Assembly Asymmetric Organocatalysis: A Combined Experimental and Computational Investigation
-
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
-
supporting information
p. 14740 - 14749
(2016/11/18)
-
- Catalytic Enantioselective Conversion of Epoxides to Thiiranes
-
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
-
supporting information
p. 5230 - 5233
(2016/05/19)
-
- Enantioselective epoxidation of olefins with H2O2 catalyzed by bioinspired aminopyridine manganese complexes
-
A novel family of bioinspired manganese(II) complexes bearing chiral aminopyridine ligands that possessed additional aromatic groups and strong donating dimethylamino groups were synthesized and characterized. These manganese complexes exhibited efficient
- Shen, Duyi,Qiu, Bin,Xu, Daqian,Miao, Chengxia,Xia, Chungu,Sun, Wei
-
supporting information
p. 372 - 375
(2016/02/19)
-
- Titanium cis-1,2-diaminocyclohexane (cis-DACH) salalen catalysts for the asymmetric epoxidation of terminal non-conjugated olefins with hydrogen peroxide
-
Chiral Ti salalen complexes catalyze the asymmetric epoxidation of terminal non-conjugated olefins with hydrogen peroxide. Modular ligands based on cis-1,2-diaminocyclohexane (cis-DACH) were developed, giving high yields and enantiomeric excesses (ee, up to 96%) at catalyst loadings as low as 0.1-0.5mol%, and even under solvent-free conditions.
- Wang, Qifang,Neud?rfl, J?rg-M.,Berkessel, Albrecht
-
p. 247 - 254
(2015/07/07)
-
- Highly enantioselective olefin epoxidation controlled by helical confined environments
-
Helical mesoporous materials of the MCM-41 type are important materials that can be prepared by onepot synthesis procedures with a co-surfactant. A control of the characteristics at a local level is of the most important in the view of the applications of such materials. However, there are not many studies relating such features with synthetic approaches. In this work, we prepared both helical and regular channel materials from Si-based MCM-41 type. Afterward, a bpy derivative was used as ligand to coordinate MoII/VI. The complexes and the new materials were tested as the catalytic precursors in the epoxidation of cis-cyclooctene, styrene, 1-octene, R-(+)-limonene and trans-hex-2-en-1-ol, using tert-butylhydroperoxide (TBHP) as oxidant. Although almost all the catalysts were 100% selective toward the epoxide, the conversions were in general good. The major achievement of these catalysts is an outstanding stereocontrol of the reaction products. In addition, these catalysts were found to be very effective under several circumstances. This is certainly an important contribution for such concept and may render such materials further applications where chiral recognition is important.
- Fernandes, Cristina I.,Saraiva, Marta S.,Nunes, Teresa G.,Vaz, Pedro D.,Nunes, Carla D.
-
-
- Grafting of a chiral Mn(iii) complex on graphene oxide nanosheets and its catalytic activity for alkene epoxidation
-
A chiral Mn(iii) complex supported by a covalent grafting method on modified graphene oxide was synthesized using 3-chloropropyltrimethoxysilane as a reactive surface modifier. The heterogeneous catalyst was characterized by X-ray diffraction, Fourier transform infrared spectra, thermogravimetric analysis, ultraviolet-visible spectra, nitrogen adsorption-desorption isotherms, transmission electron microscopy and atomic absorption spectroscopy. The catalytic potential of the heterogeneous catalyst and comparison with its homogeneous counterpart were studied for enantioselective epoxidation of various alkenes using m-chloroperbenzoic acid as an oxidant and it showed high selectivity and comparable catalytic reactivity with its homogeneous analogue. In addition, higher enantioselectivity and higher yield were observed in the presence of 4-methylmorpholine N-oxide and pyridine N-oxide, respectively. The catalyst was reused for several runs without significant loss of activity and selectivity.
- Nasseri, Mohammad Ali,Allahresani, Ali,Raissi, Heidar
-
p. 26087 - 26093
(2014/07/08)
-
- Bioproduction of chiral epoxyalkanes using styrene monooxygenase from rhodococcus sp. ST-10 (RhSMO)
-
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
-
p. 3443 - 3450
(2015/02/05)
-
- A mononuclear manganese complex of a tetradentate nitrogen ligand - Synthesis, characterizations, and application in the asymmetric epoxidation of olefins
-
A new chiral manganese complex (C1) bearing a tetradentate nitrogen ligand containing chiral bipyrrolidine and benzimidazole moieties was prepared. The structure of C1 was confirmed by ESI-MS and crystallography. This manganese complex is an active catalyst for the asymmetric epoxidation of various olefins with excellent conversion (up to 99%) and high enantiomeric excess (up to 96%ee) with hydrogen peroxide as the oxidant in the presence of 2-ethylhexanoic acid or acetic acid. Compared with previous structurally similar manganese complexes with different diamine backbones (C2, cyclohexanediamine; C3, diamine from L-proline), C1 showed improved asymmetric induction, especially for simple olefins such as styrene derivatives and substituted chromene. The possible reasons for the improvement of the ee values are discussed in the text on the basis of the crystal structures of the manganese complexes.
- Shen, Duyi,Miao, Chengxia,Wang, Shoufeng,Xia, Chungu,Sun, Wei
-
supporting information
p. 5777 - 5782
(2015/02/19)
-
- A magnetically recyclable Fe3O4@SiO2/Mn(III) chiral salen complex as a highly selective and versatile heterogeneous nanocatalyst for the oxidation of olefins and sulfides
-
In this study, a new magnetically recoverable heterogeneous Mn(iii) nanocatalyst (MHMC) was developed by covalent grafting of a homogeneous chiral Mn(iii) salen complex (HMC) onto the surface of a Fe3O4/SiO2 core-shell. The structural and chemical nature of MHMC was characterized by different techniques. The catalytic activity of the MHMC and comparison with its homogeneous analogue were studied for the enantioselective epoxidation of various alkenes to epoxide compounds using tert-butyl hydroperoxide (TBHP) as an oxidant. The MHMC showed higher enantioselectivity and comparable catalytic reactivity to its homogeneous analogue with benefits such as facile recovery and recycling of the heterogeneous catalyst. The results showed that a higher enantioselectivity and yield were observed in the presence of N-methylmorpholine N-oxide (NMNO). The catalytic activity of this complex was also tested in the oxidation of sulfides using aqueous 30% H2O2 in excellent yields. The catalyst was reused for several runs without significant loss in activity and selectivity.
- Allahresani, Ali,Nasseri, Mohammad Ali
-
p. 60702 - 60710
(2015/02/19)
-
- Asymmetric hydrolytic kinetic resolution with recyclable polymeric Co(iii)-salen complexes: A practical strategy in the preparation of (S)-metoprolol, (S)-toliprolol and (S)-alprenolol: Computational rationale for enantioselectivity
-
A series of chiral polymeric Co(iii)-salen complexes based on a number of achiral and chiral linkers were synthesized and their catalytic performances were assessed in the asymmetric hydrolytic kinetic resolution of terminal epoxides. The effects of the linker were judiciously studied and it was found that in the case of the chiral BINOL-based polymeric salen complex 1, there was an enrichment in catalyst reactivity and enantioselectivity of the unreacted epoxide, particularly in the case of short as well as long chain aliphatic epoxides. Good isolated yields of the unreacted epoxide (up to 46% compared to 50% theoretical yield) along with high enantioselectivity (up to 99%) were obtained in most cases using catalyst 1. Further studies showed that catalyst 1 could retain its catalytic activity for six cycles under the present reaction conditions without any significant loss in activity or enantioselectivity. To show the practical applicability of the above synthesized catalyst we have synthesised some potent chiral β-blockers in moderate yield and high enantioselectivity using complex 1. The DFT (M06-L/6-31+G??//ONIOM(B3LYP/6-31G?:STO-3G)) calculations revealed that the chiral BINOL linker influences the enantioselectivity achieved with Co(iii)-salen complexes. Further, the transition state calculations show that the R-BINOL linker with the (S,S)-Co(iii)-salen complex is energetically preferred over the corresponding S-BINOL linker with the (S,S)-Co(iii)-salen complex for the HKR of 1,2-epoxyhexane. The role of non-covalent C-H?π interactions and steric effects has been discussed to control the HKR reaction of 1,2-epoxyhexane.
- Roy, Tamal,Barik, Sunirmal,Kumar, Manish,Kureshy, Rukhsana I.,Ganguly, Bishwajit,Khan, Noor-Ul H.,Abdi, Sayed H. R.,Bajaj, Hari C.
-
p. 3899 - 3908
(2015/02/19)
-
- Titanium salalen catalysts based on cis-1,2-diaminocyclohexane: Enantioselective epoxidation of terminal non-conjugated olefins with H 2O2
-
Terminal, non-conjugated olefins, such as 1-octene, are difficult to epoxidize asymmetrically. Ti salalen complexes based on cis-1,2- diaminocyclohexane catalyze this demanding reaction giving high yields and enantioselectivities (up to 95 % ee), with H2O2 as the oxidant. The X-ray structures of the μ-oxo and peroxo complexes shed light on the coordination behavior of this novel class of ligands.
- Berkessel, Albrecht,Guenther, Thomas,Wang, Qifang,Neudoerfl, Joerg-M.
-
supporting information
p. 8467 - 8471
(2013/09/02)
-
- Monodisperse crosslinked pHEMA particle-supported chiral Mn(III)salen catalyst for asymmetric epoxidation of olefin
-
Monodisperse crosslinked poly(hydroxyethyl methacrylate) particles (pHEMA) were synthesized for immobilization of the chiral Mn(III)salen homogeneous catalyst by axial coordination. The pHEMA-Mn(III)salen catalyst was subsequently characterized by FT-IR, UV and scanning electron microscopy. The results showed that, the heterogeneous Mn(III)salen catalysts also exhibited high activity and enantioselectivity compared to the homogeneous catalyst for the disubstituted cyclic indene and 6-cyano-2,2-dimethylchromene. Moreover, the catalysts were easily separated from the reaction systems and could be renewed several times without significant loss of catalytic activity. Meanwhile, the enantiomeric excess (ee) value remained at 80% in the eighth cycle. The pHEMA support, immobilized by Mn(III)salen, probably acted as a mediator of the reaction between the substrate and the oxidant, and enhanced the stability of the Mn(III)salen compound. Copyright
- Wei, Saili,Tang, Yuhai,Zhao, Ruiqin,Xu, Guojin,Zheng, Yuansuo
-
experimental part
p. 114 - 120
(2012/06/01)
-
- Direct stereospecific amination of alkyl and aryl pinacol boronates
-
The direct amination of alkyl and aryl pinacol boronates is accomplished with lithiated methoxyamine. This reaction directly provides aliphatic and aromatic amines, stereospecifically, and without preactivation of the boronate substrate.
- Mlynarski, Scott N.,Karns, Alexander S.,Morken, James P.
-
p. 16449 - 16451,3
(2020/09/15)
-
- Iron(III) catalyzed direct synthesis of cis -2,7-disubstituted oxepanes. the shortest total synthesis of (+)-isolaurepan
-
Prins cyclization of bis-homoallylic alcohols with aldehydes catalyzed by iron(III) salts shows excellent cis selectivity and yields to form 2,7-disubstituted oxepanes. The iron(III) is able to catalyze this process with unactivated olefins. This cyclization was used as the key step in the shortest total synthesis of (+)-isolaurepan.
- Purino, Martín A.,Ramírez, Miguel A.,Daranas, Antonio H.,Martín, Víctor S.,Padrón, Juan I.
-
supporting information
p. 5904 - 5907
(2013/02/25)
-
- A novel layered organic polymer-inorganic hybrid zinc poly (styrene-phenylvinylphosphonate)-phosphate immobilized chiral salen Mn(III) catalyst large-scale asymmetric epoxidation of unfunctionalized olefins
-
A novel layered organic polymer-inorganic hybrid zinc poly (styrene-phenylvinylphosphonate)-phosphate (ZnPS-PVPA) has been synthesized under mild conditions and diphenol-modified ZnPS-PVPA was used to successfully immobilize the chiral salen Mn(III) by axial coordination. The obtained heterogeneous chiral catalysts exhibited excellent activities and enantioselectivities using sodium periodate as an oxidant for asymmetric epoxidation of unfunctionalized olefins, especially for the epoxidation of α-methylstyrene (conversion: up to 97%; ee: exceed 99%). Moreover, these synthesized catalysts were relatively stable and could be expediently separated from the reaction system, and could be recycled at least ten times without obvious loss of activity and enantioselectivity. These novel catalysts could be efficiently used in large-scale reactions with the enantioselectivity being maintained at the same level, which offer a great possibility for application in industry.
- Hu, Xiaoyan,Fu, Xiangkai,Xu, Jiangwei,Wang, Changwei
-
experimental part
p. 2797 - 2804
(2011/08/10)
-
- Biaryl-bridged salalen ligands and their application in titanium-catalyzed asymmetric epoxidation of olefins with aqueous H2O2
-
A series of biaryl-bridged salalen ligands together with their titanium complexes have been designed and synthesized. The Ti complexes could serve as highly efficient catalysts for the asymmetric epoxidation of a wide range of olefins, giving the corresponding epoxides with high ee values. A biaryl-bridged salalen titanium complex was developed and used in the enantioselective epoxidation of a range of olefins with aqueous hydrogen peroxide as the oxidant. Notably, the intramolecular dinuclear Ti catalyst possessing a biaryl bridge is highly efficient for the reaction, especially using terminal aromatic olefins as substrates.
- Xiong, Donglu,Hu, Xiaoxue,Wang, Shoufeng,Miao, Cheng-Xia,Xia, Chungu,Sun, Wei
-
experimental part
p. 4289 - 4292
(2011/09/15)
-
- Nonheme manganese-catalyzed asymmetric oxidation. A lewis acid activation versus oxygen rebound mechanism: Evidence for the "third oxidant"
-
The catalytic properties of a series of chiral nonheme aminopyridinylmanganese(II) complexes [LMnII(OTf)2] were investigated. The above complexes were found to efficiently catalyze enantioselective olefin oxidation to the corresponding epoxides with different oxidants (peroxycarboxylic acids, alkyl hydroperoxides, iodosylarenes, etc.) with high conversions and selectivities (up to 100%) and enantiomeric excesses (up to 79%). The effect of the ligand structure on the catalytic performance was probed. Epoxidation enantioselectivities were found to be strongly dependent on the structure of the oxidants (performic, peracetic, and m-chloroperbenzoic acids; tert-butyl and cumyl hydroperoxides; iodosylbenzene and iodosylmesitylene), thus bearing evidence that the terminal oxidant molecule is incorporated in the structure of the oxygen-transferring intermediates. High-valence electron-paramagnetic-resonance-active manganese complexes [LMnIV=O]2+ and [LMnIV(μ-O) 2MnIIIL]3+ were detected upon interaction of the starting catalyst with the oxidants. The high-valence complexes did not epoxidize styrene and could themselves only contribute to minor olefin oxidation sideways. However, the oxomanganese(IV) species were found to perform the Lewis acid activation of the acyl and alkyl hydroperoxides or iodosylarenes to form the new type of oxidant [oxomanganese(IV) complex with a terminal oxidant], with the latter accounting for the predominant enantioselective epoxidation pathway in the nonheme manganese-catalyzed olefin epoxidations.
- Ottenbacher, Roman V.,Bryliakov, Konstantin P.,Talsi, Evgenii P.
-
scheme or table
p. 8620 - 8628
(2010/12/20)
-
- Chemo- And stereodivergent preparation of terminal epoxides and bromohydrins through One-Pot biocatalysed reactions: Access to enantiopure Five- and Six-Membered N-Heterocycles
-
Different enantiopure terminal epoxides or bromohydrins have chemoselectively been synthesised in one-pot starting from the corresponding a-bromo ketones through alcohol dehydrogenase (ADH)-catalysed processes adding an organic cosolvent and tuning appropriately the medium pH and the temperature. Thus, at neutral pH enantiopure bromohydrins were obtained while using basic conditions (pH 9.5-10) epoxides were isolated as the main product. Furthermore, by simple selection of the biocatalyst, chemo- and stereodivergent transformations were achieved to obtain, e.g., enantiopure prolinol or piperidin-3-ol.
- Bisogno, Fabricio R.,Cuetos, Anibal,Orden, Alejandro A.,Kurina-Sanz, Marcela,Lavandera, Ivan,Gotor, Vicente
-
supporting information; experimental part
p. 1657 - 1661
(2010/09/18)
-
- Synthesis of salan (salalen) ligands derived from binaphthol for titanium-catalyzed asymmetric epoxidation of olefins with aqueous H2O2
-
A series of chiral salan (salalen) ligands, easily prepared from the aldehyde derived from chiral binaphthol, are effective ligands for the titanium-catalyzed asymmetric epoxidation of olefins with aqueous H2O2 as the oxidant. One of
- Xiong, Donglu,Wu, Mei,Wang, Shoufeng,Li, Fuwei,Xia, Chungu,Sun, Wei
-
experimental part
p. 374 - 378
(2010/06/14)
-
- Biocatalytic cascade for the synthesis of enantiopure β-azidoalcohols and β-hydroxynitriles
-
A three-step, two-enzyme, one-pot reaction sequence starting from prochiral a-chloroketones leading to enantiopure (3- azidoalcohols and (3-hydroxynitriles is described. Asymmetric bioreduction of a-chloroketones by hydrogen transfer catalysed by an alcohol dehydrogenase (ADH) established the stereogenic centre in the first step to furnish enantiopure chlorohydrin intermediates. Subsequent biocatalysed ring closure to the epoxide and nucleophilic ring opening with azide, N3-, or cyanide, CN-, both catalysed by a nonselective halohydrin dehalogenase (Hhe) proceeded with full retention of configuration to give enantiopure (-azidoalcohols and (3-hydroxynitriles, respectively. Both enantiomers of various optically pure (-azidoalcohols and (-hydroxynitriles were synthesised.
- Schrittwieser, Joerg H.,Lavandera, Ivan,Seisser, Birgit,Mautner, Barbara,Kroutil, Wolfgang
-
experimental part
p. 2293 - 2298
(2009/08/17)
-
- Shifting the equilibrium of a biocatalytic cascade synthesis to enantiopure epoxides using anion exchangers
-
Hydroxide-loaded anion exchangers have been successfully employed to shift the equilibrium of a one-pot, two-step, two-enzyme cascade reaction affording enantiopure epoxides starting from prochiral α-chloroketones. The α-chloroketones were asymmetrically reduced employing an alcohol dehydrogenase and then transformed further to the corresponding epoxides employing halohydrin dehalogenases. Each epoxide enantiomer could be obtained with up to 93% conversion in enantiomerically pure form (>99% ee). In contrast to previous studies the amount of hydride donor (2-propanol) could be reduced due to favoured halohydrin formation in the reduction of α-chloroketones.
- Schrittwieser, Joerg H.,Lavandera, Ivan,Seisser, Birgit,Mautner, Barbara,Lutje Spelberg, Jeffrey H.,Kroutil, Wolfgang
-
experimental part
p. 483 - 488
(2009/07/25)
-
- A general approach to medium-sized ring ethers via hydrolytic and oxidative kinetic resolutions: stereoselective syntheses of (-)-cis-lauthisan and (+)-isolaurepan
-
A short and enantioselective approach to medium ring ethers and its application to the syntheses of (-)-cis-lauthisan and (+)-isolaurepan are described. The synthetic strategy features Jacobson's Hydrolytic Kinetic Resolution (HKR), oxidative resolution of secondary alcohol, and highly diastereoselective Et3SiH/TMSOTf-promoted reductive cyclization of a hydroxy ketone to give exclusively the different medium-sized cis-disubstituted cyclic ethers.
- Tripathi, Divya,Pandey, Satyendra Kumar,Kumar, Pradeep
-
body text
p. 2226 - 2231
(2009/07/18)
-
- Directed evolution of an enantioselective epoxide hydrolase: Uncovering the source of enantioselectivity at each evolutionary stage
-
Directed evolution of enzymes as enantioselective catalysts in organic chemistry is an alternative to traditional asymmetric catalysis using chiral transition-metal complexes or organocatalysts, the different approaches often being complementary. Moreover, directed evolution studies allow us to learn more about how enzymes perform mechanistically. The present study concerns a previously evolved highly enantioselective mutant of the epoxide hydrolase from Aspergillus niger in the hydrolytic kinetic resolution of racemic glycidyl phenyl ether. Kinetic data, molecular dynamics calculations, molecular modeling, inhibition experiments, and X-raystructural work for the wild-type (WT) enzyme and the best mutant revea l the basis of the large increase in enantioselectivity (E = 4.6 versus E = 115). The overall structures of the WT and the mutant are essentially identical, but dramatic differences are observed in the active site asrevealed by the X-ray structures. All of the experimental and computati onal results support a model in which productive positioning of the preferred (S)-glycidyl phenyl ether, but not the (R)-enantiomer, forms the basis of enhanced enantioselectivity. Predictions regarding substrate scope and enantioselectivity of the best mutant are shown to be possible.
- Reetz, Manfred T.,Bocola, Marco,Wang, Li-Wen,Sanchis, Joaquin,Cronin, Annette,et al.
-
supporting information; experimental part
p. 7334 - 7343
(2009/10/17)
-
- Efficient and flexible synthesis of chiral γ- And δ-lactones
-
An efficient and highly flexible synthesis for chiral γ- and δ-lactones with high enantiomeric purity is described (>99% ee and 57-87% overall yield). The protocol involves alkylation of chiral 1,2-oxiranes with terminally unsaturated Grignard reagents. Subsequent oxidative degradation (OsO4-Oxone) of the terminal double bond from chiral alk-1-en-5-ols and alk-1-en-6-ols affords 4- or 5-hydroxy acids and γ- and δ-lactones after acidic workup. The flexibility and efficiency of the protocol is illustrated by the synthesis of several alkanolides and alkenolides, hydroxy fatty acids and dihydroisocoumarins. The Royal Society of Chemistry 2008.
- Habel, Andreas,Boland, Wilhelm
-
supporting information; experimental part
p. 1601 - 1604
(2008/10/09)
-
- Titanium-catalyzed asymmetric epoxidation of non-activated olefins with hydrogen peroxide
-
A greener oxidation: A titanium(salalen) complex catalyzes the asymmetric epoxidation of aliphatic (non-activated) olefins using aqueous hydrogen peroxide as the oxidant. Reactions with aliphatic terminal and Z olefins furnish the corresponding epoxides in good yields with high enantioselectivities of up to 97% ee.
- Sawada, Yuji,Matsumoto, Kazuhiro,Katsuki, Tsutomu
-
p. 4559 - 4561
(2008/09/16)
-
- A practical and versatile access to dihydrosalen (salalen) ligands: Highly enantioselective titanium in situ catalysts for asymmetric epoxidation with aqueous hydrogen peroxide
-
A modular synthesis for chiral and nonsymmetrical salalen ligands (i.e., mono-reduced salens), carrying an imine and an amine functionality has been developed. The ligands can be assembled in situ by Schiff base formation of an N-(2-hydroxybenzyl)diamine with a salicylic aldehyde, thus allowing rapid and easy variation/optimization of the ligand structure. Aiming at optimal activity and enantioselectivity in the titanium-catalyzed asymmetric epoxidation of non-functionalized olefins, a positional scanning of the two ligand halves was carried out. High epoxide yields were achieved, and up to 98% ee. The composition of the titanium complex catalysts was determined by high resolution mass spectrometry and X-ray crystallography for one selected example.
- Berkessel, Albrecht,Brandenburg, Marc,Leitterstorf, Eva,Frey, Julia,Lex, Johann,Schaefer, Mathias
-
p. 2385 - 2391
(2008/09/19)
-
- Practical two-step synthesis of an enantiopure aliphatic terminal (S)-epoxide based on reduction of haloalkanones with "designer cells"
-
A practical biocatalytic method for the synthesis of aliphatic β-halogenated (S)-alcohols as epoxide precursors by means of an enantioselective reduction of the corresponding ketones with recombinant whole cells, bearing an alcohol dehydrogenase and a glucose dehydrogenase, was developed. The biotransformations operate at high substrate concentrations of up to 208 g/L, and afford the (S)-β-halohydrins with both high conversions of >95% and enantioselectivities of >99% ee. Base-induced cyclization of the β-halohydrin intermediates gave the desired (S)-epoxides in high yield and enantiomeric purity (>99% ee).
- Berkessel, Albrecht,Rollmann, Claudia,Chamouleau, Francoise,Labs, Stefanie,May, Oliver,Groeger, Harald
-
p. 2697 - 2704
(2008/09/19)
-
- Stereo-complementary two-step cascades using a two-enzyme system leading to enantiopure epoxides
-
A novel one-pot, two-step, two-enzyme cascade is described. Pro-chiral α-chloro ketones are stereoselectively reduced to the corresponding halohydrins as an intermediate by a biocatalytic hydrogen transfer process. The intermediate is transformed to the corresponding epoxide by a non-enantioselective halohydrin dehalogenase. Thus, by combining a Prelog- or anti-Prelog alcohol dehydrogenase with a non-selective halohydrin dehalogenase, enantiopure (R)- as well as (S)-epoxides were obtained.
- Seisser, Birgit,Lavandera, Ivan,Faber, Kurt,Spelberg, Jeffrey H. Lutje,Kroutil, Wolfgang
-
p. 1399 - 1404
(2008/03/28)
-
- Single enantiomer epoxides by bromomandelation of prochiral alkenes
-
A combination of mandelic acid and N-bromosuccinimide efficiently converts prochiral alkenes into a readily separable 1:1 mixture of the bromomandelates. The diastereomerically pure bromomandelates are then converted into a variety of enantiomerically pure products. Terminal alkenes are converted into enantiomerically pure epoxides. Cyclohexene is converted into enantiomerically pure cis-2-azidocyclohexanol and cis-2-phenylthiocyclohexanol.
- Taber, Douglass F.,Liang, Jiang-Lin
-
p. 431 - 434
(2007/10/03)
-
- Regio- and stereospecific formation of protected allylic alcohols via zirconium-mediated SN2′ substitution of allylic chlorides
-
A new, highly regio- and stereospecific SN2′ substitution reaction between a zirconium oxo complex and allylic chloride has been achieved. The resulting allylic alcohol or TBS-protected allylic ether products were isolated in good to excellent yields with a wide range of E-allylic chlorides. A mechanism for the SN2′ allylic substitution consistent with kinetic, stereochemical, and secondary isotope effect studies was proposed. Copyright
- Fox, Richard J.,Lalic, Gojko,Bergman, Robert G.
-
p. 14144 - 14145
(2008/09/18)
-
- PROCESS FOR PRODUCING OPTICALLY ACTIVE EPOXY COMPOUND, COMPLEX FOR USE IN THE PROCESS, AND PROCESS FOR PRODUCING THE SAME
-
There is provided a method for industrially producing optically active epoxy compounds by asymmetrically epoxidizing prochiral unsaturated compounds with an oxidant using as a catalyst a single substance or a di-μ-oxo dimer derived therefrom represented by any of the following formulae (I), (I'), (II), (II'), (III), (III'), (IV), and (IV'): [wherein R1s are independently an alkyl group or an aryl group; R2s are independently an alkyl group or an aryl group; R3s are independently an alkyl group or an aryl group, provided that two R3s may be bonded with each other to form a ring; R4s are independently a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a nitro group, or a cyano group; M is TiY2 (Y is Cl, alkoxide, or a μ-oxo ligand)].
- -
-
Page/Page column 20-21
(2010/11/28)
-
- Asymmetric epoxidation of terminal alkenes with hydrogen peroxide catalyzed by pentafluorophenyl PtII complexes
-
Easily accessible chiral PtII complexes 1 allow highly enantioselective and completely regioselective asymmetric epoxidation of terminal alkenes with hydrogen peroxide. Copyright
- Colladon, Marco,Scarso, Alessandro,Sgarbossa, Paolo,Michelin, Rino A.,Strukul, Giorgio
-
p. 14006 - 14007
(2007/10/03)
-
- Enantioselective epoxidation of terminal alkenes to (R)- and (S)-epoxides by engineered cytochromes P450 BM-3
-
Cytochrome P450 BM-3 from Bacillus megaterium was engineered for enantioselective epoxidation of simple terminal alkenes. Screening saturation mutagenesis libraries, in which mutations were introduced in the active site of an engineered P450, followed by recombination of beneficial mutations generated two P450 BM-3 variants that convert a range of terminal alkenes to either (R)- or (S)epoxidc (up to 83 % ee) with high catalytic turnovers (up to 1370) and high epoxidation selectivities (up to 95%). A biocatalytic system using E. coli lysates containing P450 variants as the epoxidation catalysts and in vitro NADPH regeneration by the alcohol dehydrogenase from Thermoanaerobium brockii generates each of the epoxide enantiomers, without additional cofactor.
- Kubo, Takafumi,Peters, Matthew W.,Meinhold, Peter,Arnold, Frances H.
-
p. 1216 - 1220
(2007/10/03)
-
- Hydrolytic kinetic resolution of epoxides catalyzed by chromium(III)-endo, endo-2,5-diaminonorbornane-salen [Cr(III)-DIANANE-salen] complexes. Improved activity, low catalyst loading
-
The hydrolytic kinetic resolution (HKR) of terminal epoxides, using chiral chromium(III)-salen catalysts based on DIANANE (endo,endo-2,5-diaminonorbornane) , was studied. A broad substrate scope was found for the chromium(III)-DIANANE catalysts, and very low loadings (down to 0.05 mol%) were needed to achieve high enantiomeric purities of both the remaining epoxides and the product diols (up to >99% ee). Besides monosubstituted epoxides, 2-methyl-2-n-pentyloxirane, which is an example for 2,2-disubstituted epoxides, could be ring-opened in an asymmetric fashion with water in the presence of an electronically tuned chromium-(III)-DIANANE complex.
- Berkessel, Albrecht,Ertuerk, Erkan
-
p. 2619 - 2625
(2007/10/03)
-