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See detailEnantiomeric separation of clenbuterol by transient ITP-CE-MS
Toussaint, B.; Bergmann, J.; Hubert, Philippe ULg et al

Poster (1999)

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See detailEnantiomeric separation of N-protected amino acids by non-aqueous capillary electrophoresis with dimeric forms of quinine and quinidine derivatives serving as chiral selectors
Piette, Vincent ULg; Lindner, W.; Crommen, Jacques ULg

in Journal of Chromatography. A (2002), 948(1-2), 295-302

A non-aqueous capillary electrophoretic method with quinine and tert.-butyl carbamoylated quinine as chiral selectors was developed previously for the enantioseparation of N-protected amino acids. This ... [more ▼]

A non-aqueous capillary electrophoretic method with quinine and tert.-butyl carbamoylated quinine as chiral selectors was developed previously for the enantioseparation of N-protected amino acids. This system was here applied as a screening tool for a fast evaluation of the chiral discrimination potential of six new dimeric forms of carbamoylated quinine and quinidine derivatives as chiral additives: 1,3-phenylene-bis(carbamoylated quinine), 1,6-hexamethylene-bis(carbamoylated quinine), 1,6-hexamethylene-bis(carbamoylated quinidine), trans-1,4-cyclohexylene-bis(carbamoylated quinine), trans-1,4-cyclohexylene-bis(carbamoylated-11-dodecylthio-dihydroquinine) and trans-1,4-cyclohexylene-bis(carbamoylated-11-dodecylsulfinyl-dihydroquinine). A series of 24 chiral acids, as various benzoyl, 3,5-dinitrobenzoyl (DNB) and 3,5-dinitrobenzyloxycarbonyl amino acid derivatives were investigated with regards to enantioselectivity employing these different dimeric chiral selectors. The composition of the background electrolyte was 12.5 mM ammonia, 100 mM octanoic acid, and 10 mM chiral selector in an ethanol-methanol (60:40, v/v) mixture and the enantioseparations were performed at 15 degreesC and in the reversed polarity mode at -25 kV. With these dimeric chiral selectors, higher enantioselectivity values, compared to those obtained with monomeric derivatives, were usually achieved, especially with the dimers containing dodecyl substituents. For example, an a value of 4 and a resolution value of 78 were obtained for DNB-phenylalanine, using trans-1,4-cyclohexylene-bis(carbamoylated-11-dodecylthio-dihydroquinine) as selector. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailEnantiomeric Separation of Pirlindole by Liquid Chromatography Using Different Types of Chiral Stationary Phases
Ceccato, Attilio ULg; Hubert, Philippe ULg; De Tullio, Pascal ULg et al

in Journal of Pharmaceutical & Biomedical Analysis (1998), 18(4-5), 605-14

The enantioseparation of pirlindole by liquid chromatography (LC) was investigated using three different chiral stationary phases (CSPs) containing either cellulose tris-(3,5-dimethylphenylcarbamate ... [more ▼]

The enantioseparation of pirlindole by liquid chromatography (LC) was investigated using three different chiral stationary phases (CSPs) containing either cellulose tris-(3,5-dimethylphenylcarbamate) (Chiralcel OD-R), ovomucoid (OVM) or beta-cyclodextrin (beta-CD). The effects of the mobile phase pH on retention, enantioselectivity and resolution were studied. Methanol and acetonitrile were tested as organic modifiers while the influence of the addition to the mobile phase of sodium alkanesulfonates or sodium perchlorate was also investigated. Sodium perchlorate was only used on the Chiralcel OD-R column while sodium alkanesulfonates were tested as mobile phase additives on the three kinds of CSPs. The enantioseparation of pirlindole could be obtained on all CSPs tested, the best results with respect to chiral resolution being achieved on the Chiralcel OD-R and the OVM columns. The use of sodium octanesulfonate (NaOS) was found to improve the enantioseparation of pirlindole on the OVM column while enantioselectivity was considerably enhanced by addition of sodium perchlorate on the Chiralcel OD-R column. [less ▲]

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See detailEnantiomeric separations by capillary electrophoresis applications in pharmaceutical, biomedical and environmental analysis, chapitre #L-7
Crommen, Jacques ULg; Fillet, Marianne ULg; Bechet, Isabelle et al

in Buszewski, B. (Ed.) New analytical methods for environmental control and monitoring (1995)

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See detailEnantiomeric Separations of Drugs Using Mixtures of Charged and Neutral Cyclodextrins
Fillet, Marianne ULg; Hubert, Philippe ULg; Crommen, Jacques ULg

in Journal of Chromatography. A (2000), 875(1-2), 123-34

An overview on the use of mixtures of neutral and charged cyclodextrins as chiral additives for the enantioseparation of drugs by capillary electrophoresis is presented. These so called dual cyclodextrin ... [more ▼]

An overview on the use of mixtures of neutral and charged cyclodextrins as chiral additives for the enantioseparation of drugs by capillary electrophoresis is presented. These so called dual cyclodextrin systems can often provide unique selectivities. A brief theoretical background illustrating the influence of the chiral discrimination ability and the effective mobility of the two cyclodextrins on the overall selectivity of the enantiomeric separation is given. Typical examples of applications in the pharmaceutical field, based on the simultaneous use of a charged (cationic or anionic) and neutral cyclodextrins, are described. [less ▲]

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See detailEnantioresolution of basic pharmaceuticals using cellulose tris(4-chloro-3-methylphenylcarbamate) as chiral stationary phase and polar organic mobile phases.
Dossou, Katina Sourou Sylvestre ULg; Chiap, Patrice ULg; Chankvetadze, Bezhan et al

in Journal of Chromatography. A (2009), 1216(44), 7450-5

A polysaccharide-based chiral stationary phase (Sepapak-4), with cellulose tris(4-chloro-3-methylphenylcarbamate) as chiral selector, has been investigated in liquid chromatography (LC). Its ... [more ▼]

A polysaccharide-based chiral stationary phase (Sepapak-4), with cellulose tris(4-chloro-3-methylphenylcarbamate) as chiral selector, has been investigated in liquid chromatography (LC). Its enantioresolution power was evaluated towards 13 basic amino-drugs with widely different structures and polarities, using polar organic mobile phases. After preliminary experiments, acetonitrile was selected as the main mobile phase component, to which a low concentration of diethylamine (0.1%) was systematically added in order to obtain efficient and symmetrical peaks. Different organic solvents were first added in small proportions (5-10%) to acetonitrile to modulate analyte retention. Polar organic modifiers were found to decrease retention and enantioresolution while hexane had the opposite effect, indicating normal-phase behaviour under these conditions. The addition of an organic acid (formic, acetic or trifluoroacetic acid) was found to strongly influence the retention of the basic amino drugs in these nonaqueous systems. The nature and proportion of the acidic additive in the mobile phase had also deep impact on enantioresolution. Therefore, the studied compounds could be subdivided in three groups in respect to the acidic additive used. All analytes could be enantioseparated in relatively short analysis times (10-20min) using these LC conditions. [less ▲]

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See detailEnantioselective Determination of Oxprenolol in Human Plasma Using Dialysis Coupled on-Line to Reversed-Phase Chiral Liquid Chromatography
Ceccato, Attilio ULg; Toussaint, B.; Chiap, Patrice ULg et al

in Journal of Pharmaceutical & Biomedical Analysis (1997), 15(9-10), 1365-74

A fully automated method for the determination of the enantiomers of oxprenolol in human plasma was developed, involving dialysis through a cellulose acetate membrane, clean-up and enrichment of the ... [more ▼]

A fully automated method for the determination of the enantiomers of oxprenolol in human plasma was developed, involving dialysis through a cellulose acetate membrane, clean-up and enrichment of the dialysate on a short precolumn and subsequent chiral liquid chromatographic (LC) analysis. All sample handling operations were executed automatically by a sample processor equipped with a robotic arm (ASTED system). The trace enrichment column (TEC) was packed with octadecylsilica. After conditioning of the TEC with the LC mobile phase and pH 3.0 acetate buffer. After the enrichment step, the analyte was transferred by the LC mobile phase to the analytical column by means of a switching valve. The influence of different parameters of the dialysis process on the recovery of oxprenolol was first investigated using achiral LC conditions. The volume as well as the aspirating and dispensing flow rates of the acceptor solution were the main parameters studied. Oxprenolol was separated on a C18 stationary phase used for the enantioseparation of oxprenolol was a Chiralcel OD-R column which contained cellulose tris (3,5-dimethylphenylcarbamate) coated on silica as chiral selector. The corresponding mobile phase consisted of a mixture of pH 6.0 phosphate buffer containing NaClO4 at 0.45 M concentration and acetonitrile (70:30 v/v). UV detection was performed at 273 nm. The method developed was validated. Recoveries for each enantiomer of oxprenolol were about 80%. The method was found to be linear in the 50-2500 ng ml-1 concentration range (r2 = 0.999 for both enantiomers) and good results with respect to intra- and inter-day reproducibility as well as accuracy were obtained. [less ▲]

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See detailEnantioselective synhteses of n.c.a. L-2-[18F]fluoro-4-chlorophenylalanine and of L-(a-methyl)-2-[18F]fluoro-4-chlorophenylalanine.
Al-Darwich, M. J.; Plenevaux, Alain ULg; Lemaire, Christian ULg et al

in Journal of Nuclear Medicine : Official Publication, Society of Nuclear Medicine (1994), 35

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See detailEnantioselective Syntheses and Absolute Configuration of the Ladybird Defence Alkaloids (+)-Calvine and (+)-2-Epicalvine
Laurent, Pascal ULg; Braekman, Jean-Claude; Daloze, Désiré

in European Journal of Organic Chemistry (2000), 11

Enantiomerically pure (+)-calvine (1a) and (+)-2-epicalvine (Ib), two piperidine alkaloids isolated from ladybird beetles of the genus Calvia (Coccinellidae), were synthesized by two different strategies ... [more ▼]

Enantiomerically pure (+)-calvine (1a) and (+)-2-epicalvine (Ib), two piperidine alkaloids isolated from ladybird beetles of the genus Calvia (Coccinellidae), were synthesized by two different strategies starting from (-)-2,3,6,7,8,8a-hexahydro-3-phenyl-5H-[1,3]oxazolo[3,2-a]pyridine-5-carbonitrile (2). The key steps of these syntheses are the stereocontrolled formation of an asymmetric centre a to the nitrogen atom of 2 and the subsequent introduction of the methoxycarbonylmethyl substituent at the u'-position. Comparison of the optical rotations of the synthetic benzoates (12a) and (12b) with those of the corresponding benzoates derived from the natural compounds has revealed the absolute configuration of (+)-calvine to be (2S,6S) and that of (+)-2-epicalvine to be (2R,6S). [less ▲]

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See detailEnantioselective syntheses of n.c.a. L-(a-methyl)-[b-11C]-4-chlorophenylalanine and L-(a-[11C]methyl-tryptophan.
Plenevaux, Alain ULg; Al-Darwich, M. J.; Lemaire, Christian ULg et al

in Journal of Labelled Compounds & Radiopharmaceuticals (1994), 35

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See detailENANTIOSELECTIVE SYNTHESES OF NCA (S)-L-[BETA-C-11]-4-CHLOROPHENYLALANINE AND (S)-L-(ALPHA-METHYL)-[BETA-C-11]-4-CHLOROPHENYLALANINE
Plenevaux, Alain ULg; Al-Darwich, M. J.; Lemaire, Christian ULg et al

in Applied Radiation & Isotopes (1994), 45(3), 361-369

The radiolabeling of (S)-L-4-chlorophenylalanine and (S)-L-(alpha-methyl)-4-chlorophenylalanine were realized with carbon-11 at position beta through a radiochemical synthesis relying on the highly ... [more ▼]

The radiolabeling of (S)-L-4-chlorophenylalanine and (S)-L-(alpha-methyl)-4-chlorophenylalanine were realized with carbon-11 at position beta through a radiochemical synthesis relying on the highly enantioselective reaction between 4-chloro[alpha-C-11]benzyl bromide and the lithium enolate of (S)-1-(t-butyloxycarbonyl)-2-(t-butyl)-3-methyl-1,3-imidazolidine-4-one for (S)-L-[beta-C-11]-4-chlorophenylalanine and of (2S,5S)-1-(t-butyloxycarbonyl)-2-(t-butyl)-3,5-dimethyl-1,3-imidazolidin e-4-one for (S)-L-(alpha-methyl)-[beta-C-11]-4-chlorophenylalanine. Quantities of about 25-35 mCi were obtained at the end of synthesis, ready for injection, after hydrolysis and HPLC purification with a radiochemical yield of 19% corrected to EOB within 45 min. The enantiomeric excesses were shown to be greater than or equal to 97% for both molecules without chiral separation. The radiochemical and the chemical purities of the final compounds were greater than or equal to 98% and the specific activity at the end of synthesis ranged between 250-800 mCi/mu mol. [less ▲]

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See detailEnantioselective syntheses of no-carrier-added (nca) (S)-4-chloro-2 F-18 fluorophenylalanine and (S)-(alpha-methyl)-4-chloro-2 F-18 fluorophenylalanine
Al-Darwich, M. J.; Plenevaux, Alain ULg; Lemaire, Christian ULg et al

in Journal of Fluorine Chemistry (1996), 80(2), 117-124

(S)-4-Chloro-2-fluorophenylalanine and (S)-( a-methyl)-4-chloro-2-fluorophenylalanine were synthesized and labeled with no carrier added (n.c.a.) fluorine-18 through a radiochemical synthesis relying on ... [more ▼]

(S)-4-Chloro-2-fluorophenylalanine and (S)-( a-methyl)-4-chloro-2-fluorophenylalanine were synthesized and labeled with no carrier added (n.c.a.) fluorine-18 through a radiochemical synthesis relying on the highly enantioselective reaction between 4-chloro-2-[18F] fluorobenzyl iodide and the lithium enolate of (2s) -1-( tert-butyloxycarbonyl) -2-( tert-butyl)-3-methyl- 1,3-imidazolidine-4-one for (S) -4-chloro-2- [18F] fluorophenylalanine and (2S,5S)-1-( tert-butyloxycarbonyl) -2-( tert-butyl) -3,5-dimethyl- 1,3-imidazolidine-4-one for (S) -( a-methyl) -4-chloro-2- [18F] fluorophenylalanine. Quantities of about 20-25 mCi were obtained at the end of synthesis, ready for injection after hydrolysis and high performance liquid chromatography (HPLC) purification, with a radiochemical yield of 17%-20% corrected to the end of bombardment after a total synthesis time of 90-105 min from [18F] fluoride. The enantiomeric excesses were shown to be 97% or more for both molecules without chiral separation and the radiochemical and chemical purities were 98% or better. [less ▲]

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