Journal articles: 'Chiral Substrates'

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Matthews, Jermey N. A. "Shedding light on chiral substrates." Physics Today 64, no. 11 (November 2011): 19. http://dx.doi.org/10.1063/pt.3.1320.

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Coscolín, Cristina, Mónica Martínez-Martínez, Jennifer Chow, Rafael Bargiela, Antonio García-Moyano, Gro Bjerga, Alexander Bollinger, et al. "Relationships between Substrate Promiscuity and Chiral Selectivity of Esterases from Phylogenetically and Environmentally Diverse Microorganisms." Catalysts 8, no. 1 (January 5, 2018): 10. http://dx.doi.org/10.3390/catal8010010.

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Substrate specificity and selectivity of a biocatalyst are determined by the protein sequence and structure of its active site. Finding versatile biocatalysts acting against multiple substrates while at the same time being chiral selective is of interest for the pharmaceutical and chemical industry. However, the relationships between these two properties in natural microbial enzymes remain underexplored. Here, we performed an experimental analysis of substrate promiscuity and chiral selectivity in a set of 145 purified esterases from phylogenetically and environmentally diverse microorganisms, which were assayed against 96 diverse esters, 20 of which were enantiomers. Our results revealed a negative correlation between substrate promiscuity and chiral selectivity in the evaluated enzymes. Esterases displaying prominent substrate promiscuity and large catalytic environments are characterized by low chiral selectivity, a feature that has limited commercial value. Although a low level of substrate promiscuity does not guarantee high chiral selectivity, the probability that esterases with smaller active sites possess chiral selectivity factors of interest for industry (>25) is significantly higher than for promiscuous enzymes. Together, the present study unambiguously demonstrates that promiscuous and selective esterases appear to be rare in nature and that substrate promiscuity can be used as an indicator of the chiral selectivity level of esterases, and vice versa.

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Ferraccioli, Raffaella. "Progress on the Stereoselective Synthesis of Chiral Molecules Based on Metal-Catalyzed Dynamic Kinetic Resolution of Alcohols with Lipases." Symmetry 13, no. 9 (September 19, 2021): 1744. http://dx.doi.org/10.3390/sym13091744.

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Metal/lipase-combo catalyzed dynamic kinetic resolution (DKR) of racemic chiral alcohols is a general and practical process to obtain the corresponding enantiopure esters R with quantitative conversion. The use of known Ru-catalysts as well as newly developed homogeneous and heterogeneous metal catalysts (Fe, V) contributed to make the DKR process more sustainable and to expand the substrate scope of the reaction. In addition to classical substrates, challenging allylic alcohols, tertiary alcohols, C1-and C2-symmetric biaryl diols turned out to be competent substrates. Synthetic utility further emerged from the integration of this methodology into cascade reactions leading to linear/cyclic chiral molecules with high ee through the formation of multiple bonds, in a one-pot procedure.

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Mu, Xiaojing, Xiaoqi Yi, Shangyou Xiao, Chengshan Wang, Gang Chen, and Yan Li. "Substrates for Paraoxonase." Current Pharmaceutical Design 24, no. 5 (May 2, 2018): 615–27. http://dx.doi.org/10.2174/1381612824666171213102310.

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Background: Paraoxonase (PON) is a family of calcium-dependent hydrolases, which is related to many diseases. Elucidation of PON physiological roles, active center and all applications in medical fields are dependent on its substrates. Objective: The reports about PON substrates scattered in a long span of period are collected to afford clue for drug design, diagnosis of PON status and other academic purposes. Method: PON substrates from 133 references are classified and compared. Structurally, PON substrates are generally classified as organic phosphorous esters, lactones and arylesters. Some phosphoramidates, organophosphorous obidoximes, aryl carboxylic acid amides and special fatty alcohol esters as PON substrates are also included. Results: The electron nature, steric hindrance and hydrophilicity of substrate substituents affecting the PON catalytic ability, binding ability and specificities are discussed. Drugs, prodrugs and naturally endogenous molecules in life processes activated or inactivate by PON are reviewed. Interestingly, some organophosphate and lactone substrates are preferably hydrolyzed by one of the PON1R192Q allozymes, and such a substrate is generally essential for differentiating the three PON1192R phenotypes by using a dual-substrate method. Intricately, some chiral substrates are hydrolyzed by PON stereoselectively. Conclusion: As more substrates are synthesized and characterized, more facts about PON structure and catalytic properties (including PON active center and catalytic mechanism) will be revealed, and therefore the use of PON as a drug target or as an accurate disease marker will be achieved.

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Recchimurzo, Alessandra, Federica Balzano, Gloria Uccello Barretta, Luca Gherardi, Milo Malanga, and Federica Aiello. "Silylated-Acetylated Cyclodextrins as Chiral Sensors for the Enantiodiscrimination of Fluorinated Anesthetics." Molecules 28, no. 6 (March 20, 2023): 2804. http://dx.doi.org/10.3390/molecules28062804.

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Silylated-acetylated cyclodextrin (CD) derivatives have recently been investigated, via nuclear magnetic resonance (NMR) spectroscopy, as chiral sensors for substrates that are endowed and devoid of fluorine atoms, and the importance of Si-F interaction in the discrimination phenomena has been assessed. Here, the contributions of both superficial interactions and inclusion processes were further evaluated by extending the records to other chiral fluorinated substrates of interest for pharmaceutical applications. Non-equivalences were measured for both the 1H and 19F resonances in equimolar mixtures with the CDs; the promising results also supported the use of chiral sensors in sub-stoichiometric amounts. Finally, the occurrence of inclusion processes was evaluated by analyzing the intermolecular dipolar interactions by means of ROESY (Rotating-frame Overhauser Enhancement Spectroscopy) experiments. The study confirmed that the γCD derivative is the best chiral solvating agent for the fluorinated substrates investigated, likely due to the higher number of silyl moieties that can be involved in Si-F interactions. The contribution of inclusion processes to the enantiodiscrimination was also confirmed by comparison with the α- and β-analogues. Overall, the CD derivatives proved to be able to discriminate fluorinated substrates even when used in sub-stoichiometric amounts.

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Bhaskararao, Bangaru, and Raghavan B. Sunoj. "Two chiral catalysts in action: insights into cooperativity and stereoselectivity in proline and cinchona-thiourea dual organocatalysis." Chemical Science 9, no. 46 (2018): 8738–47. http://dx.doi.org/10.1039/c8sc03078b.

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Increasing use of two chiral catalysts in cooperative asymmetric catalysis in recent years raises some fundamental questions on chiral compatibility between the catalysts, modes of activation, and relative disposition of substrates within the chiral environment of the catalysts for effective asymmetric induction.

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Librizzi, Paulina, Aneek Biswas, Roger Chang, Xiang-Tian Kong, Matthew Moocarme, Gaurav Ahuja, Ilona Kretzschmar, and Luat T. Vuong. "Broadband chiral hybrid plasmon modes on nanofingernail substrates." Nanoscale 12, no. 6 (2020): 3827–33. http://dx.doi.org/10.1039/c9nr07394a.

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Inverted glancing angle deposition produces closely-spaced, out-of-plane structures around apertures. These nanofingernails exhibit chiral hybrid multi-polar modes, tilted Poynting vector power flows, and hotspots that depend on illuminating circular-polarization handedness.

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8

Müller, Christiane, and Thorsten Bach. "Chirality Control in Photochemical Reactions: Enantioselective Formation of Complex Photoproducts in Solution." Australian Journal of Chemistry 61, no. 8 (2008): 557. http://dx.doi.org/10.1071/ch08195.

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In recent years, new methods have been developed that allow for the photochemical formation of enantiomerically pure or enantiomerically enriched compounds in solution. Major strategies presented in this review rely on the use of chiral complexing agents either in a supermolecular assembly or in a defined 1:1 substrate-template complex. In addition, organocatalytic approaches and a chirality transfer from inherently chiral substrates obtained by spontaneous crystallization are discussed. Synthetic applications show that the area of enantioselective photochemistry has left the state of infancy and is about to become a mature but continuously challenging area of modern chemistry.

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Pozar, D. M. "Microstrip antennas and arrays on chiral substrates." IEEE Transactions on Antennas and Propagation 40, no. 10 (1992): 1260–63. http://dx.doi.org/10.1109/8.182462.

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Sukenik, Nir, Francesco Tassinari, Shira Yochelis, Oded Millo, Lech Tomasz Baczewski, and Yossi Paltiel. "Correlation between Ferromagnetic Layer Easy Axis and the Tilt Angle of Self Assembled Chiral Molecules." Molecules 25, no. 24 (December 20, 2020): 6036. http://dx.doi.org/10.3390/molecules25246036.

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The spin–spin interactions between chiral molecules and ferromagnetic metals were found to be strongly affected by the chiral induced spin selectivity effect. Previous works unraveled two complementary phenomena: magnetization reorientation of ferromagnetic thin film upon adsorption of chiral molecules and different interaction rate of opposite enantiomers with a magnetic substrate. These phenomena were all observed when the easy axis of the ferromagnet was out of plane. In this work, the effects of the ferromagnetic easy axis direction, on both the chiral molecular monolayer tilt angle and the magnetization reorientation of the magnetic substrate, are studied using magnetic force microscopy. We have also studied the effect of an applied external magnetic field during the adsorption process. Our results show a clear correlation between the ferromagnetic layer easy axis direction and the tilt angle of the bonded molecules. This tilt angle was found to be larger for an in plane easy axis as compared to an out of plane easy axis. Adsorption under external magnetic field shows that magnetization reorientation occurs also after the adsorption event. These findings show that the interaction between chiral molecules and ferromagnetic layers stabilizes the magnetic reorientation, even after the adsorption, and strongly depends on the anisotropy of the magnetic substrate. This unique behavior is important for developing enantiomer separation techniques using magnetic substrates.

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Miyabe, Hideto, Ryuta Asada, and Yoshiji Takemoto. "Cascade radical reaction of substrates with a carbon–carbon triple bond as a radical acceptor." Beilstein Journal of Organic Chemistry 9 (June 13, 2013): 1148–55. http://dx.doi.org/10.3762/bjoc.9.128.

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The limitation of hydroxamate ester as a chiral Lewis acid coordination moiety was first shown in an intermolecular reaction involving a radical addition and sequential allylation processes. Next, the effect of hydroxamate ester was studied in the cascade addition–cyclization–trapping reaction of substrates with a carbon–carbon triple bond as a radical acceptor. When substrates with a methacryloyl moiety and a carbon–carbon triple bond as two polarity-different radical acceptors were employed, the cascade reaction proceeded effectively. A high level of enantioselectivity was also obtained by a proper combination of chiral Lewis acid and these substrates.

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Klyuev, Dmitriy, Anatoly Neshcheret, Oleg Osipov, and Aleksandr Potapov. "Mathematical Modeling of Multi-Element Antenna Arrays with Chiral Metamaterials Substrates Using Singular Integral Equations." EPJ Web of Conferences 224 (2019): 02002. http://dx.doi.org/10.1051/epjconf/201922402002.

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In this paper, a physical model of the multi-element antenna arrays (MEAA) has been considered and a self-consistent numerical method for solving the problem of current distribution on the MEAA surface with chiral metamaterials substrate has been proposed. The algorithm of the input admittance matrix elements for chiral layer based on the conductive left and right-handed helices has been developed and elements of the matrix surface impedances for investigated structures have been found. A set of singular integral equations with a Cauchy kernel for calculating the current density on the surface of the MEAA has been derived. A numerical solution of the set is a well-posed in the sense of Hadamard. Calculations of current distribution on the MEAA surface, impedance characteristics of a three-element antenna array and the dependence of the isolation levels between emitters on the chirality parameter have been performed and analysed. It has been shown that the use of chiral substrates can substantially increase the isolation between emitters.

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Бузова, М. А., Д. С. Клюев, М. А. Минкин, А. М. Нещерет, and Ю. В. Соколова. "Решение электродинамической задачи для микрополосковой излучающей структуры с киральной подложкой." Письма в журнал технической физики 44, no. 11 (2018): 80. http://dx.doi.org/10.21883/pjtf.2018.11.46200.17147.

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AbstractWe present a solution of the electrodynamic problem for a microstrip radiating structure with a substrate of a chiral metamaterial using the singular integral representation of the field, which in turn is reduced to a singular integral equation with the Cauchy-type singularity relative to the longitudinal component of the surface current density. Graphs of the current distribution for different types of substrates and the chirality parameters of a substrate are given.

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14

Kamlar, Martin, Jan Vesely, and Ramon Rios Torres. "ChemInform Abstract: Diastereoselective Pauson-Khand Reaction Using Chiral Pool Techniques (Chiral Substrates)." ChemInform 44, no. 18 (April 11, 2013): no. http://dx.doi.org/10.1002/chin.201318269.

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15

Xue, Ya-Ping, Cheng-Hao Cao, and Yu-Guo Zheng. "Enzymatic asymmetric synthesis of chiral amino acids." Chemical Society Reviews 47, no. 4 (2018): 1516–61. http://dx.doi.org/10.1039/c7cs00253j.

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Trushin O.S., Fattakhov I.S., Popov A.A., Mazaletsky L.A., Lomov A.A., Zakharov D.M., Gaidukasov R.A., Miakonkikh A.V., and Shendrikova L.A. "Tailoring magnetic anisotropy and optical characteristics of nanostructural Co films by oblique angle deposition." Physics of the Solid State 65, no. 6 (2023): 953. http://dx.doi.org/10.21883/pss.2023.06.56107.16h.

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Thin Co films on inclined Si(001) substrates were obtained by electron-beam evaporation. It has been established that at angles of incidence of the evaporated material on the substrate of more than 80o (oblique angle deposition), arrays of free-standing Co nanocolumns with a cross section of 25 nm and an aspect ratio (length/transverse size) of at least 15 are formed on the substrate surface. In this case, the magnetic easy axis of the film is oriented along the axis of the nanocolumns, which leads to the appearance of a normal component of the magnetization vector to the film surface. When the substrate rotation is turned on, an array of nanospirals is formed. With a fast rotation of the substrate (30 rpm), the magnetic easy axis approaches the normal to the film surface. At a slow substrate rotation (0.6 pm), an array of nanocoils is formed, imparting pronounced chiral properties to the film. Keywords: nanostructuring, thin films, oblique angle deposition, chiral structures.

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17

Adamčíková, Ľubica, Katarína Kučárová, and Peter Ševčík. "The Belousov-Zhabotinskii Oscillatory Reaction Involving Some Organic Chiral Substrates." Collection of Czechoslovak Chemical Communications 62, no. 5 (1997): 739–45. http://dx.doi.org/10.1135/cccc19970739.

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Oscillatory systems of the Belousov-Zhabotinskii (BZ) type were studied using the following substrates: D-gluconic and D-galactonic acids, their lactones, and D-glucose and D-galactose. The systems were either nitrogen purged or left undisturbed. It is suggested that during the induction period (IP), reactions occur giving rise to the active substrate in the BZ system which need not be identical with the organic substance with which the oscillatory system starts up. A special dependence of the IP on sulfuric acid concentration was measured, exhibiting a minimum and a maximum; the dependence on perchloric acid concentration displayed a minimum.

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Miyaji, Ryota, Yuuki Wada, Akira Matsumoto, Keisuke Asano, and Seijiro Matsubara. "Bifunctional organocatalysts for the asymmetric synthesis of axially chiral benzamides." Beilstein Journal of Organic Chemistry 13 (August 2, 2017): 1518–23. http://dx.doi.org/10.3762/bjoc.13.151.

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Bifunctional organocatalysts bearing amino and urea functional groups in a chiral molecular skeleton were applied to the enantioselective synthesis of axially chiral benzamides via aromatic electrophilic bromination. The results demonstrate the versatility of bifunctional organocatalysts for the enantioselective construction of axially chiral compounds. Moderate to good enantioselectivities were afforded with a range of benzamide substrates. Mechanistic investigations were also carried out.

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Ito, Hajime, Shinichiro Ito, Yusuke Sasaki, Kou Matsuura, and Masaya Sawamura. "Copper-catalyzed substitution of allylic carbonates with diboron: A new approach to allylboronate synthesis." Pure and Applied Chemistry 80, no. 5 (January 1, 2008): 1039–45. http://dx.doi.org/10.1351/pac200880051039.

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Copper-catalyzed γ-selective substitution of allylic carbonates with diboron provides a new method for the efficient synthesis of allylboronates. Optically active α-chiral allylboronates were synthesized through the reaction of chiral allylic carbonates with bis(pinacolato)diboron in the presence of achiral Cu(I)-catalyst with highly efficient chirality transfer. Additionally, in the presence of a chiral Cu(I) catalyst, optically active α-chiral allylboronates were obtained with >90 % ee through the reaction of prochiral substrates with the diboron.

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20

Cetin, Adnan. "Chiral Catalysts Utilized in the Nucleophilic Addition of Dialkyl-zinc Reagents to Carbonyl Compounds." Letters in Organic Chemistry 17, no. 8 (August 18, 2020): 571–85. http://dx.doi.org/10.2174/1570178617666191220145038.

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The aim of this review is an overview of diverse dialkyl zinc pro-chiral aldehydes addition reactions. One way of conducting asymmetric reactions is through the use of chiral catalyst. Therefore, new chiral ligands have attracted considerable attention in organic chemistry. Carbon-carbon bond formation reactions are an active research topic. The addition of dialkyl zinc to pro-chiral aldehydes is one of these popular reactions. Also, the chiral amino alcohols are important substrates for drug synthesis. These chiral ligands can be prepared by a simple synthetic way from easily accessible starting materials. This article reviews current catalyst reactions with the addition of dialkyl zinc to carbonyl compounds.

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Basavaiah, D., V. V. L. Gowriswari, P. K. S. Sarma, and P. Dharma Rao. "Chiral acrylates as substrates in baylis-hillman reaction." Tetrahedron Letters 31, no. 11 (January 1990): 1621–24. http://dx.doi.org/10.1016/0040-4039(90)80033-i.

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22

Sheng, X. Q., and E. K. N. Yung. "Analysis of microstrip antennas on finite chiral substrates." International Journal of RF and Microwave Computer-Aided Engineering 14, no. 1 (2003): 49–56. http://dx.doi.org/10.1002/mmce.10115.

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23

Zhang, Mingliang, Victor Pacheco-Peña, Yao Yu, Wenxiang Chen, Nicholas J. Greybush, Aaron Stein, Nader Engheta, Christopher B. Murray, and Cherie R. Kagan. "Nanoimprinted Chiral Plasmonic Substrates with Three-Dimensional Nanostructures." Nano Letters 18, no. 11 (September 26, 2018): 7389–94. http://dx.doi.org/10.1021/acs.nanolett.8b03785.

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Bakonyi, Daniel, Christine Toelzer, Michael Stricker, Werner Hummel, Karsten Niefind, and Harald Gröger. "Expanding the Application Range of Microbial Oxidoreductases by an Alcohol Dehydrogenase from Comamonas testosteroni with a Broad Substrate Spectrum and pH Profile." Catalysts 10, no. 11 (November 4, 2020): 1281. http://dx.doi.org/10.3390/catal10111281.

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Alcohol dehydrogenases catalyse the conversion of a large variety of ketone substrates to the corresponding chiral products. Due to their high regio- and stereospecificity, they are key components in a wide range of industrial applications. A novel alcohol dehydrogenase from Comamonas testosteroni (CtADH) was identified in silico, recombinantly expressed and purified, enzymatically and biochemically investigated as well as structurally characterized. These studies revealed a broad pH profile and an extended substrate spectrum with the highest activity for compounds containing halogens as substituents and a moderate activity for bulky–bulky ketones. Biotransformations with selected ketones—performed with a coupled regeneration system for the co-substrate NADPH—resulted in conversions of more than 99% with all tested substrates and with excellent enantioselectivity for the corresponding S-alcohol products. CtADH/NADPH/substrate complexes modelled on the basis of crystal structures of CtADH and its closest homologue suggested preliminary hints to rationalize the enzyme’s substrate preferences

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Adam, M., C. Damblon, B. Plaitin, L. Christiaens, and J. M. Frère. "Chromogenic depsipeptide substrates for β-lactamases and penicillin-sensitive dd-peptidases." Biochemical Journal 270, no. 2 (September 1, 1990): 525–29. http://dx.doi.org/10.1042/bj2700525.

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Various ester and thioester derivatives of hippuric acid have been prepared which were substrates of both beta-lactamases and DD-peptidases. The thioesters were more rapidly hydrolysed by nearly all the enzymes. Surprisingly, the enzymes acted rather efficiently on substrates which did not contain any chiral centre.

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Jain, Nilesh, Ravi B. Patel, and Ashutosh V. Bedekar. "Modified Kagan's amide: synthesis and application as a chiral solvating agent for hydrogen-bonding based chiral discrimination in NMR." RSC Advances 5, no. 57 (2015): 45943–55. http://dx.doi.org/10.1039/c5ra06959a.

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A modified Kagan's amide, N-((S)-1-(3,5-bis(trifluoromethyl)phenyl)ethyl)-3,5-dinitrobenzamide has been designed, synthesized and screened as a Chiral Solvating Agent for discrimination of optically active substrates.

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Ríos, Pablo, Tiddo J. Mooibroek, Tom S. Carter, Christopher Williams, Miriam R. Wilson, Matthew P. Crump, and Anthony P. Davis. "Enantioselective carbohydrate recognition by synthetic lectins in water." Chemical Science 8, no. 5 (2017): 4056–61. http://dx.doi.org/10.1039/c6sc05399h.

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Zgorzelak, Mikołaj, Jakub Grajewski, Jacek Gawroński, and Marcin Kwit. "Solvent-assisted synthesis of a shape-persistent chiral polyaza gigantocycle characterized by a very large internal cavity and extraordinarily high amplitude of the ECD exciton couplet." Chemical Communications 55, no. 16 (2019): 2301–4. http://dx.doi.org/10.1039/c8cc10184a.

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Verpaalen, Rob C. P., Michael G. Debije, Cees W. M. Bastiaansen, Haris Halilović, Tom A. P. Engels, and Albertus P. H. J. Schenning. "Programmable helical twisting in oriented humidity-responsive bilayer films generated by spray-coating of a chiral nematic liquid crystal." Journal of Materials Chemistry A 6, no. 36 (2018): 17724–29. http://dx.doi.org/10.1039/c8ta06984k.

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Holland, Herbert L., Carl D. Turner, Peter R. Andreana, and Doan Nguyen. "Article." Canadian Journal of Chemistry 77, no. 4 (April 1, 1999): 463–71. http://dx.doi.org/10.1139/v99-068.

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The enantioselective oxidation of a series of heterocyclic prochiral sulfides to chiral sulfoxides has been examined using the fungal biocatalysts Helminthosporium species NRRL 4671 and Mortierella isabellina ATCC 42613. Methylthiofuranyl and -thiophenyl substrates gave (S)-configuration products in low to moderate enantiomeric purity on biotransformation with H. species, but pyridyl sulfides with the nitrogen atom located at an optimal distance of 8-10 Å from the sulfur centre gave (S) sulfoxides of high enantiomeric purity. The biotransformation of appropriately substituted benzothiane substrates by M. isabellina also gave products of high enantiomeric purity, but with (R) configuration at sulfur. The acceptability of the substrate and the configuration of sulfur oxidation by both H. species and M. isabellina for the range of substrates examined were found to be consistent with predictions based on cubic space models for these oxidations.Key words: bioconversion, biotransformation, Helminthosporium, Mortierella isabellina, sulfide, sulfoxide.

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Morrison, D. J., J. M. Blackwell, and W. E. Piers. "Mechanistic insights into perfluoroaryl borane-catalyzed allylstannations: Toward asymmetric induction with chiral boranes." Pure and Applied Chemistry 76, no. 3 (January 1, 2004): 615–23. http://dx.doi.org/10.1351/pac200476030615.

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The perfluoroaryl borane B(C6F5)3 is an effective catalyst for a variety of organic transformations. In the hydrosilation of carbonyl functions, it activates the silane rather than the carbonyl substrate. In allylstannation reactions, two competing reaction pathways are observed, one involving tin cation catalysis, the other "true" borane catalysis. For B(C6F5)3, the former mechanism dominates, while for the weaker Lewis acid PhB(C6F5)2, the latter pathway is more prominent. Thus, chiral boranes of similar Lewis acid strength to PhB(C6F5)2 have the potential to mediate asymmetric allylstannation of aldehyde substrates.

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Merelli, Bérangère, Laurence Menguy, Estelle Soubeyrand-Lenoir, and Jean-Claude Cherton. "Determination of the enantiomeric composition of chiral delta-2-thiazolines-1,3 by1H and19F NMR spectroscopy using chiral solvating agents." Spectroscopy 20, no. 3 (2006): 95–107. http://dx.doi.org/10.1155/2006/698685.

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Studies of the perturbing effect of chiral solvating agents (CSAs) namely the fluoroalcohols5aand5bupon the NMR spectra of chiral Δ2-thiazolines1presenting interesting insecticidal properties demonstrated the ability of these CSAs to afford diastereomeric solvates from these substrates providing their enantiomeric discrimination. Thus, for five of the six tested Δ2-thiazolines1Aand1Bthere is at least one possibility to proceed to their enantiomeric discrimination either by1H or19F NMR using mostly5bas CSA.

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Han, Jung Tae, Jin Yong Lee, and Jaesook Yun. "Asymmetric synthesis of γ-chiral borylalkanes via sequential reduction/hydroboration using a single copper catalyst." Chemical Science 11, no. 33 (2020): 8961–65. http://dx.doi.org/10.1039/d0sc03759a.

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Mimura, Shohei, Sho Mizushima, Yohei Shimizu, and Masaya Sawamura. "Copper-catalyzed enantioselective conjugate reduction of α,β-unsaturated esters with chiral phenol–carbene ligands." Beilstein Journal of Organic Chemistry 16 (March 31, 2020): 537–43. http://dx.doi.org/10.3762/bjoc.16.50.

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A chiral phenol–NHC ligand enabled the copper-catalyzed enantioselective conjugate reduction of α,β-unsaturated esters. The phenol moiety of the chiral NHC ligand played a critical role in producing the enantiomerically enriched products. The catalyst worked well for various (Z)-isomer substrates. Opposite enantiomers were obtained from (Z)- and (E)-isomers, with a higher enantiomeric excess from the (Z)-isomer.

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Soundararajan, Karthikeyan, Helen Ratna Monica Jeyarajan, Raju Subimol Kamarajapurathu, and Karthik Krishna Kumar Ayyanoth. "Facile and innovative catalytic protocol for intramolecular Friedel–Crafts cyclization of Morita–Baylis–Hillman adducts: Synergistic combination of chiral (salen)chromium(III)/BF3·OEt2 catalysis." Beilstein Journal of Organic Chemistry 17 (August 26, 2021): 2186–93. http://dx.doi.org/10.3762/bjoc.17.140.

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The chiral (salen)Cr(III)/BF3·OEt2 catalytic combination was found to be an effective catalyst for intramolecular Friedel–Crafts cyclization of electron-deficient Morita–Baylis–Hillman adducts. In presence of mild reaction conditions the chiral (salen)Cr(III)/BF3·OEt2 complex affords 2-substituted-1H-indenes from unique substrates of Morita–Baylis–Hillman adducts via an easy operating practical procedure.

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Ramachary, Dhevalapally B., and Kodambahalli S. Shruthi. "Asymmetric synthesis of tetrahydroquinolines through supramolecular organocatalysis." Org. Biomol. Chem. 12, no. 25 (2014): 4300–4304. http://dx.doi.org/10.1039/c4ob00570h.

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Functionalized chiral tetrahydroquinolines were synthesized through supramolecular organocatalysis using quinidine-NH-thiourea 3c/l-phenylalanine 4i followed by reductive amination from the simple substrates.

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Uemura, Naohiro, Seiya Toyoda, Waku Shimizu, Yasushi Yoshida, Takashi Mino, and Masami Sakamoto. "Absolute Asymmetric Synthesis Involving Chiral Symmetry Breaking in Diels–Alder Reaction." Symmetry 12, no. 6 (June 1, 2020): 910. http://dx.doi.org/10.3390/sym12060910.

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Efficient generation and amplification of chirality from prochiral substrates in the Diels–Alder reaction (DA reaction) followed by dynamic crystallization were achieved without using an external chiral source. Since the DA reaction of 2-methylfuran and various maleimides proceeds reversibly, an exo-adduct was obtained as the main product as the reaction proceeded. From single crystal X-ray structure analysis, it was found that five of ten exo-adducts gave conglomerates. When 2-methylfuran and various maleimides with a catalytic amount of TFA were reacted in a sealed tube, the exo-DA adducts were precipitated from the solution, while the reaction mixtures were continuously ground and stirred using glass beads. Deracemization occurred and chiral amplification was observed for four of the substrates. Each final enantiomeric purity was influenced by the crystal structure, and when enantiomers were included in the disorder, they reached an enantiomeric purity reflecting the ratio of the disorder. The final ee value of the 3,5-dimethylphenyl derivative after chiral amplification was 98% ee.

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Banerjee-Ghosh, Koyel, Oren Ben Dor, Francesco Tassinari, Eyal Capua, Shira Yochelis, Amir Capua, See-Hun Yang, et al. "Separation of enantiomers by their enantiospecific interaction with achiral magnetic substrates." Science 360, no. 6395 (May 10, 2018): 1331–34. http://dx.doi.org/10.1126/science.aar4265.

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It is commonly assumed that recognition and discrimination of chirality, both in nature and in artificial systems, depend solely on spatial effects. However, recent studies have suggested that charge redistribution in chiral molecules manifests an enantiospecific preference in electron spin orientation. We therefore reasoned that the induced spin polarization may affect enantiorecognition through exchange interactions. Here we show experimentally that the interaction of chiral molecules with a perpendicularly magnetized substrate is enantiospecific. Thus, one enantiomer adsorbs preferentially when the magnetic dipole is pointing up, whereas the other adsorbs faster for the opposite alignment of the magnetization. The interaction is not controlled by the magnetic field per se, but rather by the electron spin orientations, and opens prospects for a distinct approach to enantiomeric separations.

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Puentes, Cira Mollings, and Thomas J. Wenzel. "Phosphated cyclodextrins as water-soluble chiral NMR solvating agents for cationic compounds." Beilstein Journal of Organic Chemistry 13 (January 6, 2017): 43–53. http://dx.doi.org/10.3762/bjoc.13.6.

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The utility of phosphated α-, β- and γ-cyclodextrins as water-soluble chiral NMR solvating agents for cationic substrates is described. Two sets of phosphated cyclodextrins, one with degrees of substitution in the 2–6 range, the other with degrees of substitution in the 6–10 range, are examined. Results with 33 water-soluble cationic substrates are reported. We also explored the possibility that the addition of paramagnetic lanthanide ions such as praseodymium(III) and ytterbium(III) further enhances the enantiomeric differentiation in the NMR spectra. The chiral differentiation with the phosphated cyclodextrins is compared to prior results obtained with anionic carboxymethylated cyclodextrins. There are a number of examples where a larger differentiation is observed with the phosphated cyclodextrins.

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Zhang, Qingfeng, Taylor Hernandez, Kyle W. Smith, Seyyed Ali Hosseini Jebeli, Alan X. Dai, Lauren Warning, Rashad Baiyasi, et al. "Unraveling the origin of chirality from plasmonic nanoparticle-protein complexes." Science 365, no. 6460 (September 26, 2019): 1475–78. http://dx.doi.org/10.1126/science.aax5415.

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Plasmon-coupled circular dichroism has emerged as a promising approach for ultrasensitive detection of biomolecular conformations through coupling between molecular chirality and surface plasmons. Chiral nanoparticle assemblies without chiral molecules present also have large optical activities. We apply single-particle circular differential scattering spectroscopy coupled with electron imaging and simulations to identify both structural chirality of plasmonic aggregates and plasmon-coupled circular dichroism induced by chiral proteins. We establish that both chiral aggregates and just a few proteins in interparticle gaps of achiral assemblies are responsible for the ensemble signal, but single nanoparticles do not contribute. We furthermore find that the protein plays two roles: It transfers chirality to both chiral and achiral plasmonic substrates, and it is also responsible for the chiral three-dimensional assembly of nanorods. Understanding these underlying factors paves the way toward sensing the chirality of single biomolecules.

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41

Hong, Suk-Bong, and Frank M. Raushel. "Stereochemical preferences for chiral substrates by the bacterial phosphotriesterase." Chemico-Biological Interactions 119-120 (May 1999): 225–34. http://dx.doi.org/10.1016/s0009-2797(99)00031-9.

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Yadav, J. S., and S. Nanda. "Novel chiral lipoxygenase substrates: design and synthesis. Part 2." Tetrahedron: Asymmetry 12, no. 23 (December 2001): 3223–34. http://dx.doi.org/10.1016/s0957-4166(02)00009-5.

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Murphy, James P., Mark Nieuwenhuyzen, Karen Reynolds, Pakala K. S. Sarma, and Paul J. Stevenson. "Chiral dienamides- substrates for asymmetric synthesis of amido cyclohexenes." Tetrahedron Letters 36, no. 52 (December 1995): 9533–36. http://dx.doi.org/10.1016/0040-4039(95)02040-3.

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Mumtaz, Salma, Israel Cano, Nargis Mumtaz, Ahmed Abbas, Jairton Dupont, and Humaira Yasmeen Gondal. "Supramolecular interaction of non-racemic benzimidazolium based ion pairs with chiral substrates." Physical Chemistry Chemical Physics 20, no. 32 (2018): 20821–26. http://dx.doi.org/10.1039/c8cp03881c.

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Zhou, Huan, Wenlei Zhao, Tao Zhang, Haodong Guo, Haizhou Huang, and Mingxin Chang. "Enantioselective Synthesis of 2-Substituted Pyrrolidines via Intramolecular Reductive Amination." Synthesis 51, no. 13 (May 7, 2019): 2713–19. http://dx.doi.org/10.1055/s-0037-1611533.

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Catalyzed by the complex generated in situ from iridium and the chiral ferrocene ligand, tert-butyl (4-oxo-4-arylbutyl)carbamate substrates were deprotected and then reductively cyclised to form 2-substituted arylpyrrolidines in a one-pot manner, in which the intramolecular reductive amination was the key step. A range of chiral 2-substituted arylpyrrolidines were synthesised in up to 98% yield and 92% ee.

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Metallinos, Costa, Ngan Tran, and Dusty Cadwallader. "Diastereoselective Synthesis of Alkylated 1,4-Cyclohexadiene Esters Using Epimeric Pyrroloimidazolones." Synthesis 53, no. 01 (August 24, 2020): 182–92. http://dx.doi.org/10.1055/s-0040-1707351.

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A pair of ortho-benzoate esters containing epimeric pyrroloimidazolones undergo sequential Birch reduction and diastereoselective alkylation to provide products ranging from 88:12 to >95:5 diastereomeric ratio (dr) for the syn-epimer, and 50:50 to 95:5 dr for the anti-epimer. The stereochemistry of the products is confirmed by a combination of X-ray crystallography on a key anti-epimer-derived product, in combination with specific rotation measurements of enantiomers that are prepared from the syn or anti starting materials. A diastereomerically pure allyl-substituted substrate is shown to undergo Cope rearrangement, which transposes the quaternary chiral center to a remote position without racemization. This work is complementary to asymmetric reductive alkylation reported previously by Schultz using anisole substrates with chiral benzamide auxiliaries in that the pyrroloimidazolones act as surrogates for the methoxy group.

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Zhang, Yue Cheng, Jing Yuan Gao, Nai Yue Shi, and Ji Quan Zhao. "Synthesis of Chiral Tridentate Ligands Embodying the Bispidine Framework and their Application in the Enantioselective Addition of Diethylzinc to Aldehydes." Advanced Materials Research 396-398 (November 2011): 1236–43. http://dx.doi.org/10.4028/www.scientific.net/amr.396-398.1236.

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Several new chiral tridentate ligands with the bispidine moiety were synthesized from N-alkyl bispidines and chiral amino (or hydroxyl) acids. The synthesized ligands were used as catalysts in the enantioselective addition of diethylzinc to several aromatic aldehydes and an aliphatic aldehyde. High yield and enantioselectivity were received in the cases of aromatic aldehydes as substrates especially when the employed chiral ligand has a hydroxyl group attached to the chiral center. The effect of the structure, the amount of tridentate chiral ligands, solvent and temperature on the enantioselectivity of the addition products were studied. A possible mechanism for the addition of diethylzinc to aldehydes in the presence of bispidine-derived ligands were proposed based upon the catalytic reaction results and referred to the mechanisms proposed for other reaction systems in literatures.

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Thomas, Fabian, Dominik Steden, Alexander Eith, Alexander Hoffmann, and Sonja Herres-Pawlis. "Chiral bis(pyrazolyl)methane copper(I) complexes and their application in nitrene transfer reactions." Zeitschrift für Naturforschung B 76, no. 10-12 (October 29, 2021): 835–47. http://dx.doi.org/10.1515/znb-2021-0140.

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Abstract In this study, chiral bis(pyrazolyl)methane copper(I) acetonitrile complexes were applied to generate two novel terminal copper tosyl nitrene complexes with the nitrene generating agent SPhINTs in dichloromethane at low temperatures. The syntheses of the chiral bis(pyrazolyl)methane ligands are based on pulegone and camphor, members of the natural chiral pool. The chiral copper(I) acetonitrile complexes were applied as catalysts in the copper nitrene mediated aziridination reaction of different styrene derivatives and the C–H amination of various substrates. The reactions afforded good yields, but low enantiomeric excess under mild conditions. The nitrene species have been characterized with UV/Vis and EPR spectroscopy and the products of the decay by ESI mass spectrometry.

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Wu, Xianqing, Mohini Shrestha, and Yifeng Chen. "Asymmetric Synthesis of α-Alkylated γ-Lactam via Nickel/8-Quinim-Catalyzed Reductive Alkyl-Carbamoylation of Unactivated Alkene." Synlett 32, no. 10 (January 14, 2021): 955–61. http://dx.doi.org/10.1055/a-1353-7605.

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AbstractChiral-auxiliary-mediated synthesis represents the most frequently used synthetic tool for the induction of chirality on α-position of γ-lactams in organic synthesis. However, the general strategy requires the stoichiometric use of chiral reagents with multiple manipulation steps. Transition-metal-catalyzed asymmetric alkene dicarbofunctionalization using readily available substrates under mild conditions allows the simultaneous construction of two vicinal chemical bonds and a chiral carbon center, hence, gain expedient access to chiral heterocycles. Herein, we disclose a Ni-catalyzed enantioselective reaction of 3-butenyl carbamoyl chloride and primary alkyl iodide enabled by a newly designed chiral 8-quinoline imidazoline ligand (8-Quinim). This protocol features broad functional group tolerance and high enantioselectivities, achieving unprecedented synthesis of chiral nonaromatic heterocycles via catalytic reductive protocol.1 Introduction2 Development of 8-Quinim Ligand3 Nickel/8-Quinim-Catalyzed Enantioselective Synthesis of Chiral α-Alkylated γ-Lactam4 Conclusion and Outlook

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Makino, Yoshihide, Kousuke Inoue, Tohru Dairi, and Nobuya Itoh. "Engineering of Phenylacetaldehyde Reductase for Efficient Substrate Conversion in Concentrated 2-Propanol." Applied and Environmental Microbiology 71, no. 8 (August 2005): 4713–20. http://dx.doi.org/10.1128/aem.71.8.4713-4720.2005.

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ABSTRACT Phenylacetaldehyde reductase (PAR) is suitable for the conversion of various aryl ketones and 2-alkanones to corresponding chiral alcohols. 2-Propanol acts as a substrate solvent and hydrogen donor of coupled cofactor regeneration during the conversion of substrates catalyzed by PAR. To improve the conversion efficiency in high concentrations of substrate and 2-propanol, selection of a PAR mutant library and the subsequent rearrangement of mutations were attempted. With only a single selection round and following the manual combination of advantageous mutations, PAR was successfully adapted for the conversion of high concentrations of substrate with concentrated 2-propanol. This method will be widely applicable for the engineering of enzymes potentially valuable for industry.

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Journal articles on the topic 'Chiral Substrates'

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