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  • 1995-1999  (1,265)
  • 1860-1869
  • 1997  (1,265)
  • Organic Chemistry  (824)
  • Cell & Developmental Biology  (441)
  • Nuclear reactions
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Years
  • 1995-1999  (1,265)
  • 1860-1869
Year
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Enantiomeric separation of some piperidine-2,6-dione drugs using chiralcel OJ-R column (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 10-12 
    Details
    ISSN: 0899-0042
    Keywords: piperidine-2,6-dione ; chiral recognition ; enantioselectivity ; elution order ; cellulose based chiral stationary phase ; reversed phase mode ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A newly developed reversed phase cellulose tris(4-methyl benzoate) known as Chiralcel OJ-R was used to investigate the chiral recognition and enantiomeric separation of eight racemic piperidine-2,6-dione compounds - namely, aminoglutethimide and its major metabolite acetylaminoglutethimide, glutethimide, cyclohexylamino-glutethimide, pyridoglutethimide, thalidomide, phenglutarimide, and 3-phenylacetyl-amino-2,6-piperidinedione (antineoplaston A-10). Chiral separation of these compounds was achieved under varying ratios of the mobile phase, except for phenglutarimide and 3-phenylacetylamino-2,6-piperidinedione, for which separation was unsuccessful. Possible chiral recognition mechanisms are also presented. Chirality 9:10-12, 1997. © 1997 Wiley-Liss, Inc.
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  • 2
    Electronic Resource
    Electronic Resource
    Differential stereoselective pharmacokinetics of pantoprazole, a proton pump inhibitor in extensive and poor metabolizers of pantoprazole - a preliminary study (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 17-21 
    Details
    ISSN: 0899-0042
    Keywords: proton pump inhibitor ; pantoprazole ; stereoselective pharmacokinetics ; genetic polymorphism ; human ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pantoprazole (PAN) is a proton pump inhibitor that is administered as a racemic mixture. The pharmacokinetics of PAN enantiomers were investigated in extensive metabolizers (EMs) and apparent poor metabolizers (PMs) of PAN who received a single 40, 60, or 80 mg oral dose of racemic PAN as enteric-coated formulation. In the EMs, the serum concentrations of (-)-PAN were slightly higher than those of (+)-PAN at each dose level. The (+)/(-) ratios for the area under the concentration-time curve (AUC) and the half-life were 0.58-0.89 and 0.62-0.88, respectively. In the PMs, the serum concentrations of both enantiomers were much higher than those in the EMs at each dose level and significant differences in pharmacokinetics of (+)- and (-)-PAN were observed. The half-lives for (+)-PAN were 2.67-3.77 times longer than those for (-)-PAN. The AUCs for (+)-PAN were 2.65-3.45 times greater than those for (-)-PAN. Therefore, the metabolism of (+)-PAN is impaired to a greater extent than (-)-PAN in the PMs, which resulted in the stereoselective disposition of PAN in the PMs. It has been suggested that the EMs and the PMs of PAN could be differentiated by determining the (+)/(-) enantiomer ratio in serum at one time point, possibly 2-6 h after oral dosing, because the (+)/(-) enantiomer ratios in the PMs were opposite those in the EM subjects. Chirality 9:17-21, 1997 © 1997 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Configurational assignment of optically active hydroperoxy homoallylic alcohols and the corresponding diols by circular dichroism and multidimensional gas chromatography (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 69-74 
    Details
    ISSN: 0899-0042
    Keywords: diols ; hydroperoxides ; absolute configuration ; exciton coupling ; circular dichroism ; enantiomeric separation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Allylic hydroperoxides are a class of compounds of versatile synthetic utility. Optically active diastereomeric hydroperoxy homoallylic alcohols and their corresponding diols are easily available through horseradish peroxidase (HRP)-catalyzed kinetic resolution of racemic hydroperoxides. Here we describe the assignment of the absolute configuration of the optically active products and substrates obtained after HRP-catalysis by the circular dichroism exciton chirality method. Moreover, the analytical-scale separation of the enantiomers based on multidimensional gas chromatography on chiral columns is presented. Since the enantiomeric elution order on the ciral columns was constituted, the absolute stereochemistry of optically active allylic diols can easily be deduced by their retention times on β-cyclodextrins. Chirality 9:69-74, 1997. © 1997 Wiley-Liss, Inc.
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  • 4
    Electronic Resource
    Electronic Resource
    Possible uses of micellar electrokinetic capillary chromatography and high-performance liquid chromatography for the chiral discrimination of some pyrethroids (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 162-166 
    Details
    ISSN: 0899-0042
    Keywords: stereoisomer separation ; cyclodextrin ; pesticide ; capillary electrophoresis ; high-performance liquid chromatography ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Micellar electrokinetic capillary chromatography (MECC) and high-performance liquid chromatography (HPLC) were used for the separation of stereoisomers of the lipophilic uncharged pyrethroids cypermethrin, alphamethrin, permethrin, and fenpropathrin. Different kinds of cyclodextrin (β-cyclodextrin, hydroxypropyl-β-cyclodextrin, dimethyl-β-cyclodextrin, and γ-cyclodextrin), surfactants (sodium dodecyl sulphate [SDS] and cetyltrimethylammonium bromide [CTAB]), and cations of background electrolyte (sodium, ammonium, TRIS, and Ammediol) were tested. Optimized conditions (background electrolyte: 50 mmol/l sodium phosphate, pH ≈ 2.5, 150 mmol/l SDS, 150 mg/ml γ-cyclodextrin) allowed the separation of alphamethrin, the eight cypermethrin stereoisomers being eluted in seven peaks and the separation of two enantiomers of fenpropathrin with resolution Rs = 10 and with n ≃ 500,000 theoretical plates. Different experimental conditions, e.g., mobile phase composition, temperature, injected amount, and flow rate, were also optimized in HPLC experiments. The optimal conditions (stationary phase: ChiraDex, 5 μm; mobile phase: 150 mmol triethylamine/l with H2SO4 in water (pH = 3.5) with methanol or acetonitrile; flow rate: 0.8 or 0.6 ml/min; temperature: ambient or 30°, 20°, or 10°C; experimental conditions were modified according to the type of analysis) allow chiral discrimination of alphamethrin enantiomers and analysis of permethrin stereoisomers. MECC offers higher efficiency and shorter analysis time than HPLC, but under tested conditions it was shown that the methods complement each other. Chirality 9:162-166, 1997. © 1997 Wiley-Liss, Inc.
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  • 5
    Electronic Resource
    Electronic Resource
    Polymer-supported chiral diol as ligand of Ti(IV) for enantioselective Diels-Alder reaction (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 191-197 
    Details
    ISSN: 0899-0042
    Keywords: TADDOL ; titanium complexes ; chiral Lewis acid ; polymer-supported ; polystyrene-divinylbenzene ; enantioselective ; Diels-Alder ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the first polymer-supported TADDOL is reported. Its efficiency as chiral ligand of Ti(IV) was studied in the Diels-Alder cycloaddition of cyclopentadiene to 3-crotonoyl-1,3-oxazolidin-2-one, and was superior to that observed for its homogeneous equivalent. (4R,5R)-α,α,α′,α′-2-pentaphenyl-4,5-dimethanol-1,3-dioxolane. Recycling of the heterogeneous Ti(IV)-TADDOLate was also studied, being the most suitable method for the repreparation of the catalyst from the ligand after use. Chirality 9:191-197, 1997. © 1997 Wiley-Liss, Inc.
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  • 6
    Electronic Resource
    Electronic Resource
    Chiral recognition in liquid chromatography utilising chargeable cyclodextrins for resolution of doxazosin enantiomers (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 184-190 
    Details
    ISSN: 0899-0042
    Keywords: rac-doxazosin ; doxazosin ; liquid chromatography ; chiral ; carboxymethyl-β-cyclodextrin ; optimisation ; central composite design ; mobile phase additive ; experimental design ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chromatographic resolution of rac-doxazosin using reversed-phase high performance liquid chromatography (HPLC) with the chargeable chiral mobile phase additive, carboxymethyl-β-cyclodextrin (CM-β-CD), is described. The effects of different modifiers (acetonitrile, methanol and tetrahydrofuran), pH, temperature, and cyclodextrin concentration were investigated to (a) assess the key chromatographic parameters for subsequent chemometric optimisation, and (b) explore the enantioselective mechanism. Assuming a 1:1 complex between each doxazosin enantiomer and CM-β-CD, studies of the relationship between the capacity factors (k′) and functions of CM-β-CD concentration indicate that the mechanisms for retention and chiral selectivity are comparable with those proposed earlier by Sybilska et al.1 Stability constants (KG) calculated for rac-doxazosin complexed with CM-β-CD (647 ± 55 and 594 ± 45 M-1 for each enantiomer respectively) are significantly larger than those calculated for the barbiturates complexed with β-CD (ca. 101-108 M-1).1 Investigations on pH indicate an ionic or ion-pair interaction between the anionic CM-β-CD and the cationic doxazosin enantiomers.A central composite design was used to optimise the key chromatographic parameters: pH, methanol (v/v) and CM/β-CD concentration. The Kaiser peak separation index, Pi, was used for the response function. The predicted response for this chiral separation has been compared with that observed experimentally and samples of the four-dimensional response surface have been assessed for their value in showing robustness. Chirality 9:184-190, 1997. © 1997 Wiley-Liss, Inc.
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  • 7
    Electronic Resource
    Electronic Resource
    Chiral discrimination by NMR spectroscopy of ephedrine and N-methylephedrine induced by β-cyclodextrin, heptakis(2,3-di-O-acetyl)β-cyclodextrin, and heptakis (6-O-acetyl)β-cyclodextrin (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 211-219 
    Details
    ISSN: 0899-0042
    Keywords: 1H NMR β-cyclodextrin ; heptakis(2,3-di-O-acetyl)β-cyclodextrin ; heptakis(6-O-acetyl)β-cyclodextrin ; ephedrine derivatives ; job technique ; ROESY ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: NMR spectroxcopy has been used to compare the interaction of ephedrine and N-methylephedrine with β-cyclodextrin, heptakis(2,3-di-O-acetyl)β-cyclodextrin, heptakis(6-O-acetyl)β-cyclodextrin. The stoichiometry of the complexes formed between all three cyclodextrins and N-methylephedrine was found to be 1:1 by UV spectroscopy by means of the Job technique. NMR spectra of the single enantiomers of ephedrine and N-methylephedrine in the presence of all three cyclodextrins gave information about the parts of the ligands which interact differently with the host molecules and may be responsible for the chiral discrimination. To quantify the complex stabilities, binding constants were calculated from the changes in the chemical shifts of the ligand signals upon complexation. Analyses of the coupling constants of both species showed that no significant conformational change occurs upon complexation. ROESY spectra of these optical isomers with all three cyclodextrins provided detailed information about the geometry of the complexes. Different intermolecular cross-peaks between the individual isomers of ephedrine and N-Methylephedrine were found for native β-cyclodextrin and its 2,3-diacetylated derivative but not for 6-acetyl cyclodextrin. Analyses of the intramolecular cross-signals of the ligands confirmed that no significant conformational change occurs upon complexation. Chirality 9:211-219, 1997. © 1997 Wiley-Liss, Inc.
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  • 8
    Electronic Resource
    Electronic Resource
    Binding cross-reactivity of Boc-phenylalanine enantiomers on molecularly imprinted polymers (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 233-237 
    Details
    ISSN: 0899-0042
    Keywords: non-covalent molecular imprinting ; Scatchard plot ; batch rebinding ; site specificity ; boc-amino acids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A potential problem associated with molecularly imprinted polymer (MIP) sorbents is that of cross-reactivity. In this study three MIPs (imprinted with Boc-L-phenylalanine, Boc-L-alanine, Boc-L-glutamic acid) plus a non-imprinted control were prepared and examined for their ability to bind differentially the enantiomers of boc-protected phenylalanine in an effort to quantify cross-reactivity and to develop a predictive model. Batch rebinding studies showed a degree of predictability for a number of MIP-ligand pairs, but other combinations showed unexpectedly high levels of cross-reactivity. Despite the general acceptance of heterogeneity of MIP binding sites, many previous studies report linear Scatchard plots, which is indicative of binding site homogeneity. The data from this study produced curves, clearly demonstrating heterogeneity. The theoretical and practical implications of this heterogeneity are discussed. Chirality 9:233-237, 1997. © 1997 Wiley-Liss, Inc.
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  • 9
    Electronic Resource
    Electronic Resource
    Asymmetric hydrolyses of 1,2- and 1,3-diacetoxycyclohexanes with the cultured suspension cells of Marchantia polymorpha (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 250-253 
    Details
    ISSN: 0899-0042
    Keywords: 1,2-diacetoxycyclohexanes ; 1,3-diacetoxycyclohexanes ; 2,3-diacetoxynorbornanes ; 2,7-diacetoxynorbornane ; enantioselective hydrolysis ; biocatalyst ; cultured plant cells ; Marchantia polymorpha ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Very high enantioselectivities were observed in the hydrolysis of racemic 1,2- and 1,3-diacetoxycyclohexanes and their derivatives by cultured cells of Marchantia polymorpha in suspension. Asymmetry was also induced in the hydrolyses of meso-1,2- and 1,3-diacetates to the corresponding monoacetates. These findings indicate that these cultured cells hydrolyze the acetoxyl groups enantioselectively at the stereogenic center of R-configuration. Chirality 9:250-253, 1997. © 1997 Wiley-Liss, Inc.
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  • 10
    Electronic Resource
    Electronic Resource
    A mechanistic investigation of the microbial chiral inversion of 2-phenylpropionic acid by Verticillium lecanii (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 254-260 
    Details
    ISSN: 0899-0042
    Keywords: microbial chiral inversion ; 2-phenylpropionic acid ; kinetic isotope effect ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Previous investigations have described the development of nongrowing suspension of Verticillium lecanii as a microbial model of the mammalian chiral inversion of the 2-arylpropionic acids (2-APAs). Mechanistic studies in mammals have shown that inversion involves loss of the α-methine proton but retention of the original atoms at the β-methyl position, and a mechanism has been proposed involving enzymatic epimerisation of acyl-CoA thioester derivatives of the substrate. Inversion of the 2-APAs by V. lecanii exhibits extensive intersubstrate variation in the presence, rate, extent, and direction of inversion, which are different from those observed in mammalian systems, possibly indicating differences in the mechanism of inversion between mammalian and microbial cells. This study involved the investigation of proton/deuterium exchange by 1H-nuclear magnetic resonance following incubation of deuterated derivatives of 2-phenylpropionic acid (2-PPA), a model compound, in cell suspensions of V. lecanii and incubation of undeuterated 2-PPA in cell suspensions containing D2O. The results indicated that the inversion of 2-PPA by V. lecanii also involved exchange of the α-methine proton but complete retention on the original atoms at the β-methyl position. No kinetic deuterium isotope effect was observed, indicating that loss of the α-methine proton is not the rate-limiting step of the inversion process. This suggests that the observed differences between microbial and mammalian systems probably involve the stereoselective acyl-CoA thioester formation step and not the subsequent epimerisation of the resultant diastereomers. Chirality 9:254-260, 1997. © 1997 Wiley-Liss, Inc.
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  • 11
    Electronic Resource
    Electronic Resource
    Enantioseparation of N-protected α-amino acid derivatives by liquid-liquid extraction technique employing stereoselective ion-pair formation with a carbamoylated quinine derivative (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 268-273 
    Details
    ISSN: 0899-0042
    Keywords: enantioselective transport ; single two-phase liquid-liquid extraction ; N-protected α-amino acid derivatives ; quinine carbamate-type chiral selectors ; chiral anion-exchange carrier ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two-phase liquid-liquid extraction experiments were undertaken to study the enantioselective transport of the chiral N-protected α-amino acid derivatives from an aqueous buffer solution into an organic phase employing highly lipophilic carbamoylated quinine as chiral selector and phase transfer carrier, respectively. The chiral separation, derived from enantioselective ion-pair formation and differential solubility in the aqueous and organic phases of diastereomeric associates thus formed has been shown to be primarily dependent on the structure of the selectand, the nature of the organic solvent, the molar ratio of a given chiral selector to selectand in the two phases, and the pH of the aqueous phase. Extracted enantiomers were recovered by back-extraction using a relatively polar acidic medium in which the selector is barely insoluble. Thus, the enantiomeric purity of N-(3,5-dinitrobenzoyl)-leucine exceeded 95% enantiomeric excess with 70% overall yield with a single extraction and back-extraction step. Chirality 9:268-273, 1997. © 1997 Wiley-Liss, Inc.
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  • 12
    Electronic Resource
    Electronic Resource
    Allosteric modulation by single enantiomers of a C3-chiral 1,4-benzodiazepine of the gamma aminobutyric acid type A receptor channel expressed in Xenopus oocytes (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 286-290 
    Details
    ISSN: 0899-0042
    Keywords: Xenopus oocytes ; stereochemistry ; chiral chromatography ; chiral benzodiazepines ; enantioselective modulation of GABAA receptor ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Xenopus laevis oocytes injected with Poly(A)+-RNA isolated from neuronal tissue express membrane proteins peculiar to the origin of mRNA. The translation of gamma aminobutyric acid type A (GABAA) receptors has been shown by dose/ response behavior of GABA and the reversible blockade of the GABA-induced current by picrotoxin. This current was analyzed quantitatively under two electrode voltage-clamp conditions. This methodology has been applied for the first time to study the functional properties of the receptor as a function of the stereochemistry of the ligands. The (+)-S and (-)-R enantiomers of a water-soluble benzodiazepine derivative, 7-chloro-1,3-dihydro-3-hemisuccinyloxy-5-phenyl-1,4-benzodiazepin-2-one (OXHEM), obtained by preparative high performance liquid chromatographic (HPLC) resolution on chiral stationary phase, act as agonists in the in vitro modulation of the chloride channel. The (+)-S-OXHEM enantiomer was the more active. Chirality 9:286-290, 1997. © 1997 Wiley-Liss, Inc.
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  • 13
    Electronic Resource
    Electronic Resource
    Effect of sialic acid residues of human α1-acid glycoprotein on stereoselectivity in basic drug-protein binding (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 291-296 
    Details
    ISSN: 0899-0042
    Keywords: capillary electrophoresis ; high-performance frontal analysis ; propranolol ; verapamil ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The function of sialic acid groups at the terminal of sugar chains of human α1-acid glycoprotein (AGP) was investigated with respect to chiral discrimination between optical isomers of basic drugs, using high-performance capillary electrophoresis/frontal analysis (HPCE/FA), a novel analytical method developed for the determination of unbound drug concentration with ultramicrosample volume (100-200 nl). Native human AGP and desialylated AGP were used as test proteins, and propranolol (PRO) and verapamil (VER) were used as model drugs. The unbound concentration of (S)-VER was 1.31 times higher than that of (R)-VER in native AGP solution. This selectivity was not affected by desialylation. Further, enzymatic elimination of galactose residues, which neighbored sialic acid groups, did not change the binding of either isomer of VER. On the other hand, the unbound concentration of (R)-PRO was 1.27 times higher than that of (S)-PRO in native AGP solution. Desialylation caused the unbound concentration of (S)-PRO to rise to the same level of (R)-PRO, resulting in loss of enantioselectivity. Thus, it follows that sialic acid groups of AGP, as a whole, are not responsible for chiral recognition between enantiomers of VER but are involved in enantioselectivity toward the isomers of PRO. Chirality 9:291-296, 1997. © 1997 Wiley-Liss, Inc.
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  • 14
    Electronic Resource
    Electronic Resource
    Pharmacokinetics of reboxetine enantiomers in the dog (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 303-306 
    Details
    ISSN: 0899-0042
    Keywords: reboxetine ; enantiomers ; dog ; pharmacokinetics ; HPLC determination ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reboxetine, (RS)-2-[(RS)-α-(2-ethoxyphenoxy)benzyl]morpholine methanesulphonate, is a racemic compound and consists of a mixture of the (R,R)- and (S,S)-enantiomers. The pharmacokinetics of reboxetine enantiomers were determined in a crossover study in three male beagle dogs. Each animal received the following oral treatments, separated by 1-week washout period: 10 mg/kg reboxetine, 5 mg/kg (R,R)- and 5 mg/kg (S,S)-. Plasma and urinary levels of the reboxetine enantiomers were monitored up to 48 h post-dosing using an enantiospecific HPLC method with fluorimetric detection (LOQ: 1.1 ng/ml in plasma and 5 ng/ml in urine for each enantiomer). After reboxetine administration mean tmax was about 1 h for both enantiomers. Cmax and AUC were about 1.5 times higher for the (R,R)- than for the (S,S)-enantiomer, mean values ± SD being 704 ± 330 and 427 ± 175 ng/ml for Cmax and 2,876 ± 1,354 and 1,998 ± 848 ng.h/ml for AUC, respectively. No differences between the (R,R)- and (S,S)-enantiomers were observed in t½ (3.9 h). Total recovery of the two enantiomers in urine was similar, the Ae (0-48 h) being 1.3 ± 0.7 and 1.1 ± 0.7% of the enantiomer dose for the (R,R)- and the (S,S)-enantiomers, respectively. No marked differences in the main plasma pharmacokinetic parameters were found for either enantiomer on administration of the single enantiomers or reboxetine. No chiral inversion was observed after administration of the separate enantiomers, as already observed in humans. Chirality 9:303-306, 1997. © 1997 Wiley-Liss, Inc.
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  • 15
    Electronic Resource
    Electronic Resource
    Enantioselective retardation of rac-propranolol from matrices containing cellulose derivatives (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 307-312 
    Details
    ISSN: 0899-0042
    Keywords: stereoselective release ; stereoselective dissolution ; propranolol ; enantiomers ; cellulose derivatives ; tablet matrices ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dissolution characteristics of propranolol enantiomers from tablet formulations containing cellulose, or one of eight cellulose derivatives, were determined under a range of conditions. The derivatives examined were: cellulose tris(phenylcarbamate) (1), cellulose tris(2,3-dichlorophenylcarbamate) (2), cellulose tris 2,4-dichlorophenylcarbamate (3), cellulose tris(2,6-dichlorophenylcarbamate) (4), cellulose tris(2,3-dimethylphenylcarbamate) (5), cellulose tris(3,4-dichlorophenylcarbamate) (6), cellulose tris (3,5-dichlorophenylcarbamate) (7), cellulose tris(3,5-dimethylphenylcarbamate) (8). In water at 25°C, the release rates of (-)R-propranolol were generally greater than those of (-)-S-propranolol, although these differences were not always statistically significant; only compounds 5 and 8 demonstrated significant enantioselectivity. Using compound 8 in further experiments, statistically significant stereoselective dissolution of propranolol HCl was observed in buffer pH 7.4 at 25°C (intrinsic dissolution rates: 0.41 ± 0.01 mgcm2min-1 for R-propranolol and 0.30 ± 0.02 mgcm2min-1 for S-propranolol; P = 0.003). The cumulative amounts of enantiomers released at every time point were also found to be statistically significant (mean ratio R:S 1.25 ± 0.05). The observed low stereoselectivity of 8 with propranolol base was probably attributable to low solubility in pH 7.4 buffer, although stereoselective release did increase with time. This suggested that there is a relationship between stereoselectivity and contact time in an aqueous environment. Results also suggested that increased temperature may affect the release process as well as stereoselective interactions of 8 with individual enantiomers. To conclude, differential release of rac-propranolol from cellulose derivative matrices has been demonstrated, which supports the principle of stereoselective retardation as a potential means of stereoselective drug delivery for solid dosage forms. Chirality 9:307-312, 1997. © 1997 Wiley-Liss, Inc.
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  • 16
    Electronic Resource
    Electronic Resource
    Studies on the in vitro inversion of flurbiprofen (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 317-319 
    Details
    ISSN: 0899-0042
    Keywords: NSAID metabolism ; rat liver microsomes ; metabolic pathway ; He-Ne laser ; (+)-(R)-1-phenylethylamides ; HPLC separation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper reports in vitro studies on the metabolic inversion of flurbiprofen (FL), an arylpropionic acid antiinflammatory agent (2-APA). The inversion was studied with both rac-FL and R-FL, by incubation with rat hepatic microsomes, in the presence of either CoASH and ATP or NADPH. The two isomers of the drug were separated as their (+)-(R)-1-phenylethylamides by direct phase high-performance liquid chromatography on a silica gel column with an achiral mobile phase. The inversion was more pronounced in the presence of CoASH and ATP for both the racemate and the R-isomer, which supports the key role of CoA thioesters in the metabolic inversion of profens. The inversion observed in the presence of NADPH suggests that, when the incubation is run with hepatic microsomes, a CYP450-mediated pathway is also active. In order to get more insight into the CYP450-mediated inversion pathway, we studied the effect of irradiating microsomes with a low dose of He-Ne laser radiation (0.2 J). Such irradiation caused a significant increase in inversion at all times studied and normalized the anomalous value of inversion observed at 15 min in his pathway. Chirality 9:317-319, 1997. © 1997 Wiley-Liss, Inc.
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    Chiral Assay of Atenolol Present in Microdialysis and Plasma Samples of Rats Using Chiral CBH as Stationary Phase (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 329-334 
    Details
    ISSN: 0899-0042
    Keywords: atenolol ; enantiomers ; liquid chromatography ; cellobiohydrolase I ; chiral CBH ; coupled-columns ; cellobiose ; peak compression ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two different enantioselective chiral chromatographic methods were developed and validated to investigate the disposition of the β1-receptor antagonist atenolol in blood and in brain extracellular fluid of rats (tissue dialysates). System A for the plasma samples was a one-column chromatographic system with a Chiral CBH column with an aqueous buffer as mobile phase into which cellobiose was added for selective regulation of the retention of the internal standard, (S)-metoprolol. The plasma samples were analysed after a simple extraction procedure. The limit of quantitation was 0.2 μg/ml for the atenolol enantiomers. The repeatability of the medium concentration quality control plasma sample (6.0 μg rac-atenolol/ml) was 11-18% for the enantiomers. The dynamic linear range of the plasma samples was 0.5-20 μg/ml. For system B, since atenolol is an extremely hydrophilic drug, the tissue dialysate sample required a much more sensitive system as compared to the plasma samples. A coupled column system was used for peak compression of the enantiomers in the eluate after the separation on the Chiral CBH column, hence increasing the detection sensitivity. The limit of quantification was 0.045 μg/ml for the atenolol enantiomers in artificial CSF. The repeatability of the medium concentration quality control samples (0.1 and 4.0 μg rac-atenolol/ml in artificial CSF and Hepes Ringer, respectively) was 2.8-9.3% for the two enantiomers. The dynamic linear range of the brain samples was 0.05-1.0 and 0.5-20 μg/ml in artificial CSF and Hepes Ringer, respectively. Chirality 9:329-334, 1997. © 1997 Wiley-Liss, Inc.
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    Enantioseparation on 4-halogen-substituted phenylcarbamates of amylose as chiral stationary phases for high-performance liquid chromatography (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 63-68 
    Details
    ISSN: 0899-0042
    Keywords: enantioseparation ; chiral stationary phase ; HPLC ; amylose phenylcarbamate ; chiral discrimination ; resolution ; enantiomer ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four 4-halogen-substituted phenylcarbamate derivatives of amylose were prepared and their chiral recognition abilities as chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) were evaluated and compared with those of the corresponding cellulose derivatives. The amylose derivatives with fluoro, chloro, bromo, or iodo group at the four-position on the phenyl group were found to show higher chiral resolving ability than the corresponding cellulose derivatives. Among four amylose derivatives 4-fluoro- and 4-chlorophenylcarbamates showed an excellent chiral recognition ability. Especially, amylose tris(4-chlorophenylcarbamate) resolved (±)-1,2,2,2-tetraphenylethanol with a very high α value (α = 8.29). In order to obtain useful information concerning the chiral recognition mechanism of this resolution, we also performed enantioseparation of a variety of analogous racemic alcohols, and found that both the hydroxy and bulky triphenylmethyl groups of the racemate are essential for the effective chiral recognition. Chirality 9:63-68, 1997. © 1997 Wiley-Liss, Inc.
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    Synthesis, chromatographic resolution and chiroptical properties of carboxyibuprofen stereoisomers: Major metabolites of ibuprofen in man (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 75-87 
    Details
    ISSN: 0899-0042
    Keywords: stereoselective synthesis ; carboxyibuprofen diastereoisomers ; circular dichroism ; chiral LC separation ; ibuprofen ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chromatographic resolution of the four stereoisomers of carboxyibuprofen, a major metabolite of ibuprofen in man, was achieved using a Chiralpak AD chiral stationary phase (CSP) (J.T. Baker, Milton, Keynes, UK). The elution order of the stereoisomers was determined to be 2′S,2R; 2′R,2R; 2′R,2S; 2′S,2S by a combination of stereoselective synthesis of diastereoisomeric mixtures and analysis of the two diastereoisomers isolated from human urine following the administration of (S)-ibuprofen. The individual stereoisomers were isolated by semipreparative chiral phase chromatography and characterized by circular dichroism spectroscopy. Chirality 9:75-87, 1997. © 1997 Wiley-Liss, Inc.
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    Erratum: Rondelli, I., Corsaletti, R., Redenti, E., Acerbi, D., Delcanale, M., Amari, G., Ventura, P. New method for the resolution of the enatiomers of 5,6-dihydroxy-2-methyl-aminotetralin by selective derivatization and HPLC. Chirality 8:381-389, 1996 (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 89-89 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the article listed above, the caption for Figure 5 should read as“Ionspray mass spectra of the negatively charged [DPB-CHF 1024] (A) and [DPB-CHF 1024 urea derivative] (B) complexes. The m/z values referred to the normal masses of ions.” rather than “Collision-activated dissociation spectrum of….”.The authors apologize for the error.
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    On the minimum requirements for chiral recognition (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 103-103 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
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    Comparison of capillary electrophoresis and liquid chromatography for the enantiomeric separation of α-phosphonosulfonic acids (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 104-108 
    Details
    ISSN: 0899-0042
    Keywords: capillary electrophoresis ; HPLC, α-phosphonosulfonic acid ; enantiomers, β-cyclodextrin ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantiomers of α-phosphonosulfonic acids were completely resolved by capillary electrophoresis using β-cyclodextrin as a chiral selector in a borate electrolyte and HPLC using a chiral AGP column. The methods were used to quantitate the R-enantiomer present as an impurity in the S-enantiomer, a potential cardiovascular drug candiate. Chirality 9:104-108, 1997. © 1997 Wiley-Liss, Inc.
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    Optical rotation detection for reversed phase HPLC: Investigation of solvent effects (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 122-125 
    Details
    ISSN: 0899-0042
    Keywords: enantiomeric excess determination ; polarimetry ; HPLC ; enantiomers ; solvent effects ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Investigations into the parameters affecting the sensitivity of polarimetric detectors for the determination of enantiomeric excess by achiral HPLC are presented. The results obtained showed that the specific optical rotation of an analyte was highly sensitive to the methanol content of the mobile phase. The purpose of this short communication is to demonstrate that “off-line” optical rotation measurements are a necessary part of the method development process for successful use of polarimetric detectors. Chirality 9:122-125, 1997, © 1997 Wiley-Liss, Inc.
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    1,3,5-Triazine multiselector systems: New tools for chiral discrimination (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 113-121 
    Details
    ISSN: 0899-0042
    Keywords: 1,3,5-triazine ; chiral discrimination ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2-Hexylamino-4-[(S)-1-(1-naphthyl)ethylamino]-6-L-valyl-L-valyl-L-valine isopropylester-1,3,5-triazine (1), a molecule characterized by two different chiral selectors, and 2-hexylamino-4,6-bis-L-valyl-L-valyl-L-valine isopropylester-1,3,5-triazine (2) and 2-ethoxy-4-hexylamino-6-[(S)-1-(1-naphthyl) ethylamino]-1,3,5-triazine (3), systems in which a single kind of chiral selector is present, have been prepared. The enantiodiscriminating ability in solution of the three compounds toward the N-3,5-dinitrobenzoyl derivatives of 1-phenylethylamine (4) or valine methylester (5) has been investigated by 1H nuclear magnetic resonance (NMR) spectroscopy: 1 shows an improved versatility, relative to 2 and 3, as a chiral solvating agent for NMR spectroscopy. On the basis of the indications obtained, the usefulness of 2-chloro-4-[(S)-1-(1-naphthyl)ethylamino]-6-L-val-L-val-L-valine isopropylester-1,3,5-triazine (1a), a direct precursor of 1, as chiral solvating agent for the determination by NMR of the enantiomeric compositions of derivatives of amines, amino alcohols, amino acids, and carboxyl acids bearing a 3,5-dinitrophenyl moiety, has been demonstrated. Chirality 9:113-121, 1997. © 1997 Wiley-Liss, Inc.
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    Enantioselective determination of FCE 28833, a new potential antiischemic agent, in gerbil plasma using column switching HPLC with UV detection (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 133-138 
    Details
    ISSN: 0899-0042
    Keywords: anti-ischemic agent ; gerbil ; enantiomeric resolution ; column switching ; chiral crown ether ; HPLC ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A sensitive and selective high performance liquid chromatographic method using an automated column switching technique for the determination of FCE 28833 enantiomers in gerbil plasma was developed. After solid-liquid extraction using a Supelcosil C18 cartridge FCE 28833 was eluted on a clean-up column (Spherisorb CN) and the enantiomers were separated using an analytical chiral column (Crownpack CR(+)). The mobile phase (15% methanol in HClO4 1 mM) was directed through the columns at a flow rate of 1 ml/min and the fraction eluted between 13 and 40 min was transferred from the clean-up column into the analytical column. FCE 28833 enantiomers were monitored at 257 nm. The limit of quantitation of the method was 20 ng/ml plasma for both enantiomers and proved to be linear, precise, and accurate for the assay of both enantiomers in the 20-6,000 ng/ml concentration range. No interference from the blank gerbil plasma sample was observed. The suitability of the method was assessed using plasma samples obtained from male gerbils treated with a single oral dose (400 mg/kg) of FCE 28833. Chirality 9:133-138, 1997. © 1997 Wiley-Liss, Inc.
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    Direct resolution of propranolol and bupranolol by thin-layer chromatography using cellulose derivatives as stationary phase (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 139-144 
    Details
    ISSN: 0899-0042
    Keywords: thin-layer chromatography ; propranolol ; bupranolol ; enantiomers ; cellulose derivatives ; chiral stationary phase ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cellulose triphenylcarbamate derivatives have been used as stationary phases for resolution of the enantiomers of the β-blockers propranolol and bupranolol by TLC. The derivatives examined were: cellulose trisphenylacarbamate (1), cellulose tris(2,3-dichlorophenyl carbamate) (2), cellulose tris(2,4-dichlorophenyl carbamate) (3), cellulose tris(2,6-dichlorophenyl carbamate) (4), cellulose tris (2,3-dimethylphenyl carbamate) (5), cellulose tris(3,4-dichlorophenyl carbamate) (6), cellulose tris(3,5-dichlorophenyl carbamate) (7), and cellulose tris(3,5-dimethylphenyl carbamate) (8). A variety of mobile phases were used to achieve useful separations and the effects of solvent polarity are also discussed. The best resolution of rac-propranolol was obtained on CSP 8 (RfR = 0.26, RfS = 0.06, α = 4.33) in mobile phase hexane:propan-2-ol (80:20 v/v). The best resolution of rac-bupranolol was obtained on CSP 5 (RfR = 0.29, RfS = 0.09, α = 3.22) in mobile phase hexane:propan-2-ol (80:20 v/v). These results demonstrated the potential of cellulose triphenylcarbamates as chiral stationary phases in TLC and indicate that this is potentially a useful method for the direct, simple, and rapid (within 30 min) resolution of racemates in the analytical control of enantiomeric purity. Physical aspects such as problems in cracking of the CSP, adhesion to plate, and interference of spot detection due to triphenylcarbamate chromphores are also discussed, along with the method employed to overcome them. Chirality 9:139-144, 1997. © 1997 Wiley-Liss, Inc.
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    Capillary electrophoretic chiral resolution of vicinal diols by complexation with borate and cyclodextrin: Comparative studies on different cyclodextrin derivatives (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 153-156 
    Details
    ISSN: 0899-0042
    Keywords: chiral separation ; β-cyclodextrin derivatives ; capillary electrophoresis ; vicinal diols ; borate complexation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Capillary electrophoretic enantioseparation of compounds containing vicinal diol groups have been investigated using different β-cyclodextrin (CD) derivatives and borate as a background electrolyte. Both native β-CD and several β-CD derivatives are examined. Chiral recognition is attributed to both enantioselective inclusion of the analyte into the chiral cavity of the CD and complexation with borate. The influence of concentration of the chiral selector, pH, and organic modifiers on the resolution was studied. Four diols were baseline separated. Chirality 9:153-156, 1997. © 1997 Wiley-Liss, Inc.
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    Liquid chromatographic resolution of cyclic sulfoximides and their sulfoxide precursors on an N,N′-diallyl-L-tartardiamide-based chiral stationary phase (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 167-172 
    Details
    ISSN: 0899-0042
    Keywords: chromatographic resolution ; enantiomers ; sulfoximide ; sulfoximine ; sulfoxide ; hydrogen bonding ; DATD-based CSP ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two O,O′-diaroyl derivatives of an N,N′-diallyl-L-tartardiamide-based CSP, 3,5-dimethylbenzoyl (CSP I) and 4-tert-butylbenzoyl (CSP II), have been investigated and compared with respect to retention behaviour and resolving capabilities of a series of endocyclic sulfoximides of the 1-R-3-oxo-benzo[d]-isothia (IV)-azole 1-oxide type (R = methyl, octyl, 2′-carboxyphenyl, and 2′-carbethoxyphenyl) and their corresponding sulfoxide precursors. For the sulfoximides, selectivities of 1.44, 1.27, 1.28, and 1.20, respectively, were found on CSP II when eluted with 15% 2-propanol in hexane. Both the sulfoximide compounds and their sulfoxide precursors are well resolved by CSPs I and II. The retention was larger on the former phase, indicating that the molecular skeletons of the analytes studied interact, through hydrogen bonding, more strongly with CSP I than CSP II. Chirality 9:167-172, 1997. © 1997 Wiley-Liss, Inc.
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    Enantioselective separation of enantiomeric amides on three amylose-based chiral stationary phases: Effects of backbone and carbamate side chain chiralities (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 173-177 
    Details
    ISSN: 0899-0042
    Keywords: chiral high-performance liquid chromatography ; polysaccharides ; structure-retention relationships ; amides ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of enantiomeric amides have been chromatographed on three amylose-based chiral stationary phases (CSPs): amylose tris(3,5-dimethylphenylcarbamate) (AD-CSP), amylose tris (S-phenylethylcarbamate) (AS-CSP), and amylose tris(R-phenylethyl-carbamate) (AR-CSP). The relative retentions and enantioselectives of the solutes on the three CSPs were compared and basic structure-retention relationships developed to describe the chromatographic results. The data indicate that for these solutes the observed elution order was a function of the chirality of the amylose backbone, while the magnitude of the enantioselective separations was affected by the chirality of the carbamate side chain. Chirality 9:173-177, 1997. © 1997 Wiley-Liss, Inc.
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    Enantioselective separation of chiral arylcarboxylic acids on an immobilized human serum albumin chiral stationary phase (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 178-183 
    Details
    ISSN: 0899-0042
    Keywords: chiral recognition mechanisms ; quantitative structure ; enantioselective retention relationships ; chiral chromatography ; enantioselective separations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of 12 chiral arylcarboxylic acids were chromatographed on an immobilized human serum albumin chiral stationary phase (HSA-CSP). The effects of solute structure on chromatographic retentions and enantioselective separations were examined by linear regression analysis and the construction of quantitative structure-enantioselective retention relationships. Competitive displacement studies were also conducted using R-ibuprofen as the displacing agent. The results indicate that the enantioselective retention of the solutes takes place at the indole-benzodiazepine site (site II) on the HSA molecule and that chiral recognition is affected by the hydrophobicity and steric volume of the solutes. The displacement studies also identified a cooperative allosteric interaction induced by the binding of R-ibuprofen to site II. Chirality 9:178-183, 1997. © 1997 Wiley-Liss, Inc.
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    Preparation of polyamino acid catalysts for use in Juliá asymmetric epoxidation (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 198-202 
    Details
    ISSN: 0899-0042
    Keywords: oligopeptide ; amino acid N-carboxyanhydride ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This article describes improvements in the Juliá asymmetric epoxidation reaction. The oligopeptides needed for the study were synthesised from N-carboxyanhydrides (NCAs) employing various initiators, such as water, 1,3-diaminopropane (DAP), and cross-linked aminomethylpolystyrene (CLAMPS) 1. Chirality 9:198-202, 1997. © 1997 Wiley-Liss, Inc.
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    Chiral separation machinery using new crystalline inclusion hosts: Match/mismatch in the enantiomer recognition of (R,S)-1-methoxy-2-propanol effected by a borneol/fenchol building block exchange in the host molecule (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 203-210 
    Details
    ISSN: 0899-0042
    Keywords: chiral selectors ; natural product derived hosts ; optically active hosts ; clathrate hosts ; bulky diols ; inclusion compounds ; host-guest complexes ; chiroselective cocrystallization ; crystal packing analysis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New chiral host molecules 1 and 2 involving a bulky terpenoid unit and aromatic ethyne spacer groups were synthesized using Pd-catalyzed cross-coupling reactions of (+)-2α-ethynyl-2β-hydroxybornane (4) or (+)-2α-ethynyl-2β-hydroxyfenchane (5) with 9,10-dibromoanthracene. Host compounds 1 and 2 from crystalline inclusions with 1-methoxy-2-propanol (3) in 1:1 and 1:2 stoichiometry, respectively. In the case of 1, complete enantiomer resolution (ee 〉 99%) of 3 is effected in one cocrystallization step. However, constitutional isomer 2 failed in the enantiomer separation of 3, which might be explained due to the different crystal lattice buildup of these cocrystals. Chirality 9:203-210, 1997. © 1997 Wiley-Liss, Inc.
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    Chiral discrimination using a quartz crystal microbalance and comparison with gas chromatographic retention data (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 225-232 
    Details
    ISSN: 0899-0042
    Keywords: quartz crystal microbalance ; electronic nose ; fragrance ; odour ; detection ; chemical sensor ; cyclodextrin ; chiral discrimination ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Quartz crystal microbalances (QCMB) have been constructed using 10 MHz AT cut quartz crystals coated with heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin, heptakis(6-O-methyl-2,3-di-O-pentyl)-β-cyclodextrin, and octakis(6-O-methyl-2,3-di-O-pentyl)-γ-cyclodextrin as 50% and 20% (w/w) solutions in OV1701. The reduction in frequency seen on exposure of each coated QCMB to pure enantiomeric forms of α- and β-pinene and cis- and trans-pinane show that statistically significant (P = 0.05, n = 7) differences are observed between the enantiomeric pairs. The apparent preferential binding shown by the QCMB for enanciomers of α- and β-pinene and cis- and trans-pinane have been compared with the elution order observed on the corresponding gas chromatographic stationary phase. The magnitude of the observed separation factor (calculated as the ratio of the OV1701 normalised frequency shift) is seen to be dependent upon the chiral stationary phase concentration. These results indicate that on-line determination of enantiomeric excess and concentration of certain monoterpenes is possible at room temperature using QCMB in conjunction with chiral gas chromatographic stationary phases. Chirality 9:225-232, 1997. © 1997 Wiley-Liss, Inc.
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    Ideal enantiomeric resolution by recrystallization of a racemic compound (part 4): Relationship between enantiomeric resolution phenomenon and crystal properties (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 220-224 
    Details
    ISSN: 0899-0042
    Keywords: racemic compound crystal ; mixed crystal of (+) and (-) enantiomers ; enantiomeric enrichment in solution ; reversal of chirality ; X-ray powder diffraction ; chiral sulfonium sulfonate ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new example of a racemate showing unusual enantiomeric resolution phenomenon, in which simple recrystallization of the racemate leads to remarkable enantiomeric enrichment of either enantiomer up to 100% ee in the mother liquor, has been found. This compound is (±)-[2-[4-(3-ethoxy-2-hydroxypropoxy)phenylcarbamoyl]-ethyl]dimethylsulfonium p-nitrobenzenesulfonate [EtOCH2CH(OH)CH2OC6H4NHCOCH2CH2SMe2+O2NC6H4SO3-] [(±)-SN]. By repeating recrystallization of (±)-SN and the resulting deposited crystals successively and collecting the resulting enantiomerically enriched mother liquors with the same chirality sense, highly efficient enantiomeric resolution of the racemate into its separate enantiomers has been accomplished. The relationship between the occurrence of this enantiomeric resolution phenomenon and the crystal properties has been investigated with respect to SN and its aryl- and alkylsulfonate derivatives. The mode of enantiomeric resolution of (±)-SN was similar to that of para-substituted benzenesulfonate derivatives (±)-ST (4-MeC6H4SO3-) and (±)-SC (4-ClC6H4SO3-) previously reported, whereas the unsubstituted derivative (±)-SB (C6H5SO3-) and alkysulfonate derivatives (±)-SO (n-C8H17SO3-) and (±)-SM (CH3SO3-) did not show such an enantiomeric resolution phenomenon. The crystalline form of the former racemates that underwent the enantiomeric resolution was racemic compounds, while the latter were mixed crystals (solid solutions) composed of the respective optical antipodes. Chirality 9:220-224, 1997. © 1997 Wiley-Liss, Inc.
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    Helically twisted chiral cyanine dyes: Influence of chromophore length on observed and calculated rotatory strengths (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 243-249 
    Details
    ISSN: 0899-0042
    Keywords: chiral polymethine dyes ; circular dichroism ; helicity ; helicity rules ; cis-peak ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis, chiroptical properties, and quantum-mechanical calculations of the monomethine dye 3 and of the trimethine dyes 7 and 11 are reported. In 3 and 11, the chromophore is forced into a twisted all-Z-conformation by steric interaction of the end groups in the former and the presence of a t-butyl group in the mesoposition of the latter, which is manifest in the UV/Vis spectra not only in the reduced intensity of the longest wavelength absorption, but also in the occurrence, at shorter wavelength, of a “cis-peak.” Chiral substitution of the end groups serves as chiral anchor to discriminate between otherwise enantiomeric forms and makes them amenable to chiroptical investigation. The results are in agreement with theoretically calculated chiroptical data based on helically twisted cyanine chromophores. They support the contention that not only the sense of the helix, but also its length determines the sign of the associated Cotton effect. Chirality 9:243-249, 1997. © 1997 Wiley-Liss, Inc.
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    Mobile phase effects on enantiomer resolution using molecularly imprinted polymers (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 238-242 
    Details
    ISSN: 0899-0042
    Keywords: non-covalent molecular imprinting ; hydrogen bonding parameters ; solvent properties ; chiral separation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The aim of this study was to rationalise retention behaviour of a chiral solute on molecularly imprinted polymer (MIP) HPLC stationary phases in terms of variation of the mobile phase. It is generally held that the most important interaction governing the separation of enantiomers on such materials is H-bonding, and that retention times increase with decreasing H-bonding potential of the mobile phase. Previous studies have largely concerned mobile phases containing chloroform with acetic acid as a polar modifier. Boc-L-Phenylalanine (Boc-L-Phe-OH) MIPs were prepared, processed, and packed into HPLC columns, which were then used to investigate the retention characteristics of Boc-L-Phe-OH and Boc-D-Phe-OH with a range of mobile phases. The main observations were as follows: (1) in chloroform-based mobile phases there was generally a linear relationship between the H-bond donator factor of the polar modifier and capacity (K′). Results also indicated a hydrogen bond donor parameter value for a polar modifier at which retention became concentration independent; (2) For given values of K′L, K′D varied depending on the polar modifier, indicating that enantiomer resolution was solvent dependent; (3) Using mobile phases based on solvents of lower polarity/H-bonding potential than chloroform, substantial increases in K′ were observed, although enantioselectivity was greatly reduced. Chirality 9:238-242, 1997. © 1997 Wiley-Liss, Inc.
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    Emulsion liquid membranes for chiral separations: Selective extraction of rac-phenylalanine enantiomers (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 261-267 
    Details
    ISSN: 0899-0042
    Keywords: industrial scale ; phenylalanine ; enhancing enantioselectivity ; membrane solvent ; chiral extraction ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We describe the use of emulsion liquid membrane technology to perform chiral separations on low molecular weight species. We have reviewed liquid membrane technology in the context of existing process scale chiral separations. We illustrate the potential of this new technique by presenting our results on the selective extraction of phenylalanine enantiomers, using copper (II) N-decyl-(L)-hydroxyproline as a chiral selector in an emulsion liquid membrane configuration. This is compared with an analogous batch solvent extraction system. Initial batch enantiomeric excesses of greater than 40% were observed with the emulsion liquid membrane system compared with around 25% for the solvent extraction system. It was also noted that the system is not limited by the equilibrium capacity constraints of the solvent extraction system. We have shown that kinetic chiral liquid membrane technology offers high productivity and flexibility compared with analogous process scale chiral technologies. Recent transfer of highly specific chiral reversed-phase high-performance liquid chromatographic chemistries have shown that “one-stop” enantiomeric excesses of commercial interest (〉95%) are achievable using kinetic chiral liquid membrane systems. Solvent and temperature selection strategies also have been outlined as means of increasing the enantioselectivity of existing liquid membrane extraction chemistries. Chirality 9:261-267, 1997. © 1997 Wiley-Liss, Inc.
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    AMPA receptor agonists: Resolution, configurational assignment, and pharmacology of (+)-(S)- and (-)-(R)-2-amino-3-[3-hydroxy-5-(2-pyridyl)-isoxazol-4-yl]-propionic acid (2-Py-AMPA) (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 274-280 
    Details
    ISSN: 0899-0042
    Keywords: chiral HPLC ; resolution ; enantiomeric purity ; configurational assignment ; circular dichroism ; AMPA receptor affinity ; electrophysiology ; AMPA receptor agonism ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have previously shown that whereas (RS)-2-amino-3-(3-hydroxy-5-phenylisoxazol-4-yl)propionic acid (APPA) shows the characteristics of a partial agonist at (RS)-2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA) receptors, (S)-APPA is a full AMPA receptor agonist and (R)-APPA a weak competitive AMPA receptor antagonist. This observation led us to introduce the new pharmacological concept, functional partial agonism. Recently we have shown that the 2-pyridyl analogue of APPA, (RS)-2-amino-3-[3-hydroxy-5-(2-pyridyl)isoxazol-4-yl]propionic acid (2-Py-AMPA), is a potent and apparently full AMPA receptor agonist, and this compound has now been resolved into (+)- and (-)-2-Py-AMPA (ee ≥ 99.0%) by chiral HPLC using a Chirobiotic T column. The absolute stereochemistry of the enantiomers of APPA has previously been established by X-ray analysis, and on the basis of comparative studies of the circular dichroism spectra of the enantiomers of APPA and 2-Py-AMPA, (+)- and (-)-2-Py-AMPA were assigned the (S)- and (R)-configuration, respectively. In a series of receptor binding studies, neither enantiomer of 2-Py-AMPA showed detectable affinity for kainic acid receptor sites or different sites at the N-methyl-D-aspartic acid (NMDA) receptor complex. (+)-(S)-2-Py-AMPA was an effective inhibitor of [3H]AMPA binding (IC50 = 0.19 ± 0.06 μM) and a potent AMPA receptor agonist in the rat cortical wedge preparation (EC50 = 4.5 ± 0.3 μM) comparable with AMPA (IC50 = 0.040 ± 0.01 μM; EC50 = 3.5 ± 0.2 μM), but much more potent than (+)-(S)-APPA (IC50 = 5.5 ± 2.2 μM; EC50 = 230 ± 12 μM). Like (-)-(R)-APPA (IC50 〉 100 μM), (-)-(R)-2-Py-AMPA (IC50 〉 100 μM) did not significantly affect [3H]AMPA binding, and both compounds were week AMPA receptor antagonists (Ki = 270 ± 50 and 290 ± 20 μM, respectively). Chirality 9:274-280, 1997. © 1997 Wiley-Liss, Inc.
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    Stereoselective inhibition of rat brain cyclooxygenase by dexketoprofen (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 281-285 
    Details
    ISSN: 0899-0042
    Keywords: dexketoprofen ; enantiomer ; stereoselectivity ; brain ; cyclooxygenase ; rat ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Although it has been assumed that the effects of nonsteroidal antiinflammatory drugs (NSAIDs) are mainly the result of their action on local synthesis of prostaglandins, there is growing evidence to suggest that they may also exert a central analgesic action. Some authors have suggested that inhibition of prostaglandin synthesis in the brain could contribute to the analgesic action. The effect of dexketoprofen trometamol (tromethamine salt of the enantiomer (+)-S-ketoprofen) on prostaglandin synthesis was investigated in rat brain fragments and in cyclooxygenase preparations from rat brain microsomes. Effects of the (-)-R-enantiomer and the racemic mixture were also evaluated. Significant levels of prostaglandin F2α (PGF2α) were synthesized in rat brain fragments after 10 min of incubation at 37°C. Dexketoprofen was found to be a potent inhibitor of this PGF2α production in rat brain (IC50 = 6.2 nM), and it completely suppressed PGF2α production at 1 μM concentration. In addition, inhibition of PGF2α synthesis by dexketoprofen was highly stereoselective since the enantiomer (-)-R-ketoprofen was significantly less potent (IC50 = 294 nM); with this enantiomer, even at high concentrations such as 1 μM, less than 60% inhibition was achieved. These results correlated with those obtained in the study of racemic ketoprofen and its enantiomers on cyclooxygenase activity of rat brain microsomes, where dexketoprofen also inhibited enzymatic activity stereoselectively. IC50 values obtained for dexketoprofen, (-)-R-ketoprofen, and rac-ketoprofen were 3.5 μM, 45.3 μM, and 5.8 μM, respectively. The above results could be related to the potent analgesic effect of dexketoprofen observed in vivo, which was also stereoselective. Taken together, these findings suggest that prostaglandin synthesis inhibition in rat brain by dexketoprofen could be associated, at least in part, with the analgesic effect of this NSAID. Chirality 9:281-285, 1997. © 1997 Wiley-Liss, Inc.
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    Electronic Resource
    Topical administration of racemic ibuprofen (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 313-316 
    Details
    ISSN: 0899-0042
    Keywords: ibuprofen ; topical administration ; chromatography ; skin metabolism ; percutaneous penetration ; chiral ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In vitro experiments to investigate possible stereoselective aspects of the topical administration of ibuprofen have been conducted. Incubation of ibuprofen with rat skin homogenates in the presence of coenzyme A, ATP, and magnesium provided no evidence for the formation of ibuprofenyl coenzyme A (the initial intermediate in the metabolic inversion of [R]- to [S]-ibuprofen). Similar incubation studies gave no indication of a change in the enantiomeric ratios of ibuprofen over the time course of the experiments. Percutaneous penetration studies of ibuprofen gel through porcine skin indicated that the ibuprofen enantiomer levels in the reservoir solutions were consistent with racemic ibuprofen having traversed the skin with no metabolic inversion. These results suggest that, in the models studied, skin metabolism does not result in the chiral inversion of (R)- to (S)-ibuprofen and that the topical administration of ibuprofen will result in the delivery of 50% “isomeric ballast.” Chirality 9:313-316, 1997. © 1997 Wiley-Liss, Inc.
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    Preliminary pharmacokinetic study of ibuprofen enantiomers after administration of a new oral formulation (ibuprofen arginine) to healthy male volunteers (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 297-302 
    Details
    ISSN: 0899-0042
    Keywords: anti-inflammatory drugs ; ibuprofen ; clinical pharmacokinetics ; bioinversion ; enantiomers ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pharmacokinetics of ibuprofen enantiomers were investigated in a crossover study in which seven healthy male volunteers received single oral doses of 800 mg racemic ibuprofen as a soluble granular formulation (sachet) containing L-arginine (designated trade name: Spedifen®), 400 mg (-)R-ibuprofen arginine or 400 mg (+)S-ibuprofen arginine.Plasma levels of both enantiomers were monitored up to 480 minutes after drug intake using an enantioselective analytical method (HPLC with ultraviolet detection) with a quantitation limit of 0.25 mg/l.Substantial inter-subject variability in the evaluated pharmacokinetic parameters was observed in the present study. After (+)S-ibuprofen arginine, the following mean pharmacokinetic parameters ±SD were calculated for (+)S-ibuprofen: tmax 28.6 ± 28.4 min; Cmax 36.2 ± 7.7 mg/l; AUC 86.4 ± 14.9 mg · h/l; t½ 105.2 ± 20.4 min. After (-)R-ibuprofen arginine, the following mean pharmacokinetic parameters were calculated for (+)S-ibuprofen and (-)R-ibuprofen, respectively: tmax 90.0 ± 17.3 and 50.5 ± 20.5 min; Cmax 9.7 ± 3.0 and 35.3 ± 5.0 mg/l; AUC 47.0 ± 17.2 and 104.7 ± 27.7 mg · h/l; t½ 148.1 ± 63.6 and 97.7 ± 23.3 min. After racemic ibuprofen arginine, the following mean pharmacokinetic parameters were calculated for (+)S- and (-)R-ibuprofen, respectively: tmax 30.7 ± 29.1 and 22.9 ± 29.8 min.; Cmax 29.9 ± 5.6 and 25.6 ± 4.4 mg/l; AUC 105.1 ± 23.0 and 65.3 ± 15.0 mg · h/l; t½ 136.6 ± 20.7 and 128.6 ± 45.0 min. Tmax values of S(+)- and (-)R-ibuprofen after a single dose of 400 mg of each enantiomer did not differ significantly from the corresponding parameters obtained after a single dose of 800 mg of racemic ibuprofen arginine, indicating that the absorption rate of (-)R- and (+)S-ibuprofen is not different when the two enantiomers are administered alone or as a racemic compound. An average of 49.3 ± 9.0% of a dose of the (-)R-ibuprofen arginine was bioinverted into its antipode during the study period (480 minutes post-dosing). The percent bioinversion during the first 30 minutes after (-)R-ibuprofen arginine intake averaged 8.1 ± 3.9%. The mean AUC of (+)S-ibuprofen calculated after 800 mg racemic ibuprofen arginine (105.1 ± 23.0 mg · h/l) was lower than the mean AUC value obtained by summing the AUCs of (+)S-ibuprofen after administration of 400 mg (+)S-ibuprofen arginine and 400 mg (-)R-ibuprofen arginine (133.4 ± 26.6 mg · h/l).In conclusion, the administration of Spedifen® resulted in very rapid absorption of the (+)S-isomer (eutomer) with tmax values much lower than those observed for this isomer when conventional oral solid formulations such as capsules or tablets of racemic ibuprofen are administered. This characteristic is particularly favourable in those conditions in which a very rapid analgesic effect is required. Chirality 9:297-302, 1997. © 1997 Wiley-Liss, Inc.
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    Improvement of enantioselective syntheses and chiral high resolution gas chromatographic analyses of (+)-2-allyl-2-carboethoxy-cyclopentanol (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 321-324 
    Details
    ISSN: 0899-0042
    Keywords: Saccharomyces cerevisiae ; asymmetric β-keto-ester reduction ; enzymatic kinetic resolution ; chiral 2-allyl-2-carboethoxy-cyclopentanol ; chiral high resolution gas chromatography ; chiral stationary phase ; β-cyclodextrin derivative ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The improvement of the biocatalytic reduction of 2-allyl-carboethoxy-cyclopentanone (2) to the corresponding cyclopentanol derivative (+)-(1R,2R)-(1) was accomplished employing baker's yeast in organic media. This chiral cyclopentanol derivative (1), analyzed by high resolution gas chromatography performed over β-cyclodextrin stationary phase, was obtained in 38% yield (〉99% e.e.). Chirality 9:321-324, 1997. © 1997 Wiley-Liss, Inc.
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    Calorimetric determination of differential integral heats of solution for a set of diastereomeric salt pairs (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 325-328 
    Details
    ISSN: 0899-0042
    Keywords: enthalpy ; heat of fusion ; chiral recognition ; crystalline state ; polymorphism ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heats of solution in dimethyl sulfoxide (DMSO) have been determined for the diastereomeric salts (-)-(R)-methamphetammonium (+)-(RR)-bitartrate and (-)-(R)-methamphetammonium (-)-(SS)-bitartrate, (+)-(R)-α-phenethylammonium (-)-(R)-2-phenylbutyrate and (-)-(S)-α-phenethylammonium (-)-(R)-2-phenylbutyrate, and of a new polymorph of (+)-(1S2R)-ephedrinium (-)-(R)-mandelate. The heats of solution for these salts were found to be 11.4 and 10.0 kcal/mol, 15.6 and 14.0 kcal/mol, and 7.4 kcal/mol, respectively.Differential enthalpy contributions to chiral discrimination computed from these numbers are 1.4, 1.6, and 2.1 kcal/mol for the methamphetammonium bitartrates, α-phenethylammonium (-)-2-phenylbutyrates, and ephedrinium mandelates, respectively. The new and previously observed (Zingg et al. J Am Chem Soc 110:1565-1580, 1988) polymorphs of the (+)-(1S2R)-ephedrinium (-)-(R)-mandelate are separated by nearly 1 kcal/mol.Comparison of differential heats of solution with the corresponding differential heats of fusion suggests that heats of fusion differences do not properly represent the energy differences useful for diastereomeric salt separations. Chirality 9:325-328, 1997. © 1997 Wiley-Liss, Inc.
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    Improved chromatographic performance of a modified human albumin based stationary phase (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 335-340 
    Details
    ISSN: 0899-0042
    Keywords: chiral chromatography ; cys34 modified human serum albumin ; ethacrynic acid ; protein binding ; enantioselectivity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Derivatization of the free cys34 in human serum albumin (HSA) anchored to a silica matrix has been performed by in situ reaction with ethacrynic acid. This modification, which is reported to occur under physiological conditions, gives rise in practice to a new column with different binding properties with respect to the column based on the native protein. Significant differences were observed in the binding of drugs known to bind to site I, (R)-(S)-warfarin and phenylbutazone, and to site II, 1,4-benzodiazepin-2-ones and nonsteroidal anti-inflammatory agents. In particular, the chromatographic retentions markedly decreased for most of the drugs, and, in the case of chiral compounds, significant differences were often observed in the behavior of the two enantiomers, with higher values of enantioselectivity obtained for some of the examined compounds. Furthermore, the noncovalent binding of ethacrynic acid to the protein modifies the binding properties of the albumin. Chirality 9:335-340, 1997. © 1997 Wiley-Liss, Inc.
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    Chiral recognition by the copper(II) complex of 6-deoxy-6-N-(2-methylaminopyridine)-β-cyclodextrin (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 341-349 
    Details
    ISSN: 0899-0042
    Keywords: chiral recognition ; amino acids ; ternary copper(II) complexes ; stability constants ; EPR ; circular dichroism ; fluorescence ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A modified β-cyclodextrin bearing a 2-aminomethylpyridine binding site for copper(II) (6-deoxy-6-[N-(2-methylamino)pyridine)]-β-cyclodextrin, CDampy was synthesized by C6-monofunctionalization. The acid-base properties of the new ligand in aqueous solution were investigated by potentiometry and calorimetry, and its conformations as a function of pH were studied by NMR and circular dichroism (c.d.). The formation of binary copper(II) complexes was studied by potentiometry, EPR, and c.d. The copper(II) complex was used as chiral selector for the HPLC enantiomeric separation of underivatized aromatic amino acids. Enantioselectivity in the overall stability constants of the ternary complexes with D- or L-Trp was detected by potentiometry, whereas the complexes of the Ala enantiomers did not show any difference in stability. These results were consistent with a preferred cis coordination of the amino group of the ligand and of the amino acid in the ternary complexes (“cis effect”), which leads to the inclusion of the aromatic side chain of D-Trp, but not of that of L-Trp. In Trp-containing ternary complexes, the two enantiomers showed differences in the fluorescence lifetime distribution, consistent with only one conformer of D-Trp and two conformers of L-Trp, and the latter were found to be more accessible to fluorescence quenching by acrylamide and KI. Chirality 9:341-349, 1997. © 1997 Wiley-Liss, Inc.
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    O-methylation of (+)-(R)- and (-)-(S)-6,7-dihydroxy-1-methyl-1,2,3,4-tetra-hydroisoquinoline (salsolinol) in the presence of pig brain catechol-o-methyltransferase (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 367-372 
    Details
    ISSN: 0899-0042
    Keywords: enantiomers ; salsolinol ; dopamine ; catechol-O-methyltransferase ; high-performance liquid chromatography ; electrochemical detection ; brain ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (+)-(R)- and (-)-(S)-salsolinol, dopamine-derived tetrahydroisoquinolines, were tested as substrates of pig brain soluble and membrane-bound catechol-O-methyltransferase (COMT) and as inhibitors of O-methylation of dopamine by soluble COMT in vitro. Methylation products were separated by high-performance liquid chromatography with electrochemical detection. Quantification of the products showed that O-methylation of (+)-(R)-salsolinol by soluble COMT afforded the 7-O-methylated product salsoline preferentially, whereas (-)-(S)-salsolinol yielded almost equivalent amounts of the 6- and 7-methyl ethers. Unlike O-methylation by soluble COMT, 7-O/6-O-methylation ratio produced by membrane-bound COMT varied with (+)-(R)-salsolinol concentration. As to the O-methylation of dopamine by soluble COMT, comparable competitive inhibition was observed with both (+)-(R)- and (-)-(S)-salsolinol. Chirality 9:367-372, 1997. © 1997 Wiley-Liss, Inc.
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    On the odor of the enantiomers of Madrol® (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 380-385 
    Details
    ISSN: 0899-0042
    Keywords: asymmetric synthesis ; campholene aldehyde derivatives ; fragrance compounds ; sandalwood odor ; santalum album L ; structure-odor-relationships ; molecular similarity ; molecular modeling ; computer-aided fragrance design ; molecular surface comparison ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The asymmetric syntheses of the enantiomers of Madrol® (1) are described and their odor properties evaluated. (1S)-(-)-1 exerts a powerful sandalwood odor with some animalic undertones, whereas its antipode smells sweet and flowery rather than like sandalwood. Molecular surface comparisons show remarkable deviations in the hydrophobic parts of the two enantiomers. Chirality 9:380-385, 1997. © 1997 Wiley-Liss, Inc.
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    Book review: “Chiral Reactions in Heterogeneous Catalysis” (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 390-390 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
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    Book review: “Modern Conformational Analysis” (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 391-391 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
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  • 50
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    Enantiomeric separation of amino alcohols using Z-L-glu-L-pro or Z-L-glu-D-pro as chiral counter ions and hypercarb as the solid phase (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 650-655 
    Details
    ISSN: 0899-0042
    Keywords: direct separation ; chiral ion-pair chromatography ; di-anionic N-derivatized dipeptides ; aminoalcohols ; column temperature ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper describes the synthesis of two new N-derivatized dipeptides. The two compounds, N-benzyloxycarbonyl-L-glutamyl-L-proline (Z-L-glu-L-pro) and N-benzyloxycarbonyl-L-glutamyl-D-proline (Z-L-glu-D-pro), were tested as chiral counter ions for the enantiomeric resolution of amino alcohols. The chiral counter ions were dissolved in a polar solvent, e.g., methanol and porous graphitic carbon, Hypercarb, were used as the achiral solid phase. The enantiomers of several of the tested compounds were baseline separated using Z-L-glu-L-pro as the chiral counter ion but no enantioselective retention was obtained using its diastereoisomer Z-L-glu-D-pro. The influence of solute structure as well as the importance of converting the chiral counter ion to its dianionic form will be described together with the effect of column temperature on enantioselective retention. Chirality 9:650-655, 1997. © 1997 Wiley-Liss, Inc.
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    Optical resolution by preferential crystallization of (2RS,3SR)-2-amino-3-chlorobutanoic acid hydrochloride (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 656-660 
    Details
    ISSN: 0899-0042
    Keywords: β-chloro-α-amino acid ; conglomerate ; successive optical resolution ; racemic structure ; (2RS,3SR)-ACB · HCl ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (2RS,3SR)-2-Amino-3-chlorobutanoic acid hydrochloride [(2RS,3SR)-ACB · HCl] was found to exist as a conglomerate based on the melting point, infrared spectrum, and solubility. Optical resolution by preferential crystallization of (2RS,3SR)-ACB · HCl was achieved to yield both (2R,3S)- and (2S,3R)-ACB · HCl of 80-100% optical purities. The obtained (2R,3S)- and (2S,3R)-ACB · HCl were recrystallized, taking into account the solubility of (2RS,3SR)-ACB · HCl, to give efficiently optically pure (2R,3S)- and (2S,3R)-ACB · HCl. Treatment of the purified (2R,3S)- and (2S,3R)-ACB · HCl with triethylamine gave optically pure (2R,3S)- and (2S,3R)-2-amino-3-chlorobutanoic acid, respectively. Chirality 9:656-660, 1997. © 1997 Wiley-Liss, Inc.
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    Absolute stereochemistry of 2-hydroxyglutaric acid present in methanopterin (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 678-680 
    Details
    ISSN: 0899-0042
    Keywords: methanopterin ; absolute stereochemistry ; 2-hydroxyglutaric acid ; sarcinopterin ; folates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The absolute stereochemistry of the 2-hydroxyglutaric acid present in methanopterin and its α-glutamyl derivative, sarcinapterin, has been determined to be (S). Thus, the absolute stereochemistry of the 2-hydroxyglutaric acid present in the side chain of these modified folates is the same as the L-glutamic acid present in the side chain of folates. Chirality 9:678-680, 1997. © 1997 Wiley-Liss, Inc.
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    Optimization of chiral resolution using packed columns with carbon dioxide-based mobile phases (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 672-677 
    Details
    ISSN: 0899-0042
    Keywords: chiral SFC ; SubFC ; SFC ; methanol modified CO2 ; efficiency ; selectivity ; retention ; packed column SFC ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optimization of chiral resolution, using carbon dioxide based mobile phases, must take into consideration the individual contributions of analyte retention, selectivity, and efficiency. Each of these factors may be independently affected by changes in pressure, temperature, or state of the mobile phase. The ability to control retention by different means reflects an advantage of carbon dioxide based mobile phases over conventional HPLC mobile phases. Utilization of this advantage requires that the effects of each of these factors on each contributor to resolution be known. The cumulative effect that each of these variables has on retention, selectivity and efficiency suggests that maximum resolution is obtained using low pressures and temperatures. Maximum resolution (at fixed k′) results from low temperatures and high pressures. The latter may be of more practical importance when speed of analyses and detection limits are considered. Chirality 9:672-677, 1997. © 1997 Wiley-Liss, Inc.
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    Chiral resolution and absolute configuration of the enantiomers of 5-acetyl-2-methyl-4-methylsulfinyl-6-phenyl-3(2H)-pyridazinone and evaluation of their platelet aggregation inhibitory activity (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 681-685 
    Details
    ISSN: 0899-0042
    Keywords: 5-acetyl-2-methyl-4-methylsulfinyl-6-phenyl-3(2H)-pyridazinone ; chromatographic chiral resolution ; absolute configuration ; X-ray crystallographic analysis ; antiplatelet activity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In a series of 5-acyl-6-phenyl-2,4-substituted-3(2H)-pyridazinones the derivative 1a, with a sulfur stereogenic center, had the most potent activity as human platelet aggregation inhibitor. The resolution of rac-1a was successfully performed by chiral chromatography on Chiralcel OD-R, OD-H, and Chiralpak AD columns and scaled up to a preparative level. The absolute configuration of (-)-(S)-1a was determined by X-ray crystallographic analysis. In vitro human platelet aggregation inhibitory activity was evaluated. Both the enantiomers showed IC50 values in the same micromolar range, but the (-)-(S) isomer was slightly more potent [(S)/(R) potency ratio was 4/1]. Chirality 9:681-685, 1997. © 1997 Wiley-Liss, Inc.
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    Temperature effects for chiral separations using various bulk fluids in near-critical mobile phases (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 693-698 
    Details
    ISSN: 0899-0042
    Keywords: supercritical fluid chromatography ; subcritical fluid chromatography ; HFC-134a ; 1,1,1,2-tetrafluoroethane ; carbon dioxide ; chiral selectivity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As supercritical fluid chromatography becomes more accepted as a facile means for the separation of chiral compounds, the need for mobile phases that can readily solubilize these polar compounds grows. Prior studies suggest that HFC-134a may prove suitable due to its very high eluotropic strength compared to carbon dioxide-based mobile phases. A comparison is made between ethanol-modified carbon dioxide, HFC-134a, and decafluoropentane as to their relative eluotropic strength, selectivity, and efficiency for three chiral compounds using a Whelk O-1 chiral bonded phase. The bulk component of the mobile phase was found to have relatively little effect on chiral selectivity over the range of 5° to 95°C. Chirality 9:693-698, 1997. © 1997 Wiley-Liss, Inc.
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    Enantioselective determination of the hydroxylated metabolites of mexiletine in human plasma (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 732-738 
    Details
    ISSN: 0899-0042
    Keywords: hydroxymethylmexiletine ; p-hydroxymexiletine ; circular dichroism ; diastereomer HPLC ; validation ; plasma ; pharmacokinetics ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pre-column derivatization with o-phthaldialdehyde and N-acetyl-l-cysteine was used for liquid-chromatographic diastereomeric resolution of p-hydroxymexiletine (PHM) and hydroxymethylmexiletine (HMM), metabolites of mexiletine formed by aromatic and aliphatic hydroxylation, respectively. The resulting diastereomeric derivatives were resolved on a C18 column and monitored by fluorescence detection. The diastereomeric elution order for both metabolites was determined on the basis of the circular dichroism spectra of each eluted fraction. Plasma samples (500 μl) showed recoveries greater than 75% for both the metabolites. Calibration curves in plasma samples were linear over the concentration ranges 10-500 and 20-1,000 ng/ml for each enantiomer of PHM and HMM, respectively. The limits of quantitation were found to be 10.0 and 5.0 ng/ml for both enantiomers of PHM and HMM. The within-day and between-day coefficients of variation were less than 10%. The assay was shown to be suitable for a pharmacokinetic study performed in a patient with ventricular arrhythmias following the short-term oral treatment of 200 mg t.i.d. of racemic mexiletine hydrochloride. Chirality 9:732-738, 1997. © 1997 Wiley-Liss, Inc.
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    Editor's note: Honorary issues for Chirality Medal Award winners (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 393-393 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
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    Infelicitous stereochemical nomenclature (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 428-430 
    Details
    ISSN: 0899-0042
    Keywords: asymmetric synthesis ; chiral ; geometrical isomers ; homochiral ; optical isomers ; optical purity ; stereogenic center ; thalidomide ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Misuse of current stereochemical terms is discussed, including terms that should be avoided altogether and replaced by other, standard ones. The reasons for using the proper terms and avoiding the infelicitous ones are pointed out. Chirality 9:428-430, 1997. © 1997 Wiley-Liss, Inc.
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    Synthesis and chiroptical properties of a novel C2-symmetric binaphthyl phosphortriamide (”chiral HMPA“) (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 431-434 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By use of an asymmetric Ullmann coupling involving chiral naphthalene oxazolines 1, the title compounds were prepared in good yields and with high diastereoselectivity. Hydrolysis of the binaphthyl oxazolines 2 led to the di-aldehydes 5, which were transformed into the azepine derivative, 6. The latter was treated with the appropriate phosphoryl halide to access the chiral HMPA systems 7 and 9. The CD spectra of the chiral azepine 6 and the chiral phosphoramides 7 and 9 were measured and showed a strong positive CD couplet near 225 nm, consistent with the P axial chirality (S configuration). Semi-empirical CNDO/S molecular orbital calculations of the CD spectrum of 6 satisfactorily reproduced the major features of the observed spectrum. Chirality 9:431-434, 1997. © 1997 Wiley-Liss, Inc.
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    Key intermediates in cyclotriveratrylene chemistry: A new route to the enantiomers of C3-cyclotriphenolene and cryptophane-C (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 446-453 
    Details
    ISSN: 0899-0042
    Keywords: cyclotriveratrylene ; cyclotriphenolene ; cryptophane ; thiovanillin ; resolution ; enantiomers ; diastereoisomers ; circular dichroism ; exciton chirality ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new route to (+)-(M) and (-)-(P)-cyclotriphenolene (1) is described, starting from 4-mercapto-3-methoxybenzaldehyde (thiovanillin (7)), which was converted into rac-3-methoxy-4-[(1-carboxyethyl)thio]benzyl alcohol (9). The latter was resolved by crystallization of its cinchonidine salts to give (-)-9, to which (S) absolute configuration was assigned. On reaction with formic acid, (-)-(S)-9 afforded the C3-cyclotiveratrylene diastereomers (-)-(P)-11a and (-)-(M)-11b which were separated and submitted to Raney Ni desulfuration to give the (+) and (-)-cyclotrianisylene enantiomers (4), which in turn were converted to (+) and (-)-1 on demethylation. Finally, (-)-1 was transformed into (+)-cryptophane-C according to a previously described method. Chirality 9:446-453, 1997. © 1997 Wiley-Liss, Inc.
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    Building block for (+)-strigol (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 463-468 
    Details
    ISSN: 0899-0042
    Keywords: lipase ; enantioselective ester formation ; Mosher ester analysis ; (+)-(1S)-camphor-10-sulfonic acid ; (+)-strigol ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A route to (-)-(S)-4-benzyloxy-2-[(tert-butyl-diphenyl-silyloxy)-methyl]-1-butanol (2e) starting from an achiral 1,3-propanediol derivative is described. Chirality 9:463-468, 1997. © 1997 Wiley-Liss, Inc.
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    Stereoselective synthesis of some chiral α-ferrocenyl carbenium ions (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 478-486 
    Details
    ISSN: 0899-0042
    Keywords: planar chirality ; diastereoselectivity ; Lewis acid catalyst ; catalyzed Diels-Alder reaction ; α-ferrocenyl carbenium ions ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of chiral ferrocenyl carbocations is described starting from enantiopure orthosubstituted ferrocenylcarboxaldehydes. Secondary or tertiary carbocations have been prepared by ionization of an alcohol precursor. The stereochemistry of secondary α-ferrocenylcarbenium ions has been defined. Preliminary tests as Lewis acid catalysts have been performed. Chirality 9:478-486, 1997. © 1997 Wiley-Liss, Inc.
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    Asymmetric syntheses of 5- and 6-membered carbocyclic serine analogs via an intramolecular Strecker synthesis (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 459-462 
    Details
    ISSN: 0899-0042
    Keywords: α-substituted serine ; conformationally restricted amino acid ; imine-enamine equilibrium ; chiral transfer ; 1-amino-2-hydroxycyclopentanecarboxylic acid ; 1-amino-2-hydroxycyclohexanecarboxylic acid ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformationally restricted analogs of serine possessing a 5- or 6-membered carbocyclic ring, 1 and 2, were synthesized in an optically active form in short steps. The syntheses were started with rac-1, 1-dimethoxy-2-cyclopentanol and rac-trans-1,2-cyclohexanediol, respectively. The key to the present syntheses was a diastereoselective construction of a chiral amino nitrile group onto the ketone group of 5 or 11. This was achieved by the use of an internal Strecker reaction to give optically pure amino nitriles 7a and 13a, respectively. In this reaction, the original chirality derived from phenylalanyl group was efficiently transplanted into both the ketone and α-hydroxyl groups via an imine-enamine equilibrium of the ketimine intermediate 6 or 12. Phenylalanyl moiety of the Strecker adducts was removed by oxidative and hydrolytic treatments of the amino nitriles to give the titled amino acids. Chirality 9:459-462, 1997. © 1997 Wiley-Liss, Inc.
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    Synthetic and model computational studies of molar rotation additivity for interacting chiral centers: A reinvestigation of van't Hoff's principle (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 469-477 
    Details
    ISSN: 0899-0042
    Keywords: hennoxazole A ; optical activity ; rotational strength ; molar rotation ; optical superposition ; fragment synthesis ; configuration interaction ; transition moments ; CNDO/OPTIC ; stereochemistry ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: When plane-polarized light impinges on a solution of optically active molecules, the polarization of the light that emerges is rotated. This simple phenomenon arises from the interaction of light with matter and is well understood, in principle. van't Hoff's rule of optical superposition correlates the molar rotation with the individual contributions to optical activity of isolated centers of asymmetry. This straightforward empirical additivity rule is rarely used for structure elucidation nowadays because of its limitations in the assessment of conformationally restricted or interacting chiral centers. However, additivity can be used successfully to assign the configuration of complex natural products such as hennoxazole A if appropriate synthetic partial structures are available. Therefore, van't Hoff's principle is a powerful stereochemical complement to natural products' total synthesis. The quest for reliable quantitative methods to calculate the angle of rotation a priori has been underway for a long time. Both classical and quantum methods for calculating molar rotation have been developed. Of particular practical importance for determining the absolute structure of molecules by calculation is the manner in which interactions between multiple chiral centers in a single molecule are included, leading to additive or non-additive optical rotation angles. This problem is addressed here using semi-empirical electronic structure models and the Rosenfeld equation. Chirality 9:469-477, 1997. © 1997 Wiley-Liss, Inc.
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    Synthesis of novel 3′-trifluoromethyl taxoids through effective kinetic resolution of racemic 4-CF3-β-lactams with baccatins (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 487-494 
    Details
    ISSN: 0899-0042
    Keywords: kinetic resolution ; baccatin ; taxoids ; paclitaxel ; docetaxel ; diastereoselective ; asymmetric synthesis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coupling of racemic 1-tBoc-4-CF3-β-lactams with various C-10 modified baccatins has resulted in CF3-taxoids with diastereoselectivities ranging from 9:1 to one single isomer. The observed high diastereoselectivity is ascribed to the highly efficient enantiomer-differentiation by the enantiopure lithium alkoxide of a baccatin III in the coupling reaction with a racemic 1-tBoc-β-lactam. These novel CF3-taxoids have also been shown to exhibit significant increases in activity against various cancer cell lines compared to either paclitaxel or docetaxel. In addition, the first asymmetric synthesis of a CF3-β-lactam via chiral ester enolate-imine cyclocondensation was performed with 50% enantioselectivity. Chirality 9:487-494, 1997. © 1997 Wiley-Liss, Inc.
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    Organoboranes for synthesis. 18. C2-symmetric α,α′-disubstituted-2,6-pyridinedimethanols as catalytic chiral ligands for the enantioselective nucleophilic addition of diethylzinc to aldehydes (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 506-511 
    Details
    ISSN: 0899-0042
    Keywords: organoboranes ; B-chlorodiisopinocampheylborane ; asymmetric reduction ; asymmetric allylboration ; enantioselective addition ; nucleophilic addition ; diethylzinc, electronic, and steric effects ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several new chiral auxiliaries with differing steric and electronic environments, such as α,α′-dimethyl-2,6-pyridinedimethanol, α,α′-ditrifluoromethyl-2,6-pyridinedimethanol, α,α′-dipentafluoroethyl-2,6-pyridinedimethanol, and α,α′-diallyl-2,6-pyridinedimethanol, have been examined and compared with α,α′-di-t-butyl-2,6-pyridinedimethanol for their ability to control the enantioselective addition of diethylzinc to benzaldehyde. The best chiral ligand has been tested for other representative aldehydes with varying steric and electronic requirements. The product alcohols are obtained in 21-78% ee. Chirality 9:506-511, 1997. © 1997 Wiley-Liss, Inc.
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    Absolute configuration of macrocyclic spermidine alkaloids (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 523-528 
    Details
    ISSN: 0899-0042
    Keywords: macrocyclic spermidine alkaloids ; stereoselective synthesis ; absolute configuration ; biogenesis ; stereochemistry ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this short review of several macrocyclic spermidine alkaloids, special consideration has been given to the correct determination of the absolute configuration at their chiral centers. The bases of interest are characterized by possessing a 13-membered macrocyclic lactam ring incorporating spermidine and either cinnammic or fatty acid precursorial units. In this context, the synthesis of some of these alkaloids is presented and the first total synthesis of optically pure (+)-(S)-viburnine, and (-)-(S)-celafurine is reported. Finally, a common initial step in biosynthesis starting with an enzyme-catalyzed Michael addition of spermidine to an α,β-unsaturated acid is proposed. Chirality 9:523-528, 1997. © 1997 Wiley-Liss, Inc.
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    Long-distance control in stereoselective reduction of 3-[3-(4′-bromo[1,1′-biphenyl]-4-yl)-3-keto-1-phenylpropyl]-4-hydroxy-2H-1-benzopyran-2-one: Relative configuration of prevailing diastereomer and absolute configuration of its enantiomers (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 512-522 
    Details
    ISSN: 0899-0042
    Keywords: asymmetric induction ; stereoselective reduction ; syn/anti diasteroselectivity ; circular dichroism (CD) ; coupled chromophores ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Depending on the reducing agent and reaction conditions, diastereoselective reduction of 3-[3-(4′-bromo[1,1′-biphenyl]-4-yl)-3-keto-1-phenylpropyl]-4-hydroxy-2H-1-benzopyran-2-one (2) proceeds with different stereoselectivity; a surprisingly high, approximately 90% d.e. of 4A is achieved with NaBH4 in MeOH at low temperature. Resulting diastereomeric racemates 4A and 4B are separated and their respective syn and anti configurations are assigned on the bases of mechanic considerations, supported by the 1H-NMR spectra and conformational analysis based on MM2 calculations. The syn diastereomer 7A, 4-OMe derivative of 4A, was partially resolved by acylation at C(3)-OH with S-(-)-camphanic acid to camphanyl ester 12 of (-)-7A, leaving (+)-enantiomer 7A. The assignment of absolute 1R,3S-configuration to (-)-7A is based on comparison of its CD spectrum with those of the model compounds S-14 and R-15, which represent partial chromophores 4-hydroxy-2H-1-benzopyran-2-one (4-hydroxycoumarin) A, and 4′-bromo-1,1′-biphenyl B; their exciton coupling in (-)-7A is suggested. Chirality 9:512-522, 1997. © 1997 Wiley-Liss, Inc.
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    Direct resolution, characterization, and stereospecific binding properties of an atropisomeric 1,4-benzodiazepine (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 495-505 
    Details
    ISSN: 0899-0042
    Keywords: stereoselective protein binding ; chiral HPLC ; circular dichroism ; stereoselective receptor binding ; HSA ; preparative HPLC ; atropisomeric benzodiazepine ; stereochemistry ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chromatographic resolution of 7-chloro-1,3-dihydro-1-(1,1-dimethylethyl)-5-(2-fluorophenyl)-2H-1,4-benzodiazepin-2-on (7), the 2′-fluoro, N1-tert-butyl analogue of diazepam, was attained on both analytical and preparative (mgs) scales, by using several chiral stationary phases (CSPs). The stereochemistry of this compound was characterized by means of 1H-NMR Nuclear Overhauser Effect (NOE) analysis. The single enantiomers of 7 were tested for their configuration and stereochemical stability by circular dichroism (CD), and their interaction with the central nervous system (CNS) benzodiazepine receptor was assayed, showing a significant difference in their binding affiities. Protein binding studies with human serum albumin (HSA, the main benzodiazepine carrier in human plasma) immobilized on a silica stationary phase revealed that HSA also preferentially binds one stereoisomer of 7. However, both on line CD detection and stereospecific interaction with other common drugs clearly demonstrated that the stereoselectivity of immobilized HSA for 7 is opposite to that for all the other studied benzodiazepines. In addition, HSA stereoselectivity for 7 is opposite to CNS receptor binding stereoselectivity for the same compound. Such HSA anomalous stereoselectivity for 7 was also confirmed in aqueous buffer solution by competitive displacement studies. Compared to other chiral 1,4-benzodiazepines, compound 7 thus shows several anomalous binding properties: HSA and the CNS receptor demonstrated opposite enantioselective discrimination; HSA has reversed enantioselectivity for compound 7; and HSA stereospecifically binds the low-affinity enantiomer. Chirality 9:495-505, 1997. © 1997 Wiley-Liss, Inc.
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    Chiroptical properties, structure, and absolute configuration of heterosubstituted 2(5H)-furanones (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 537-544 
    Details
    ISSN: 0899-0042
    Keywords: Circular dichroism ; helicity rule ; X-ray structure determination ; ultraviolet spectra ; n - π* and π - π* bands ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiroptical properties of a series of 3 and/or 4-heterosubstituted 2(5H)-furanones were investigated with respect to correlation with absolute configuration. The n - π* and π - π* Cotton effects have been assigned on the basis of comparison with the UV spectra in solvents of varying polarity. It is demonstrated that the n - π* transition in 4-amino substituted 2(5H)-furanones appears at shorter wavelength with respect to the π - π* transition. With the exception of 4-pyrrolidino and 4-benzylamino substituted 2(5H)-furanones, other heterosubstituted 2(5H)-furanones follow the butenolide configurational rule (Gawronski et al. J. Org. Chem. 61:1513-1515, 1996). Absolute configuration of 2(5H)-furanone derivatives can also be assigned according to the sign of the Cotton effect (of unknown origin) at 200-230 nm. The structure of four representative sulfur and nitrogen substituted 2(5H)-furanones has been analyzed by X-ray diffraction. The results indicate planarity of the furanone ring and extended conjugation in 4-amino substituted 2(5H)-furanones. Chirality 9:537-544, 1997. © 1997 Wiley-Liss, Inc.
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    Excitatory amino acid receptor antagonists: Resolution, absolute stereochemistry, and pharmacology of (S)- and (R)-2-amino-2-(5-tert-butyl-3-hydroxyisoxazol-4-yl)acetic acid (ATAA) (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 529-536 
    Details
    ISSN: 0899-0042
    Keywords: diastereomeric salt resolution ; chiral HPLC ; enantiomeric purity ; absolute stereochemistry ; X-ray crystallography ; NMDA receptor antagonist ; AMPA receptor antagonist ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have previously shown that (RS)-2-amino-2-(5-tert-butyl-3-hydroxyisoxazol-4-yl)acetic acid (ATAA) is an antagonist at N-methyl-D-aspartic acid (NMDA) and (RS)-2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA) receptors. We have now resolved ATAA via diastereomeric salt formation using N-BOC protected ATAA and (R)- and (S)-phenylethylamine. Enantiomeric purities (ee 〉 98%) of (R)- and (S)-ATAA were determined using the Crownpak CR(-) and CR(+) columns, respectively. The absolute configuration of (R)-ATAA was established by an X-ray crystallographic analysis of the (R)-phenylethylamine salt of N-BOC-(R)-ATAA. Like ATAA, neither (R)- nor (S)-ATAA significantly affected (IC50 〉 100 μM) the receptor binding of tritiated AMPA, kainic acid, or (RS)-3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid, the latter being a competitive NMDA antagonist. Electrophysiological experiments, using the rat cortical wedge preparation, showed the NMDA antagonist effect as well as the AMPA antagonist effect of ATAA to reside exclusively in the (R)-enantiomer (Ki = 75 ± 5 μM and 57 ± 1 μM, respectively). Neither (R)- nor (S)-ATAA significantly reduced kainic acid-induced excitation (Ki 〉 1,000 μM). Chirality 9:529-536, 1997. © 1997 Wiley-Liss, Inc.
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    Enantiomeric recognition of aralkyl ammonium salts by chiral pyridino-18-crown-6 ligands: Use of circular dichroism spectroscopy (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 545-549 
    Details
    ISSN: 0899-0042
    Keywords: circular dichroism (CD) ; chiral crown ethers ; enantiomeric recognition ; heterochiral complexing ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: CD studies were performed on the enantiomeric recognition of chiral aralkyl ammonium salts 1-3 by chiral pyridino-18-crown-6 ligands 4 and 6. Heterochiral complexing was found to result in larger spectral effects in both the 1Lb and 1La band regions of the chiral crown ethers. Based on the results reported herein, CD spectroscopy can be an efficient tool for discriminating between enantiomeric chiral aralkyl ammonium salts and determining the stoichiometry and relative stability of their complexes with chiral pyridino-18-crown-6 ligands. Chirality 9:545-549, 1997. © 1997 Wiley-Liss, Inc.
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    O-nitromandelic acid: A chiral solvating agent for the NMR determination of chiral diamine enantiomeric purity (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 556-562 
    Details
    ISSN: 0899-0042
    Keywords: O-nitromandelic acid ; chiral solvating agent ; NMR ; enantiomeric purity ; mandelic acid ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: O-Nitromandelic acid, easily prepared from either enantiomer of mandelic acid, has been used as a chiral solvating agent for the determination of enantiomeric purity of several diamine derivatives and other compounds using 1H NMR spectroscopy. Chirality 9:556-562, 1997. © 1997 Wiley-Liss, Inc.
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    Exciton-coupled circular dichroism (ECCD) in acyclic hydroxylated dienes: A sensitive method for the direct stereochemical assignment of lipoxygenase products (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 563-567 
    Details
    ISSN: 0899-0042
    Keywords: absolute configuration ; stereochemistry ; chromophore ; chirality ; linoleic acid ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lipoxygenases convert polyunsaturated fatty acids into a number of chiral hydroperoxides, which are involved in different biological pathways. We applied the exciton-coupled circular dichroism (ECCD) method to determine the absolute configuration of acyclic hydroxylated dienes derived from the lipoxygenase catalyzed dioxygenation of 1(Z),4(Z)-unsaturated fatty acids. The CD spectra of the 2-naphthoate derivatives of reduced hydroperoxides reveal, depending on R or S configuration of the hydroxyl group, a negative or positive chiral twist between the 2-naphthoate chromophore and the diene chromophore in the molecule. Thus, lipoxygenase stereoselectivity can be deduced from a single CD measurement. Chirality 9:563-567, 1997. © 1997 Wiley-Liss, Inc.
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    Diastereomers of 3-(S)-(1-phenylethyl)-5-methyl- and -5-phenylrhodanine: Crystal structures, conformations, and circular dichroism spectra (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 568-577 
    Details
    ISSN: 0899-0042
    Keywords: 3-(S)-(1-phenylethyl)-2-thioxo-2,3-dihydro-1,3-thiazol-4(5H)-ones ; 3-(S)-(1-phenylethyl)-rhodanines ; CD spectra ; empirical force field calculations ; theoretical calculation of CD spectra ; chromatographic diastereomer separation ; triacetylcellulose ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3-(S)-(1-phenylethyl)-5-methyl- and 5-phenyl-rhodanine have been studied by single crystal X-ray crystallography. The crystals of the 5-methyl compound were shown to contain equal amounts of the 5-(R) and 5-(S) diastereomers, while the crystals of the 5-phenyl compound only contain the 5-(S) diastereomer. The UV and CD spectra of the 5-H2 compound have been analyzed on the basis of CNDO/S calculations, and the CD spectrum has been reproduced by semiempirical calculations.The 5-methyl diastereomers can be partly separated by chromatography on triacetylcellulose, and the CD spectra of the individual forms can be evaluated. The 5-phenyl compound undergoes rapid epimerization in solution, and also for this compound the CD spectra of both forms can be evaluated. The contribution of the 5-substituent follows Ripperger's sector rule for dithiocarbamates. Chirality 9:568-577, 1997. © 1997 Wiley-Liss, Inc.
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    Application of phenylglycine methyl ester (PGME) to determination of the absolute configuration of carboxylic acids having phenylalkyl group (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 550-555 
    Details
    ISSN: 0899-0042
    Keywords: NMR ; chiral anisotropic reagent ; long-chain carboxylic acid ; Mosher's method ; absolute configuration ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (R)- and (S)-phenylglycine methyl ester (PGME) was applied to elucidate the absolute configuration of a series of aliphatic carboxylic acids, 2a and 2b (n = 1-6), which possess a phenyl group on the chain, by the process similar to the modified Mosher's method. (S)-PGME was condensed with rac-2a and 2b, and the resulting diastereomeric pair was separated for each of 2a and 2b. Δδ values were calculated from the 1H-NMR chemical shifts of (R)-2a-(or 2b)-(S)-PGME and (R)-2a-(or 2b)-PGME amides. By analyzing the positive and negative distribution patterns for each compound, it was concluded that this new method was successful to predict the absolute configuration of such type of acids, and that no significant interaction between the two phenyl groups, one in the chain and the other in the PGME, was present. Chirality 9:550-555, 1997. © 1997 Wiley-Liss, Inc.
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    Application of [Mo2(OAc)4] for determination of absolute configuration of brassinosteroid vic-diols by circular dichroism (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 578-582 
    Details
    ISSN: 0899-0042
    Keywords: 1,2-diols ; chiral Mo complexes ; transition metal complexes ; difference CD ; sum CD ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The in situ complexes of dimolybdenum tetraacetate [Mo2(OAc)4] with vicinal diols give CD spectra suitable for determination of their absolute configuration. Positive (negative) torsional angle in the O-C-C-O moiety leads to a positive (negative) Cotton effect at around 300 nm. The extension of this rule to compounds containing a second vic-diol moiety in the same molecule is studied on brassinosteroid vic-diols 1-14. It is demonstrated that the in situ method allows fast and easy configurational assignment of both glycol moieties present in brassinosteroids on the basis of the sum and difference CDs of respective pairs of (22S,23S)- and (22R,23R)-isomers. Chirality 9:578-582, 1997. © 1997 Wiley-Liss, Inc.
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    Exciton chirality of bilirubin homologs (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 604-615 
    Details
    ISSN: 0899-0042
    Keywords: circular dichroism ; mesobilirubins ; conformation ; ridge-tile shape ; molecular helicity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bilirubin, the yellow pigment of jaundice, is a bichromophoric tetrapyrrole that readily adopts either of two enantiomeric, folded conformations shaped like ridge-tiles and stabilized by a network of six intramolecular hydrogen bonds. Interconversion of these M and P helical chirality conformational enantiomers is rapid at room temperature but may be displaced toward either enantiomer by intramolecular nonbonded steric interactions. Introduction of a methyl group at the β and β′ carbons of the propionic acid chains on the symmetric bilirubin analog, mesobilirubin-XIIIα, shifts the conformational equilibrium toward the M or the P-chirality intramolecularly hydrogen-bonded conformer, depending only on the S or R stereochemistry at β and β′, resulting in pigments with intense exciton coupling circular dichroism (CD) for the ∼430 nm transition(s). Optically active synthetic analogs of bilirubin with propionic acid groups lengthened systematically to heptanoic acid (1-5) were synthesized and examined by spectroscopy to explore the influence of alkanoic acid chain length on conformation and intramolecular hydrogen bonding. In these diacids and their dimethyl esters (6-10), strong exciton chirality CD spectra are observed, and the data are correlated with molecular helicity. Chirality 9:604-615, 1997. © 1997 Wiley-Liss, Inc.
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    Luminescence studies of the stereoselectivity in the mixed-ligand complexes formed by terbium(III) with enantiomerically resolved 1,2-propanediaminetetraacetic acid and α-hydroxyphenylcarboxylic acids (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 583-592 
    Details
    ISSN: 0899-0042
    Keywords: terbium(III) ; mandelic acid ; circularly polarized luminescence ; 1,2-propanediaminetetraacetic acid ; phenyllactic acid ; stereoselectivity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It has been found that the binding of mandelic acid (MAN) at the inner coordination sphere of Tb(propanediaminetetraacetate) is profoundly affected by the enantiomeric identity of the MAN ligand, but that such stereoselective effects are absent in the formation of analogous ternary complexes containing phenyllactic acid (PLA). For Tb(PDTA)(MAN) complex species, the largest formation constants were obtained when the PDTA and MAN ligands were of the opposite absolute configuration, and the smallest were obtained when the two bound ligands were of the same configuration. The formation constants of all Tb(PDTA)(PLA) complexes were found to be equivalent to within experimental error, indicating no stereoselectivity in the formation of these ternary complexes.The circularly polarized luminescence within the Tb(III) emission bands indicated that steric interactions accompanied the binding of MAN by a Tb(PDTA) complex, which were deduced to be associated with perturbations in ligand conformations. No such effects were noted between bound PDTA and PLA ligands, where the observed CPL intensities of the ternary complexes could be calculated by a simple addition of PDTA and PLA contributions. Determinations of metal ion hydration revealed that the fully formed Tb(PDTA)(MAN) complexes were essentially anhydrous, while the fully formed Tb(PDTA)(PLA) to complexes still contained residual water. This finding indicated that the binding of MAN a Tb(PDTA) complex is accompanied by a total expulsion of all coordinated water molecules, implying the existence of a tight fit by the MAN ligand in the residual inner coordination sphere of a Tb(PDTA) complex. The lack of any demonstrable steric interactions between bound PDTA and PLA ligands implies that the PLA ligand has a smaller steric requirements than does the MAN ligand. This is thought to be due to the additional methylene group of PLA, which provides an additional spacing between the coordinating hydroxycarboxylate group and the sterically demanding phenyl group, and which appears to be sufficient to move the phenyl group out to a distance which does not require its interaction with the PDTA functionality. Chirality 9:583-592, 1997. © 1997 Wiley-Liss, Inc.
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    Chiral recognition of epoxides by 1H NMR spectroscopy in the presence of a chiral dirhodium complex (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 601-603 
    Details
    ISSN: 0899-0042
    Keywords: Mosher's acid ; 1H NMR ; epoxides ; chiral recognition ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It was found that the oxirane ring is a functional group amenable to chiral discrimination by dirhodium-MTPA complexes. Considerable signal shifts up to 0.7 ppm are observed for 1H nuclei close to the rhodium atoms in the complex. In analogy to previously reported olefins, this method appears to be comparable to the use of chiral lanthanoid shift reagents. Chirality 9: 601-603, 1997. ©1997 Wiley-Liss, Inc.
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    Preparation of polyacetylenes bearing an amino group and their application to chirality assignment of carboxylic acids by circular dichroism (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 593-600 
    Details
    ISSN: 0899-0042
    Keywords: polyphenylacetylene ; rhodium catalyst ; chiral discrimination ; circular dichroism ; induced circular dichroism ; absolute configuration ; helix ; acid-base ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Five phenylacetylenes bearing an amino group such as 4-amino (1), 3-amino (2), 4-N,N-dimethylamino (3), 4-aminomethyl (4), and 4-N,N-diisopropylamino-methyl (5) group on the phenyl group, 4-pyridylacetylene (6), and 2-pyridylacetylene (7) were synthesized and polymerized with [Rh(nbd)Cl]2 (nbd: norbornadiene). Monomer 5 showed the highest polymerizability and afforded quantitatively a fibrous polymer, whereas the other monomers showed lower reactivity and the resulting polymers were powdery. Although most polymers were not soluble in common organic solvents such as tetrahydrofuran (THF), chloroform, acetonitrile, and dimethyl sulfoxide, some polymers were soluble in the presence of carboxylic acids. Among the polyphenylacetylene derivatives, only poly-5 having a stable, highly cis-transoidal stereoregular structure exhibited an induced circular dichroism (ICD) in the UV-visible region, probably due to a prevailing one-handed helical conformation upon complexation with optically active carboxylic and α-hydroxy acids such as mandelic acid, lactic acid, and 2-phenylbutyric acid in THF, the sign of which reflected the absolute configuration of the acids. Therefore, poly-5 can be used as a novel probe for determining the chirality of acids. The α-hydroxy acids of the same configuration gave the same sign in induced Cotton effect in THF. However, carboxylic acids used in the present study showed the opposite signs to those of the α-hydroxy acids when their absolute configurations were same. The magnitude of the ICDs seems to depend on the bulkiness of the α-hydroxy acids. On the contrary, other poly(phenylacetylenes) bearing an amino group and poly(pyridylacetylenes) did not show any ICD in the presence of optically active acids, probably because of either low basicity for the acid-base complexation or low stereoregularity of the polymers. Chirality 9:593-600, 1997. © 1997 Wiley-Liss, Inc.
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    Absolute configurational assignment of self-organizing asymmetric tripodal ligand-metal complexes (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 616-622 
    Details
    ISSN: 0899-0042
    Keywords: exciton coupling ; chiral coordination complex ; C3-symmetry ; tripodal ligand ; absolute stereochemistry ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solution configuration of labile coordination complexes may be difficult to determine, even in cases in which the solid state structure is known. We have previously synthesized a series of chiral ligands which form pseudo-C3-symmetric complexes with ZnII and CuII salts that possess an available electrophilic coordination site. Molecular modeling of ZnII complexes of the chiral ligand N,N-bis[(2-quinolyl)methyl]-1-(2-pyridyl)ethanamine (α-MeBQPA) showed that the spatial arrangement of the heterocyclic arms is controlled by a substituent on one methylene arm, resulting in the adoption of an enantiomeric conformation displaying a propeller-like asymmetry. In this paper we report the application of the exciton chirality method to the determination of the conformation of asymmetric metal-ligand complexes in solution. There is a good correlation between the predicted and the observed Cotton effects, demonstrating that the geometry in solution closely resembles that predicted by computational simulations and those obtained by X-ray crystallographic studies of metal complexes with racemic and enantiomerically pure ligands. The X-ray crystallographic structure of the first optically pure complex in this series is reported. Chirality 9:616-622, 1997. © 1997 Wiley-Liss, Inc.
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    Synthesis, circular dichroism, and absolute stereochemistry of 1,1′:4′,1′-ternaphthalene compounds (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 623-625 
    Details
    ISSN: 0899-0042
    Keywords: 1,1′:4′,1′-ternaphthalene ; enantioresolution ; chiral phthalic acid amide method ; circular dichroism ; absolute stereochemistry ; CD exciton chirality method ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiopure 1,1′:4′,1′-ternaphthalene compounds were synthesized via enantioresolution of 1,1′:4′,1′-ternaphthalene-2,2′-dimethanol (2) by the chiral phthalic acid amide method. The CD spectra of chiral 1,1′:4′,1′-ternaphthalene compounds synthesized showed typical intense exciton split CD Cotton effects, from which the absolute stereochemistry of these 1,1′:4′,1′-ternaphthalene compounds was unambiguously determined by the CD exciton chirality method. Chirality 9:623-625, 1997. © 1997 Wiley-Liss, Inc.
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    Inversion barriers in sulfoxide functions studied by enantioselective liquid chromatography and chiroptical methods (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 638-642 
    Details
    ISSN: 0899-0042
    Keywords: sulfoxide function ; stereoinversion ; enantiomerization barriers ; enantioselective chromatography ; chiroptical methods ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of 2-substituted 1,3,2-benzodithiazole 1-oxides has been synthesized and the compounds resolved into enantiomers by semipreparative enantioselective liquid chromatography. The low enantiomerization barriers have been determined by chiroptical techniques and were found to be relatively independent of the 2-substituent used. The kinetic results are consistent with a pyramidal inversion mechanism and a reduced barrier due to electronic effects, favouring the transition state over the pyramidal ground state. This mechanistic rationale was further supported by data obtained from molecular modelling using AM1 geometry optimization. The absolute configurations have been determined via a comparison of their CD-spectra with those of analogs with previously determined configuration. Chirality 9:638-642, 1997. © 1997 Wiley-Liss, Inc.
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    Rotational population dependences of the hydroxymethyl group in alkyl glucopyranosides: Anomers comparison (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 626-637 
    Details
    ISSN: 0899-0042
    Keywords: alkyl glucopyranosides ; rotational population analysis ; absolute configuration determination ; circular dichroism ; nuclear magnetic resonance ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A CD and 1H NMR study of the rotamer population around the C5-C6 bond of alkyl α-d-glucopyranosides proved it to be dependent on the aglycon and its absolute configuration, showing a similar, but not identical, behavior to that of their β-anomers. Thus, the population of the gt rotamer increased as the pKa of the aglycon increased, whereas the population of the tg and gg rotamers decreased, mainly that of the tg rotamer. The results showed the existence of a clear correlation between the stereoelectronic exo-anomeric effect and the rotamer distributions, the endo-anomeric effect not being directly involved. In addition, the 1H NMR chemical shift differences (δD-δROH) of the alkyl α-d-glucopyranosides are characteristic of the absolute configuration of the aglycon, as occurred with the β-anomers. Therefore, the absolute configuration of secondary chiral alcohols or the aglyconic moiety of natural glycosides can be determined independently of the anomeric configuration, a single enantiomer being sufficient. Chirality 9:626-637, 1997. © 1997 Wiley-Liss, Inc.
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    Stereoselective disposition and chiral inversion of KE-298, a new antirheumatic drug, in rats (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 22-28 
    Details
    ISSN: 0899-0042
    Keywords: pharmacokinetics ; metabolism ; stereoselectivity ; protein binding ; binding site ; displacement ; metabolic chiral inversion ; chiral HPLC ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The present study was an attempt to elucidate the relationship between stereoselective pharmacokinetics and protein binding of KE-298 and its active metabolites, deacetyl-KE-298 (M-1) and S-methyl-KE-298 (M-2). Metabolic chiral inversion was also investigated. The levels of unchanged KE-298 in plasma after oral administration of (+)-(S)-KE-298 to rats were lower than those of (-)-(R)-KE-298, whereas the levels of M-1 and M-2 after administration of (+)-(S)-KE-298 were higher than after (-)-(R)-KE-298. In vitro, rat plasma protein binding of (+)-(S)-KE-298 was lower than that of (-)-(R)-KE-298. In contrast, the binding of (+)-(S)-M-1 and (+)-(S)-M-2 was higher than that of (-)-(R)-M-1 and (-)-(R)-M-2. Displacement studies revealed that the (+)-(S) and (-)-(R)-enantiomers of KE-298 and their metabolites bound to the warfarin binding site on rat serum albumin. These results suggest that the stereoselective plasma levels in KE-298 and its metabolites were closely related to enantiomeric differences in protein binding, attributed to quantitative differences in binding to albumin rather than to the different binding sites. Unidirectional chiral inversion was detected after oral administration of either (-)-(R)-KE-298 or (-)-(R)-M-2 to rats both yielding (+)-(S)-M-2. Chirality 9:22-28, 1997 © 1997 Wiley-Liss, Inc.
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    Optical resolution by preferential crystallization of DL-methionine hydrochloride (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 48-51 
    Details
    ISSN: 0899-0042
    Keywords: amino acid ; successive optical resolution ; conglomerate ; binary phase diagram ; racemic structure ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: DL-Methionine hydrochloride (DL-Met·HCl) was found to exist as a conglomerate, based on the infrared spectrum, solubility, and melting point. The optical resolution of DL-Met·HCl was successfully achieved by preferential crystallization into D-and L-Met·HCl. Treatment of the purified D- and L-Met·HCl with triethylamine gave D- and L-methionine of 100% optical purities. Chirality, 9;48-51, 1997. © 1997 Wiley-Liss, Inc.
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    Absolute configuration of (+)-α-dihydrotetrabenazine, an active metabolite of tetrabenazine (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 59-62 
    Details
    ISSN: 0899-0042
    Keywords: resolution of enantiomers ; chiral column chromatography ; enzyme ; X-ray crystallography ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiral column liquid chromatography and enantiospecific enzymatic hydrolysis were utilized to separate the enantiomers of α- and β-dihydrotetrabenazine and α-9-O-desmethyldihydrotetrabenazine, three benzo[a]quinolizines derived from the amine-depleting drug tetrabenazine. An X-ray crystal structure analysis of (-)-α-9-O-desmethyldihydrotetrabenazine gave an absolute structure of that compound as the 2S, 3S, 11bS isomer. Therefore, (-)-α-dihydrotetrabenazine also has the 2S, 3S, 11bS absolute configuration. (+)-α-Dihydrotetrabenazine, the single biologically active isomer from the metabolic reduction of tetrabenazine, thus has the absolute configuration of 2R, 3R, 11bR. For further in vitro and in vivo studies of the vesicular monoamine transporter, it is now possible to use the single enantiomer of radiolabeled α-dihydrotetrabenazine. Chirality 9:59-62, 1997. © 1997 Wiley-Liss, Inc.
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    Book review: “Enantioselective reactions in organic chemistry” (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 88-88 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
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  • 90
    Electronic Resource
    Electronic Resource
    Enantiomeric resolution by HPLC of axial chiral amides using amylose tris[(S)-1-phenylethylcarbamate] (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 109-112 
    Details
    ISSN: 0899-0042
    Keywords: N-arylamides ; carbohydrate carbamate ; axial chirality ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantiomeric resolution of a series of N-arylamides was examined on amylose tris[(S)-1-phenylethylcarbamate] coated onto aminopropylated 7 μm silica with 500 Å diameter pores and on naked silica 5 μm particle size with 500 Å diameter pores. The enantiomeric resolution obtained for this series was excellent on both columns. The enantioselectivity of cellulose and amylose tris (3,5-dimethylphenylcarbamate) coated onto APS-Hypersil (120 Å pore size, 5 μm particle size) was also investigated for this series of compounds. Chirality 9:109-112, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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  • 91
    Electronic Resource
    Electronic Resource
    Enantiomeric separation of five amino acids by high-performance liquid chromatography on a chiral crown ether column (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 150-152 
    Details
    ISSN: 0899-0042
    Keywords: amino acid ; stereoconversion ; racemization ; liquid chromatography ; isomer ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A chiral liquid chromatographic method was validated to analyze the D-and L-enantiomers of five amino acids contained in a commercial solution: aspartic acid, leucine, lysine, phenylalanine, and valine. These 10 compounds were separated on a chiral crown ether column with a mobile phase composed of water adjusted to pH 1.5 with perchloric acid, with ultraviolet detection at 220 nm. The method was applied to the commercial amino acid solution before and after sterilization by 5 kGy irradiation; no stereoconversion was observed following sterilization. Chirality 9:150-152, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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  • 92
    Electronic Resource
    Electronic Resource
    High-performance liquid chromatographic enantioseparation of N-protected α-amino acids using nonporous silica modified by a quinine carbamate as chiral stationary phase (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 157-161 
    Details
    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.
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  • 93
    Electronic Resource
    Electronic Resource
    Chiral nuclear magnetic resonance shift reagents: Lanthanide mixtures with 1-(1-naphthyl) ethylurea derivatives of amino acids (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 1-9 
    Details
    ISSN: 0899-0042
    Keywords: chiral solvating agents ; enantiomers ; enantiomeric excess ; chiral sulfoxides ; chiral amines ; chiral alcohols ; chiral carboxylic acids ; optical purity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Esters of 1-(1-naphthly)ethylurea derivatives of L-valine, L-leucine, L-tert-leucine, and L-proline are examined as organic-soluble chiral nuclear magnetic resonance (NMR) resolving agents. The reagents are useful for resolving the spectra of chiral sulfoxides, amines, alcohols, and carboxylic acids. Enantiomeric resolution is caused by a combination of diastereomeric effects and the different association constants of the substrates with the resolving agents. Organic-soluble lanthanide species are added to resolving agent-substrate mixtures and often enhance the enantiomeric resolution. The enhancement occurs because the substrate that exhibits weaker binding with the resolving agent is more available to bond to the lanthanide. Broadening in the spectra with lanthanides is reduced at 50°C. Enantiomeric resolution is still observed at elevated temperatures. Chirality 9:1-9, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 10 Ill.
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  • 94
    Electronic Resource
    Electronic Resource
    Steady-state clearance rates of warfarin and its enantiomers in therapeutically dosed patients (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 13-16 
    Details
    ISSN: 0899-0042
    Keywords: R-warfarin ; S-warfarin ; steady-state clearance ; patients ; AUC data ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Previous studies to identify the pharmacokinetics of R- and S-warfarin have not used steady-state area under the curve (AUC) data during therapeutic doses of racemic warfarin. Instead they have used high single doses of either racemic warfarin or a single enantiomer in volunteers or have taken a single blood sample from anticoagulated patients and assumed full compliance and a steady-state status. In this study, a series of steady-state racemic warfarin, R-warfarin, and S-warfarin serum concentrations, during a 24 h dosage interval, was measured in 10 compliant patients (5 females and 5 males) taking racemic warfarin. The anticoagulation status of all 10 patients according to the International Normalised Ratio (INR) was stable. Their mean (SD) age and weight were 67.0 (9.9) yr and 63.9 (15.4) kg. The mean (SD) clearances derived from steady-state AUC values, following therapeutic dosing, for racemic warfarin, R-warfarin, and S-warfarin were 2.40 (0.82), 2.30 (0.65), and 2.80 (1.17) ml/h/kg, respectively. The mean (SD) ratio of S-:R-warfarin clearance was 1.24 (0.40). Comparison of the clearance measured from the AUC, of these patients, to one point determinations assuming steady state for the samples drawn at either 6, 15, or 20 h after dosage (during the dosing interval) showed some statistical differences. Most single point determinations of warfarin clearance assume that a sample 12 h postdose is equivalent to that of the steady-state concentration, but in this study the steady-state concentration of only 6 patients occurred between 6 and 15 h postdose. This could explain why these studies demonstrate differences in the clearance of R- and S-warfarin compared to the values we have derived from steady-state AUC data using patients with proven compliance and therapeutic doses. Chirality 9:13-16, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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  • 95
    Electronic Resource
    Electronic Resource
    Bi-directional chiral inversion of ketoprofen in CD-1 mice (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 29-31 
    Details
    ISSN: 0899-0042
    Keywords: 2-arylpropionate ; reversible chiral inversion ; NSAIDs ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The R enantiomers of some of the 2-arylpropionic acid non-steroidal antiinflammatory drugs (NSAIDs) are known to undergo metabolic chiral inversion to their more pharmacologically active antipodes. This process is drug and species dependent and usually unidirectional. The S to R chiral inversion, on the other hand, is rare and has been observed, in substantial extents, only for ibuprofen in guinea pigs and 2-phenylpropionic acid in dogs. After i.p. administration of single doses of racemic ketoprofen or its optically pure enantiomers to male CD-1 mice and subsequent study of the concentration time-course of the enantiomers, we noticed substantial chiral inversion in both directions. Following racemic doses, no stereoselectivity in the plasma-concentration time courses was observed. After dosing with optically pure enantiomer, the concentration of the administered enantiomer predominated during the absorption phase. During the terminal elimination phase, however, the enantiomers had the same concentrations. Our observation is suggestive of a rapid and reversible chiral inversion for ketoprofen enantiomers in mice. Chirality 9:29-31, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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  • 96
    Electronic Resource
    Electronic Resource
    Enantioselective high-performance liquid chromatography assay of (+)R- and (-)S-α-lipoic acid in human plasma (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 32-36 
    Details
    ISSN: 0899-0042
    Keywords: chiral thiol derivatisation ; diastereomeric derivative ; reversed phase HPLC ; fluorescence detection ; assay validation ; enantiomer pharmacokinetics ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A specific plasma level assay for the enantiomers of α-lipoic acid is described. It makes use of liquid-liquid extraction, chemical reduction to the dithiol enantiomers, and their precolumn chiral derivatisation with o-phthalaldehyde in the presence of D-phenylalanine. The two diastereomeric derivatives are separated by reversed-phase HPLC with fluorescence detection. The working range of the assay is between 15 ng/ml (lower limit of quantitation) and 1,000 ng/ml for either enantiomer. Chirality 9:32-36, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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  • 97
    Electronic Resource
    Electronic Resource
    Stereoselective metabolism of famprofazone in humans: N-dealkylation and β-and p-hydroxylation (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 52-58 
    Details
    ISSN: 0899-0042
    Keywords: famprofazone ; stereoselective metabolism ; N-dealkylation ; β-hydroxylation ; p-hydroxylation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Following administration of famprofazone to humans, the stereoselective metabolism from the drug to its known metabolites (+,-)-ephedrine, (+,-)-pseudoephedrine, (+,-)-norephedrine, (+,-)-norpseudoephedrine, (+,-)-p-hydroxy-amphetamine, (+,-)-p-hydroxymethamphetamine, and (+,-)-p-hydroxynorephedrine was studied. The enantiomers of the metabolites were derivatized with α-methoxy-α-(trifluoromethyl)-phenylacetyl chloride (MTPA.Cl) as the chiral derivatizing agent for amino groups and N-methyl-N-trimethylsilyl trifluoroacetamide (MSTFA) or N-methyl-N-triethylsilyl trifluoroacetamide (MTESTFA) as protecting agents of the hydroxyl groups. The diastereomeric derivatives were well separated by capillary gas-liquid chromatography and determined by mass spectrometry with selected-ion monitoring (SIM). (-)-Methamphetamine, (-)-amphetamine, (-)-p-hydroxyamphetamine, and-(-)-hydroxymethamphetamine were excreted in greater amounts than their enantiomers after administration of racemic famprofazone; and (-)-ephedrine, (-)-pseudoephedrine, (-)-norephedrine, and (-)-norpseudoephedrine were found in higher concentration than their enantiomers. Famprofazone was metabolized by product and substrate stereoselective N-dealkylation, β-hydroxylation, and p-hydroxylation, metabolites of which may be predominantly responsible for the side effects of famprofazone. Chirality 9:52-58, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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  • 98
    Electronic Resource
    Electronic Resource
    Stereoselective effects of chiral clofibric acid analogs on rat peroxisome proliferator-activated receptor α (rPPARα) activation and peroxisomal fatty acid β-oxidation (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 37-47 
    Details
    ISSN: 0899-0042
    Keywords: stereoselectivity ; fatty-acyl CoA oxidase ; H4IIEC3 cells ; CV-1 cells ; structure-activity relationships ; absolute configuration assignment ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiomers of a series of substituted analogs of 2-(4-chloronhenoxy)-acetic acid (CPAA) were synthesized and used to examine the influence of steric and structural parameters on peroxisome proliferation. The effects of these compounds were studied on the activation of the peroxisome proliferator-activated receptor α (PPARα) in CV-1 cells using an in vitro co-transfection assay. Selected sets of isomers were tested for their ability to increase peroxisomal fatty acyl-CoA oxidase (ACO) activity in H4IIEC3 (rat Reuber hepatoma) cells. Of the series of 2-substituted analogs studied, the isomers of the n-propyl and phenyl derivatives of CPAA showed a high degree of stereoselectivity [(S)-isomer ≫ (R)-isomer]. In general, the potency of the compound to activate the receptor increased with the size of the 2-alkyl substituent. Among the 4-chlorobenzyloxy- and 4-(4′-chlorophenyl)benzyloxy- analogs studied, 2-[4-(4′-chlorophenyl)-benzyloxy]-propanoic acid exhibited a high degree of stereoselectivity in both the biological systems studied [(R) ≫ (S)]. The congeners of 2-methyl substituted CPAA showed a reverse stereoselectivity [(R) 〉 (S)] as compared to the other 2-substituted analogs [(S) 〉 (R)]. Our results indicate that (1) both structural and steric characteristics of CPAA analogs play an important role in the activation of rPPARα and on stimulation of peroxisomal ACO activities, and (2) clofibric acid and analogs exert their peroxisome proliferative effects by interaction with a specific site on a protein. The enantiomers of the 2-n-propyl and the 2-phenyl CPAA analogs may be useful as mechanistic probes in elucidating the nature of this binding site. Chirality 9:37-47, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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  • 99
    Electronic Resource
    Electronic Resource
    Enantiomerization of Environmentally Significant Overcrowded Polychlorinated Biphenyls (PCBs) (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 350-353 
    Details
    ISSN: 0899-0042
    Keywords: xenobiotics ; pollutants ; non-planar aromatics ; chirality ; atropisomerism ; ab initio calculations ; electron correlation ; density functional theory ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rotational barriers of overcrowded PCBs are predicted by ab initio methods including electron correlation, thus settling the controversy between theory and experiment. For 2,2′,3,3′,4,6′-hexachlorobiphenyl (PCB 132), an enantiomerization barrier of 185 kJ/mol is calculated by B3LYP/6-31G*, in excellent agreement with the experimental data. Chirality 9:350-353, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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  • 100
    Electronic Resource
    Electronic Resource
    Stereoselective pharmacokinetics of ibuprofen in rats: effect of enantiomer-enantiomer interaction in plasma protein binding (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 354-361 
    Details
    ISSN: 0899-0042
    Keywords: ibuprofen ; enantiomers ; stereoselective ; interactions ; plasma protein binding ; rat ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stereoselective pharmacokinetics of ibuprofen (IB) enantiomers were studied in rats. Unidirectional conversion from R-ibuprofen (R-IB) to S-ibuprofen (S-IB) was observed following intravenous administration. S-IB concentrations in plasma following racemate administration were simulated according to a conventional compartmental model using the parameters obtained after the administration of individual enantiomers, and resulted in overestimation of S-IB concentrations.Binding of IB enantiomers measured in rat plasma was stereoselective, the binding of R-IB being more favorable than that of S-IB. Moreover, there are interactions between IB enantiomers in binding, which may cause the increase of distribution volumes of IB enantiomers in the presence of their antipodes. Hence simulated S-IB concentrations according to a conventional compartment model were significantly greater than those observed. Indeed, when the enantiomer-enantiomer interactions were taken into account, simulation of S-IB concentrations in plasma following racemate administration was in good agreement with observed values. Therefore, interactions between stereoisomers as well as dispositional stereoselectivity have to be considered when pharmacokinetics of stereoisomers after administration of the racemate are compared to those after administration of individual isomers. Chirality 9:354-361, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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