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Chiral separation

Min-Seob Seo, Sumin Jang, Hyunwoo Kim
A chiral aluminum solvating agent (CASA) was demonstrated to be a general and efficient reagent for 1H NMR chiral analysis of alcohols. The sodium salt of the CASA (CASA-Na) showed a complete baseline peak separation of the hydroxyl group for various chiral alcohols including primary, secondary, and tertiary alcohols with alkyl and aryl substituents in CD3CN. Due to the weak intermolecular interaction, 1H NMR measurement at low temperature (-40 to 10 °C) was required.
March 16, 2018: Chemical Communications: Chem Comm
Francisco Lopez-Tapia, Christine Brotherton-Pleiss, Peibin Yue, Heide Murakami, Ana Carolina Costa Araujo, Bruna Reis Dos Santos, Erin Ichinotsubo, Anna Rabkin, Raj Shah, Megan Lantz, Suzie Chen, Marcus A Tius, James Turkson
The molecular determinants for the activities of the reported benzoic acid (SH4-54), salicylic acid (BP-1-102), and benzohydroxamic acid (SH5-07)-based STAT3 inhibitors were investigated to design optimized analogues. All three leads are based on an N -methylglycinamide scaffold, with its two amine groups condensed with three different functionalities. The three functionalities and the CH2 group of the glycinamide scaffold were separately modified. The replacement of the pentafluorobenzene or cyclohexylbenzene, or replacing the benzene ring of the aromatic carboxylic or hydroxamic acid motif with heterocyclic components (containing nitrogen and oxygen elements) all decreased potency...
March 8, 2018: ACS Medicinal Chemistry Letters
Rui Guo, Bin Lin, Xin-Yue Shang, Le Zhou, Guo-Dong Yao, Xiao-Xiao Huang, Shao-Jiang Song
Eight new phenylpropanoids (1a/1b, 2-4, 5a/5b and 6) including two pairs of enantiomers (1a/1b and 5a/5b), along with a known analogue (7) were isolated from the fruit of Crataegus pinnatifida. Their structures were elucidated using comprehensive spectroscopic methods. Compounds 1a/1b and 5a/5b were separated successfully by chiral chromatographic column. The absolute configurations of enantiomers were determined by comparison between the experimental and calculated electronic circular dichroism (ECD) spectra...
March 10, 2018: Fitoterapia
Naohiro Kameta, Jiuchao Dong, Hiroharu Yui
A series of nanotubes with a dense layer of short poly(ethylene glycol) (PEG) chains on the inner surface are prepared by means of a coassembly process using glycolipids and PEG derivatives. Dehydration of the PEG chains by heating increases the hydrophobicity of the nanotube channel and fluorescent-dye-labeled amino acids are extracted from bulk solution. Rehydration of the PEG chains by cooling results in back-extraction of the amino acids into the bulk solution. Because of the supramolecular chirality of the nanotubes, amino acid enantiomers can be separated in the back-extraction procedure, which is detectable with the naked eye as a change in fluorescence as the amino acids are released from the nanotubes...
March 13, 2018: Small
David Avnir
A unique materials' methodology enables the doping of metals with functional molecules, polymers, enzymes, and nanoparticles. The resulting materials have either the combined properties of the metal and the dopants, or new, sometimes synergetic properties that are not found in the separate components, emerge. Metals that have been doped so far include gold, silver, copper, iron, gallium, palladium, platinum, and several alloys. Numerous applications have been demonstrated including catalysis, biocatalysis, bioactivity, electrochemistry (including new type of batteries), corrosion resistance, induction of chirality, tailoring unconventional properties to metals, and more...
March 12, 2018: Advanced Materials
Rosa M Girón, Jiangkun Ouyang, Ludovic Favereau, Nicolas Vanthuyne, Jeanne Crassous, Salvatore Filippone, Nazario Martín
[60]Fullerene and its rarely explored reversible covalent chemistry have been harnessed as an efficient alternative for the chiral resolution of racemates. By using only catalytic amounts of chiral agents, stereodivergent 1,3-dipolar cycloadditions of racemic helicenes onto [60]fullerene were carried out. The formed helicene/fullerene diastereomers were easily separated by conventional chromatography, and afterward, a simple catalyzed 1,3-dipolar retro-cycloaddition afforded helicene starting materials in high optical purity...
March 9, 2018: Organic Letters
Tiffany Abitbol, Doron Kam, Yael Levi-Kalisman, Derek G Gray, Oded Shoseyov
A series of four cellulose nanocrystal (CNC) suspensions were prepared from bleached softwood kraft pulp using different conditions of sulfuric acid hydrolysis. The CNCs were identical in size (95 nm in length × 5 nm in width) but had different surface charges corresponding to the harshness of the hydrolysis conditions. Consequently, it was possible to isolate the effects of surface charge on the self-assembly and rheology viscosity of the CNC suspensions across a range of surface charges from 0.27 %S to 0...
March 7, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Meng Li, Yu Zhao, Li Zhou, Jia Yu, Jian Wang, Xingjie Guo
In this work, the enantiomeric separation of ten anticholinergic drugs was first examined on two derivative polysaccharide chiral stationary phases (CSPs), i.e., Chiralpak ID and Chiralpak IA in the normal phase mode. Except for scopolamine hydrobromide, the remaining nine analytes could be completely separated with good resolutions using both columns under the optimized mobile phase conditions. And the enantiomeric discrimination ability of the studied CSPs towards nine analytes was in the order of Chiralpak ID > Chiralpak IA...
March 7, 2018: Electrophoresis
Hannes Konrad Buchholz, Matthias Stein
Accurate lattice energies of organic crystals are important i.e. for the pharmaceutical industry. Periodic DFT calculations with atom-centered Gaussian basis functions with the Turbomole program are used to calculate lattice energies for several non-covalently bound organic molecular crystals. The accuracy and convergence of results with basis set size and k-space sampling from periodic calculations is evaluated for the two reference molecules benzoic acid and naphthalene. For the X23 benchmark set of small molecular crystals accurate lattice energies are obtained using the PBE-D3 functional...
March 5, 2018: Journal of Computational Chemistry
Tamar Khatiashvili, Rusudan Kakava, Iza Matarashvili, Hadi Tabani, Chiara Fanali, Alessandro Volonterio, Tivadar Farkas, Bezhan Chankvetadze
The present study reports successful separations of enantiomers of selected chiral sulfoxides with very high separation factor in high-performance liquid chromatography by using chiral columns prepared with the chiral selector cellulose tris(4-chloro-3-methylphenylcarbamate). High separation factors were observed in polar organic, as well as in hydrocarbon-alcohol-type mobile phases. The key structural components of the solute for obtaining high chiral recognition are discussed as well as thermodynamic quantities of analyte adsorption on the chiral stationary phase were determined...
February 26, 2018: Journal of Chromatography. A
Bing Yu, Shuai Zhang, Guoling Li, Hailin Cong
Owing to enantiomers' identical physical and chemical properties, separation work in the chiral environments is still a great challenge.and chemical properties. Chromatographic techniques employing chiral stationary phases (CSPs) have been developed as powerful tools for the chiral analysis and preparation of pure enantiomers. Here we report a facile synthesis of vancomycin stationary phase based on diazotized silica. Monodisperse silica particles were synthesized by a modified Stöber method. The obtained silica particles were modified by self-assembly photosensitive diazoresin (DR) and vancomycin on the surface...
May 15, 2018: Talanta
Haizhen Zhang, Min Huang, Weiwei Yu, A'wei Zhang, Kankan Zhang, Deyu Hu
A simple and rapid method for enantioselective determination of dufulin in cucumber and soil was developed by liquid chromatography with tandem mass spectrometry. The enantiomers were separated on a Superchiral S-OD chiral cellulose tris(3,5-dimethylphenylcarbamate) column at 20 °C, with a mixture of acetonitrile and water (0.1% formic acid) (52:48, v/v) as mobile phase at a flow rate of 0.65 mL/min. The pretreatment conditions were optimized using an orthogonal test, and the optimized method showed good linearity and sensitivity...
March 3, 2018: Biomedical Chromatography: BMC
Srikanth Gattu, Cassandra L Crihfield, Grace Lu, Lloyd Bwanali, Lindsay Veltri, Lisa A Holland
Capillary electrophoresis provides a rapid, cost-effective platform for enzyme and substrate characterization. The high resolution achievable by capillary electrophoresis enables the analysis of substrates and products that are indistinguishable by spectroscopic techniques alone, while the small volume requirement enables analysis of enzymes or substrates in limited supply. Furthermore, the compatibility of capillary electrophoresis with various detectors makes it suitable for KM determinations ranging from nanomolar to millimolar concentrations...
February 27, 2018: Methods: a Companion to Methods in Enzymology
Philippe Kalck, Martine Urrutigoïty
In the context of atom economy and low environmental impact, synthesis of amines by an efficient catalytic process is of great importance to produce these building blocks for fine chemical industry. The one-pot hydroaminomethylation of alkenes is a tandem reaction which involves three successive steps under CO/H2 pressure to perform the catalyzed hydroformylation of the alkene into the corresponding aldehyde followed by its condensation with a N-H function and the catalyzed hydrogenation of the imine/enamine intermediate into the corresponding saturated amine...
March 1, 2018: Chemical Reviews
Sérgio R Domingos, Cristóbal Pérez, Melanie Schnell
Chiroptical spectroscopy techniques for the differentiation of enantiomers in the condensed phase are based on an established paradigm that relies on symmetry breaking using circularly polarized light. We review a novel approach for the study of chiral molecules in the gas phase using broadband rotational spectroscopy, namely microwave three-wave mixing, which is a coherent, nonlinear, and resonant process. This technique can be used to generate a coherent molecular rotational signal that can be detected in a manner similar to that in conventional Fourier transform microwave spectroscopy...
February 28, 2018: Annual Review of Physical Chemistry
Xichong Ye, Jie Zhang, Jiaxi Cui, Xinhua Wan
Novel polymeric inhibitors with lower critical solution temperatures in water were prepared and used to mediate the crystallization of racemic asparagine monohydrate, leading to chiral separation with 88.6 ee%. They could be recollected by simply elevating the temperature with a high yield of around 95% and reused without compromising the stereoselectivity and stability.
February 27, 2018: Chemical Communications: Chem Comm
Zhi-Ping Yan, Xu-Feng Luo, Kang Liao, Zi-Xuan Lin, Zheng-Guang Wu, Yong-Hui Zhou, You-Xuan Zheng
Four novel chiral iridium(iii) complexes with triplex stereogenic centers were synthesized by introducing chiral carbon atoms into cyclometalated and ancillary ligands, and separated into eight isomers, which coincide with the old Chinese philosophy Eight Trigrams. The electron circular dichroism and circularly polarized luminescence spectra of four pairs of isomers show perfect mirror images with a dissymmetry factor (glum factor) of around 0.003.
February 26, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Yu-Xi Wang, Le Zhou, Jie Wang, Bin Lin, Xiao-Bo Wang, Xiao-Xiao Huang, Shao-Jiang Song
To develop potential agents for slowing the progression of Alzheimer's disease, two pairs of new enantiomeric lignans, including a couple of rarely 8',9'-dinor-3',7-epoxy-8,4'-oxyneolignanes named (7S, 8S)- and (7R, 8R)-pithecellobiumin A (1a/1b) and a pair of 2',9'-epoxy-arylnaphthalenes named (7R, 8R, 8'R)- and (7S, 8S, 8'S)-pithecellobiumin B (2a/2b) were separated by chiral high performance liquid chromatography (HPLC). Their planar structures were elucidated by spectroscopic data analyses. The absolute configurations were determined by comparing of experimental and calculated electronic circular dichroism (ECD)...
February 14, 2018: Bioorganic Chemistry
Shanshan He, Yunchao He, Lingping Cheng, Yaling Wu, Yanxiong Ke
Novel chiral ionic liquid stationary phases based on chiral imidazolium were prepared. The ionic liquid chiral selector was synthesized by ring opening of cyclohexene oxide with imidazole or 5,6-dimethylbenzimidazole, and then chemically modified by different substitute groups. Chiral stationary phases were prepared by bonding to the surface of silica sphere through thioene "click" reaction. Their enantioselective separations of chiral acids were evaluated by high-performance liquid chromatography...
February 24, 2018: Chirality
Andrea N L Batista, Fernando M Dos Santos, João M Batista, Quezia B Cass
Chiral natural product molecules are generally assumed to be biosynthesized in an enantiomerically pure or enriched fashion. Nevertheless, a significant amount of racemates or enantiomerically enriched mixtures has been reported from natural sources. This number is estimated to be even larger since the enantiomeric purity of secondary metabolites is rarely checked in the natural product isolation pipeline. This latter fact may have drastic effects on the evaluation of the biological activity of chiral natural products...
February 23, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
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