The Experts below are selected from a list of 1410 Experts worldwide ranked by ideXlab platform
Ivan Jelinek - One of the best experts on this subject based on the ideXlab platform.
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chiral analysis of biogenicdl amino acids derivatized by urethane protected α amino acidn carboxyanhydride using capillary zone electrophoresis and micellar electrokinetic chromatography
Electrophoresis, 2002Co-Authors: Martin Pumera, Martin Flegel, Luděk Lepsa, Ivan JelinekAbstract:A new analytical method for enantioselective separation of DL-amino acids derivatized by N-fluorenylmethoxycarbonyl-L-alanyl N-carboxyanhydride (FMOC-L-Ala-NCA) using capillary electrophoresis was developed. Separation parameters, such as composition and pH of the background electrolyte, and concentration of Gamma-Cyclodextrin (in capillary zone electrophoresis) and sodium dodecyl sulfate (in micellar electrokinetic chromatography) were optimized. The separation method was validated and it suits well for purity analysis. Detection limit of the method was 0.2% of the minor enantiomer in the major one. The level of racemization in coupling during solid-phase peptide synthesis was studied using capillary electrophoresis with Gamma-Cyclodextrin as a chiral selector. The anchorage of the first (C-terminal) amino acid derivative to the solid supports bearing the hydroxylic groups is the key step of the synthesis affecting the extent of its racemization. FMOC-L-phenylalanine was chosen as the suitable model amino acid derivative making it possible to study the degree of racemization of N-fluorenylmethoxycarbonyl-L-alanine-L-phenylalanine synthesized on different polymer resins, using the different condensation agents.
Daniel W Armstrong - One of the best experts on this subject based on the ideXlab platform.
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use of native and derivatized Cyclodextrin based and macrocyclic glycopeptide based chiral stationary phases for the enantioseparation of pterocarpans by hplc
Journal of Liquid Chromatography & Related Technologies, 2005Co-Authors: M M Warnke, Clifford R Mitchell, Roman V Rozhkov, D E Emrich, Richard C Larock, Daniel W ArmstrongAbstract:Abstract The enantioselectivity of native and derivatized Cyclodextrin stationary phases and macrocyclic glycopeptides for chiral pterocarpans was evaluated using high performance liquid chromatography (HPLC). All enantiomers could be baseline resolved in the reverse phase mode on Cyclodextrin‐based Cyclobond chiral stationary phases (CSPs). The hydroxypropyl‐β‐Cyclodextrin, acetyl‐β‐Cyclodextrin, and Gamma‐Cyclodextrin CSPs show the broadest enantioselectivity in the reverse phase mode. Some compounds were baseline separated on the ristocetin A and vancomycin macrocyclic glycopeptide chiral stationary phases in the reverse phase mode. Separations on the ristocetin A columns produced the highest resolutions (up to ∼7.1) in this study. The 3,5‐dimethylphenyl carbamate derivatized Cyclodextrin column showed the broadest enantioselectivity in normal phase LC. Of the macrocyclic glycopeptide CSPs, ristocetin A and teicoplanin aglycone (Chirobiotic R and TAG, respectively) showed enantioselectivity for the mos...
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separation of racemic sulfoxides and sulfinate esters on four derivatized Cyclodextrin chiral stationary phases using capillary gas chromatography
Journal of Chromatography A, 2002Co-Authors: Jared L Anderson, Jie Ding, Ryan D Mcculla, William S Jenks, Daniel W ArmstrongAbstract:The separation of 17 chiral sulfoxides and eight chiral sulfinate esters by gas chromatography (GC) on four derivatized Cyclodextrin chiral stationary phases (CSPs) (Chiraldex G-TA, G-BP, G-PN, B-DM) is presented. Many of these compounds are structural isomers or part of a homologous series. Differences in enantioselectivity of the methyl phenyl sulfoxide isomers on the derivatized Gamma Cyclodextrin and the heptakis 2,6-di-O-methyl-beta-Cyclodextrin (i.e. B-DM) CSPs are discussed. Under the conditions of this study, the molecular mass cut-off for the GC separation of these compounds was approximately 230. Compounds of higher molecular mass were not eluted from the CSPs at reasonable times and temperatures, but these higher molecular mass enantiomers can be separated by liquid chromatography and capillary electrophoresis. The enantiomeric separation and elution order of a sulfinate ester containing two stereogenic centers as well as 15 chiral sulfoxides is presented. The G-TA and B-DM CSPs generally gave opposite elution orders for most of the compounds studied.
Martin Pumera - One of the best experts on this subject based on the ideXlab platform.
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chiral analysis of biogenicdl amino acids derivatized by urethane protected α amino acidn carboxyanhydride using capillary zone electrophoresis and micellar electrokinetic chromatography
Electrophoresis, 2002Co-Authors: Martin Pumera, Martin Flegel, Luděk Lepsa, Ivan JelinekAbstract:A new analytical method for enantioselective separation of DL-amino acids derivatized by N-fluorenylmethoxycarbonyl-L-alanyl N-carboxyanhydride (FMOC-L-Ala-NCA) using capillary electrophoresis was developed. Separation parameters, such as composition and pH of the background electrolyte, and concentration of Gamma-Cyclodextrin (in capillary zone electrophoresis) and sodium dodecyl sulfate (in micellar electrokinetic chromatography) were optimized. The separation method was validated and it suits well for purity analysis. Detection limit of the method was 0.2% of the minor enantiomer in the major one. The level of racemization in coupling during solid-phase peptide synthesis was studied using capillary electrophoresis with Gamma-Cyclodextrin as a chiral selector. The anchorage of the first (C-terminal) amino acid derivative to the solid supports bearing the hydroxylic groups is the key step of the synthesis affecting the extent of its racemization. FMOC-L-phenylalanine was chosen as the suitable model amino acid derivative making it possible to study the degree of racemization of N-fluorenylmethoxycarbonyl-L-alanine-L-phenylalanine synthesized on different polymer resins, using the different condensation agents.
Venkatachalam. Mani - One of the best experts on this subject based on the ideXlab platform.
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Separation of chiral silicon compounds using permethylated .alpha.-, .beta.-, and .Gamma.-Cyclodextrin capillary GC columns
Analytical Chemistry, 1993Co-Authors: Binyamin. Feibush, Cole L. Woolley, Venkatachalam. ManiAbstract:Permethylated α-, β-, and γ-Cyclodextrin GC stationary phases were used to resolve racemic silane derivatives, R 1 R 2 Si * PhMe. Particularly good resolutions were obtained on the β-CD phase for racemates containing a silanol group, R 1 =OH
Massimo Morbidelli - One of the best experts on this subject based on the ideXlab platform.
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enantiomer separation of α ionone using gas chromatography with Cyclodextrin derivatives as chiral stationary phases
Journal of Chromatography A, 1999Co-Authors: Francesca Quattrini, Giovanni Biressi, Markus Juza, Marco Mazzotti, Claudio Fuganti, Massimo MorbidelliAbstract:The gas chromatographic enantiomer separation of alpha-ionone was studied with three different chiral stationary phases using as chiral selectors: (1) heptakis(2,3,6-tri-O-methyl)-beta-Cyclodextrin, dissolved in polysiloxane PS-086, (2) octakis(2,6-di-O-pentyl-3-O-trifluoroacetyl)-Gamma-Cyclodextrin and (3) octakis(2,6-di-O-pentyl-3-O-butanoyl)-Gamma-Cyclodextrin, both dissolved in polysiloxane SE-54. The influence of the concentration of the chiral selector in the polysiloxane, coated on Chromosorb P AW-DMCS 80-100 mesh, is described and discussed, as well as the effect of Chromosorb loading. The feasibility of the preparative gas chromatographic separation of the enantiomers of alpha-ionone is considered; in order to provide a term of comparison, the estimated performances are compared with those achieved in the separation of the enantiomers of the inhalation anaesthetic enflurane.
