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  • 1
    Digitale Medien
    Digitale Medien
    Evaluation of the macrocyclic antibiotic vancomycin as a chiral selector for capillary electrophoresis (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 496-509 
    Details
    ISSN: 0899-0042
    Schlagwort(e): enantiomeric separations ; macrocyclic antibiotics capillary electrophoresis ; vancomycin ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Vancomycin is one of a family of related macrocyclic glycopeptide antibiotics that were discovered by scientists at the Eli Lilly Company in the 1950s. It has been used to treat severe staphylococcal infections, particularly when bacterial resistance to other antibiotics has developed. Vancomycin is a naturally occurring chiral compound and has a number of stereogenic centers. Furthermore, it contains a variety of functionalities that are known to be useful for enantioselective interactions (e.g., hydrogen bonding groups, hydrophobic pockets, aromatic groups, amide linkages, etc.). The physicochemical properties of vancomycin, including its stability in solution, are discussed as they pertain to capillary electrophoresis. Over 100 racemates were resolved including many nonsteroidal antiinflammatory drugs, antineoplastic compounds and N-derivatized amino acids. Many of these compounds had very high resolution factors. Optimization and the effect of different experimental parameters on the enantioselective separations are discussed. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060609
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  • 2
    Digitale Medien
    Digitale Medien
    Highly enantioselective HPLC separations using the covalently bonded macrocyclic antibiotic, ristocetin A, chiral stationary phase (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 434-483 
    Details
    ISSN: 0899-0042
    Schlagwort(e): ristocetin A ; macrocyclic antibiotic ; enantiomeric separations ; underivatized amino acids ; chiral stationary phase ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The macrocyclic glycopeptide, ristocetin A, was covalently bonded to a silica gel support and evaluated as a liquid chromatographic (LC) chiral stationary phase (CSP). Over 230 racemates were resolved in either the reversed-phase mode, the normal-phase mode, or the polar-organic mode. The retention behavior and selectivity of this CSP were examined in each mode. Optimization of separations on this column is discussed. The ristocetin A CSP appeared to be complimentary to other glycopeptide CSPs (i.e., vancomycin and teicoplanin). Column stability was excellent. The CSP was not irreversibly altered when going from one mobile phase mode to another. Chirality 10:434-483, 1998. © 1998 Wiley-Liss, Inc.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Evaluation of the macrocyclic antibiotic avoparcin as a new chiral selector for HPLC (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 627-660 
    Details
    ISSN: 0899-0042
    Schlagwort(e): avoparcin ; macrocyclic antibiotics ; enantiomeric separations ; chiral stationary phases ; verapamil ; thyroxine ; mephenytoin ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Avoparcin is a macrocyclic glycopeptide antibiotic structurally related to vancomycin, teicoplanin, and ristocetin A. When attached to 5-μm spherical silica gel, the avoparcin proved to be an effective chiral stationary phase (CSP) that could be used in the reversed-phase, normal-phase, and polar-organic modes. The avoparcin CSP was complimentary to the other macrocyclic glycopeptide CSPs in that it could resolve some racemates that the others could not, and vice versa. Some important compounds resolved on the avoparcin CSP include verapamil, thyroxine, mephenytoin, and 2-imidazolidone-4-carboxylic acid. The use of this CSP and the optimization of separations on it are discussed. Avoparcin appears to be a useful addition to this family of CSPs. Chirality 10:627-660, 1998. © 1998 Wiley-Liss, Inc.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Capillary electrophoretic enantiomeric separations using the glycopeptide antibiotic, teicoplanin (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 8 (1996), S. 88-107 
    Details
    ISSN: 0899-0042
    Schlagwort(e): teicoplanin ; glycopeptide antibiotics ; capillary electrophoresis ; enantioselectivity ; separation ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Teicoplanin is the third in a series of macrocyclic glycopeptide antibiotics that has been evaluated as a chiral selector in capillary electrophoresis (CE). It was used to resolve over 100 anionic racemates at low selector concentrations. Like the other related glycopeptide antibiotics, its enantioselectivity tends to be opposite to that of the ansa-type antibiotics which prefers cationic compounds, particularly amines. Factors that affect teicoplanin-based enantioseparations include the selector concentration, pH, and the concentration of the organic modifier. The temperature and the nature and strength of the buffer are also known-to affect the stability of the chiral selector as well as the enantioseparation. Teicoplanin exhibited some features that were not noted with the other glycopeptide antibiotics. For example, it aggregates (forms micelles) in aqueous solutions and this influences its enantioselectivity. Unlike the other studied glycopeptides, teicoplanin precipitates in alcohol-water mixtures. It also binds less to the capillary wall than vancomycin as evidenced by the faster electroosmotic flow velocity. The micellization of teicoplanin is pH dependent so that the effect of pH on enantiorecognition is more complex for teicoplanin than for other chiral selectors. Also it is shown that the simple model proposed to explain the role of organic modifiers in cyclodextrin-based CE enantioseparations may not apply to these and other systems. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Liquid chromatographic separation of anomeric forms of saccharides with cyclodextrin bonded phases (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 1 (1989), S. 27-37 
    Details
    ISSN: 0899-0042
    Schlagwort(e): mutarotation ; sugars ; carbohydrates ; isomeric ; separation ; temperature effects ; selectvity ; optimization ; hemiacetal ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A brief review of sugar stereochemistry is given. The separation of 84 different pairs of anomers was accomplished on both α- and β-cyclodextrin columns. Five different mobile phases were evaluated. The separation of anomers temperature, flow rate, and so on. The separation of anomers that mutarotate is somewhat more difficult than those that do not. Prior knowledge as to the rate of mutaroation is useful so that the chromatographic conditions can be arranged to minimize any deleterious effects on the separation.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530010108
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  • 6
    Digitale Medien
    Digitale Medien
    A covalently bonded teicoplanin chiral stationary phase for HPLC enantioseparations (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 474-497 
    Details
    ISSN: 0899-0042
    Schlagwort(e): enantiomeric separations ; teicoplanin ; macrocyclic antibiotic ; amino acids ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A macrocyclic glycopeptide antibiotic containing a hydrophobic “tail” is covalently attached to silica gel via linkage chains. This material is extensively evaluated as a chiral stationary phase (CSP) for HPLC. The relevant structural features of the teicoplanin molecule which make it an effective chiral selector are discussed. The teicoplanin CSP appears to have excellent enantioselectivity for native amino acids, peptides, α-hydroxycarboxylic acids, and a variety of neutral analytes including cyclic amides and amines. Enantio-separations can be achieved in the reversed phase, normal phase, and “polar-organic” modes. This chiral selector is stable and the integrity of the CSP is excellent in all separation modes. Hence it can be considered a highly effective multimodal column. Optimization of these separations is discussed in terms of both selectivity and efficiency. Results indicate that the surface loading of the chiral selector affects all relevant separation parameters. A hypothesis is proposed to explain the enhanced efficiency obtained when using teicoplanin CSPs with higher surface coverage. It appears that teicoplanin is a widely applicable, highly effective chiral selector for HPLC enantioseparations. © 1995 Wiley-Liss, Inc.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530070614
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