Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 11
    ISSN: 0899-0042
    Keywords: high-performance liquid chromatography ; nonporous chiral stationary phase ; MICRA NPS ; tert-butyl carbamoylated quinine selector ; weak chiral anion exchanger ; N-protected α-amino acids ; DNP ; DNB ; DNZ ; mobile phase optimization ; DryLab ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this study, tert-butyl carbamoylated quinine as chiral selector was immobilized on nonporous silica (NPS) 1.5 μm particles developed by MICRA, and this new chiral stationary phase (CSP) was packed into a 3.3 cm column (4.6 mm ID). A series of various N-protected α-amino acids was chosen as chiral selectands, including 3.5-dinitrobenzyloxycarbonyl amino acids (DNZ-AAs). In order to optimize the chromatographic conditions with this novel CSP and to apply it to the resolution of acidic analytes the following parameters have been varied and studied: pH of the mobile phase, buffer concentration, and percentage of methanol or acetonitrile in the mobile phase. DryLabR software was applied to optimize enantioseparation by simulating chromatographic functions of experimental conditions for isocratic and/or gradient runs. Thus, we were able to resolve a set of test compounds within several minutes, whereby our attention was particularly drawn to the resolution of DNZ-AA derivatives. Chirality 9:157-161, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 12
    ISSN: 0899-0042
    Keywords: hyperthyroidism ; (R)-4-hydroxypropranolol ; peripheral conversion ; metabolites of propranolol ; negative chronotropic effect ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The inhibiting effect of (R,S)-propranolol on peripheral T4/T3 conversion can be related to the (R)-isomer. The intention of this study is to clarify if (R)-4-hydroxypropranolol, a main metabolite of (R)-propranolol, develops the same or even a stronger effect on peripheral thyroxine metabolism as the parent drug. (R)-4-hydroxypropranolol was synthesized via (R)-4-methoxypropranolol and their optical purity was checked chromatographically. Twenty patients suffering from hyperthyroidism were divided into five groups and treated with (R)-4-hydroxypropranolol · HCl in dosages from 12 to 75 mg per day in a placebo controlled study over a period of 5 days. The serum hormone levels and resting pulse rate were measured. No significant changes of thyroid parameter could be observed but a significant decrease of resting pulse rate under treatment with 75 mg (R)-4-hydroxypropranolol occurred. It could be concluded that (R)-4-hydroxypropranolol possesses negative chronotropic effects but develops no changes in thyroid hormone metabolism in hyperthyroid patients.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 13
    ISSN: 0899-0042
    Keywords: enantiomers ; chirality ; beta-blockers ; iodocyanopindolol ; cardiology ; adrenergic receptors ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In a randomized, double-blind, cross-over study in 12 healthy volunteers, the effects of single oral doses of 100 mg rac-atenolol were compared during exercise to those of equal amounts of the optically pure enantiomers, i.e., 50 mg (R)- and 50 mg (S)-atenolol. The mean rate pressure product decreased with rac-atenolol (-37%; P 〈 0.01) and half-dosed (S)-atenolol (-35%; P 〈 0.01) to the same extent, whereas (R)-atenolol caused no effect. Radioligand binding studies in beta-adrenergic receptors of the guinea pig heart yielded a eudismic ratio of 46 for (S)- to (R)-atenolol. The mean AUCs, maximal plasma concentrations, and plasma half-lives of the enantiomers were similar regardless of whether they were administered as optically pure enantiomers or as racemic mixture. On the other hand, the AUC of (R)-atenolol was 1.08-fold greater (P 〈 0.01) than that of the (S)-enantiomer. The reason for this finding remains unclear. We conclude that only (S)-atenolol, but not (R)-atenolol, contributes to the beta-blocking effect of currently used rac-atenolol since the same effect can be elicited with the (S)-enantiomer alone. © 1993 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 14
    ISSN: 0899-0042
    Keywords: atenolol ; nitrile formation ; stability ; chromatography ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chemical stability of the acetamido moiety of the β-blocker atenolol toward possible dehydration causing a nitrile formation during an acid-catalyzed chiral derivatization procedure with O,O′-(R,R)-diacylated tartaric acid anhydrides was elucidated. All the necessary reference compounds including the oxazolidine-2-one derivatives of the respective aminopropanols were synthesized, their structures confirmed by various spectroscopic methods, and chromatographically compared using HPLC and GC-MS. In the course of this work it was shown that the acetamido moiety of atenolol is quite stable toward dehydrating agents but shows a significant thermolability, e.g., in the injection system of a GC, which leads to the dehydrated form of atenolol namely, “nitriloatenolol.” © 1994 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 15
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The recent developments in enantioselective HPLC-separation techniques are impressive and are driven by industrial and academic interests; thus there is for instance a high demand for developing stereoselective assays for chiral drugs in biological fluids. The beta-blocking agents, which possess an amino- propanol- or -ethanol side chain with at least one chiral centre, represent one of the most intensively investigated groups of more than 40 drugs introduced world wide. Seven of the most popular beta-blockers were chosen as representatives: atenolol; betaxolol; carvedilol; metoprolol; pindolol; propranolol; and sotalol, these span the whole range of lipophilicity to hydrophilicity (polarity). Enantioselective HPLC bioassays for these β-blockers published so far, including techniques based on chiral derivatizing agents (CDAs), chiral stationary phases (CSPs) and chiral mobile phase additives (CMPAs) have been reviewed and documented in the light of general aspects together with pharmacokinetic and pharmacodynamic considerations.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 16
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Biomedical Chromatography 3 (1989), S. 153-156 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An automated column-switching HPLC system is described for the simultaneous determination of midodrine, an alpha-adrenergic stimulating drug, and its active metabolite, ST-1059. Serum or plasma (850 μ L) is directly injected onto a RP 18 (30 μm particle size) pre-column (9 × 4 mm ID) which acts as an on-line liquid-solid extractor and analyte enrichment system. The injection is followed by washing steps. The fraction containing the analytes is transferred onto an analytical RP18 column via step gradient elution where the final analysis is performed. Fluorescence detection is used (λex 290 nm and λem 322 nm), and method detection limits of 0.8 ng/mL plasma were reached. These were sufficiently low to determine the plasma concentration-time profiles for both compounds following oral administration of 2.5 mg and 5 mg midodrine hydrochloride. The assay in serum or plasma was linear in the range of 1 to 15 ng analyte/mL, the recovery was 〉95%, and the reproducibility was sufficient. The assay was rugged and was maintained by routinely changing the home-made, dry packed pre-column every 20th serum injection.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 17
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 333 (1989), S. 730-730 
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Microchimica acta 104 (1991), S. 113-128 
    ISSN: 1436-5073
    Keywords: enantioseparation ; liquid chromatography ; chiral recognition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this brief overview diverse chiral recognition models and chiral host-guest (selector-selectand, SO-SA) relationships which are used in enantioselective chromatography are discussed. In particular it is focussed on aspects of chiral interactions on (a) small molecular “brush type” chiral stationary phases (CSPs) and on (b) biopolymer and synthetic polymer type CSPs. The importance and the great variability of intermolecular SO-SA bindings via complementary contact sites, also in connection with molecule conformations, is stressed. Some representative and selected examples of chromatographic enantioseparations are presented.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 19
    Electronic Resource
    Electronic Resource
    Springer
    Microchimica acta 95 (1988), S. 123-126 
    ISSN: 1436-5073
    Keywords: diffuse reflectance ; infrared spectroscopy ; quantitative analysis ; HPLC phase characterization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Chemically modified silica gels are investigated with respect to identity, purity and degree of surface coverage using diffuse reflectance FTIR (DRIFT) Spectroscopy. We report the results for two bonded HPLC phases, pyrene butyric acid propylamido- and octadecyl-groups grafted on irregular porous silica gel. For quantitative determination calibration standards are prepared by adsorbing structurally similar ligand compounds onto the surface of the silica gel; these coated materials give linear calibration curves up to a concentration of 1 mmol/g modified silica gel.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 20
    ISSN: 0935-6304
    Keywords: High-performance liquid chromatography ; β-methyl amino acids ; enantioseparation ; quinine-derived chiral stationary phase ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A quinine-derived chiral anion-exchange stationary phase was used for the direct high-performance liquid chromatographic separation of the enantiomers of the N-protected unusual β-substituted α-amino acids, β-methylphenylalanine, β-methyltyrosine, β-methyltryptophan, and β-methyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid. The readily prepared 2,4-dinitrophenyl and tert-butyloxycarbonyl derivatives were well separated, and in most cases the separation of all four stereoisomers of these β-methyl-α-amino acids could be obtained in one chromatographic run. The elution sequences of the enantiomers of the different derivatives were determined and revealed a dependence on the type of the N-protecting group. In this context, the effects of different protecting groups (acetyl, tert-butyloxycarbonyl, benzoyl, 3,5-dinitrobenzoyl, benzyloxycarbonyl, 3,5-dinitrobenzyloxycarbonyl, 2,4-dinitrophenyl, and 9-fluorenylmethoxycarbonyl) on the chromatographic behavior were investigated.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...