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Lee J.,Chiral Technologies Inc. | Lee J.T.,Chiral Technologies Inc. | Watts W.L.,Chiral Technologies Inc. | Barendt J.,Chiral Technologies Inc. | And 6 more authors.
Journal of Chromatography A | Year: 2014

Polysaccharide-derived selectors are often used in the separation of enantiomers by supercritical fluid chromatography (SFC). Their recognition patterns are normally investigated with alcohols and acetonitrile as modifiers. The present paper describes the results of a research program designed by Pfizer and Chiral Technologies Inc. to explore the potential of other solvents (i.e. ethyl acetate, tetrahydrofuran, dichloromethane) in SFC by using a series of polysaccharide-derived supports with broad solvent versatility (CHIRALPAK IA, IB, IC, ID, IE and IF). The contribution of such extended solvent range to the overall success rate, as well as to overcome racemization, solubility and stability issues was confirmed by using standard non-proprietary samples and research molecules. Elution patterns with such lower polarity solvents, compared to alcohols, and the role of the different additives were also investigated. © 2014 Elsevier B.V.All rights reserved.

Harrison A.,Palacky University | Melchionna M.,Palacky University | Franco P.,Chiral Technologies Europe | Hlavac J.,Palacky University
New Journal of Chemistry | Year: 2014

3,6-Dihydro-2H-1,2-oxazines were synthesised via solid-phase synthesis to afford mixtures of stereo- and regioisomers. The analytical conditions for the analysis of the isomer ratio suitable for checking of reaction conditions of possible stereoselective synthesis were developed with the use of HPLC including chiral stationary phases (CSPs) based on chiral polysaccharide derivatives immobilized on a silica support. It was found that those CSPs based on an amylose backbone were more efficient than those based on cellulose for the molecules investigated. Additionally, analytical samples without complete purification could be separated under the same conditions. The asymmetric induction causing the difference in the stereoisomer ratio was observed, when an oxazine ring was built up directly on a chiral moiety. A chiral aminoacid separated from the construction site by an achiral aromatic ring did not influence the ratio of stereoisomers. The analytical conditions developed were thus verified for use in the optimisation of the regio- and stereoselective synthesis of 3,6-dihydro-2H-1,2-oxazines. The conditions are suitable for solid-phase synthesis methodology often used in high throughput synthesis of biologically active compounds. This journal is © the Partner Organisations 2014.

Jovanovic P.,University of Belgrade | Randelovic J.,University of Belgrade | Ivkovic B.,University of Belgrade | Suteu C.,Chiral Technologies Europe | And 2 more authors.
Journal of the Serbian Chemical Society | Year: 2014

Chiral, polysubstituted proline esters, obtained via cycloaddition reactions of azomethine ylides, were studied as organocatalysts in the Michael reaction of aldehydes/ketones and vinylsulphones. Under optimised reaction conditions employing 10 mol % of the catalyst in wet CH2Cl2, the yields of the products were generally good while the enantioselectivity varied, reaching up to 52 %. © 2014 SCS.

Franco P.,Chiral Technologies Europe | Zhang T.,Chiral Technologies Europe | Gargano A.,University of Vienna | Mahut M.,University of Vienna | And 2 more authors.
LC GC Europe | Year: 2012

Quinine- and quinidine-derived anion-exchanger chiral stationary phases are versatile tools for enantiomer separation of acidic compounds in high performance liquid chromatography (HPLC). This article demonstrates their recognition ability in specific HPLC applications, involving enantiomer resolution and piasmid topoisomer separation. The extension of their applications from HPLC to supercritical fluid chromatography (SFC) was also investigated, with the aim of assessing the influence of a series of parameters and gaining insight into the general approaches for SFC method development and optimization.

Zhang T.,Chiral Technologies Europe | Holder E.,Chiral Technologies Europe | Franco P.,Chiral Technologies Europe | Lindner W.,University of Vienna
Journal of Chromatography A | Year: 2014

CHIRALPAK ZWIX(+) and ZWIX(-) are cinchona alkaloid-derived zwitterionic chiral stationary phases (CSPs) containing a chiral sulfonic acid motif which serves as negatively charged interaction site. They are versatile for direct enantiomer resolution of amino acids and many other ampholytic compounds by HPLC. The synergistic double ion-pairing between the zwittrionic chiral selector and the ampholyte is the basis for interaction and chiral recognition mechanisms. ZWIX(+) and ZWIX(-) type CSPs or columns behave pseudo-enantiomerically and provide the feature of reversing enantiomer elution order by column switching. In the current study, extensive experimental work was carried out with the aim of developing schemes for an efficient generic screening and proposing straightforward approaches for method optimization on these ZWIX columns. Various chromatographic parameters were investigated using a large series of diverse amino acids and analogues for the purpose. The role of methanol (MeOH) as the protic solvent in the mobile phase is confirmed to be essential. The presence of water in a low percentage is beneficial for peak shape, resolution, analysis speed, sample solubility and MS detection performance. The involvement of acetonitrile (ACN) or tetrahydrofuran (THF) can help for adjusting retention time and selectivity. Incorporation of a suitable pair of acidic-basic additives at a right ratio in the mobile phase is determinant as well for the double ion-pairing mechanism. 50 mM formic acid+25mM diethylamine (or ammonium hydroxide) in MeOH/ACN/H2O and in MeOH/THF/H2O at 49:49:2 (by volume) are recommended as the starting mobile phases for method development. Some other parameters are also considered in the proposed scheme to achieve successful enantioselective or stereoselective separation of the ampholytes. © 2014 Elsevier B.V.

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