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- Stereoselective Accumulation of Propranolol Enantiomers in K562 and K562/ADR Cells. [JOURNAL ARTICLE]
- Chirality 2013 May 9.
The stereoselective uptake of propranolol enantiomers was investigated by using the K562 and K562 adriamycin-resistant cell line (K562/ADR) as a model. An enantioselective RP-HPLC method was applied to determine the accumulation of propranolol (PPL) stereoisomers in K562 and K562/ADR cells. The concentration, time and temperature dependent studies showed that the accumulation of S-(-)-PPL was higher than R-(+)-PPL in K562 cells and uptake of R-(+)-PPL was significantly higher than that of S-(-)-PPL in K562/ADR cells. The results indicate the enantioselective accumulation of propranolol enantiomers in K562 and K562 / ADR cells. Chirality 00:000-000, 2013. © 2013 Wiley Periodicals, Inc.
- Stereoselective Degradation and Microbial Epimerization of Triadimenol in Soils. [JOURNAL ARTICLE]
- Chirality 2013 May 9.
Triadimenol is a widely used triazole fungicide and consists of four stereoisomers with 1R,2S, 1S,2R, 1R,2R, and 1S,2S configurations. The trans-enantiomeric pair (1R,2S-isomer and 1S,2R-isomer) is also called triadimenol-A and the cis-enantiomeric pair (1R,2R-isomer and 1S,2S-isomer) triadimenol-B. In this study, the stereoselective degradation and chiral stability of triadimenol in two soils were investigated in details. The dissipation of technical triadimenol, a 6:1 mixture of triadimenol-A and triadimenol-B, showed significant epimerization from triadimenol-A to triadimenol-B occurred along with the dissipation process. The degradation exhibited some stereoselectivity, resulting in a concentration order of 1S,2S > 1R,2R > 1R,2S > 1S,2R or 1S,2S > 1R,2R > 1S,2R > 1R,2S at the end of the 100 days incubation for Baoding soil or Wuhan soil, respectively. Further incubation of triadimenol-B revealed no epimerization, i.e. triadimenol-B was configurationally stable in soil, and 1R,2R-triadimenol degraded slightly slower in the former part and slightly faster in the later part of the incubation than 1S,2S-triadimenol. Moreover, by incubation of enantiopure 1S,2R-triadimenol and 1R,2S-triadimenol, the results documented the epimerization for each enantiomer occurred at both C-1 and C-2 positions. Finally, the present work also documented that the enantiomerization reaction for all the four stereoisomers was nearly negligible in the soils. Chirality 00:000-000:, 2013. © 2013 Wiley Periodicals, Inc.
- Stereodynamics of Nitrogen Chiral Centers in aza-β(3) -Cyclodipeptides. [JOURNAL ARTICLE]
- Chirality 2013 May 9.
The present work is devoted to the synthesis, conformational analysis, and stereodynamic study of aza-β(3) -cyclodipeptides. This pseudopeptidic ring shows E/Z hydrazide bond isomerism, eight-membered ring conformation, and chirotopic nitrogen atoms, all of which are elements that are prone to modulate the ring shape. The (E,E) twist boat conformation observed in the solid state by X-ray diffraction is also the ground conformation in solution, and emerges as the lowest in energy when using quantum chemical calculations. The relative configuration associated with ring chirality and with the two nitrogen chiral centers is governed by steric crowding and adopts the (P)SN SN /(M)RN RN combination which projects side chains in equatorial position. The nitrogen pyramidal inversion (NPI) at the two chiral centers is correlated with the ring reversal. The process is significantly hindered as was shown by VT-NMR experiments run in C2 D2 Cl4 , which did not make it possible to determine the barrier to inversion. Finally, these findings make it conceivable to resolve enantiomers of aza-β(3) -cyclodipeptides by modulating the backbone decoration appropriately. Chirality 00:000-000, 2013. © 2013 Wiley Periodicals, Inc.
- A Validated Normal Phase LC Method for Enantiomeric Separation of Rasagiline Mesylate and Its (S)-Enantiomer on Cellulose Derivative-Based Chiral Stationary Phase. [JOURNAL ARTICLE]
- Chirality 2013 May 9.
A simple, sensitive, and robust normal-phase isocratic HPLC-UV method was developed and validated for the enantiomeric separation of rasagiline mesylate and its (S)-enantiomer. The rasagiline and its (S)-enantiomer were resolved on a Chiralcel-OJ-H (4-methylbenzoate cellulose coated on silica) column using a mobile phase consisting of n-hexane:isopropyl alcohol:ethanol:diethyl amine (96:2:2:0.01) at a flow rate of 1.0 ml/min. The column temperature was maintained at 27 °C and elution was monitored at 215 nm. The resolution (Rs ) between the enantiomers was found to be more than 2.0. The limit of detection and the limit of quantification of the (S)-enantiomer were found to be 0.35 and 1.05 µg/ml, respectively. The developed method was validated as per ICH guidelines with respect to linearity, limit of detection and quantification, accuracy, precision, and robustness-and satisfactory results were obtained. The sample solution and mobile phase were found to be stable up to 48 h. The method is useful for routine evaluation of the quality of rasagiline mesylate in bulk drug-manufacturing units. Chirality 00:000-000, 2013. © 2013 Wiley Periodicals, Inc.
- Enantiomeric fraction determination of 2-arylpropionic acids in a package plant membrane bioreactor. [Journal Article]
- Chirality 2013 May; 25(5):301-7.
Enantiomeric compositions of three 2-arylpropionic acid (2-APA) drugs, ibuprofen, naproxen, and ketoprofen, were monitored in a membrane bioreactor (MBR) treating municipal effluent in a small rural town in Australia. Specific enantiomers were determined as amide diastereomers using the chiral derivatizing reagent, (R)-1-phenylethylamine (PEA), followed by gas chromatography-tandem mass spectrometry (GC-MS/MS). The six individual enantiomers were quantified by isotope dilution and the enantiomeric fractions (EFs) were determined. Over four separate sampling events, ibuprofen EF ranged from 0.88 to 0.94 (median 0.93) in the influent and 0.38 to 0.40 (median 0.39) in the effluent. However, no significant change in ketoprofen EF was observed, with influent EFs of 0.56-0.60 (median 0.58) and effluent EFs 0.54-0.68 (median 0.56). This is the first report of enantiospecific analysis of ketoprofen in municipal wastewater and it is not yet clear why such different behavior was observed compared to ibuprofen. Naproxen EF was consistently measured at 0.99 in the influent and ranged from 0.86 to 0.94 (median 0.91) in the effluent. This study demonstrates that EF is a relatively stable parameter and does not fluctuate according to concentration or other short-term variables introduced by sampling limitations. The enantiospecific analysis of chiral chemicals presents a promising approach to elucidate a more thorough understanding of biological treatment processes and a potential tool for monitoring the performance of key biological pathways. Chirality 25:301-307, 2013. © 2013 Wiley Periodicals, Inc.
- Absolute configuration and predominant conformations of a chiral crown ether-based colorimetric sensor: a vibrational circular dichroism spectroscopy and DFT study of chiral recognition. [Journal Article]
- Chirality 2013 May; 25(5):294-300.
In the present work, we report a comprehensive vibrational circular dichroism (VCD) spectroscopic study of a chiral crown ether which features an axial chiral 3.3'-diphenyl-1,1'-binaphthyl group as chiral moiety. By comparing the experimental and calculated VCD spectra, we show that the presumably very flexible crown ether preferably adopts only one ring conformation. Conformational flexibility is observed in the 2,4-dinitrophenyl-diazophenol group, which was previously introduced for colorimetric detection of primary amines and amino alcohols (Cho et al., Chirality 2011;23:349-353). The VCD spectra of the host-guest complexes with phenyl glycinol (PG) and phenyl alaninol have been studied as well. Based on the spectra calculated, it is shown that the diastereomeric complexes in general can be differentiated using VCD spectroscopy. Furthermore, the experimental VCD spectra of the complexes of the host molecule with PG support the above finding. Chirality 25:294-300, 2013. © 2013 Wiley Periodicals, Inc.
- Differential pharmacologic properties of the two c75 enantiomers: (+)-c75 is a strong anorectic drug; (-)-c75 has antitumor activity. [Journal Article]
- Chirality 2013 May; 25(5):281-7.
C75 is a synthetic compound described as having antitumoral properties. It produces hypophagia and weight loss in rodents, limiting its use in cancer therapy but identifying it as a potential anti-obesity drug. C75 is a fatty acid synthase (FAS) inhibitor and, through its coenzyme A (CoA) derivative, it acts as a carnitine palmitoyltransferase (CPT) 1 inhibitor. Racemic mixtures of C75 have been used in all the previous studies; however, the potential different biological activities of C75 enantiomers have not been examined yet. To address this question we synthesized the two C75 enantiomers separately. Our results showed that (-)-C75 inhibits FAS activity in vitro and has a cytotoxic effect on tumor cell lines, without affecting food consumption. (+)-C75 inhibits CPT1 and its administration produces anorexia, suggesting that central inhibition of CPT1 is essential for the anorectic effect of C75. The differential activity of C75 enantiomers may lead to the development of potential new specific drugs for cancer and obesity. Chirality 25:281-287, 2013. © 2013 Wiley Periodicals, Inc.
- Asymmetric zinc-catalyzed hydrosilylation of ketones and the effect of carboxylate on the enantioselectivity. [Journal Article]
- Chirality 2013 May; 25(5):275-80.
Several chiral ligands containing (R,R)-diaminocyclohexane moieties and pyrrole, furan, or benzene have been synthesized. These ligands were tested in enantioselective zinc-catalyzed hydrosilylation reactions; excellent enantioselectivities were obtained when the ligands containing (R,R)-diaminocyclohexane moieties and furan rings were used. For comparison, zinc chloride combined with different potassium carboxylate salts and ligands were also tested for catalytic hydrosilylation reactions. Chirality 25:275-280, 2013. © 2013 Wiley Periodicals, Inc.
- Biological stereoselectivity of atropisomeric natural products and drugs. [Journal Article]
- Chirality 2013 May; 25(5):265-74.
Selected examples of natural product and drug atropisomers that exhibit stereoselectivity towards receptor and enzyme targets are reviewed. The atropisomeric preference of the receptors and enzyme binding domains makes these agents attractive molecules for drug development in the treatment of various diseases. Included are commonly recognized atropisomers containing a chiral biaryl axis along with some less common examples of atropisomers without a biaryl axis. The biological targets include: antiapoptotic proteins; bacteria; microtubules; kinases; vasopressin receptors; a G-protein coupled receptor related to obesity; monocarboxylate transporters; tachykinin NK1 -receptors; cyclooxygenase-1 and squalene synthase. Chirality 25:265-274, 2013. © 2013 Wiley Periodicals, Inc.
- Space asymmetry as a possible global feature. [Journal Article]
- Chirality 2013 May; 25(5):308-11.
A series of reports in the literature indicated symmetry breaking in assemblies of chiral molecules of opposite handedness. These unexpected observations could be accounted for as being generated by the "parity violation" of the nuclear weak force, combined with an autocatalytic amplification process. However, in many such cases, in particular of chiral fluids, this putative mechanism is far from providing a reasonable explanation for such discrimination. In this article it is suggested that space may have deviated a priori from absolute symmetry, a possibility which complies with observations in atoms and molecules and may even be implicated in the asymmetrical configuration of spiral galaxies. Space asymmetry can be extrapolated to a difference between the relative statistical weights of the "right" versus the "left" directions with respect to Euclidian coordinates or, analogously, to a difference between the clockwise and anticlockwise orientations in polar coordinates. The difference in weights of these directions in space is estimated to be around 1%, based on the differences observed in density values of chiral fluids and chiral crystals of NaClO3 . The implied asymmetry of time, as the conjugated fourth dimension, suggests a similar difference in magnitude of the time coordinate in a right-handed versus left-handed space, which is feasible for experimental verification. Chirality 25:308-311, 2013. © 2013 Wiley Periodicals, Inc.