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An Amphiphilic (salen)Co Complex – Utilizing Hydrophobic Interactions to Enhance the Efficiency of a Cooperative Catalyst
An amphiphilic (salen)Co(III) complex is presented that accelerates the hydrolytic kinetic resolution (HKR) of epoxides almost 10 times faster than catalysts from commercially available sources. This was achieved by introducing hydrophobic chains that increase the rate of reaction in one of two ways – by enhancing cooperativity under homogeneous conditions, and increasing the interfacial area under biphasic reaction conditions. While numerous strategies have been employed to increase the efficiency of cooperative catalysts, the utilization of hydrophobic interactions is scarce. With the recent upsurge in green chemistry methods that conduct reactions ‘on water’ and at the oil-water interface, the introduction of hydrophobic interactions has potential to become a general strategy for enhancing the catalytic efficiency of cooperative catalytic systems. (Figure presented.).
Solís-Mu?ana, Pablo,Salam, Joanne,Ren, Chloe Z.-J.,Carr, Bronte,Whitten, Andrew E.,Warr, Gregory G.,Chen, Jack L.-Y.
supporting information
p. 3207 - 3213
(2021/06/01)

Exploring the Biocatalytic Scope of a Novel Enantioselective Halohydrin Dehalogenase from an Alphaproteobacterium
A gene encoding halohydrin dehalogenase from an alphaproteobacterium (AbHHDH) was identified, cloned and over-expressed in Escherichia coli. AbHHDH was able to catalyze the stereoselective dehalogenation of prochiral and racemic halohydrins. It showed the highest enantioselectivity in the dehalogenation of 20?mM (R,S)-2-bromo-1-phenylethanol, which yielded (S)-2-bromo-1-phenylethanol with 99% ee and 34.5% yield. Moreover, AbHHDH catalyzed the azidolysis of epoxides with low to moderate (S)-enantioselectivity. The highest enantioselectivity (E = 18.6) was observed when (R,S)-benzyl glycidyl ether was used as the substrate. A sequential kinetic resolution catalyzed by HHDH was employed for the synthesis of chiral 1-chloro-3-phenoxy-2-propanol. We prepared enantiopure (S)-isomer with a high enantiopurity of ee > 99% and a yield of 30.7% (E-value: 21.3) by kinetic resolution of 20?mM substrate. The (S)-isomer with 99% ee readily obtained from 40 to 150?mM (R,S)-1-chloro-3-phenoxy-2-propanol. Taken together, the results of this study demonstrate the applicability of this HHDH for the production of optically active compounds. [Figure not available: see fulltext.].
Xue, Feng,Ya, Xiangju,Xiu, Yuansong,Tong, Qi,Wang, Yuqi,Zhu, Xinhai,Huang, He
p. 629 - 637
(2019/01/25)

Aromatic donor-acceptor interaction promoted catalyst assemblies for hydrolytic kinetic resolution of epichlorohydrin
Three generations of Co(iii)-salen complexes containing electron-deficient aromatic moieties (acceptors) have been synthesized. When electron-rich aromatic compounds (donors) were introduced, these complexes were designed to form catalyst assemblies through aromatic donor-acceptor interaction. For all three generations of complexes, the addition of a proper donor led to higher catalytic efficiency in the hydrolytic kinetic resolution (HKR) of epichlorohydrin. The reaction rates are in the following order: Generation 3 > Generation 2 > Generation 1. The aromatic donor-acceptor interaction was verified by NMR spectroscopy and UV-vis absorption spectroscopy studies. These results demonstrated that aromatic donor-acceptor interaction can be a valuable driving force in the assembly of supramolecular catalysts.
Blechschmidt, Daniel R.,Woodhouse, Matthew D.,Inagaki, Sebastien,Whitfield, Melita,Ogunsanya, Ayokunnumi,Yoder, Aaron,Lilly, Daniel,Heim, Eric W.,Soucie, Luke N.,Liang, Jian,Liu, Yu
supporting information
p. 172 - 180
(2019/01/04)

Molecular modification of a halohydrin dehalogenase for kinetic regulation to synthesize optically pure (S)-epichlorohydrin
Asymmetric synthesis of chiral epichlorohydrin (ECH) from 1,3-dichloro-2-propanol (1,3-DCP) using halohydrin dehalogenases (HHDHs) is of great value due to the 100% theoretical yield and high enantioselectivity. The vital problem in the asymmetric synthesis is to prepare optically pure ECH. In this study, key amino acid residues located at halide ion channels of HheC (P175S/W249P) (HheCPS) were modified to regulate the kinetic parameters. HheCPS I81W, F86N and V94R were constructed with the corresponding halide ion channels destroyed. The catalytically efficiencies (kcat/Km) of the three mutants exhibited 0.38-, 0.23- and 0.23-fold decrease toward (S)-ECH and the reverse reaction was significantly inhibited. As the results, (S)-ECH was synthesized with >99% enantiomeric excess (e.e.) and 63.42%, 67.08% and 57.01% yields, respectively, under 20 mM 1,3-DCP as substrate. To our knowledge, this is the first investigation of the molecule kinetic modification of HHDHs and also the first report for the biosynthesis of optically pure (S)-ECH from 1,3-DCP using HHDHs.
Zhang, Xiao-Jian,Deng, Han-Zhong,Liu, Nan,Gong, Yi-Chuan,Liu, Zhi-Qiang,Zheng, Yu-Guo
p. 154 - 160
(2019/01/08)

Imido-P(v) trianion supported enantiopure neutral tetrahedral Pd(II) cages
Charge-neutral chiral hosts are attractive due to their ability to recognize a wide range of guest functionalities and support enantioselective processes. However, reports on such charge-neutral cages are very scarce in the literature. Here, we report an enantiomeric pair of tetrahedral Pd(ii) cages built from chiral tris(imido)phosphate trianions and oxalate linkers, which exhibit enantioselective separation capabilities for epichlorohydrin, β-butyrolactone, and 3-methyl- and 3-ethyl cyclopentanone.
Rajasekar, Prabhakaran,Pandey, Swechchha,Paithankar, Harshad,Chugh, Jeetender,Steiner, Alexander,Boomishankar, Ramamoorthy
supporting information
p. 1873 - 1876
(2018/02/23)

Homochiral Metal-Organic Cage for Gas Chromatographic Separations
Metal-organic cages (MOCs) as a new type of porous material with well-defined cavities were extensively pursued because of their relative ease of synthesis and their potential applications in host-guest chemistry, molecular recognition, separation, catalysis, gas storage, and drug delivery. Here, we first reported that a homochiral MOC [Zn3L2] is explored to fabricate [Zn3L2] coated capillary column for high-resolution gas chromatographic separation of a wide range of analytes, including n-alkanes, polycyclic aromatic hydrocarbons, and positional isomers, especially for racemates. Various kinds of racemates such as alcohols, diols, epoxides, ethers, halohydrocarbons, and esters were separated with good enantioselectivity and reproducibility on the [Zn3L2] coated capillary column. The fabricated [Zn3L2] coated capillary column exhibited significant chiral recognition complementary to that of a commercial β-DEX 120 column and our recently reported homochiral porous organic cage CC3-R coated column. The results show that the homochiral MOCs will be very attractive as a new type of chiral selector in separation science.
Xie, Sheng-Ming,Fu, Nan,Li, Li,Yuan, Bao-Yan,Zhang, Jun-Hui,Li, Yan-Xia,Yuan, Li-Ming
p. 9182 - 9188
(2018/07/21)

Asymmetric Hydrolytic and Aminolytic Kinetic Resolution of Racemic Epoxides using Recyclable Macrocyclic Chiral Cobalt(III) Salen Complexes
New chiral macrocyclic cobalt(III) salen complexes were synthesized and used as catalyst for the asymmetric kinetic resolution (AKR) of terminal epoxides and glycidyl ethers with aromatic/aliphatic amines and water as nucleophiles. This is the first occasion where a Co(III) salen complex demonstrated its ability to catalyze AKR as well as hydrolytic kinetic resolution (HKR) reactions. Excellent enantiomeric excesses of the epoxides, the corresponding amino alcohols and diols (upto 99%) with quantitative yields were achieved by using the chiral Co(III) salen complexes in dichloromethane at room temperature. This protocol was further extended for the synthesis of two important drug molecules, i.e., (S)-propranolol and (R)-naftopidil. The catalytic system was also explored for the synthesis of chirally pure diols and chiral cyclic carbonates using carbon dioxide as a greener renewable C1 source. The catalyst was recycled for upto 5 catalytic cycles with retention of enantioselectivity. (Figure presented.).
Tak, Rajkumar,Kumar, Manish,Menapara, Tusharkumar,Gupta, Naveen,Kureshy, Rukhsana I.,Khan, Noor-ul H.,Suresh
supporting information
p. 3990 - 4001
(2017/11/22)

Chiral oligomers of spiro-salencobalt(III)X for catalytic asymmetric cycloaddition of epoxides with CO2
Several new chiral oligomers of spiro-salenCo(III)X (spiro = 1.1′-spirobiindane-7.7′-diol) complexes have been designed, synthesized, and characterized by nuclear magnetic resonance (NMR), infrared (IR), and elemental analyses, in which, the chiral spiro moieties are first introduced into a scaffold of chiral salenCo catalysts. They were used to catalyze the asymmetric cycloaddition of epoxides with carbon dioxide. Under very mild reaction conditions, a kinetic resolution of racemic epoxides with CO2 was smoothly initiated by these chiral oligomer catalysts with good enantioselectivities, which can be attributed to the match effect between chiral backbones of salen and spiro. High stability and easy recyclability are their major advantages.
Zhu, Zhouhe,Zhang, Yuqian,Wang, Kai,Fu, Xiying,Chen, Fengjuan,Jing, Huanwang
p. 50 - 53
(2016/05/10)

Engineering the epoxide hydrolase from Agromyces mediolanus for enhanced enantioselectivity and activity in the kinetic resolution of racemic epichlorohydrin
The biocatalytic production of enantiopure epichlorohydrin (ECH) has been steadily attracting more attention. For industrial applications, it is important to obtain an epoxide hydrolase (EH) that possesses the desired enantioselectivity. Site-saturation and site-directed mutagenesis of the Ser207, Asn240 and Trp182 positions were used to generate variants of EH from Agromyces mediolanus ZJB120203 with enhanced enantioselectivity for the kinetic resolution of racemic ECH. The best variant, VDF (W182F/S207V/N240D), displayed a 7-fold enhanced enantioselectivity toward racemic ECH, with an increase in the enantiomeric ratio value (E value) preferring the (R)-ECH enantiomer from 12.9 of wild-type to 90.0, as well as a 1.7-fold improvement in activity. Furthermore, we successfully applied the created recombinant Escherichia coli whole cells expressing variant VDF in the kinetic resolution of racemic ECH. Enantiopure (S)-ECH could be obtained with an enantiopurity of >99% ee and a yield of 40.5% from 450 mM racemic ECH, which is better than those of other reported EHs. These results demonstrated that the EH obtained in this study could be applied for the efficient resolution of racemic ECH.
Xue, Feng,Liu, Zhi-Qiang,Wan, Nan-Wei,Zhu, Hang-Qin,Zheng, Yu-Guo
p. 31525 - 31532
(2015/04/22)

A One-Step Biocatalytic Process for (S)-4-Chloro-3-hydroxybutyronitrile using Halohydrin Dehalogenase: A Chiral Building Block for Atorvastatin
(S)-4-Chloro-3-hydroxybutyronitrile [(S)-CHBN] was used as a chiral building block for the preparation of atorvastatin. In this study, (R,S)-epichlorohydrin [(R,S)-ECH] and 1,3-dichloro-2-propanol (1,3-DCP) were investigated to prepare (S)-CHBN by using the halohydrin dehalogenase HheC from Agrobacterium radiobacter AD1. Preparing (S)-CHBN from (R,S)-ECH gave a modest enantiomeric excess (ee), whereas by using 1,3-DCP as the substrate, (S)-CHBN was obtained with 97.3 % ee after pH optimization. However, a low ee value and low yield of (S)-CHBN were obtained if the substrate concentration was increased to 10 g L-1. To obtain a higher ee value and yield, 16 mutants were constructed and screened. The variant W249F with improvements in activity and enantioselectivity was identified and applied at a 1,3-DCP loading of 10 g L-1, which gave (S)-CHBN in 86 % yield with 97.5 % ee in 1 h. This is the first report of a one-step biocatalytic process for the preparation of (S)-CHBN from prochiral 1,3-DCP.
Wan, Nan-Wei,Liu, Zhi-Qiang,Xue, Feng,Shen, Zhen-Yang,Zheng, Yu-Guo
p. 2446 - 2450
(2015/08/24)

Dinuclear salen cobalt complex incorporating Y(OTf)3: enhanced enantioselectivity in the hydrolytic kinetic resolution of epoxides
The activation of inactive Jacobsen's chiral salen Co(ii) (salen = N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine) compound is attained by dinuclear chiral salen Co(iii)-OTf complex formation with yttrium triflate. The yttrium metal not only displays a promoting effect on electron transfer, but also assists in forming two stereocentres of a Lewis acid complex with Co(iii)-OTf. We found that the binuclear Co-complex significantly enhanced reactivity and enantioselectivity in the hydrolytic kinetic resolution of terminal epoxides compared to its analogous monomer and kinetic data are also consistent with these results.
Patel, Deepak,Kurrey, Ganesh Ram,Shinde, Sandip S.,Kumar, Pradeep,Kim, Geon-Joong,Thakur, Santosh Singh
p. 82699 - 82703
(2015/10/19)

Efficient synthesis of (S)-epichlorohydrin in high yield by cascade biocatalysis with halohydrin dehalogenase and epoxide hydrolase mutants
Enantioselective biotransformation of prochiral 1,3-DCP by halohydrin dehalogenases (HHDHs) is particularly attractive since 100% yield of chiral epichlorohydrin (ECH) may be obtained. HheC mutant (P175S/W249P) displayed greatly improved enantiomeric excess (ee) of (S)-ECH from 5% to 95.3% in the catalyzed dehalogenation of 1,3-DCP at pH 8.0. (S)-ECH was enantioselectively biotransformed from 40 mM 1,3-DCP with 92.3% ee and 93.2% yield at pH 10.0. To increase the ee of (S)-ECH, the catalysis was carried out using HheC mutant coupled with epoxide hydrolase mutant and the maximum yield and ee of (S)-ECH reached 91.2% and > 99%.
Xue, Feng,Liu, Zhi-Qiang,Wang, Ya-Jun,Zhu, Hang-Qin,Wan, Nan-Wei,Zheng, Yu-Guo
p. 147 - 149
(2015/10/19)

A novel enantioselective epoxide hydrolase from Agromyces mediolanus ZJB120203: Cloning, characterization and application
A new strain Agromyces mediolanus ZJB120203, capable of enantioselective epoxide hydrolase (EH) activity was isolated employing a newly established colorimetric screening and chiral GC analysis method. The partial nucleotide sequence of an epoxide hydrolase (AmEH) gene from A. mediolanus ZJB120203 was obtained by PCR using degenerate primers designed based on the conserved domains of EHs. Subsequently, an open reading frame containing 1167 bp and encoding 388 amino acids polypeptide were identified. Expression of AmEH was carried out in Escherichia coli and purification was performed by Nickel-affinity chromatography. The purified AmEH had a molecular weight of 43 kDa and showed its optimum pH and temperature at 8.0 and 35 C, respectively. Moreover, this AmEH showed broad substrates specificity toward epoxides. In this study, it is demonstrated that the AmEH could unusually catalyze the hydrolysis of (R)-ECH to produce enantiopure (S)-ECH. Enantiopure (S)-ECH could be obtained with enantiomeric excess (ee) of >99% and yield of 21.5% from 64 mM (R,S)-ECH. It is indicated that AmEH from A. mediolanus is an attractive biocatalyst for the efficient preparation of optically active ECH.
Xue, Feng,Liu, Zhi-Qiang,Zou, Shu-Ping,Wan, Nan-Wei,Zhu, Wen-Yuan,Zhu, Qing,Zheng, Yu-Guo
p. 409 - 417
(2014/04/03)

Asymmetric ring opening of terminal epoxides via kinetic resolution catalyzed by chiral (salen)Co mixture
The highly enantioselective hydrolytic kinetic resolution (HKR) of racemic terminal epoxides by bimetallic chiral (salen)Co and (salen)Co(III)-OAc mixture provides a simple and effective method for the synthesis of enantiomerically enriched terminal epoxides (ee > 99%) and diols. At the equimolar amounts of bimetallic chiral (salen)Co and (salen)Co(II)-OAc, the catalytic activity increases more than two times in comparison with (salen)Co(III)-OAc used alone. The mixed catalytic system can be recycled and reused. No significant loss of catalytic activity was observed after three runs.
Jiang, Chengjun
experimental part
p. 691 - 696
(2011/11/30)

Shell cross-linked micelle-based nanoreactors for the substrate-selective hydrolytic kinetic resolution of epoxides
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
supporting information; experimental part
p. 14260 - 14263
(2011/11/05)

Synthesis of chiral epichlorohydrin by chloroperoxidase-catalyzed epoxidation of 3-chloropropene in the presence of an ionic liquid as co-solvent
Asymmetric epoxidation of 3-chloropropene can be catalyzed by chloroperoxidase (CPO) from Caldariomyces fumago to prepare (R)-epichlorohydrin (ECH) in homogenous phosphate buffer/ionic liquid mixtures using t-butyl hydroperoxide (TBHP) as O2 donor. Reaction conditions were optimized by the investigation of the choice of oxidants, the presence of ionic liquids (ILs), pH effect and CPO consumption. The best ECH yield reached 88.8% within a duration of 60 min with high enantiomeric excesses (e.e. 97.1%) at pH 5.5 and room temperature, using 1-ethyl-3-methylimidazolium [EMIM][Br] as co-solvent. The ILs with shorter carbon chain was more efficient on chiral ECH preparation.
Wu, Jinyue,Liu, Chen,Jiang, Yucheng,Hu, Mancheng,Li, Shuni,Zhai, Quanguo
experimental part
p. 727 - 731
(2010/07/06)

Cooperative activation in the hydrolytic kinetic resolution of epoxides by a bis-cobalt(III)salen-calix[4]arene hybrid
A chiral, bimetallic cobalt(III)salen-calix[4]arene hybrid structure was prepared and tested in the hydrolytic kinetic resolution (HKR) of racemic epoxides. Kinetic studies have revealed that the two catalytic units on the upper rim of the calixarene scaffold are able to activate the reactants in a cooperative and primarily intramolecular mode. High enantioselective behaviour was observed and besides, a higher stability was found for the bimetallic catalyst as compared to a monometallic reference complex.
Wezenberg, Sander J.,Kleij, Arjan W.
supporting information; experimental part
p. 85 - 91
(2010/06/21)

Factors influencing recyclability of Co(III)-salen catalysts in the hydrolytic kinetic resolution of epichlorohydrin
The recyclability of Co(III)-salen catalysts, where salen is defined by (R,R)-N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine, for the hydrolytic kinetic resolution (HKR) of racemic epichlorohydrin is a strong function of the counterion of the Co(III)-salen catalyst. The nature of the counterion determines whether the HKR reaction follows primarily a bimetallic or monometallic reaction path, which significantly affects catalyst recyclability. For example, Co(III)-salen initially containing the nucleophilic Cl- counterion catalyzes the HKR of epichlorohydrin according to a bimetallic reaction path but loses activity upon recycle, as Cl- is replaced with OH- during the reaction. In contrast, a Co(III)-salen catalyst containing non-nucleophilic SbF6- counterion catalyzes the reaction according to a monometallic reaction path and is quite stable during multiple recycles, albeit at a low rate with less selectivity. A mixed catalyst system with Co(III)-salen initially containing Cl- to which Co(III)-salen with SbF6- is later added demonstrates high activity and high stability to recycling. Additional experiments with Co(III)-salen initially containing the acetate counterion reveal a progressive decline in activity with multiple recycles even after regeneration with acetic acid between runs, suggesting a destructive role of the regeneration process.
Jain, Surbhi,Venkatasubbaiah, Krishnan,Jones, Christopher W.,Davis, Robert J.
experimental part
p. 8 - 15
(2010/05/01)

NEW CHIRAL SALEN CATALYSTS AND METHODS FOR THE PREPARATION OF CHIRAL COMPOUNDS FROM RACEMIC EPOXIDES BY USING THEM
The present invention relates to new chiral salen catalysts and the preparation method of chiral compounds from racemic epoxides using the same. More specifically, it relates to new chiral salen catalysts that have high catalytic activity due to new molecular structures and have no or little racemization of the generated target chiral compounds even after the reaction is completed and can be also reused without catalyst regeneration treatment, and its economical preparation method to mass manufacture chiral compounds of high optical purity, which can be used as raw materials for chiral food additives, chiral drugs, or chiral crop protection agents, etc., using the new chiral salen catalysts.
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Page/Page column 28

(2009/01/24)

Engineering polymer-enhanced bimetallic cooperative interactions in the hydrolytic kinetic resolution of epoxides
Through systematic variations of the length of oligo(ethylene glycol)-based linkers and the catalyst density of poly(styrene)-supported cobalt-salen catalysts, we have elucidated an optimal catalyst flexibility and density of polymeric Co-salen catalysts for the hydrolytic kinetic resolution (HKR) of racemic terminal epoxides that follows a bimetallic cooperative pathway. The optimized polymeric catalyst brings the two cooperative Co-salen units to a favorable proximity efficiently and hence displays significantly improved catalytic performance in the HKR compared with its monomeric small molecule analogue. Complex Co(5b), representing the most active poly(styrene)-supported HKR catalyst known so far, can effect the resolution of a variety of epoxides to reach ≥ 98 % ee in 6-24 h with a low cobalt loading of 0.01-0.1 mol%.
Zheng, Xiaolai,Jones, Christopher W.,Weck, Marcus
supporting information; experimental part
p. 255 - 261
(2009/04/08)

4(2)-Methoxyphenyl glycerol ethers in the synthesis of nonracemic di-O,O-acylglycerols
Effective methods for the synthesis of nonracemic 4-and 2-methoxyphenyl glycerol ethers from nonracemic 3-chloropropanediols and by direct resolution of the racemate, respectively, were developed. Some existing discrepancies related to the to chiroptical properties of their derivatives were eliminated. Both ethers were used to synthesize nonracemic 3-O-aryloxy-1,2-di-O',O'-palmitoyl glycerols.
Bredikhina,Novikova,Efremov,Sharafutdinova,Bredikhin
experimental part
p. 2320 - 2323
(2010/02/15)

A simple and efficient approach to 1,3-aminoalcohols: application to the synthesis of (+)-negamycin
A short and practical enantioselective synthesis of (+)-negamycin has been achieved in high enantio- and diastereomeric excess using an iterative Jacobsen's hydrolytic kinetic resolution as the key step.
Naidu, S. Vasudeva,Kumar, Pradeep
p. 3793 - 3796
(2008/02/06)

Asymmetric reactions on chiral catalysts entrapped within a mesoporous cage
The encapsulation of homogeneous chiral catalysts, e.g. Co(Salen) and Ru-TsDPEN, in the mesoporous cage of SBA-16 is demonstrated; the encapsulated catalysts show performance as good as that of the homogeneous catalysts, and can be recycled for more than 10 times without significant loss of catalytic performance. The Royal Society of Chemistry.
Yang, Hengquan,Li, Jun,Yang, Jie,Liu, Zhimin,Yang, Qihua,Li, Can
p. 1086 - 1088
(2008/01/03)

Modular approach for the development of supported, monofunctionalized, salen catalysts
We report a modular approach toward polymer-supported, metalated, salen catalysts. This strategy is based on the synthesis of monofunctionalized Mn- and Co-salen complexes attached to a norbornene monomer via a stable phenylene-acetylene linker. The resulting functionalized monomers can be polymerized in a controlled fashion using ring-opening metathesis polymerization. This polymerization method allows for the synthesis of copolymers, resulting in an unprecedented control over the catalyst density and catalytic-site isolation. The obtained polymeric manganese and cobalt complexes were successfully used as supported catalysts for the asymmetric epoxidation of olefins and the hydrolytic kinetic resolution of epoxides. All polymeric catalysts showed outstanding catalytic activities and selectivities comparable to the original catalysts reported by Jacobsen. Moreover, the copolymer-supported catalysts are more active and selective than their homopolymer analogues, providing further proof that catalyst density and site isolation are key toward highly active and selective supported salen catalysts.
Holbach, Michael,Weck, Marcus
p. 1825 - 1836
(2007/10/03)

Poly(styrene)-supported co-salen complexes as efficient recyclable catalysts for the hydrolytic kinetic resolution of epichlorohydrin
Here we describe an unprecedented synthetic approach to poly-(styrene)-supported chiral salen ligands by the free radical polymerization of an unsymmetrical styryl-substituted salen monomer (H2salen = bis(salicylidene)ethylenediamine). The new method allows for the attachment of salen moieties to the polymer main chain in a flexible, pendant fashion, avoiding grafting reactions that often introduce ill-defined species on the polymers. Moreover, the loading of the salen is controlled by the copolymerization of the styryl-substituted salen monomer with styrene in different ratios. The polymeric salen ligands are metallated with cobalt(II) acetate to afford the corresponding supported Co-salen complexes, which are used in the hydrolytic kinetic resolution of racemic epichlorohydrin, exhibiting high reactivity and enantioselectivity. Remarkably, the copolymer-supported Co-salen complexes showed a better catalytic performance (>99% ee, 54 % conversion, one hour) in comparison to the homopolymeric analogues and the small molecule Co-salen complex. The soluble poly(styrene)-supported catalysts were recovered by precipitation after the catalytic reactions and were recycled three times to afford almost identical enantiomeric excesses as the first run, with slightly reduced reaction rates.
Zheng, Xiaolai,Jones, Christopher W.,Weck, Marcus
p. 576 - 583
(2008/09/20)

Synthesis of optically active 2-hydroxy monoesters via-kinetic resolution and asymmetric cyclization catalyzed by heterometallic chiral (salen) Co complex
The binuclear chiral (salen) Co complexes bearing Lewis acids of Al and Ga catalyze regio- and enantioselective ring opening of terminal epoxides with carboxylic acids. The ring opened product of epichlorohydrin with carboxylic acids followed by cyclization step in the presence of catalyst and base represent straightforward, efficient methods for the synthesis of enatiomerically enriched (>99% ee) valuable terminal epoxides. Strong synergistic effects of different Lewis acid of Co-Al and Co-Ga were exhibited in the catalytic process.
Li, Wenji,Thakur, Santosh Singh,Chen, Shu-Wei,Shin, Chang-Kyo,Kawthekar, Rahul B.,Kim, Geon-Joong
p. 3453 - 3457
(2007/10/03)

A new dinuclear chiral salen complexes for asymmetric ring opening and closing reactions: Synthesis of valuable chiral intermediates
A new dinuclear chiral Co(salen) complexes bearing group 13 metals have been synthesized and characterized. The easily prepared complexes exhibited very high catalytic reactivity and enantioselectivity for the asymmetric ring opening of epoxides with H2O, chloride ions and carboxylic acids and consequently provide enantiomerically enriched terminal epoxides (>99% ee). It also catalyzes the asymmetric cyclization of ring opened product, to prepare optically pure terminal epoxides in one step. The homogeneous dinuclear chiral Co(salen) have been covalently immobilized on MCM-41. The potential benefits of heterogenization include facilitation of catalyst separation and recyclability requiring very simple techniques. The system described is very efficient.
Thakur, Santosh Singh,Chen, Shu-Wei,Li, Wenji,Shin, Chang-Kyo,Kim, Seong-Jin,Koo, Yoon-Mo,Kim, Geon-Joong
p. 1862 - 1872
(2007/10/03)

Highly reactive and enantioselective kinetic resolution of terminal epoxides with H2O and HCl catalyzed by new chiral (salen)Co complex linked with Al
The asymmetric hydrolytic kinetic resolution (HKR) of racemic terminal epoxides by new easily synthesized dimeric chiral (salen)Co bearing Al, provides a practical and straightforward method for the synthesis of enantiomerically enriched terminal epoxides (>99% ee) and diols. An inorganic acid, HCl is applied first time for the asymmetric ring opening reaction of terminal epoxides. Reactions are conveniently carried out at room temperature under an air atmosphere.
Thakur, Santosh Singh,Li, Wenji,Kim, Seong-Jin,Kim, Geon-Joong
p. 2263 - 2266
(2007/10/03)

KINETIC RESOLUTION METHOD
A method for stereoselective chemical synthesis, includes the steps of: (A) reacting a nucleophile and a chiral or prochiral cyclic substrate, said substrate comprising a carbocycle or a heterocycle having a reactive center susceptible to nucleophilic attack by the nucleophile, in the presence of a chiral non-racemic catalyst to produce a product mixture comprising a stereoisomerically enriched product wherein the product mixture further comprises a catalyst residue, at least a portion of the catalyst residue is in a first oxidation state, and the catalyst residue in the first oxidation state is active in catalyzing degradation of the stereoisomerically enriched product, and (B) chemically or electrochemically changing the oxidation state of the catalyst residue form the first oxidation state to a second oxidation state, wherein catalyst residue in the second oxidation state is less active in catalyzing degradation of the stereoisomerically enriched product than is catalyst residue in the first oxidation state. The method reduces erosion of the chiral purity of the stereoisomerically enriched product and reduces the chemical transformation to side products of the stereoisomerically enriched product and co-product(s). The deactivated catalyst is recoverable and recyclable.
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(2010/02/06)

Enzymatic dynamic kinetic resolution of epihalohydrins
The haloalcohol dehalogenase from Agrobacterium radiobacter AD1 catalyses the reversible ring closure of vicinal haloalcohols to produce epoxides and halides. In the ring opening of epoxides, nonhalide nucleophiles such as N 3- are accepted. The enantioselective irreversible ring opening of an epihalohydrin by N3-, combined with racemisation caused by a reversible ring opening by a halide, resulted in an enzymatic dynamic kinetic resolution yielding optically active (S)-1-azido-3-halo-2-propanol. With epichlorohydrin as a substrate, the rate of ring opening by N3- was higher than the rate of racemisation, resulting in a mixed kinetic resolution and dynamic kinetic resolution. With epibromohydrin as the substrate, the racemisation rate was higher than the rate of ring opening, resulting in an efficient dynamic kinetic resolution. By optimising the pH of the medium and the concentrations of N 3- and Br-, the product (S)-1-azido-3-bromo-2- propanol could be obtained in 84% yield and 94% ee. An (R)-enantiomer selective ring closure of this bromoalcohol, catalysed by the same enzyme, caused a simultaneously occurring kinetic resolution, yielding when the conversion progressed, an increase in enantiopurity of (S)-1-azido-3-bromo-2-propanol to >99% ee with a yield of 77%. This compound and the ring-closed product glycidyl azide can be used as chiral synthetic building blocks.
Lutje Spelberg, Jeffrey H.,Tang, Lixia,Kellogg, Richard M.,Janssen, Dick B.
p. 1095 - 1102
(2007/10/03)

Mechanistic Investigation Leads to a Synthetic Improvement in the Hydrolytic Kinetic Resolution of Terminal Epoxides
The mechanism of the hydrolytic kinetic resolution (HKR) of terminal epoxides was investigated by kinetic analysis using reaction calorimetry. The chiral (salen)Co-X complex (X = OAc, OTs, Cl) undergoes irreversible conversion to (salen)Co-OH during the course of the HKR and thus serves as both precatalyst and cocatalyst in a cooperative bimetallic catalytic mechanism. This insight led to the identification of more active catalysts for the HKR of synthetically useful terminal epoxides. Copyright
Nielsen, Lars P. C.,Stevenson, Christian P.,Blackmond, Donna G.,Jacobsen, Eric N.
p. 1360 - 1362
(2007/10/03)

Commercialization of the hydrolytic kinetic resolution of racemic epoxides: Toward the economical large-scale production of enantiopure epichlorohydrin
The hydrolytic kinetic resolution of racemic terminal epoxides utilizing chiral (salen)Co(III) catalysts provides practical access to enantiopure epoxides and diols. However, general issues surrounding catalyst activation combined with the specific problem of racemization of epichlorohydrin served to make the large-scale production of (R)- or (S)-epichlorohydrin difficult and uneconomical. A process for the large-scale production and isolation of active (salen)Co(III)OAc catalyst and a method of catalyst reduction after reaction using ascorbic acid have been developed to overcome these issues.
Larrow, Jay F.,Hemberger, Karl E.,Jasmin, Serge,Kabir, Hocine,Morel, Phillipe
p. 3589 - 3592
(2007/10/03)

Highly selective hydrolytic kinetic resolution of terminal epoxides catalyzed by chiral (salen)CoIII complexes. Practical synthesis of enantioenriched terminal epoxides and 1,2-diols
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.
p. 1307 - 1315
(2007/10/03)

Highly enantioselective resolution of terminal epoxides using polymeric catalysts
Poly-salen-Co(III) complexes were employed in the hydrolytic kinetic resolution (HKR) of terminal epoxides and ee's up to 98% were obtained. In the HKR of epichlorohydrin, the polymeric catalysts can be recovered and modified for recycling. The recovered
Song, Yuming,Yao, Xiaoquan,Chen, Huilin,Bai, Changmin,Hu, Xinquan,Zheng, Zhuo
p. 6625 - 6627
(2007/10/03)

Hydrolytic kinetic resolution of terminal epoxides catalyzed by fluorous chiral Co(salen) complexes
Cobalt complexes of fluorous chiral salen ligands have been synthesized and tested as catalysts in the hydrolytic kinetic resolution of terminal epoxides. Whereas the activity of heavily fluorinated complexes was found to be rather low, a 'light fluorous' complex was shown to be an efficient and highly selective catalyst for this asymmetric ring-opening reaction. Several strategies for the isolation of reaction products and the recovery of the fluorous catalyst are also discussed.
Cavazzini, Marco,Quici, Silvio,Pozzi, Gianluca
p. 3943 - 3949
(2007/10/03)

Highly active oligomeric (salen)Co catalysts for asymmetric epoxide ring-opening reactions
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Ready,Jacobsen
p. 2687 - 2688
(2007/10/03)

Distannoxane-catalyzed selective acetylation of 3-chloropropane-1,2- diol: A convenient synthesis of enantiopure epichlorohydrin
A distannoxane catalyst effects exclusive acetylation of the primary alcohol of 3-chloropropane-1,2-diol. This reaction provides a convenient access to enantiopure epichlorohydrin.
Orita, Akihiro,Ito, Toshihide,Yasui, Yutaka,Otera, Junzo
p. 1927 - 1929
(2007/10/03)

Total synthesis of muconin by efficient assembly of chiral building blocks
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Schaus, Scott E.,Branalt, Jonas,Jacobsen, Eric N.
p. 4876 - 4877
(2007/10/03)

Practical access to highly enantioenriched c-3 building blocks via hydrolytic kinetic resolution
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Furrow, Michael E.,Schaus, Scott E.,Jacobsen, Eric N.
p. 6776 - 6777
(2007/10/03)

Enantioselective hydrolysis of aryl, alicyclic and aliphatic epoxides by Rhodotorula glutinis
Enantioselective epoxide hydrolysis by yeasts has been demonstrated for the hydrolysis of several aryl, alicyclic and aliphatic epoxides by a strain of Rhodotorula glutinis. High enantioselectivity was obtained in the hydrolysis of methyl substituted aryl and aliphatic epoxides whereas selectivity towards terminal epoxides in all cases was lower. Homochiral vicinal diols were formed from several methyl substituted epoxides and also from meso epoxides. Kinetic resolution of trans-1-phenyl-1,2-epoxypropane was studied in more detail.
Weijers, Carel A. G. M.
p. 639 - 647
(2007/10/03)

Cardiotonics
Method for prophylaxis and treatment of heart diseases using a carbostyril derivative of formula: STR1 wherein R1 is H or CN, and R2 and R3 are each H, alkyl optionally substituted by OH, cycloalkyl, alkenyl, phenyl, phenylalkyl having optionally substituents of alkoxyalkoxy, halogen, alkoxy, NO2, alkyl, CN, alkylthio or alkylsulfinyl on phenyl ring and having optionally OH-substituent on alkyl moiety, phenylsulfonylalkyl having optionally alkoxy substituent on phenyl ring, phenylthioalkyl, phenylsulfinylalkyl having optionally substituents of halogen or alkoxy on phenyl ring, phenoxyalkyl having optionally substituents of halogen or alkoxy on phenyl ring, pyridylalkyl having optionally substituents of halogen or alkoxy on pyridine ring, thienylalkyl, benzoylalkyl, anilinothiocarbonyl, benzoyl, pyridyl, phenylalkenyl, or group of --A-NR4 R5 (R4 and R5 are each alkyl or phenyl having optionally substituents of halogen or alkoxy on phenyl ring, and A is alkylene which may be interrupted with O), and a salt thereof, and novel carbostyril derivatives, and pharmaceutical composition for prophylaxis and treatment of heart diseases containing said novel carbostyril derivative.
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(2008/06/13)

Attempted Kinetic Resolution of 1,2-Diols by Camphorquinone: Generation of (R)-(Chloromethyl)oxirane
The epichlorohydrin (R)-(chloromethyl)oxirane has been prepared from rac-3-chloropropane-1,2-diol by means of the chiral ketone D-camphorquinone (1,7,7-trimethylbicycloheptane-2,3-dione).These reactions lead to intermediate dioxolanes which can be converted directly into oxiranes.This conversion was effected by reduction of the C-2-ketone of the dioxolane intermediate with sodium borohydride prior to reaction with hydrogen bromide-acetic acid followed by treatment of the resulting acetoxy bromide with sodium ethane-1,2-diolate.The diastereoselective formation of other dioxolanes was also investigated by reaction of D-camphorquinone with ethane-1,2-diol, propane-1,2-diol, and 3,3-dimethylbutane-1,2-diol.
Ellis, Martin K.,Golding, Bernard T.,Maude, Antony B.,Watson, William P.
p. 747 - 755
(2007/10/02)

A Convenient Chemoenzymatic Synthesis of (R)- and (S)-(Chloromethyl)oxirane
(R)- and (S)-1-Chloro-3-tosyloxypropan-2-ol have been prepared by biocatalysed enantioselective esterification in hexane, and in turn could be readily converted into optically active (chloromethyl)oxirane in high yield.
Chen, Ching-Shih,Liu, Yeuk-Chuen,Marsella, Michael
p. 2559 - 2561
(2007/10/02)

A NEW APPROACH TO 1,7-DIOXASPIROUNDEC-4-ENES VIA METALLATED ALLENOL ETHERS. SYNTHESIS OF LACRIMIN A.
Key steps in the first total synthesis of Lacrimin A (2) include (a) the use of methoxyallene as an enone-1,3-dianion equivalent; (b) the use of a new copper-catalysed migratory insertion reaction to construct a tri-substituted alkene stereoselectively; and (c) the use of a Pd(0)-catalysed coupling reaction to generate an isochromanone ring.
Takle, Andrew,Kocienski, Philip
p. 4503 - 4516
(2007/10/02)

A CHEMOENZYMATIC ACCESS TO OPTICALLY ACTIVE 1,2-EPOXIDES
Lipase-catalyzed transacylation in organic media was employed to produce optically active α-hydroxy tosylate which could be readily converted to the corresponding 1,2-epoxides with high optical purity.
Chen, Ching-Shih,Liu, Yeuk-Chuen
p. 7165 - 7168
(2007/10/02)

Ethylene biosynthesis. Synthesis and study of racemic, (1R,2S)-, and (1S,2R)-1-amino-2-(hydroxymethyl)cyclopropanecarboxylic acid
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Pirrung,Dunlap,Trinks
p. 1301 - 1310
(2007/10/02)

Preparative Production of Optically Active Esters and Alcohols Using Esterase-Catalyzed Stereospecific Transesterification in Organic Media
A novel enzymatic approach to the production of optically active alcohols and esters from racemates is developed.It involves the use of esterase catalyzed transesterifications carried out in biphasic aqueous-organic mixtures.Water-insoluble substrates constitute the organic phase, while the enzyme is located in the aqueous phase.Since the fraction of the latter phase can be made very low, such an arrangement solves the problem of both the competition of an alcohol (the nucleophile) with water in the enzymatic reaction and poor solubility of most organic esters and alcohols in water.By use of porous supports (Sepharose or Chromosorb) filled with aqueous solutions of hog liver carboxyl esterase as a stereoselective catalyst and methyl propionate as a matrix ester, the following optically active alcohols and their propionic esters were produced on a preparative scale: 3-methoxy-1-butanol, 3-methyl-1-pentanol, 3,7-dimethyl-1-octanol, and β-citronellol.To overcome a rather narrow substrate specificity of hog liver carboxyl esterase, a nonspecific lipase from yeast (Candida cylindracea) also was employed as a stereoselective transesterification catalyst.Using an aqueous solution of this enzyme confined to the pores of Chromosorb and tributyrin as a matrix ester, we have prepared gram amounts of the following optically active alcohols and their butyric esters: 2-butanol, sec-phenethyl alcohol, 2-octanol, 1-chloro-2-propanol and 2,3-dichloro-1-propanol (subsequently nonenzymatically converted to optically active propylene oxide and epichlorohydrin, respectively), 6-methyl-5-hepten-2-ol, and 1,2-butanediol.
Cambou, Bernard,Klibanov, Alexander M.
p. 2687 - 2692
(2007/10/02)

Kinetic Resolution of 1,2-Diols with D-Camphorquinone; Preparation of (R)-(Chloromethyl)oxirane
Acid-catalysed reaction of D-camphorquinone with racemic 1,2-diols (e.g. 3-chloropropane-1,2-diol) under kinetically controlled conditions yields a predominant diastereoisomeric acetal, that can be easily converted into an optically pure epoxide.
Ellis, Martin K.,Golding, Bernard T.,Watson, William P.
p. 1600 - 1602
(2007/10/02)

Preparation of epihalohydrin enantiomers
Processes for preparing (S) or (R) epihalohydrin and an (S) substituted glycerol intermediate are disclosed.
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(2008/06/13)