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Ya Wei Li, Li Ming Wang, Ying Jin, Sheng Chang
Cinchona alkaloid derivatives as organocatalysts were applied in the asymmetric aza-Friedel-Crafts reaction of α-naphthol with aryl aldimines. The desired chiral aminoarylnaphthols were obtained in 85% enantiomeric excess.
June 18, 2017: Chirality
V A Kuznetsova, A K Visheratina, A Ryan, I V Martynenko, A Loudon, C M Maguire, F Purcell-Milton, A O Orlova, A V Baranov, A V Fedorov, A Prina-Mello, Y Volkov, Y K Gun'Ko
Chirality strongly influences many biological properties of materials, such as cell accumulation, enzymatic activity, and toxicity. In the past decade, it has been shown that quantum dots (QDs), fluorescent semiconductor nanoparticles with unique optical properties, can demonstrate optical activity due to chiral ligands bound on their surface. Optically active QDs could find potential applications in biomedical research, therapy, and diagnostics. Consequently, it is very important to investigate the interaction of QDs capped with chiral ligands with living cells...
June 13, 2017: Chirality
Carla Fernandes, Maria Elizabeth Tiritan, Sara Cravo, Ye' Zaw Phyo, Anake Kijjoa, Artur M S Silva, Quezia B Cass, Madalena M M Pinto
Six chiral derivatives of xanthones (CDXs) were covalently bonded to silica, yielding the corresponding xanthonic chiral stationary phases (XCSPs). The new XCSPs were packed into stainless-steel columns with 150 x 4.6 mm i.d. Moreover, the greening of the chromatographic analysis by reducing the internal diameter (150 x 2.1 mm i.d.) of the liquid chromatography (LC) columns was also investigated. The enantioselective capability of these phases was evaluated by LC using different chemical classes of chiral compounds, including several types of drugs...
June 13, 2017: Chirality
Yongjing Liu, Xiaoying Wang
A ligand-exchange micellar electrokinetic capillary electrophoresis system with copper(II)-L-isoleucine complexes as the chiral selector incorporated in micelles of sodium dodecyl sulfate (SDS) was developed for the enantioseparation of ofloxacin and its four related substances (impurities A, C, E, and F). The effects of important parameters affecting separation such as buffer pH, SDS concentration, chiral selector concentration, and organic additive were investigated in detail. Under optimum experimental conditions, enantioseparation of ofloxacin, impurities A, C, E, and F enantiomers was accomplished with resolutions of 4...
May 31, 2017: Chirality
Christian Merten, Michael Dirkmann, Frank Schulz
The absolute configuration (AC) of the common precursor of the fusicoccane family of terpenoids, fusicocca-2,10(14)-diene (FCdiene), had only been deduced by a lengthy total synthesis, or indirectly from crystal structures of fusicoccin A. However, in particular the AC determinations based on downstream products of the terpene synthase intrinsically overlook potential epimerization reactions. In this contribution, we confirm the relative stereochemistry of FCdiene by comparison of experimental and predicted (13) C-NMR chemical shifts, and finally determine the absolute configuration from an analysis of its infrared and vibrational circular dichroism spectra...
May 30, 2017: Chirality
Hongxing Dong, Danxia Zhang, Hailong Lin, Yudan Wang, Lijia Liu, Meixia Zheng, Xiaobo Li, Chunhong Zhang, Junqing Li, Peng Zhang, Juhyok So
Acrylamide (AM) was copolymerized with ethylene glycol dimethacrylate (EGDMA) in the presence of (R)-1,1'-binaphthalene-2-naphthol (BINOL) as the template molecules on the surface of silica gel by a free radical polymerization to produce a chiral stationary phase based on the surface molecularly imprinted polymer (SMIP-CSP). The SMIP-CSP showed a much better separation factor (α = 4.28) than the CSP based on the molecularly imprinted polymer (MIP-CSP) without coating on the silica gel (α = 1.96) during the chiral separation of BINOL enantiomers by high-performance liquid chromatography...
May 25, 2017: Chirality
Pei Wang, Yue Liu, Ya-Lun Zhang, Chao-Shan Da
Highly enantioselective arylation of aryl aldehydes catalyzed by (S)-H8 -BINOL-Ti(Oi-Pr)2 complex in the presence of N-methylmorpholine (NMM) as an effective and inexpensive additive is described for the first time. We found high enantioselectivity and yield but successfully reduced the equivalents of nucleophiles triarylaluminums by 50% compared with our previous report. The practicability of the process was thereby greatly increased.
May 25, 2017: Chirality
Oliver Trapp, Nina Berova, John Caldwell
No abstract text is available yet for this article.
May 23, 2017: Chirality
Hui Liu, Peng Wang, Zhiqiang Zhou, Donghui Liu
Under normal conditions, the environmental behaviors of pesticides are affected by complex environmental factors and the manner of administration together with constraints. In order to meet the actual needs, we imitated the experiment and found that the degradation rate of pyriproxyfen in soils rendered complex changes. Rac-pyriproxyfen was successfully chiral separated on an AZ-H column and the residue analysis method was in accord with the demand of pesticide analysis. The results indicated that pyriproxyfen dissipated at a faster rate in Heilongjiang soil and Hainan soil, while at a much slower speed in another three soils and sand...
May 18, 2017: Chirality
Arkadii V Tarasevych, Anton I Kostyukov, Mark G Baronskiy, Alexander A Rastorguev, Jean-Claude Guillemin, Valeriy N Snytnikov
Luminescent spectroscopy combined with the technique of luminescent probing with rare earth ions (europium, gadolinium, terbium) and an actinide ion (uranyl) was used to differentiate enantiopure and racemic alanine, the simplest chiral proteinogenic amino acid. Using the achiral luminescent probes, small differences between pure L and DL alanine in the solid state were strongly amplified. Based on the observed electronic transitions of the probes, the position of the triplet level of the coordinated alanine was estimated...
May 3, 2017: Chirality
Joni Agustian, Azlina Harun Kamaruddin, Hassan Y Aboul-Enein
As the (R)-enantiomer of racemic atenolol has no β-blocking activity and no lack of side effects, switching from the racemate to the (S)-atenolol is more favorable. Transesterification of racemic atenolol using free enzymes investigated as a resource to resolve the racemate via this method is limited. Screenings of enzyme, medium, and acetyl donor were conducted first to give Pseudomonas fluorescens lipase, tetrahydrofuran, and vinyl acetate. A statistical design of the experiment was then developed using Central Composite Design on some operational factors, which resulted in the conversions of 11...
April 25, 2017: Chirality
Hao Wu, Xiaolin He, Huifen Dong, Qingyan Zhou, Yongsong Zhang
Imazethapyr (IM) is a chiral herbicide composed of an (-)-R-enantiomer and an (+)-S-enantiomer with differential herbicidal activity. In this study, the effects of microbial organisms, humidity, and temperature on the selective degradation of the (-)-R- and (+)-S-enantiomers of IM were determined in silty loam (SL) and clay loam (CL) soil with different pH values. The (-)-R-enantiomer of IM was preferentially degraded in two soils under different microorganism, humidity, and temperature conditions. The average half-lives of R-IM ranged from 43 to 66...
April 19, 2017: Chirality
Feng Chen, Hong-Xia Ren, Yu Yang, Shan-Ping Ji, Zheng-Bing Zhang, Fang Tian, Lin Peng, Li-Xin Wang
Chiral diamine catalysts 11a-e derived from α,α-diphenyl prolinol were prepared and successfully applied to the Michael addition of aromatic oximes to α,β-unsaturated aldehydes in mediocre to good yields (up to 78%) and good to high enantioselectivities (up to 93% ee).
April 18, 2017: Chirality
Svetlana G Kozlova, Denis P Pishchur, Marsel R Gallyamov
Differential scanning calorimetry and nuclear magnetic resonance were used to investigate thermal effects in the guest-host systems where homochiral metal-organic sorbent [Zn2 (bdc)(S-lac)(dmf)] is considered as a host while 1-phenylethanol enantiomers and their racemic mixture serve as guest molecules. A maximum energy gain from the guest-host interaction was observed in the system with the racemic mixture. The effect of host-guest recognition was revealed for the case of the host and guest having a similar type of chirality in the presence of antipode guest molecules...
March 29, 2017: Chirality
Ryoma Ishidate, Tomoyuki Ikai, Shigeyoshi Kanoh, Eiji Yashima, Katsuhiro Maeda
Novel poly(biphenylylacetylene) derivatives bearing two acetyloxy groups at the 2- and 2'-positions and an alkoxycarbonyl group at the 4'-position of the biphenyl pendants (poly-Ac's) were synthesized by the polymerization of the corresponding biphenylylacetylenes using a rhodium catalyst. The obtained stereoregular (cis-transoidal) poly-Ac's folded into a predominantly one-handed helical conformation accompanied by a preferred-handed axially twisted conformation of the biphenyl pendants through noncovalent interactions with a chiral alcohol and both the induced main-chain helicity and the pendant axial chirality were maintained, that is, memorized, after complete removal of the chiral alcohol...
March 29, 2017: Chirality
Yin Zhao, Lu Yin, Jingjing Liu, Hailing Chen, Wei Zhang
Conjugated homopolymer poly(9,9-bis(3-((S)-2-methylbutylpropanoate))fluorene) (PSF) with chiral pendants was synthesized and characterized. Dissolution experiments show that PSF is well dissolved in racemic limonene at high temperature and begins aggregating upon sequential cooling treatment. The corresponding assemblies were transferred to quartz plate by the spin-coating method. Comparably, film casting from chloroform solution was also prepared. Upon annealing thermal treatments, these PSF films exhibited perfect mirror circular dichroism (CD) Cotton effects and dissymmetry ratios...
March 28, 2017: Chirality
Jia Yu, Jing Tang, Xiaowei Yuan, Xingjie Guo, Longshan Zhao
Separations of six dihydropyridine enantiomers on three commercially available cellulose-based chiral stationary phases (Chiralcel OD-RH, Chiralpak IB, and Chiralpak IC) were evaluated with high-performance liquid chromatography (HPLC). The best enantioseparation of the six chiral drugs was obtained with a Chiralpak IC (250 × 4.6 mm i.d., 5 μm) column. Then the influence of the mobile phase including an alcohol-modifying agent and alkaline additive on the enantioseparation were investigated and optimized...
March 28, 2017: Chirality
Imran Ali, Mohd Suhail, Zeid A Alothman, Abdulrahman Alwarthan
Chiral resolution of baclofen, bupropion, and etodolac profens was obtained with amylose derivatized chiral reversed stationary phase (carbamate groups). The eluent used for bupropion and etodolac was MeOH-water (20:80, v/v) and for baclofen was water-methanol (95:5, v/v). The eluent run rates, finding wavelength and temperature, were 1.0 mL/min, 220 nm and 27 ± 1 °C for all the eluents. The magnitude of the retardation factors for S- and R-enantiomers of baclofen, bupropion, and etodolac were 1.37, 2...
July 2017: Chirality
Maria L Carraro, Andreia Palmeira, Maria E Tiritan, Carla Fernandes, Madalena M M Pinto
The enantioresolution and determination of the enantiomeric purity of 32 new xanthone derivatives, synthesized in enantiomerically pure form, were investigated on (S,S)-Whelk-O1 chiral stationary phase (CSP). Enantioselectivity and resolution (α and RS ) with values ranging from 1.41-6.25 and from 1.29-17.20, respectively, were achieved. The elution was in polar organic mode with acetonitrile/methanol (50:50 v/v) as mobile phase and, generally, the (R)-enantiomer was the first to elute. The enantiomeric excess (ee) for all synthesized xanthone derivatives was higher than 99%...
June 2017: Chirality
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