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Chirality

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https://www.readbyqxmd.com/read/28439971/resolution-determination-of-enantiomeric-purity-and-chiral-recognition-mechanism-of-new-xanthone-derivatives-on-s-s-whelk-o1-stationary-phase
#1
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%...
April 25, 2017: Chirality
https://www.readbyqxmd.com/read/28439969/factors-screening-to-statistical-experimental-design-of-racemic-atenolol-kinetic-resolution-via-transesterification-reaction-in-organic-solvent-using-free-pseudomonas-fluorescens-lipase
#2
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
https://www.readbyqxmd.com/read/28437017/determination-of-the-enantiomeric-purity-of-the-selective-dopamine-transporter-inhibitor-r-r-4-2-benzhydryloxyethyl-1-4-fluorobenzyl-piperidin-3-ol
#3
Patrick Neiens, Georg Höfner, Klaus T Wanner
(+)-R,R-D-84 ((+)-R,R-4-(2-benzhydryloxyethyl)-1-(4-fluorobenzyl)piperidin-3-ol) is a promising pharmacological tool for the dopamine transporter (DAT), due to its high affinity and selectivity for this target. In this study, an analytical method to ascertain the enantiomeric purity of this compound was established. For this purpose, a high-performance liquid chromatographic (HPLC) method, based on a cellulose derived chiral stationary phase (CSP) was developed. The method was characterized concerning its specificity, linearity, and range...
April 24, 2017: Chirality
https://www.readbyqxmd.com/read/28436118/enantioselective-potential-of-polysaccharide-based-chiral-stationary-phases-in-supercritical-fluid-chromatography
#4
Gabriela Kucerova, Kveta Kalikova, Eva Tesarova
The enantioselective potential of two polysaccharide-based chiral stationary phases for analysis of chiral structurally diverse biologically active compounds was evaluated in supercritical fluid chromatography using a set of 52 analytes. The chiral selectors immobilized on 2.5 μm silica particles were tris-(3,5-dimethylphenylcarmabate) derivatives of cellulose or amylose. The influence of the polysaccharide backbone, different organic modifiers, and different mobile phase additives on retention and enantioseparation was monitored...
April 24, 2017: Chirality
https://www.readbyqxmd.com/read/28429401/synthesis-of-l-threitol-based-crown-ethers-and-their-application-as-enantioselective-phase-transfer-catalyst-in-michael-additions
#5
Zsolt Rapi, Tamás Nemcsok, Ádám Pálvölgyi, György Keglevich, Alajos Grün, Péter Bakó
A few new l-threitol-based lariat ethers incorporating a monoaza-15-crown-5 unit were synthesized starting from diethyl l-tartrate. These macrocycles were used as phase transfer catalysts in asymmetric Michael addition reactions under mild conditions to afford the adducts in a few cases in good to excellent enantioselectivities. The addition of 2-nitropropane to trans-chalcone, and the reaction of diethyl acetamidomalonate with β-nitrostyrene resulted in the chiral Michael adducts in good enantioselectivities (90% and 95%, respectively)...
April 21, 2017: Chirality
https://www.readbyqxmd.com/read/28422452/enantioselective-synthesis-of-s-naproxen-using-immobilized-lipase-on-chitosan-beads
#6
Saeedeh L Gilani, Ghasem D Najafpour, Hamid D Heydarzadeh, Aliakbar Moghadamnia
S-naproxen by enantioselective hydrolysis of racemic naproxen methyl ester was produced using immobilized lipase. The lipase enzyme was immobilized on chitosan beads, activated chitosan beads by glutaraldehyde, and Amberlite XAD7. In order to find an appropriate support for the hydrolysis reaction of racemic naproxen methyl ester, the conversion and enantioselectivity for all carriers were compared. In addition, effects of the volumetric ratio of two phases in different organic solvents, addition of cosolvent and surfactant, optimum pH and temperature, reusability, and inhibitory effect of methanol were investigated...
April 19, 2017: Chirality
https://www.readbyqxmd.com/read/28422447/lc-ms-ms-and-chiroptical-spectroscopic-analyses-of-multidimensional-metabolic-systems-of-chiral-thalidomide-and-its-derivatives
#7
Yoshiyuki Ogino, Masahito Tanaka, Togo Shimozawa, Toru Asahi
Enantiomeric thalidomide undergoes various kinds of biotransformations including chiral inversion, hydrolysis, and enzymatic oxidation, which results in several metabolites, thereby adding to the complexity in the understanding of the nature of thalidomide. To decipher this complexity, we analyzed the multidimensional metabolic reaction networks of thalidomide and related molecules in vitro. Characteristic patterns in the amount of various metabolites of thalidomide and related molecules generated during a combination of chiral inversion, hydrolysis, and hydroxylation were observed using liquid chromatography-tandem mass spectrometry and chiroptical spectroscopy...
April 19, 2017: Chirality
https://www.readbyqxmd.com/read/28422383/liquid-and-subcritical-fluid-chromatographic-enantioseparation-of-n-%C3%AE-fmoc-proteinogenic-amino-acids-on-quinidine-based-zwitterionic-and-anion-exchanger-type-chiral-stationary-phases-a-comparative-study
#8
Gyula Lajkó, Nóra Grecsó, Gábor Tóth, Ferenc Fülöp, Wolfgang Lindner, István Ilisz, Antal Péter
Stereoselective high-performance liquid chromatographic and subcritical fluid chromatographic separations of 19 N(α) -Fmoc proteinogenic amino acid enantiomers were carried out by using Quinidine-based zwitterionic and anion-exchanger-type chiral stationary phases Chiralpak ZWIX(-) and QD-AX. For optimization of retention and enantioselectivity, the ratio of bulk solvent components (MeOH/MeCN, H2 O/MeOH, or CO2 /MeOH) and the nature and concentration of the acid and base additives (counter- and co-ions) were systematically varied...
April 19, 2017: Chirality
https://www.readbyqxmd.com/read/28422324/optical-resolution-and-mechanism-using-enantioselective-cellulose-sodium-alginate-and-hydroxypropyl-%C3%AE-cyclodextrin-membranes
#9
Li-Ming Yuan, Wei Ma, Mei Xu, Hui-Lin Zhao, Yuan-Yuan Li, Rui-Lin Wang, Ai-Hong Duan, Ping Ai, Xue-Xian Chen
Chiral solid membranes of cellulose, sodium alginate, and hydroxypropyl-β-cyclodextrin were prepared for chiral dialysis separations. After optimizing the membrane material concentrations, the membrane preparation conditions and the feed concentrations, enantiomeric excesses of 89.1%, 42.6%, and 59.1% were obtained for mandelic acid on the cellulose membrane, p-hydroxy phenylglycine on the sodium alginate membrane, and p-hydroxy phenylglycine on the hydroxypropyl-β-cyclodextrin membrane, respectively. To study the optical resolution mechanism, chiral discrimination by membrane adsorption, solid phase extraction, membrane chromatography, high-pressure liquid chromatography ultrafiltration were performed...
April 19, 2017: Chirality
https://www.readbyqxmd.com/read/28421627/impact-of-microorganisms-humidity-and-temperature-on-the-enantioselective-degradation-of-imazethapyr-in-two-soils
#10
REVIEW
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
https://www.readbyqxmd.com/read/28418612/an-efficient-and-enantioselective-michael-addition-of-aromatic-oximes-to-%C3%AE-%C3%AE-unsaturated-aldehydes-promoted-by-a-chiral-diamine-catalyst-derived-from-%C3%AE-%C3%AE-diphenyl-prolinol
#11
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
https://www.readbyqxmd.com/read/28403536/enantiomeric-nmr-signal-separation-behavior-and-mechanism-of-samarium-iii-and-neodymium-iii-complexes-with-s-s-ethylenediamine-n-n-disuccinate
#12
Sen-Ichi Aizawa, Masaru Okano, Takahiro Kidani
Enantiomeric (1) H and (13) C NMR signal separation behaviors of various α-amino acids and DL-tartarate were investigated by using the samarium(III) and neodymium(III) complexes with (S,S)-ethylenediamine-N,N'-disuccinate as chiral shift reagents. A relatively smaller concentration ratio of the lanthanide(III) complex to substrates was suitable for the neodymium(III) complex compared with the samarium(III) one, striking a balance between relatively greater signal separation and broadening. To clarify the difference in the signal separation behavior, the chemical shifts of β-protons for fully bound D- and L-alanine (δb (D) and δb (L)) and their adduct formation constants (Ks) were obtained for both metal complexes...
April 12, 2017: Chirality
https://www.readbyqxmd.com/read/28370482/thermal-effects-in-guest-host-systems-zn2-bdc-s-lac-dmf-%C3%A2-phetoh-a-dsc-and-nmr-study
#13
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
https://www.readbyqxmd.com/read/28370343/chromatographic-enantioseparation-by-poly-biphenylylacetylene-derivatives-with-memory-of-both-axial-chirality-and-macromolecular-helicity
#14
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
https://www.readbyqxmd.com/read/28349561/helical-screw-sense-bias-in-chiral-polyfluorene-stimulated-by-solvent
#15
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
https://www.readbyqxmd.com/read/28349560/evaluation-of-the-chiral-recognition-properties-and-the-column-performances-of-three-chiral-stationary-phases-based-on-cellulose-for-the-enantioseparation-of-six-dihydropyridines-by-high-performance-liquid-chromatography
#16
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
https://www.readbyqxmd.com/read/28332282/chirally-sensitive-collision-induced-dissociation-of-proton-bound-diastereomeric-complexes-of-tryptophan-and-2-butanol
#17
Oleksii Rebrov, Kostiantyn Kulyk, Mauritz Ryding, Richard D Thomas, Einar Uggerud, Mats Larsson
In this work we report the stereo-dependent collision-induced dissociation (CID) of proton-bound complexes of tryptophan and 2-butanol. The dissociation efficiency was measured as a function of collision energy in single collision mode. The homochiral complex was found to be less stable against CID than a heterochiral one. Additional gas dependence measurements were performed with diastereomeric complexes that confirm the findings.
March 23, 2017: Chirality
https://www.readbyqxmd.com/read/28328107/chiral-exploration-of-6-12-diphenyldibenzo-b-f-1-5-diazocine-with-stable-conformation
#18
Zheng-Yi Li, Yong Pan, Lin-Lin Jin, Yue Yin, Bao-Zhu Yang, Xiao-Qiang Sun
A first optical resolution of 6,12-diphenyldibenzo[b,f][1,5]diazocine with stable boat conformation was achieved by chiral supercritical fluid chromatography (SFC). The absolute configurations of enantiomers were first assigned and determined by X-ray crystal structure based on CIP-rules. The high optical rotation and circular dichroism spectrum were well explained by electronic helix theory. Owing to the high stabilization of boat conformation, the chiral configuration could be maintained at very high temperature, more than 200 °C, which was proved by Density Functional Theory calculations...
March 22, 2017: Chirality
https://www.readbyqxmd.com/read/28321927/enantioseparation-and-enantioselective-behavior-of-trichlorfon-enantiomers-in-sediments
#19
Xiao-Feng Gao, Jing Nie, Xiao-Kun Ouyang, Yang-Guang Wang, Wei-Jian Wu
Trichlorfon (TF), an organophosphorus insecticide, has been widely used in seawater aquaculture; it is easily degraded to the highly toxic insecticide, dichlorvos (DDVP). In this study, the enantioseparation of TF enantiomers, as well as their degradation behavior and product (DDVP) formation in mariculture pond sediments, was investigated. The results show that both TF enantiomers degrade into DDVP, which is the main degradation product. Furthermore, S-(+)-TF is preferentially degraded under natural conditions, suggesting that TF enantiomers degrade enantioselectively...
March 21, 2017: Chirality
https://www.readbyqxmd.com/read/28403568/preparative-chiral-separation-and-absolute-configuration-of-the-synthetic-pterocarpanquinone-lqb-118
#20
Gabriel S Scatena, Neila M Cassiano, Chaquip D Netto, Paulo R R Costa, Quezia B Cass, João M Batista
The racemic pterocarpanquinone LQB-118 is active, in mice and hamsters, against tegumentary and visceral leishmaniasis. This compound also presents antiinflammatory and antineoplastic activity in mice. The low level of toxicity observed in these studies makes LQB-118 a promising drug candidate. In order to conduct further biological testing to investigate enantioselectivity in the above-mentioned activities, a multimilligram amount of each enantiomer of LQB-118 was produced. Furthermore, vibrational circular dichroism (VCD) and Density Functional Theory (DFT) calculations were used to determine unambiguously their absolute configurations...
May 2017: Chirality
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