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  • 1995-1999  (1,826)
  • 1910-1914
  • 1995  (1,826)
  • Organic Chemistry  (965)
  • Chemical Engineering  (730)
  • Industrial Chemistry and Chemical Engineering
  • Nuclear reactions
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Material
Years
  • 1995-1999  (1,826)
  • 1910-1914
Year
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Formation and reactivity of acyl glucuronides: The influence of chirality (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 1-9 
    Details
    ISSN: 0899-0042
    Keywords: acyl glucuronide ; enantiomer ; epimer ; diastereomer ; nonsteroidal antiinflammatory drug ; 2-arylpropionic acid ; systemic cycling ; reactivity ; hydrolysis ; covalent binding ; drug-protein adduct ; regioisomer ; aglycone ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070102
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  • 2
    Electronic Resource
    Electronic Resource
    Retention model for the resolved enantiomers of felodipine on chiral-AGP using micellar mobile phases (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 23-27 
    Details
    ISSN: 0899-0042
    Keywords: felodipine ; retention model ; micellar mobile phases ; chiral resolution ; CHIRAL-AGP ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A retention model for the chiral separation of an uncharged solute, felodipine, on CHIRAL-AGP, using a micellar mobile phase is proposed. The model assumes the presence of two stereoselective sites and each enantiomer was found to interact with different sites. Addition of a chiral aliphatic alcohol, (+)-(S)-2-octanol, preferentially interacted with the binding site for (-)-(S)-felodipine. The monomeric form of the micellar agent (Tween® 20) competed with the enantiomers for the adsorption sites, and the formation of a 1:1 complex between the enantiomers and the micelles was assumed. The retention of the solutes was effectively controlled by adding small quantities (〈1.63 × 10-3 M) of the nonionic detergent Tween 20 to the mobile phase. Baseline separation was achieved by addition of 1.0 mM n-octylamine to the mobile phase; 8.14 × 10-4 M Tween 20 in phosphate buffer pH 7.0. The separation factor (α = 1.74) was unaffected by the detergent concentration in the presence of 1.0 mM n-octylamine. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070105
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  • 3
    Electronic Resource
    Electronic Resource
    Enantioselectivity suggests a cytosolic origin for a commercial pig liver esterase preparation (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 40-43 
    Details
    ISSN: 0899-0042
    Keywords: enantioselectivity ; pig liver esterase ; hydrolysis ; oxazepam ; chiral stationary phase HPLC ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A widely utilized pig liver esterase preparation has been found to be derived essentially exclusively from the cytosolic fraction of pig livers. Esterases in cytosol and microsomes prepared from a fresh pig liver hydrolyzed the S- and R-enantiomers of racemic oxazepam 3-acetate (rac-OXA) with specific activity ratios of approximately 2.3:1 and 1:62, respectively. Product formations were analyzed by chiral stationary phase high-performance liquid chromatography. The commercial pig liver esterase preparation showed greater activity toward S-OXA than did the esterases in the cytosolic fraction prepared from fresh pig liver. The results established that (i) esterases contained in microsomes and cytosol of pig liver have opposite enantioselectivity in the hydrolysis of rac-OXA and (ii) the commercial pig liver esterase preparation has a cytosolic origin. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070108
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  • 4
    Electronic Resource
    Electronic Resource
    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995) 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070201
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  • 5
    Electronic Resource
    Electronic Resource
    Studies in chiral symmetry breaking crystallization I: The effects of stirring and evaporation rates (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 62-68 
    Details
    ISSN: 0899-0042
    Keywords: chiral symmetry breaking ; chiral autocatalysis ; asymmetric crystallization ; origin of optical activity ; secondary nucleation ; stirred crystallization ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiral symmetry breaking can be realized in stirred crystallization of Na-ClO3. We present experimental and theoretical studies of the random distribution of crystal enantiomeric excess (cee) for various stirring and solvent evaporation rates. For a fixed solvent evaporation rate, as the stirring RPM is increased, the probability distribution of cee initially broadens and subsequently develops a sharp peak close to cee = 1. On further increase of stirring rate, the probability distribution once again broadens. This broad probability distribution becomes narrow, with a sharp peak near cee = 1, if the solvent evaporation rate is decreased. Thus we show some ways in which the probability distribution of cee can be controlled in stirred crystallization. In particular, our study shows that the stirring rate and the solvent evaporation rate can be adjusted to maximize crystal enantiomeric excess. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070203
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  • 6
    Electronic Resource
    Electronic Resource
    Circular dichroism spectroscopy of 2-aminotetralins (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 82-89 
    Details
    ISSN: 0899-0042
    Keywords: CD ; conformational behaviour ; configuration ; helicity rules ; 2-aminotetralin ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The circular dichroism (CD) spectra of a series of oxygenated 2-(dipropylamino)tetralin derivatives are reported. On the basis of known absolute configurations and conformational preferences of the compounds, the validity of published correlations between the sign of the 1Lb Cotton effect and the three-dimensional structure was examined. Contrary to predictions, substitution in position 6 or 7 of the tetralin moiety did not change the sign of the 1Lb Cotton effect. An unexpected sign inversion was, however, observed in some of the compounds containing methyl substituents in the nonaromatic ring. The occurrence of this inversion was not correlated with a change in conformational behaviour and varied depending on the position and nature of the aromatic substituent. No correlations were obvious between the sign of the 1Lb Cotton effect and the absolute configuration and conformational preferences of the compounds. Therefore, at present, CD spectroscopy does not appear to be useful in assignments of the absolute configurations of 2-(dipropylamino)tetralin derivatives. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070206
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  • 7
    Electronic Resource
    Electronic Resource
    The influence of protective groups on diastereofacial selectivity of Diels-Alder cycloaddition reactions (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 96-102 
    Details
    ISSN: 0899-0042
    Keywords: conformational effect ; intramolecular ; allylic ; stereogenic ; steric ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The diastereofacial selectivity of both inter- and intramolecular Diels-Alder reactions with dienes having an allylic stereogenic center has been studied by varying the allylic oxygen protective group. Four different hydroxy protective groups were investigated including benzyl, t-butyldiphenylsilyl, triethylsilyl, and t-butyldimethylsilyl ethers. For intermolecular reactions, the benzyl ether derivative gave the highest sπ-facial selectivity through a transition state in which the allylic stereocenter favors the CH eclipsed conformation. For intramolecular cycloadditions, the t-butyldimethylsilyl group gave a slightly higher selectivity than the benzyl ether derivative through a transition state in which the allylic stereocenter favors the CO eclipsed conformation. The opposite diastereofacial selectivity observed for inter- and intramolecular reactions is explained by considering both steric and electronic effects. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070208
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  • 8
    Electronic Resource
    Electronic Resource
    Chiral enamines derived from 2-(2′-pyrido)acetophenone and 2-(2′-quinolino)acetophenone as ligands in copper(I) catalyzed enantioselective cyclopropanations (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 115-120 
    Details
    ISSN: 0899-0042
    Keywords: chiral 1,5-bisnitrogen ligands ; homogeneous asymmetric cyclopropanation ; copper(I) complexes ; enantioselectivity ; chiral gas chromatography ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optically active enamines of 2-(2′-pyrido)acetophenone or 2-(2′-quinolino)acetophenone with (R)-1-phenylethylamine, (R)-1-(1-naphthyl)ethylamine, (R)-cyclohexylethylamine, and (R)-phenylglycinol were prepared and their copper(I) complexes used in the enantioselective cyclopropanation of styrene with ethyl- and menthyldiazoacetate. Enantioselectivities of up to 42% enantiomeric excess were obtained for cis/trans 2-phenylcyclopropan-1-carboxylic acid ethyl esters, as determined by gas-liquid chromatography (GLC) on chiral chromatographic columns. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070302
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  • 9
    Electronic Resource
    Electronic Resource
    Asymmetric hydroformylation of mono- and sesquiterpenes (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 121-127 
    Details
    ISSN: 0899-0042
    Keywords: cyclic formyl-monoterpenes ; tricyclic formyl-sesquiterpenes ; homogeneous catalyst ; rhodium-phosphine catalyst ; platinum-phosphine-tin(II)chloride catalyst ; hydroformylation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hydroformylation of (+)-(R)-limonene (1), (+)-(1R)-isolimonene (2), camphene (3), and (+)-β-cedrene (4) resulted in the regiospecific formation of the corresponding linear aldehyde in the presence of homogeneous platinum and, in some cases, rhodium catalysts. The epimeric composition could be influenced slightly by optically active catalysts formed with chiral bidentate phosphines. The relative configurations of newly formed stereogenic centers were analyzed by 1H and 13C NMR. The primarily formed aldehydes of (+)-8(15)-cedren-9-ol (5) and γ-gurjunene (6) underwent cyclization, giving a mixture of epimers of tetracyclic terpenes. Despite the moderate diastereoselection, the products are of practical importance due to their highly regioselective formation. © 1995 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070303
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  • 10
    Electronic Resource
    Electronic Resource
    Oxidation of 2-(2-bromoethyl)bromobenzene with toluene dioxygenase: Isolation and identification of new chiral synthons (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 556-559 
    Details
    ISSN: 0899-0042
    Keywords: biooxidation ; Pseudomonas putida 39/D ; absolute stereochemistry ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2(2-Bromoethyl)bromobenzene was subjected to microbial oxidation by the whole cells of Pseudomonas putida 39/D and JM109(pDTG601) yielding (3R,4S)-2-(2-bromoethyl)-bromocyclohexa-1,5-diene-3,4-diol. © 1995 Wiley-Liss, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070710
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  • 11
    Electronic Resource
    Electronic Resource
    Enantioselective influence of cyclodextrins on cleavage of chiralic esters (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 560-564 
    Details
    ISSN: 0899-0042
    Keywords: β-cyclodextrin ; β-cyclodextrin derivatives ; methyl-β-cyclodextrin ; hydrolysis ; 2-methoxy-2-phenylacetic acid-4-nitrophenylester ; methoxy mandelic acid esters ; chirality ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Assessing the reactivity of optical antipodes is of central importance in drug research. Using the model of 2-methoxy-2-phenylacetic acid-4-nitrophenylester (MPE), the rate of hydrolysis in the presence of β-cyclodextrin (CD), hydroxyethyl- and hydroxypropyl-β-CD, as well as methyl-β-CD is studied photometrically and by means of HPLC (Chiralcel-OD-R-column). Both β-CD and hydroxyalkylated-β-CD catalyze (-)-(R)-enantiomers to a larger extent than (+)-(S)-enantiomers, resulting in an enrichment of the latter. Methyl-β-CD stabilizes the ester trifold, thus abolishing chiral discrimination. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070711
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  • 12
    Electronic Resource
    Electronic Resource
    Folding of aminosuccinyl peptides: Thermodynamic data from temperature dependent circular dichroism measurements (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 605-609 
    Details
    ISSN: 0899-0042
    Keywords: aminosuccinyl peptides ; circular dichroism measurements ; II′ β-turns ; conformational equilibrium ; thermodynamics ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational equilibrium of aminosuccinyl peptides between extended conformations and an intramolecularly hydrogen bonded type II′ β-turn conformation has been studied on the peptide Boc-L-Asu-Gly-L-Ala-OMe (Asu = aminosuccinyl residue) by means of temperature dependence of circular dichroism spectra.Owing to the peculiar chiroptical and conformational properties of the Asu residue, this technique proved to be very useful for deriving thermodynamic data for the above folding process. The value of ΔH0 (-6.6 kJ mol-1), obtained for the peptide studied in a chloroformacetonitrile mixture, shows that the lower energy of the folded conformer is primarily due to the characteristic intramolecular hydrogen bond of the β turns. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070808
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  • 13
    Electronic Resource
    Electronic Resource
    Synthesis of one diastereomeric couple of the mucolytic drug domiodol [(4S, 2R,S)-2-iodomethyl-4-hydroxymethyl-1,3-dioxolane] from D-mannitol as chiral starting material (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 623-625 
    Details
    ISSN: 0899-0042
    Keywords: domiodol ; mucolytic ; chiral synthesis ; D-mannitol ; lithium iodide ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The acid-catalyzed reaction of D-mannitol 4 with bromoacetaldehyde diethyl acetal followed by periodate cleavage of the corresponding diacetal 5 afforded (4S, 2R, S)-2-bromomethyl-4-hydroxymethyl-1,3-dioxolane 3c in good yields, from which the title compound 1 is obtained by displacement of the bromine with lithium iodide. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070812
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  • 14
    Electronic Resource
    Electronic Resource
    Evaluation of the use of cyclodextrins in chiral separation of basic drug substances by capillary electrophoresis (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 219-225 
    Details
    ISSN: 0899-0042
    Keywords: chiral separation ; cyclodextrins ; basic drugs ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of the choice of type and/or concentration of cyclodextrin, other additives, the temperature surrounding the capillary, and buffer pH on the separation of some chiral basic drug substances in capillary zone electrophoresis has been evaluated. It was found that pH of the buffer and type and concentration of cyclodextrin had a major influence on the separation. © 1995 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070407
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  • 15
    Electronic Resource
    Electronic Resource
    Preparative scale enantioseparation of 1-cyclohexyl-1-phenylethyl hydroperoxide and 1,2,3,4-tetrahydro-1-naphthyl hydroperoxide on a modified cellulose stationary phase (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 243-247 
    Details
    ISSN: 0899-0042
    Keywords: chiral HPLC ; cellulose tris(3,5-dimethylphenyl carbamate) ; hydroperoxides ; enantiomers ; circular dichroism ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The analytical and preparative scale optical resolution of 1-cyclohexyl-1-phenylethyl hydroperoxide and 1,2,3,4-tetrahydro-1-napthyl hydroperoxide has been achieved by chiral HPLC on a cellulose tris(3,5-dimethylphenyl carbamate) stationary phase coated on silica gel. The method has been used to obtain several hundred milligrams of highly enriched enantiomers (%ee 〉98) which were characterized by [α]D and circular dichroism spectra, respectively. Configurational assignments were achieved for 1,2,3,4-tetrahydro-1-naphthyl hydroperoxide enantiomers. © 1995 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070410
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  • 16
    Electronic Resource
    Electronic Resource
    Degradation and racemization of zopiclone enantiomers in plasma and partially aqueous solutions (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 267-271 
    Details
    ISSN: 0899-0042
    Keywords: chirality ; cyclopyrrolone ; isomers ; racemization ; stability ; zopiclone ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We investigated the degradation and racemization of zopiclone (ZOP) enantiomers in plasma and partially aqueous solutions (ethanol:phosphate buffer). Degradation and racemization increased with increasing pH and temperature. Degradation products were identified by means of mass spectrometry, which revealed hydrolysis of the carbamate function and opening of the pyrrolidone ring. In plasma, neither degradation nor racemization occurred after 6 months of storage at -20°C and subsequent extraction. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070413
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  • 17
    Electronic Resource
    Electronic Resource
    A comparison of LC and SFC for cellulose- and amylose-derived chiral stationary phases (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 311-325 
    Details
    ISSN: 0899-0042
    Keywords: enantiomers ; pharmaceuticals ; β-blockers ; chiral stationary phases ; Chiralcel ; Chiralpak ; liquid chromatography ; supercritical fluid chromatography ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper presents a systematic comparison of liquid chromatography (LC) and supercritical fluid chromatography (SFC) for Chiralcel OD and Chiralpak AD chiral stationary phases (CSPs), performed using various chiral compounds having a known or potential pharmaceutical activity. The chiral recognition mechanisms involved in LC and SFC for the enantiomeric separation of β-blockers have been studied more particularly. As a general rule, it appears that the presence of polar functions, like primary or secondary hydroxyl or amine functions, may result in marked discrepancies in selectivity between LC and SFC. This result is peculiar to cellulose- and amylose-derived CSPs, for which the interactions involved in chiral recognition mechanism are not always well balanced, contrary to what happens for independent CSPs. In the case of chiral resolution of polar solutes or polymer-type CSPs, the analyst should try both the LC and SFC techniques to be able to choose the more stereoselective one. © 1995 Wiley-Liss, Inc.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070502
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  • 18
    Electronic Resource
    Electronic Resource
    Development of chiral drugs in Japan: An update on regulatory and industrial opinion (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 349-352 
    Details
    ISSN: 0899-0042
    Keywords: development of chiral drugs ; regulatory affairs ; industrial opinion ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The purpose of this commentary is to provide information on the present status of the racemate/enantiomer debate in Japan and current industrial and regulatory attitudes to chiral drugs in Japan. It provides an update of our previous paper (Shindo and Caldwell, Chirality 3:91-93, 1991), and the interested reader is referred to this for background information. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070507
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  • 19
    Electronic Resource
    Electronic Resource
    GABAB antagonists: Enantiopharmacology of 5-amino-4-hydroxy-2-methylvaleric acid and X-ray structure of the eutomer (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 526-533 
    Details
    ISSN: 0899-0042
    Keywords: 5-aminovaleric acid (DAVA) ; 4-OH-DAVA ; 2-Me-4-OH-DAVA ; stereoisomers ; pharmacology ; GABAB antagonist ; GABAB receptor affinity ; X-ray analysis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have previously shown that (R)-5-amino-4-hydroxyvaleric acid [(R)-4-OH-DAVA] and (S)-2-OH-DAVA bind to GABAB receptor sites and antagonize GABAB receptor-mediated function in a stereoselective manner. Furthermore, we have identified energy-minimized superimposable conformations of (R)-4-OH- and (S)-2-OH-DAVA which are assumed to reflect the receptor-active conformations of these compounds. This paper describes the in vitro enantiopharmacology of 5-amino-4-hydroxy-2-methylvaleric acid (2-Me-4-OH-DAVA). Whereas none of the four stereoisomers showed significant affinity for GABAA receptor sites or GABA uptake mechanisms in rat brain synaptic membranes, (2R,4R)-2-Me-4-OH-DAVA was shown to inhibit stereoselectively the binding of [3H]GABA to rat brain GABAB receptor sites (IC50 = 14 ± 4 μM). (2R,4R)-2-Me-4-OH-DAVA (Ki = 36 μM) and, with much lower potency, (2S,4R)-2-Me-4-OH-DAVA (Ki = 370 μM) stereoselectively antagonized GABAB receptor-mediated function in the isolated guinea pig ileum. The structure of the eutomer, (2R,4R)-2-Me-4-OH-DAVA, was established by an X-ray crystallographic analysis, and the solid-state conformation of (2R,4R)-2-Me-4-OH-DAVA was compared with the proposed receptor-active conformations of (R)-4-OH-DAVA and (S)-2-OH-DAVA. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070706
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  • 20
    Electronic Resource
    Electronic Resource
    High-Performance liquid chromatographic separation and molecular modelling of diastereomeric isoindole derivatives of amino compoundsAccording to the Cahn-Ingold-Prelog nomenclature, D-β-Mercapto-2-methylpropionic acid has the S configuration. (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 547-555 
    Details
    ISSN: 0899-0042
    Keywords: o-phthalaldehyde ; chiral ; amino acid ; amino alcohol ; thiol ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A high-performance liquid chromatography and molecular modelling study is presented for the diastereomeric adducts of a series of chiral thiol compounds and chiral amine compounds after reaction with o-phthalaldehyde (OPA). It is shown that the possibility of hydrogen bonds forming between the thiol and amino residues in the diastereomeric adducts is an important factor for obtaining good selectivity. The experimental elution orders were explained on the basis of the strength of the interaction between the polar groups of the thiol and amine constituents; it was found that the diastereomeric form having the largest distance between these groups always eluted first. Moreover, within a series of OPA derivatives, the differences between the Boltzmann weighted averages of the distances between the polar groups of the two diastereomers show a good correlation with the experimental selectivities. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070709
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  • 21
    Electronic Resource
    Electronic Resource
    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995) 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070801
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    Electronic Resource
    Electronic Resource
    Thermal behaviour, phase diagram, and spectroscopic properties of rac-indobufen and its enantiomers (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 575-579 
    Details
    ISSN: 0899-0042
    Keywords: rac-2-[4-(1,3-dihydro-1-oxo-2H-isoindol-2-yl)-phenyl]-butyric acid ; enantiomeric purity ; differential scanning calorimetry ; optical rotation, circular dichroism ; RP-HPLC ; 1H-NMR spectroscopy ; IR spectroscopy ; X-ray powder diffraction ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The binary phase diagram of the enantiomers of indobufen, 1 (Ibustrin), an antithrombotic drug, has been investigated by differential scanning calorimetry (DSC); 1 is a racemic compound (racemate) with melting point lower than that of the enantiomers. Its thermal behaviour (DSC) has been examined and is discussed in comparison with other physical methods (IR spectroscopy and X-ray powder diffraction). Absolute configuration has been assigned to the enantiomers by 1H-NMR correlations. © 1995 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070804
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    Electronic Resource
    Electronic Resource
    Synthesis of optically active diols using an efficient polymer bound cinchona alkaloid derivative (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 580-585 
    Details
    ISSN: 0899-0042
    Keywords: asymmetric dihydroxylation ; enantiomeric excesses ; polymerization ; chiral separation ; optically active diols ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new insoluble polymer containing a Cinchona alkaloid derivative has been synthesized and used as chiral ligand in the heterogeneous enantioselective dihydroxylation of olefins. It is shown that the enantioselectivity of the optically active diols obtained from both aliphatic and aromatic substrates is always comparable to that observed in the homogeneous phase under the same reaction conditions. A method for evaluating the enantiomeric excesses of the optically active products is also described. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070805
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  • 24
    Electronic Resource
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    Stereoselective disposition of hydroxychloroquine and its metabolites in rats (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 598-604 
    Details
    ISSN: 0899-0042
    Keywords: hydroxychloroquine ; metabolites ; enantiomers ; disposition ; distribution ; stereoselectivity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Racemic hydroxychloroquine-sulfate (HCQ-sulfate) was administered to rats orally. Groups of 9 male and 9 female rats received doses of 0, 8, 16, or 24 mg/kg/day for 6 weeks, followed by a reduction of the higher doses to 8 mg/kg/day for the duration of the study. Whole blood samples were collected at 0, 3, 6, 8, and 10 weeks, and eleven tissues were harvested after the tenth week. The concentrations and enantiomer ratios of the parent drug and three metabolites, desethylhydroxychloroquine (DHCQ), desethylchloroquine (DCQ), and bisdesethylchloroquine (BDCQ), were determined. The highest concentration of HCQ was found in the intestinal smooth muscle, and the lowest in the brain and adipose tissue. The highest concentrations of the metabolites were found in the liver, adrenals, and lung tissue.The metabolism of HCQ in the rats was found to be stereoselective with R/S 〉 1 for the drug and 〈 1 for the metabolites. Gender-specific differences in the proportions of the drug and its metabolites and their enantiomers in blood and tissue were found. Varying dosages appeared to have only a temporary influence on blood concentrations and not to effect the enantiomer ratios in blood. Only a limited number of tissues exhibited significant differences between dose groups. There were no observed differences in enantiomer ratios among the blood collection times. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070807
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    Stereoselective pharmacokinetics of oxprenolol, propranolol, and verapamil: Species differences and influence of endotoxin (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 616-622 
    Details
    ISSN: 0899-0042
    Keywords: oxprenolol ; propranolol ; verapamil ; enantiomers ; inflammation ; endotoxin ; protein binding ; pharmacokinetics ; species ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of endotoxin-induced inflammation was studied on the pharmacokinetics of the enantiomers of the racemic drugs oxprenolol, propranolol, and verapamil in rabbits and dogs. Enantioselective pharmacokinetics were seen for oxprenolol and propranolol in the rabbit and for propranolol and verapamil in the dog. In the dog, the enantioselective differences in plasma concentrations are due to differences in both protein binding and metabolism, whereas in the rabbit the differences are due solely to differences in metabolism. In both species endotoxin treatment increases the plasma concentrations of the enantiomers of the three drugs; both protein binding and metabolism are influenced. In rabbits and in dogs, the influence of endotoxin on the disposition of the three drugs is less enantioselective than was previously observed in the rat. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070811
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  • 26
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    Electronic Resource
    Direct HPLC separation of enantiomers of pantoprazole and other benzimidazole sulfoxides using cellulose-based chiral stationary phases in reversed-phase mode (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 612-615 
    Details
    ISSN: 0899-0042
    Keywords: enantiomeric separation ; Chiralcel OD-R ; Chiralcel OJ-R ; reversed-phase HPLC ; proton pump inhibitor ; pantoprazole ; omeprazole ; lansoprazole ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A direct, isocratic, and simple reversed-phase HPLC method was described for the separation of enantiomers of the proton pump inhibitor, rac-pantoprazole (PAN) using cellulose-based chiral stationary phases (Chiralcel OD-R and Chiralcel OJ-R). Some structurally related chiral benzimidazole sulfoxides, rac-omeprazole (OME) and raclansoprazole (LAN), were also studied. Chiralcel OJ-R was successful in the resolution of enantiomers of rac-PAN and rac-OME, while Chiralcel OD-R was most suitable for resolving the enantiomers of rac-LAN. Highest enantioselectivity to rac-PAN and rac-OME was achieved on Chiralcel OJ-R by using acetonitrile as an organic modifier, whereas methanol afforded better resolution of rac-LAN on Chiralcel OD-R than acetonitrile. Increases in buffer concentration and column temperature decreased retention and did not improve the resolution of the enantiomers on both columns. Using a mixture of 50 mM sodium perchlorate solution and acetonitrile as a mobile phase at a flow rate of 0.5 ml/min, maximum separation factors of 1.26 and 1.13 were obtained for the enantiomers of rac-PAN and rac-OME using a Chiralcel OJ-R column, while maximum separation factor of 1.16 was obtained for the enantiomers of rac-LAN using a Chiralcel OD-R column. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070810
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  • 27
    Electronic Resource
    Electronic Resource
    Chromatographic resolution of some cyclic sulfoximides derived from prochiral and chiral sulfoxides (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 541-546 
    Details
    ISSN: 0899-0042
    Keywords: chiral liquid chromatography ; chromatographic resolution ; cyclic sulfoximides ; reaction stereochemistry ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three endocyclic sulfoximides of the 1-aryl- and 1-alkyl-3-oxo-benzo[d]-isothia (IV)-azole 1-oxide type (1-substituent = 2′-carboxyphenyl, 2′-carbethoxyphenyl, and octyl, respectively) were found to be well resolved on a chiral phase derived from bovine serum albumin (BSA). Selectivities (α) of 1.74, 1.12, and 1.44, respectively, were obtained. The retention behaviour of 1-octyl-3-oxo-benzo[d]isothia(IV)-azole 1-oxide was further investigated in some detail as a function of the mobile phase composition and the elution order was established from optically active material obtained from the enantiopure sulfoxide precursor. An enantiomeric excess of 85.4% was obtained in the cyclocondensation reaction of the octyl-substituted sulfoxide precursor with hydrazoic acid to the corresponding endocyclic sulfoximide. © 1995 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070708
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    Book Review: “Symmetry: A unifying concept” By Istvan Hargittai and Magdolna Hargittai Shelter Publications Inc., Bolinas, CA, 1994 xviii + 222 pages, ISBN 0-89815-590-8, $18.00 (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 565-565 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070712
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  • 29
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    Bevantolol hydrochloride (nc-1400): Absolute configuration and direct separation of the enantiomers (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 572-574 
    Details
    ISSN: 0899-0042
    Keywords: β-blockers, bevantolol, NC-1400, epichlorohydrin, absolute configuration, enantiomer, chiral cellulose column, direct separation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of (-)-bevantolol hydrochloride from 3,4-dimethoxyphenethylamine and (S)-(+)-m-tolyl glycidyl ether derived from (R)-(-)-epichlorohydrin established the absolute configuration of the (+) and (-) enantiomer as R and S, respectively. The purity of the enantiomers was determines using a chiral cellulose column (CHIRALCEL OD®) which allowed direct separation of the enantiomers. A separation factor (α) of 4.20 and a resolution factor (Rs) of 9.21 were obtained. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070803
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    Accuracy in the chromatographic determination of extreme enantiomeric ratios: A critical reflection (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 567-571 
    Details
    ISSN: 0899-0042
    Keywords: enantiomer separation ; chromatographic resolution ; peak integration ; peak size ratio ; calibration curve ; determination of optical purity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chromatographic quantitation of very low amounts of an enantiomer in the presence of its antipode can be an extraordinary challenge. If resolution of the peaks is not complete even at extreme mass ratios an integrator will yield inaccurate results due to geometric effects. A given resolution can be adequate for peaks of similar size but result in severe overlap if one of the signals is markedly smaller. If tailing occurs, which is more the rule than the exception, the problem is especially severe for last eluted small peaks. Additional obstacles are detector nonlinearity and other sources of unsatisfactory calibration curves, overloading phenomena, and the possible lack of standards of highest optical purity. These problems have been studied by computer simulations and the liquid chromatographic separation of (R,S)-phenylethyl naphthoic acid amide on a chiral stationary phase. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070802
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    Conversion of a racemate into a single enantiomer in one step by chiral liquid chromatography: Studies with rac-2,2′-diiodobiphenyl (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 610-611 
    Details
    ISSN: 0899-0042
    Keywords: axially chiral biphenyl ; rotational energy barrier ; enantiomeric separation ; high-performance liquid chromatography ; triacetylcellulose ; deracemization ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantiomers of rac-2,2′-diiodobiphenyl were separated by liquid chromatography on microcrystalline triacetylcellulose. The conformational lability, a large separation factor α, and a suitable capacity factor k′(+) of this biphenyl allowed us to convert the racemate into 90% of enantiomerically pure (-)-2,2′-diiodobiphenyl and 10% of pure (+)-2,2′-diiodobiphenyl, respectively, by a series of in situ racemization-elution cycles. The much better retained (+)-enantiomer was racemized on the chromatographic column at 50°C after the less retained (-)-enantiomer has already been eluted at 8°C. © 1995 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070809
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  • 32
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    Pharmacokinetics and pharmacodynamics of ketoprofen enantiomers in calves (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 586-597 
    Details
    ISSN: 0899-0042
    Keywords: PK/PD modelling ; ketoprofen ; enantiomers ; calves ; NSAIDs ; chirality ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pharmacokinetics (PK) and pharmacodynamics (PD) of (S)- and (R)- ketoprofen (KTP) enantiomers were studied in calves after intravenous administration of each enantiomer at a dose of 1.5 mg/kg. Pharmacodynamic properties were evaluated using a model of acute inflammation, comprising subcutaneously implanted tissue cages stimulated by intracaveal injection of carrageenan.Chiral inversion of (R)-KTP to the (S)-antipode occurred. The R:S ratio in plasma was 33:15 min after administration, decreasing to 1:1 at 8 h. The calculated extent of inversion was 31 ± 7%. The R:S ratio in inflammatory exudate was of the order 3:1 at all the sampling times and the ratio in transudate was approximately 2:1 for 6 h, declining to 1:1 at 30 h. Only (S)-KTP was detected in biological fluids after administration of this enantiomer. Elimination half-life was longer for the (S) (2.19 h) than the (R)-enantiomer (1.30 h) and volume of distribution was also somewhat higher for the (S)-enantiomer. Body clearance values were 0.119 1/kg/h for (S)-KTP and 0.151 1/kg/h for the (R)-antipode. For (R)-KTP effects obtained were considered as a hybrid, since they potentially reflect the actions of both enantiomers. Concentrations of LTB4 and the cytokines interleukin-1, interleukin-6, and tumor necrosis factor alpha, in exudate were not significantly affected by either (R)- or (S)-KTP treatments. Inhibition of ex vivo thromboxane B2 (TxB2) synthesis, exudate prostaglandin E2 (PGE2) synthesis, β-glucuronidase release (β-glu), and bradykinin-induced skin swelling was significant in both treated groups. PK/PD modelling was applied to the (S)-KTP treatment only. EC50 values for inhibition of serum TxB2, exudate PGE2 and β-glu and BK-induced swelling were 0.047, 0.042, 0.101, and 0.038 μg/ml, respectively. It is concluded that the low EC50 values for inhibition of TxB2 and PGE2 by (S)-KTP are likely to explain the effects produced by (R)-KTP administration, since concentrations of (S)-KTP in exudate of these calves following chiral inversion were at least 5 times higher than the EC50 at all sampling times. The data for β-glu and bradykinin-induced swelling inhibition indicate possible inhibitory actions of (R)-KTP as well as (S)-KTP. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070806
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    Estimation of the rate and extent of chiral inversion using linear systems analysis (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 632-635 
    Details
    ISSN: 0899-0042
    Keywords: chiral inversion ; deconvolution ; 2-arylpropionates ; ibuprofen ; linear systems analysis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An alternative method based on linear systems analysis is presented for the analysis of concentration-time data for the enantiomers of the 2-arylpropionic acids. This approach uses deconvolution to estimate the rate and extent of chiral inversion with respect to time, assuming linear pharmacokinetics and time invariance, without the need for complicated modelling procedures. Application to data for the chiral inversion of ibuprofen in the rat indicates that this approach provides a valid alternative to previous procedures for the analysis of chiral inversion data. © 1995 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070814
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    Discrimination in resolving systems II: Ephedrine-substituted mandelic acids (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 652-676 
    Details
    ISSN: 0899-0042
    Keywords: diastereomeric salts ; molecular recognition ; hydrogen bonding ; polymorphism ; thermal analysis ; crystallography ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Binary diastereomeric (-) (1R,2S)-ephedrine salts of various mandelic acids obtained from 95% ethanol show considerable differences in solubility. Structures and some properties of the less-soluble (L) and more-soluble (M) solid phases of (-)-ephedrine with unsubstituted mandelic acid, 2-, 3-, and 4-monosubstituted halo (F, Cl, Br) mandelic acids, and 3- and 4-methylmandelic acids have been determined. Salts were found to be binary, without solvent of crystallization, and composed of double-layered arrays of alternating anions and cations linked by H-bonds normal to the layers. H-bonding links charged donors and acceptors usually along a crystallographic 2-fold screw axis. A striking discrimination is evident in that the (2R)-mandelate salts typically display a compact four-atom chain as the H-bonding repeating unit [+N - H…O( - C- - O)…H-N′, C21(4)] while the (2S)-mandelate salts adopt a more dimensionally variable six-atom chain repeating unit [+N - H…O - C- - O…H - N′, C22(6)]. Two distinct packing schemes display the shorter H-bonding chain of the (2R)-mandelates which always occurs with ephedrinium ions in the fully extended conformation. Slightly greater packing efficiency and H-bonding energies of the (2R)-mandelate salts correlates with increased fusion points, lower solubilities (95% ethanol), and higher heats of fusion relative to the phase adopted by their diastereoisomers. In contrast, (2S)-mandelate salts exhibit considerably more structural variability involving all three major ephedrinium conformations, and at least four distinct packing motifs. Mandelates with larger 3′-substituents (Cl, Br, methyl) show similar property discriminations, but these occur with an opposing trend, that is, between phases in which the less-soluble salts contain (2S)-mandelates. Salts with 2-bromomandelate do not show property disparities and their structures are dissimilar to the other phases. © 1995 Wiley-Liss, Inc.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070816
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    Selective oxidation of o-xylene to phthalic anhydride over vanadia/titania: A comparative study of integral and recycle reactor operationDedicated to Professor Dr. Manfred Baerns on the occasion of his 60th birthday (1995)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 18 (1995), S. 17-22 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two vanadia/titania catalysts, containing 1 and 8 wt% vanadia on anatase, have been investigated for the selective oxidation of o-xylene to phthalic anhydride. In a comparative study, activity and selectivity in o-xylene oxidation were measured using an integral reactor and a reactor with external product recirculation, with the objective of studying the influence of backmixing in the latter on the reaction behaviour. Adsorbed surface species were investigated by means of in-situ diffuse reflectance FT-IR spectroscopy, using an environmental chamber which corresponds to an integral reactor. No difference in activity and selectivity in o-xylene oxidation was observed between the two catalysts. FT-IR studies showed adsorbed o-xylene, benzoate and a high concentration of phthalic anhydride on the surface of both catalysts. o-Xylene oxidation follows a sequential reaction path, with o-tolualdehyde as the first intermediate and phthalide, phthalic anhydride and maleic anhydride as sequential products. No evidence was found for a direct oxidation-path of o-xylene to phthalic anhydride. Total oxidation products CO and CO2 are formed by direct oxidation of the o-xylene and by oxidation of the reaction products. Due to greatly reduced concentration and temperature gradients, the recycle reactor proved to be highly suitable for studying the extremely exothermic oxidation of o-xylene.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/ceat.270180105
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    Recommended operating range for a rotating disc contactor (1995)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 18 (1995), S. 63-67 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Influences of different parameters on diameter and height of RDC column and on mass transferred from unit column volume were investigated. The results of the calculation can assist designers in making proper choice for the operating range of RDC columns.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/ceat.270180112
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    Masthead (1995)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 18 (1995) 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270180201
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    Synthesis of tertiary amyl methyl ether (TAME): Equilibrium of the multiple reactions (1995)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 18 (1995), S. 110-117 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The octane enhancer tertiary amyl methyl ether (TAME) is produced by liquid phase synthesis from methanol and a mixture of isoamylenes, namely 2-methyl-1-butene and 2-methyl-2-butene, using a sulfonic acid ion exchange resin as catalyst. Three reactions take place simultaneously in TAME synthesis: etherification of the two methylbutenes and their isomerisation. In order to study the equilibrium of the multiple reactions in TAME synthesis, the thermodynamic properties of the compounds in the liquid phase and equilibrium constants were calculated using a modified UNIFAC method to describe the nonideality of the system. Four parameters influencing the equilibrium conversion were derived and discussed in detail. Supplemental experiments were performed at three temperatures in the range from 303 to 343 K and at different initial molar ratios of educts. Equilibrium conversions of methanol were determined from these experiments and compared with calculated values. At 298 K the predicted activity based equilibrium constant was 22.9 for TAME synthesis from 2-methyl-1-butene and 1.6 for TAME synthesis from 2-methyl-2-butene; for isomerisation of 2-methyl-1-butene to 2-methyl-2-butene a value of 14.3 was obtained.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/ceat.270180205
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  • 39
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    The effect of gas injection on the flow of immiscible liquids in horizontal pipes (1995)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 18 (1995), S. 156-165 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The flow of two immiscible liquids and the influence of an additional inserted gas phase in horizontal pipes is investigated. The experiments are carried out in a transparent horizontal pipe with an inner diameter of 59 mm and a total length of 48 m. Experimental results are presented for the flow regimes of the two phase and three phase flow of oil, water and gas mixtures. The effect of phase inversion on the pressure drop is measured. The experimental results obtained for the three phase flow of oil, water and air indicate that drag reduction is possible by injecting gas in laminar flowing mixtures of oil and water. In the aerated slug flow regime of oil, water and air a water dominated and an oil dominated flow system can be distinguished. The pressure drop of the three phase flow system is of the magnitude as the pressure drop of the two phase flow of gas and the dominating liquid phase.
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/ceat.270180303
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  • 40
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    Circulating fluid-bed reactor for coal pyrolysis (1995)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 18 (1995), S. 343-348 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A high temperature coal pyrolysis reactor was developed and its operation demonstrated on a scale of 8 t/h. Pyrolysis is performed in a circulating fluidized bed reactor at 850-950°C. The developed process was integrated into smokeless fuel production technology and tested. Experimental data and reactor performance are presented.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270180509
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    Masthead (1995)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 12 (1995) 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19950120101
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  • 42
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    A method for investigating the orientational behaviour of fibrous particles in gaseous flow (1995)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 12 (1995), S. 3-9 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A method is described by which the angular orientation distribution of fibrous particles carried in a gaseous stream may be investigated. The method is based upon the interpretation of the spatial intensity distribution or scattering profile of laser light scattered by individual fibres. The scattering instrument used to capture the profiles is described, and the mathematical computation required to ascertain the orientation of each particle at the measurement point is detailed. Illustrative results are given for a study of airborne micromachined silicon particles of 12 μm length and 1.0 μm by 1.5 μm cross-section. The method is currently being employed by the authors to investigate ways of improving the orientation control over nonspherical particles in systems such as aerodynamic particle sizers and particle shape classifiers, since lack of particle orientation control is known to adversely affect the measurement accuracy of both these types of instrument.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19950120102
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  • 43
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    Masthead (1995)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 12 (1995) 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19950120401
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  • 44
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    Dry Mechanical Dispersion of Submicron Particles (1995)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 12 (1995), S. 295-298 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Concerning the use of air classifiers with cut sizes in the micron range and lower, it is necessary to disperse the feed material properly in an air flow to avoid agglomerates larger than the desired cut size. Commonly used dispersing devices such as injectors use large amounts of air. To reduce the size and costs of the subsequent air classifiers, two new types of dispersing systems were developed, one design being related to a brush feeder and the other to a pin mill. Both apply mechanical rather than fluid mechanical forces in the dispersion process. The brush disperser achieves the same size distributions as the pin mill disperser with much less machinery. Its properties as a feeding and dispersing system are shown and its ability to disperse particles in the submicron range is confirmed by two independent particle size analysis systems: a new diffraction spectrometer and an impactor.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19950120608
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  • 45
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    Investigations on the Behaviour of an Aerodynamic Particle Sizer and its applicability to calibrate an optical particle counter (1995)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 12 (1995), S. 304-308 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The calibration of an optical particle counter (OPC) by means of the Aerodynamic Particle Sizer APS (TSI, Model 3310) was investigated. The pulse-height distribution and the aerodynamic size distribution were measured by parallel use of an OPC and the APS. A calibration curve was obtained by comparison of the two different cumulative distribution curves. First calibration results are presented for spherical particles (water droplets and glycerine droplets): A comparison of these results with Mie calculations and aerodynamic calibrations by means of sampling cyclones shows good agreement. Furthermore, measurements were carried out with non-spherical particles. Quartz dust was used for these measurements. In order to calibrate the OPC by means of the APS, the behaviour of both devices was investigated.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19950120610
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  • 46
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    Announcements (1995)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 12 (1995), S. 324-326 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19950120614
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  • 47
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    Particle Velocity Measurements in Dense Fluidized Beds (1995)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 12 (1995), S. 314-317 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The average local velocity of the upward of particles motion was determined in a dense fluidized bed by the means of a fibre optical probe. The probe consists of two independent light gates. The particles passing in front of the light gates reflect the light, generating sign sequences that are analysed by computer. From the average time difference of the sign sequences and from the distance of the light gates, the average local velocity can be calculated. The average local velocity of the particles along the height and diameter of the fluidized bed and also as a function of the fluidization air velocity was examined. It was concluded that the average local velocity is closely correlated with the local porosity of the dense fluidized bed and depends mainly on the fluidization air velocity. Using a fibre optical probe, the optimum range of the fluidization air velocity can be determined.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19950120612
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  • 48
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    Simultaneous monitoring of the enantiomeric purities of both substrate and product in the enzymatic resolution of (R,S)-2-acetoxy-3-bromopropyl para-toluenesulfonate by HPLC chiral column chromatography (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 20-22 
    Details
    ISSN: 0899-0042
    Keywords: Chiralcel OD column ; direct reaction monitoring ; β-blocker intermediate ; Amano lipase AK ; enantiomeric excess ; timolol ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantiomeric purities of both substrate, 2-acetoxy-3-bromopropyl para-toluenesulfonate (I), and product, 2-hydroxy-3-bromopropyl p-toluenesulfonate (II) were examined in one analysis. The enzymatic resolution was conducted by Amano lipase AK and the enantiomeric excess as well as the conversion rate were monitored by HPLC analysis utilizing a Chiralcel OD column. After 7 h of reaction, HPLC results indicated that the enantiomeric purities of both substrate (I) and product (II) were greater than 95% and the conversion rate was around 55%. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070104
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  • 49
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    Enantiomeric separation and recognition mechanism of 2-arylpropionic acid derivatives by high-performance liquid chromatography using a chiral column (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 28-33 
    Details
    ISSN: 0899-0042
    Keywords: ibuprofen ; loxoprofen ; CS-670 ; loxoprofen and CS-670 trans-alcohols ; enantiomer ; diastereoisomer ; chiral HPLC ; chiral recognition ; NMR ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An optical resolution of the amide derivatives of ibuprofen and the carbamate-alkylester derivatives of the trans-alcohol metabolite of loxoprofen and an analogous compound, CS-670, was studied by chiral high-performance liquid chromatography (HPLC). The chiral columns SUMIPAX OA-4000 and OA-4100 were used to investigate the enantiomeric separation behavior of these derivatives using both reversed and normal mobile phases. A better separation factor (α) of the amide and the carbamate ester derivatives was obtained in the normal mobile phase than in the reversed mobile phase HPLC. In addition, the recognition mechanisms of both amide and carbamate ester enantiomers were investigated by 1H-nuclear magnetic resonance (NMR). It is suggested that the important driving forces for the enantiomeric separation are the formation of hydrogen bonding and the charge transfer complex between these derivatives and an active site of the chiral stationary phase. © 1995 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070106
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  • 50
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    Stereoselectivity in acid-catalyzed heteronucleophilic substitution of enantiomeric 3-O-methyloxazepam and 3-O-ethyloxazepam (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 34-39 
    Details
    ISSN: 0899-0042
    Keywords: 1,4-benzodiazepines ; oxazepam ; 3-O-methyloxazepam ; 3-O-ethyloxazepam ; stereoselectivity ; racemization ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Kinetics of acid-catalyzed heteronucleophilic substitution and racemization of enantiomeric MeOX in ethanol and enantiomeric EtOX in methanol were studied by quenching reaction products at various times by neutralization. Enantiomeric contents of remaining substrate and reaction product were determined by chiral stationary phase high-performance liquid chromatography. The experimental procedure allowed the determination of the stereoselectivity (i.e., the enantiomeric ratio of a substitution product formed from an enantiomerically pure substrate) involved in the heteronucleophilic substitution reactions. The stereoselectivity was found to vary between 58:42 and 87:13, depending on the acid concentration, substrate, solvent, and temperature. The enantiomeric purity of remaining substrates was identical to that of the starting substrate, indicating that the enantiomeric substrates did not undergo a ring-opening reaction. The results provided additional evidence supporting the mechanism proposed earlier in acid-catalyzed stereoselective heteronucleophilic and homonucleophilic substitutions and the resulting racemization of enantiomeric 3-alkoxy-1,4-benzodiazepines in alcoholic solvents. © 1995 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070107
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  • 51
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    Protein binding investigation by difference circular dichroism: Native and acetylated human serum albumins (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 57-61 
    Details
    ISSN: 0899-0042
    Keywords: protein binding ; circular dichroism ; human serum albumin ; stereoselectivity ; drugs ; modified albumin ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A modified albumin was prepared by selective reaction of Lys199 with acetyl salicylic acid. Protein binding investigation was carried out on native and modified proteins by difference circular dichroism (ΔCD). Acetylation of Lys199 reduces significantly the effects of the interaction between drugs in the stereoselective HSA binding at specific binding areas. © 1995 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070202
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  • 52
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    Solubility phase diagram of praziquantel enantiomeric system (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 74-81 
    Details
    ISSN: 0899-0042
    Keywords: polymorphism ; pseudoracemate ; optical resolution ; crystallisation ; solid solution ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solubility behaviour of praziquantel enantiomeric system at -15°C, 4°C, and 15°C is presented. This system exhibits both a pseudoracemate behaviour and one which leads to the formation of enantiomerically pure crystals. For solutions with lower enantiomeric purity, the pseudoracemate behaviour is more prominent. Solid solutions are formed when the mixtures of the enantiomers are crystallised. The phase diagram shows a complete absence of a eutetic. For mixtures with higher enantiomeric purity, pure crystals of the excess enantiomer are obtained when the solution is crystallised. Temperature dependency of this polymorphism is not significant. With these phase diagrams, a method is suggested to obtain enantiomerically pure isomers of praziquantel from a partially resolved mixture. © 1995 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070205
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  • 53
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    Chiral synthesis via organoboranes. 41. The utility of B-chlorodiisopinocampheylborane for a general synthesis of enantiomerically pure drugs (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 103-110 
    Details
    ISSN: 0899-0042
    Keywords: asymmetric reduction ; DIP-Chloride ; enantiomerically pure drugs ; α-phenyl amino alcohols ; enantiopure eprozinol ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A general approach to the synthesis of enantiomerically pure α-phenyl amino alcohols via the asymmetric reduction of α-phenyl haloalkyl ketones or α-phenyl aminoalkyl ketones with B-chlorodiisopinocampheylborane is described. Using this approach, an improved synthesis of a potential antipsychotic, α-(4-fluorophenyl)-4-(2-pyrimidinyl)-1-piperazinebutanol in ≥98% ee, and the broncholdilator 1-(2-methoxy-2-phenethyl)-4-(3-hydroxy-3-phenylpropyl)piperazine (eprozinol) in ≥99% ee is achieved. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070209
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  • 54
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    Sixth international symposium on pharmaceutical and biomedical analysis (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 111-111 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070210
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  • 55
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    Macromolecular ionophores. 1. Chiral recognition properties of poly[(1→6)-2,5-anhydro-D-glucitol] toward racemic amino acid ester (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 136-139 
    Details
    ISSN: 0899-0042
    Keywords: macromolecular ionophore ; poly[(1→6)-2,5-anhydro-3,4-di-O-alkyl-D-glucitol] ; liquid-membrane transport ; amino acid ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chiral recognition property of poly[(1→6)-2,5-anhydro-3,4-di-O-alkyl-D-glucitol] (1) toward racemic RCH (CO2CH3)NH3+ · PF6- (2 · HPF6) has been studied using a transport system involving an aqueous source and receiving phases separated by a chloroform phase containing 1. Transport rates for aromatic guests 2a (R = Ph) and 2b (R = CH2Ph) were faster than those for aliphatic guests, 2c (R = CH(CH3)2) and 2d (R = CH2CH(CH3)2), using the polymer substituted with methyl groups (1a). The enantiomeric excess (e.e.) was 10.9% for 2a as a maximum value and decreased in the order of 2a 〉 2c 〉 2b = 2d. When the transport of 2a · HPF6 was carried out using the polymers with 3,4-di-O-methyl (1a), ethyl (1b), allyl (1c), and pentyl (1d) groups, the e.e. was 22.0% for 1d as a maximum value and increased in the order of 1a 〈 1b 〈 1c 〈 1d. The formation of a complex between 1a and 2a · HPF6 was confirmed by 1H and 13C NMR spectral measurements. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070305
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  • 56
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    Structural features affecting chiral resolution of cannabimimetic enantiomers by amylose 3,5-dimethylphenylcarbamate chiral stationary phase (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 140-146 
    Details
    ISSN: 0899-0042
    Keywords: cannabinoid ; enantiomers ; chiral ; chromatography ; amylose ; stationary phase ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of structural features of six pairs of enantiomers of cannabimimetic compounds on their chromatographic resolution on an amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phase was studied using various compositions of n-hexane with 2-propanol and ethanol. Structural analysis by molecular mechanics was also performed to verify that the 3D conformation within this family of compounds was preserved with substitution. The homologous enantiomeric pairs showed better resolution when there was an additional OH group near the chiral centers (position 7 on the cannabinoid structure). Better resolution was observed also for the enantiomeric pair that had the smaller alkyl side chain. These differences indicated that the additional OH group contributed to a better discrimination of the enantiomers by the chiral sites of the stationary phase and that the bulkier alkyl side chain reduced it. The chromatographic resolution of two enantiomeric pairs of nonclassical cannabinoids HU-249 and HU-250, HU-255 and HU-256, was compared both in ethanol and 2-propanol. Both enantiomeric pairs showed relatively high resolution and selectivity, but the rigid benzofuran analogs (HU-249 and HU-250) exhibited better resolution using 2-propanol, in spite of the flexibility of the open chain analog (HU-255 and HU-256) and its additional OH group. The elution order of all the cannabinoids was (+)/(-) using both solvents. Unusual solvent effects were displayed by one enantiomeric pair, Δ6-THC, which was resolved easily using 2-propanol, but whose elution order reversed with 1% ethanol in the mobile phase. Partial separation was obtained at 5% ethanol [elution order (+)/(-)] and full separation was obtained at 0.5% ethanol [elution order (-)/(+)]. © 1995 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070306
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  • 57
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    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995) 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070401
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  • 58
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    Chiroptical methods in conformational analysis (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 181-192 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: CD spectra of flexible organic molecules in solution are normally very sensitive to conformation. In a system composed of two or more chromophores joined by one or more single bonds and with one fixed or strongly preferred conformation, it is often possible to reproduce the CD spectrum by semiempirical calculations based on interactions between the electronic transitions in the respective chromophores. In a system containing two or more conformations of appreciable weight, the observed CD spectrum is the superposition of those of the individual conformations and has to be analyzed in terms of the individual calculated spectra and the relative energies of the respective conformations. The effect of temperature variation on conformational equilibria and on the composite CD spectra will be discussed and exemplified. © 1995 Wiley-Liss, Inc.
    Additional Material: 15 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070402
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  • 59
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    Aspects of chirality in overcrowded bistricyclic enes (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 199-205 
    Details
    ISSN: 0899-0042
    Keywords: stereochemistry ; strain ; intramolecular overcrowding ; nonplanar aromatics ; tetraarylethylenes ; tetrabenzofulvalenes ; semiempirical calculations ; MNDO-PM3 ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Intramolecular overcrowding in bistricyclic enes (1) requires out-of-plane deformations in order to accommodate the sterically demanding tricyclic moieties without prohibitively close contacts of nonbonded atoms. The nonplanarity of 1 introduces the notion of chirality to the arena of overcrowded aromatic enes. Deviation from coplanarity occurs by twisting around the double bond and out-of-plane bending (hence pyramidalization). The bending is realized by folding of the tricyclic moieties. The conformations of homomerous (1, × = Y) and heteromerous (1, × ≠ Y) bistricyclic enes and their mono- and disubstituted derivatives are analyzed along with their point group symmetries and chirality. The implications are illustrated using the structures of characteristic examples calculated with the semiempirical method PM3. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070404
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  • 60
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    Central composite design for the rapid optimisation of ruggedness and chiral separation of amlodipine in capillary electrophoresis (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 226-234 
    Details
    ISSN: 0899-0042
    Keywords: central composite design ; liquid chromatography ; capillary electrophoresis ; amlodipine ; cyclodextrin ; ruggedness ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Systematic optimisation with central composite design offers an efficient route for rapid optimisation of resolution with multiple interacting parameters in chiral CE. This is illustrated by separations of amlodipine with α-CD as chiral selector in the running buffer, for which the predicted performance of central composite design is assessed. The utility of response surface methodology for locating optimum ruggedness in CE is also described. © 1995 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070408
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  • 61
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    Substitution and racemization of 3-hydroxy- and 3-alkoxy-1,4-benzodiazepines in acidic aqueous solutions (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 365-375 
    Details
    ISSN: 0899-0042
    Keywords: oxazepam ; 3-O-alkyloxazepam ; temazepam ; 3-O-alkyltemazepam ; nucleophilic substitution ; racemization ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxazepam (OX), 3-O-methyloxazepam, 3-O-ethyloxazepam, temazepam (TMZ), 3-O-methyltemazepam, and 3-O-ethyltemazepam underwent acid-catalyzed nucleophilic substitution reaction (hydrolysis) in an acetonitrile-oxygen-18 water mixture to form either OX or TMZ in which the 3-hydroxyl group was either partially or fully labeled with an oxygen-18 atom. The dependence of the hydrolysis rates on solvent composition, temperature, ionic strength, and in deuterated solvent was studied by reversed-phase high-performance liquid chromatography (HPLC). The rates of racemization of enantiomeric compounds in acidic aqueous solutions were studied by both spectropolarimetry and chiral stationary phase HPLC. In acetonitrile: 2.5 M H2SO4 (4:1, v/v) at 50°C, enantiomers of OX and TMZ underwent racemization at rates ≥40-fold faster than the rates of hydrolysis. Enantiomeric 3-O-alkyl derivatives of OX and TMZ in acidic aqueous solutions did not themselves undergo racemization and it was their hydrolysis products (either OX or TMZ) that underwent racemization. © 1995 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070510
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    A new method for enantiomer enrichment: Distillation to separate the free and complexed enantiomers after partial salt formation (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 381-382 
    Details
    ISSN: 0899-0042
    Keywords: enantiomers ; enantiomeric enrichment ; optical purity ; selective separation ; α-phenylethylamine ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new method is described for the enrichment of enantiomeric mixtures having an enantiomeric ratio other than 1:1. The method is based on partial salt formation of the enantiomeric mixture with an achiral substance followed by the distillation of the free enantiomer. The distillate has a different enantiomeric composition than the starting mixture. The method was performed on enantiomeric mixtures of α-phenylethylamine using four different dicarboxilic acids. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070512
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    Chromatographic properties of composite chiral stationary phases based on cellulose derivatives (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 425-433 
    Details
    ISSN: 0899-0042
    Keywords: racemate ; enantiomer ; HPLC ; elution order ; drugs ; agrochemicals ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiral stationary phases (CSPs) prepared by mixing together two different cellulose derivatives, before or after being coated on macroporous silica gel, were developed in order to determine the mutual influence of two different polymers on global chiral recognition capacity. The chromatographic properties of these CSPs were evaluated using a wide range of racemic test solutes. The mixing method does not significantly affect the enantioselectivities. The composite CSPs obtained by cocoating of two different cellulose derivatives on silica generally exhibit chiral recognition capacities intermediate between those of the two individual phases, and thus broadening the application range of a single column. These results indicate that the simultaneous coating of two different cellulose derivatives does not significantly alter the optical resolution power of each chiral material and are discussed in relationship with the supramolecular structure of the polymeric stationary phases. © 1995 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070607
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  • 64
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    Determination of the enantiomeric purity of dihydroxy- and dimethoxy-2-aminotetralins by high-performance capillary electrophoresis with cyclodextrins as chiral selector (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 459-468 
    Details
    ISSN: 0899-0042
    Keywords: enantiomers ; chiral separation ; 2-aminotetralins ; dopamine receptor agonist ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A chiral separation of 5,6- and 6,7-dihydroxy-2-aminotetralin and of the corresponding dimethoxy analogues can be achieved by high-performance capillary electrophoresis using cyclodextrins as chiral selector. The selectivity of a number of native and derivatized cyclodextrins was screened and hydroxylalkyl-β-cyclodextrins turned out to be the most effective. Optimization of hydroxyethylcyclodextrin and hydroxypropylcyclodextrin concentration for each compound led to baseline separation (resolution factors from 1.7 to 2.3) resulting in a detection limit of 0.1% for the enantiomer present as impurity. Modifiers of the electroendosmotic flow, such as hydroxypropylcellulose and hexadecyltrimethylammoniun bromide, must be added to the background electrolyte to obtain such results. © 1995 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070612
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  • 65
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    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995) 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070701
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  • 66
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    Chiral discrimination promoted by (1S,2S)-1-phenyl-2-amino-1,3-propanediol derivatives in the asymmetric Reformatsky reaction (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 499-504 
    Details
    ISSN: 0899-0042
    Keywords: optically active aminodiols ; chiral ligands ; enantioselective reaction ; enantiomeric excess ; chiral separation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some 3-t-butyldimethylsilyloxy derivatives, synthesized from the cheap commercially available (1S,2S)-2-amino-1-phenyl-1,3-propanediol [(1S,2S)-1], have been successfully employed as new chiral ligands in the asymmetric Reformatsky reaction on aldehydic substrates. The influence both of the substrate and of the ligand on the stereochemical pathway has been investigated by varying the structure of the carbonyl substrate and of the optically active aminodiols. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070702
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  • 67
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    Absolute configurations and conformations of the opioid agonist and antagonist enantiomers of picenadol (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 518-525 
    Details
    ISSN: 0899-0042
    Keywords: crystal structure ; molecular mechanics ; MM2-87 ; opioid ligand model ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The absolute configurations of the enantiomers of the opiod picenadol [cis-1,3-dimethyl-4-propyl-4-propyl-4-(3-hydroxyphenyl)piperidine; cis-3-methyl, 4-propyl] have been determined by an X-ray crystallographic study of the chloride salt of the (+)-enantiomer. The agonist (+)-enantiomer and the antagonist (-)-enantiomer were found to have the 3R, 4R and 3S, 4S absolute configurations, respectively. The conformational properties of the enantiomers were also examined with MM2-87 calculations. There was good agreement between the computed global minimum and the crystallographic structure with the phenyl ring approximately bisecting the piperidine ring by both methods. This orientation of the phenyl ring differs from that of related opioids such as the phenylmorphans, prodines, meperidine, and ketobemidone in which the phenyl ring tends to eclipse one edge of the piperidine ring. Because the phenyl ring bisects the piperidine ring in picenadol, there is little difference in the three-dimensional orientations of the phenyl rings of the two enantiomers when one superimposes the piperidine rings. The agonist (+)-enantiomer is ambiguous with respect to an opioid ligand model, which suggests that agonist activity requires a specific range of dihedral angles for the phenyl ring. While the global minimum of the agonist is not consistent with the model, a second conformer that is only 1.2 kcal/mol above the global minimum is consistent. An alternative explanation is that agonist or antagonist activity is solely due to the presence of the 3-methyl group on the different edges of the piperidine ring. MM2-87 calculations were also performed on the opioid agonist des-3-methyl analog of picenadol and the closely related trans-1,3,4-trimethyl-4-(3-hydroxyphenyl)piperidines (trans-3-methyl, 4-methyl) in which both enantiomers are opioid antagonists. The conformational properties of these compounds are consistent with the ligand model. © 1995 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070705
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    Resolution and determination of enantiomeric purity of the enantiomers of felodipine using chiral-AGP® as stationary phase (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 147-153 
    Details
    ISSN: 0899-0042
    Keywords: direct chromatographic chiral separation of felodipine ; mobile phase pH ; column temperature ; enantiomeric purity ; restored chiral column ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A direct chiral chromatographic reversed phase method for the determination of the enantiomers of felodipine is described. The influence of charged and uncharged modifiers as well as the effect of the mobile phase pH on the enantiomeric resolution is discussed. A high mobile phase pH and the addition of 2-propanol as organic modifier gave the highest separation factor (α = 1.3). The high mobile phase pH (pH = 7.6) is outside the recommended pH limit of silica based columns but was necessary to achieve baseline resolution of (R)- and (S)-felodipine. Improvement of column efficiency by increasing column temperature was utilized for optimization of the enantiomeric resolution (Rs = 1.7). The enantiomers of felodipine and three related compounds were separated within 15 min. The enantiomeric purity of (R)- and (S)-felodipine in injections and (R)-felodipine in bulk substance was higher than 99.5% and no racemization was observed after storage at accelerated conditions. A poor Chiral-AGP® column used for a long period was restored using a simple wash step together with repacking the top of the chromatographic column. © 1995 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070307
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    Resolution by chiral hplc of the stable free radical perchlorotriphenylmethyl: Thermodynamic and chiroptical properties (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 154-157 
    Details
    ISSN: 0899-0042
    Keywords: helicity ; steric shielding ; polychlorinated ; ChiralPak OT(+) ; poly(triphenylmethyl methacrylate) ; enantiomerization barrier ; racemization kinetics ; circular dichroism ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The perchlorotriphenylmethyl radical (PTM) shows enantiomerism due to restricted internal rotations. Several chiral stationary phases have been tested in different conditions for the resolution of PTM by HPLC. Only poly(triphenylmethyl methacrylate) provided sufficient resolution for carrying out a micropreparative scale separation. Racemization of (+)- and (-)-PTM was monitored polarimetrically as a function of time. The process was found to follow strict first-order kinetics. The value of ΔG#303.8 = 23.6 Kcal · mol-1 agrees with that determined previously by HPLC with the stopped flux technique (Crespo, Doctoral Thesis, CETS Institut Químic de Sarrià, 1991). Following the helicity rules in the circular dichroism spectrum, (+)-PTM can be assumed to have (P) configuration and (-)-PTM (M) configuration. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070308
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  • 70
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    Myocardial uptake kinetics of tocainide enantiomers in the isolated perfused rabbit heart (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 163-166 
    Details
    ISSN: 0899-0042
    Keywords: drug accumulation ; indirect chiral HPLC ; (-)-menthyl chloroformate ; nonlinear regression analysis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The extent of myocardial accumulation of tocainide, administered as single enantiomers and as well as racemate, was determined in the isolated, spontaneous beating rabbit heart. The heart was retrogradely perfused at a constant rate and fractions of the perfusate were collected during and after infusion. Kinetic parameters for myocardial accumulation and disposition of tocainide were indirectly determined from drug concentration/time course in the outflow perfusate. No stereoselectivity in myocardial accumulation was observed. A two compartment model with mean half-lives for distribution and elimination of 0.60 and 3.78 min, respectively, was fitted to the accumulation and disposition data. At steady-state, tocainide enantiomers were accumulated about three times in the myocardium relative to the perfusion liquid. © 1995 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070310
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    Chiral aspects of the metabolism of ethosuximide (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 173-180 
    Details
    ISSN: 0899-0042
    Keywords: ethosuximide ; antiepileptic drugs ; chiral ; metabolism ; stereoselectivity ; gas chromatography ; cyclodextrin stationary phase ; mass spectroscopy ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ethosuximide is a chiral drug substance primarily indicated for the treatment of absence seizures. This drug is used clinically as the racemate. The urinary metabolites of ethosuximide (following i.p. administration of the racemate or individual enantiomers to rats) have been studied using chiral gas chromatography (GC) and gas chromatography-mass spectroscopy (GCMS). The metabolites identified were unchanged ethosuximide enantiomers, all four stereoisomers of 2-(1-hydroxyethyl)-2-methylsuccinimide, and a single stereoisomer of 2-ethyl-3-hydroxy-2-methylsuccinimide [derived from (R)-ethosuximide]. Preliminary quantitative studies indicate a degree of stereoselectivity in the fate of ethosuximide since the ratio of (R)- to (S)-ethosuximide in the urine was found to be 0.77:1 (0-24 h sample), 0.64:1 (24-48 h sample), and 0.83:1 (48-72 h sample). This would suggest that the (R)-isomer is preferentially metabolised. Results obtained following the administration of individual enantiomers of ethosuximide indicate that the 2-(1-hydroxyethyl)-2-methylsuccinimide diastereoisomers derived from (R)-ethosuximide are produced in approximately equal proportions [ratio 1.05:1 (0-24 h sample), 1.10:1 (24-48 h sample)], whilst those from (S)-ethosuximide are produced in unequal proportions [ratio 1.65:1 (0-24 h sample), 1.74:1 (24-48 h sample)]. © 1995 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070312
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  • 72
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    Chirality induction in cyclocopolymerization of bis(p-vinylbenzoate)s of carbohydrates with styrene: Chiroptical study of resulting polymer by exciton chirality method (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 193-198 
    Details
    ISSN: 0899-0042
    Keywords: chiral polystyrenes ; CD spectrum ; chiral auxiliary ; cyclopolymerization ; radical polymerization ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three bis(p-vinylbenzoate) monomers, 2,3-O-isopropylidene-1,4-bis-O-(p-vinylbenzoyl)-L-threitol (BIT), methyl 4,6-O-isopropylidene-2,3-bis-O-(p-vinylbenzoyl)-α,D-glucopyranoside (BIG), and 1,2:5,6-di-O-isopropylidene-3,4-bis-O(p-vinylbenzoyl)-D-mannitol (BIM), were prepared and cyclocopolymerized with styrene. The resulting copolymers were hydrolyzed with KOH to remove the chiral template, and treated with diazomethane to give poly[(methyl p-vinylbenzoate)-co-styrene] [poly(MVB-co-St)]. All the poly(MVB-co-St) had a specific rotation and their CD spectra exhibit a split Cotton effect. Poly(MVB-co-St) derived from poly(BIT-co-St) showed a positive Cotton effect at 255 nm and a negative one at 235 nm. According to the exciton chirality method, poly(MVB-co-St) possessed negative chirality, and the stereochemistry of the carbon atom attached to the 4-benzoyl group had the S configuration. The absolute configuration of poly(MVB-co-St) was determined as R for the BIG/St system and S for the BIM/St system. © 1995 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070403
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  • 73
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    Diastereoselective hydrogenations of unsymmetrically substituted aromatics (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 211-218 
    Details
    ISSN: 0899-0042
    Keywords: prochirality ; rhodium ; chiral auxiliaries ; (-)-menthol ; L-proline ; chiral cyclohexane derivatives ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Attempts to induce enantioselectivity in the catalytic hydrogenation of unsymmetrically substituted aromatics using covalently bound, well known chiral auxiliaries are described. Marked differences in stereoselectivity and rate of hydrogenolysis are noted as a function of the auxiliary used. Enantioselectivities obtained in the resulting cyclohexyl derivatives are rather poor. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070406
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  • 74
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    Chiral derivatization for separation of racemic amino and thiol drugs by liquid chromatography and capillary electrophoresis (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 235-242 
    Details
    ISSN: 0899-0042
    Keywords: ortho-phthalaldehyde, naphthalene-2,3-dicarboxaldehyde, chiral selectors, diastereoisomers, reversed-phase liquid chromatography, capillary zone electrophoresis, micellar electrokinetic chromatography, β-cyclodextrin ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Separation of racemic amino drugs (α-methylbenzeneethanamine, 6-amino-2-methyl-2-heptanol and 1-aminoethyl-benzenemethanol) and thiol drugs [N-(2-mercapto-1-oxopropyl) glycine, 2-mercaptopropanoic acid, and N-acetyl-3-mercaptovaline] has been evaluated after derivatization. ortho-Phthalaldehyde (OPA) and naphthalene-2,3-dicarboxaldehyde (NDA) were used with either homochiral thiols (N-acetyl-L-cysteine and N-acetyl-D-penicillamine) or amines [(-)-(1R,2S)-norephedrine, L-phenylalanine, L-tyrosine, and 3-hydroxy-L-tyrosine] as chiral selectors according to the analyte reactive group. The resulting 36 diastereoisomeric derivatives were studied using reversed-phase high-performance liquid chromatography (RP-HPLC) and capillary electrophoresis (CE). Of the CE modes, micellar electrokinetic chromatography (MEKC) using sodium dodecyl sulfate (SDS) as surfactant, β-cyclodextrin (β-CD)-modified capillary zone electrophoresis (β-CD-CZE), and β-CD-MEKC were applied. Results highlight respective performance of the reagents and separative techniques. All OPA derivatives of racemic amino drugs were resolved either by MEKC or β-CD-MEKC. In the case of racemic thiol drugs, 10 of the 12 OPA derivatives were resolved in β-CD-CZE. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070409
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  • 75
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    Solvent selectivity in chiral chromatography using a β-cyclodextrin-bonded phase (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 257-266 
    Details
    ISSN: 0899-0042
    Keywords: enantiomeric separation ; β-blockers ; zopiclone ; fluoxetine ; norfluoxetine ; promethazine ; apparent partition coefficient ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A β-cyclodextrin-bonded phase has been used to investigate the separation of the enantiomers of atenolol, oxprenolol, celiprolol, tertatolol, terbutaline, fluoxetine, norfluoxetine, and zopiclone, focusing on the importance of solvent selectivity. With cyclodextrin (CD)-bonded phases, chiral discrimination occurs because the two enantiomers of a racemate form inclusion complexes of different strengths within the CD cavity. The organic modifier molecules tend to compete with solutes for a definite number of adsorption sites on the stationary phase. Moreover, the ternary complex formation may play an important role in chiral recognition. In this study, it was of interest to estimate the influence of mobile phase modifiers with respect to solvent type (i.e., ACN, MeOH, EtOH, THF, i-PrOH, PrOH and t-BuOH), size and shape, and concentration. Solvent selectivity has been investigated by using different organic modifiers in mobile phases with the same polarity, and relationships were established between the logarithm of solvent partition coefficient (log Ps) and the three most important chromatographic parameters: retention time (t), resolution (R), and enantioselectivity (α). Thus, it seems that the hydrophobicity of the organic modifier becomes one of the dominant factors affecting the inclusion process phenomena. Further, the apparent partition coefficients of the compounds under study have been determined and a comparison has been attempted regarding the degree of their enantiomeric resolution. © 1995 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070412
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    Stereoselective and species-dependent kinetics of reboxetine in mouse and rat (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 285-289 
    Details
    ISSN: 0899-0042
    Keywords: reboxetine enantiomers ; rat ; mouse ; brain and plasma concentrations ; 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. In this study, brain and plasma levels of both enantiomers were determined in mice and rats after oral administration of reboxetine at doses (1.1 mg/kg, mouse; 20 mg/kg, rat) twice the respective ED50 values in the antireserpine test. Plasma and brain concentrations of each enantiomer were measured up to 6 h postdosing using an HPLC method with fluorimetric detection after derivatization with a chiral agent (FLEC). In mice and rats, brain and plasma levels of the (R,R)-enantiomer were always higher than those of the (S,S)-enantiomer. After normalization for dose, the mean AUC0-tz values of both the (R,R)- and (S,S)-enantiomers in mouse brain were about 23 and 32 times higher than in rat brain, respectively. In plasma, the corrected mean AUC0-tz values were about 5 (R,R) and 10 (S,S) times higher in mice than in rats. These results provide evidence for the higher bioavailability and/or lower clearance of both enantiomers in mice than in rats, and for a higher penetration of both enantiomers into mouse brain compared to rat brain. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070416
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    Stereoselective hydrolysis of xenobiotic esters by different cell lines from rat liver and hepatoma and its application to chiral prodrugs for designated growth suppression of cancer cells (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 297-304 
    Details
    ISSN: 0899-0042
    Keywords: cancer ; stereoselectivity ; esterase ; drug design ; electrophoresis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stereoselectivity in the hydrolysis of racemic ethyl 2-phenylacetate derivatives by cultured cells of noncancerous cell lines from rat liver (BRL, BRL 3A, Clone 9, and ARLJ301-3), spontaneously or oncogene transformed rat liver cell lines (ARLJ301-3TR1, Anr4, Anr9-1, and Anr13-1), and cancer cell lines from rat hepatoma (H4-II-E, McA-RH7777, and MH1C1) and sarcoma (XC) was studied. A strong (R)-enantiomer preference was found in the hydrolysis of ethyl 2-hydroxy- (2c) and 2-methoxy-2-phenylacetate (3c) by the noncancerous and oncogene-transformed cells and an (S)-enantiomer preference for ethyl N-acylphenylalaninates with all the present cell lines. These inclinations were, however, not recognized with ethyl 2-methoxy-2-phenylpropanoate and ethyl N-difluoroacetyl-or N-trifluoroacetylphenylalaninate. Moreover, the R preference for 3c was reversed in the reaction by hepatoma cells. Thus, the stereoselectivity is influenced by both structure of acyl group and species of cell lines. The hepatoma cells were considerably different from the noncancerous or oncogene-transformed cells in stereoselectivity. This fact was consistent with the order of colony formation in soft agar cultures (index of malignancy) and the resemblance in actively stained esterase patterns in gel electrophoresis. The stereoselective hydrolysis leads to cell-specific activation of anticancer prodrugs. This has been confirmed for the first time by the stereoselectivity of Anr4 and H4-II-E cells in the hydrolysis of a chiral mustard ester, bis(2-chloroethyl)aminophenyl 2-methoxy-2-phenylacetate (14) and by the difference of IC50 values of (R)- and (S)-14 against the two cell lines. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070418
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    Comparative toxicity of (+)-(R)- and (-)-(S)-1,2-dibromo-3-chloropropane (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 359-364 
    Details
    ISSN: 0899-0042
    Keywords: (R/S)-1,2-dibromo-3-chloropropane ; chiral GC ; bacterial mutagenicity ; nephrotoxicity ; testicular toxicity ; glutathione transferases ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The haloalkane 1,2-dibromo-3-chloropropane (DBCP), an environmental pollutant that was widely used as a soil fumigant, is a carcinogen and a mutagen and displays target-organ toxicity to the testes and the kidneys. Because little is known about effects of stereochemistry on the metabolism and toxicity of halogenated alkyl compounds and because DBCP, which has a chiral center at C-2, may show enantioselectivity in its metabolism and/or toxicities, the optically pure enantiomers of DBCP were tested in vivo in rats for organ toxicity as well as for bacterial mutagenicity. Organ toxicity studies showed that (S)-DBCP was slightly more renal toxic than (R)-DBCP but was not significantly more toxic than the racemate, and that no significant differences were observed in the extents of testicular necrosis and atrophy caused by either enantiomer or the racemate. In contrast, (R)-DBCP was more mutagenic than either (S)-DBCP or the racemate to Salmonella typhimurium (S. typhimurium) strains TA 100 and TA104. However, there was little or no enantioselectivity in glutathione S-transferase (GST)-catalyzed conjugation reactions of glutathione with DBCP based on the lack of selectivity in the rates of disappearance of the enantiomers of DBCP in the presence of glutathione (GSH) and GSTs as monitored by chiral gas chromatography (GC). © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070509
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    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995) 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070601
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  • 80
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    Determination of the enantiomers of citalopram, its demethylated and propionic acid metabolites in human plasma by chiral HPLC (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 389-395 
    Details
    ISSN: 0899-0042
    Keywords: enantioselective HPLC ; depressive patients ; citalopram ; enantioselective metabolism ; human plasma ; racemization ; optical rotation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A stereoselective HPLC assay has been developed to analyze the enantiomers of citalopram and of its three main metabolites in plasma after their separation on a Chiracel OD column. Using a fluorescence detector, the limit of quantification in plasma samples was 15, 4, 5, and 2 ng/ml for the enantiomers of citalopram (CIT), desmethylcitalopram (DCIT), didesmethylcitalopram (DDCIT), and for the citalopram propionic acid derivative (CIT-PROP), respectively. Except for CIT, all metabolites were derivatized with achiral reagents. Identification of the enantiomers was realized with an optical rotation detector which showed that the enantiomers invert their rotation depending on the polarity and nature of the solvent. Under varying conditions, a racemization study has shown that the pure enantiomers of CIT and its demethylated metabolites are configurationally stable. Preliminary results obtained with five patients treated with CIT show a mean S/R ratio of 0.7 for both CIT and its active metabolite DCIT and of 3.6 for CIT-PROP in plasma. This suggests that the pharmacologically relevant (+)-(S)-isomers of CIT and DCIT could be preferentially and steroselectively metabolized to CIT-PROP. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070602
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  • 81
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    Mechanisms of enantiomeric resolution in cyclodextrin-modified capillary electrophoretic separations of binaphthyl compounds (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 401-408 
    Details
    ISSN: 0899-0042
    Keywords: chiral separation ; molecular modeling ; inclusion complexes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantiomers of 1,1′-bi-2-naphthol, 1,1′-binaphthyl diyl hydrogen phosphate, and 1,1′-binaphthyldicarboxylic acid are separated using capillary electrophoresis with cyclodextrins added to the running buffer. It is demonstrated that the type and concentration of cyclodextrin employed are critical for maximum enantiomeric resolution. A modified version of a previously described model of enantiomeric separations in capillary electrophoresis is shown to support the observed separation behavior. Molecular modeling is employed to calculate interaction energies between the various enantiomers and cyclodextrins. A reasonable correlation between these computationally derived interaction energies and separation behavior resulted from a statistical mechanical treatment of the molecular modeling data. The importance of hydrogen bonding in inclusion complex formation was probed and the effects of minimization and solvation in molecular modeling calculations are also discussed. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070604
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  • 82
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    Racemization, enantiomerization, diastereomerization, and epimerization: Their meaning and pharmacological significance (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 396-400 
    Details
    ISSN: 0899-0042
    Keywords: configurational lability ; enantiomers ; diastereomers ; epimers ; macroscopic processes ; microscopic processes ; pharmacological time scale ; pharmaceutical time scale ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The configurational lability of enantiomers can be characterized by different terms, each defining a specific process. Racemization relates to the macroscopic and statistical process of the irreversible transformation of one of the enantiomers into the racemic mixture. Enantiomerization refers to the microscopic and molecule process of the reversible conversion of one enantiomer into the other. Methods allowing the experimental determination of rate constants of racemization (krac) and enantiomerization (kenant) are discussed, and it is shown that kenant = 1/2 krac. Neglect of this fact is a source of some confusion in the literature. When two or more elements of chirality are present in a molecule and one of them is configurationally labile, epimerization occurs, a particular case of diastereomerization. These processes of interconversion between diastereomers are kinetically more complicated than racemization and enantiomerization since the rate constants of the forward and reverse reactions are always different (kdiast/A-to-B ≠ kdiast/B-to-A), however small the difference. An important aspect of the configurational lability of stereoisomeric drugs is the time scale of the phenomenon. When interconversion occurs to a significant extent during the residence time of a drug in the body, a pharmacological time scale is implied. In contrast, the pharmaceutical time scale refers to slower rates of interconversion that affect the configurational purity of a drug during its shelf-life. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070603
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  • 83
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    Rapid chiral separation methods development by cyclodextrin-mediated capillary electrophoresis for acidic and basic compounds (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 409-414 
    Details
    ISSN: 0899-0042
    Keywords: capillary electrophoresis ; chiral separation ; cyclodextrins ; methods development ; enantiomers ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiral separation methods development using conventional techniques such as GC or HPLC requires a lot of experience, effort, and expense, due to the wide diversity of the optically active solutes and their possible chiral selectors. Capillary electrophoresis has received increased attention as an alternative technique for chiral separation due to its inherent high efficiencies and ease of methods development. However, due to the wide variety of chiral selectors available in CE, the benefits of this technique might be diminished without an appropriate methods development scheme. In this paper detailed examples are shown for fast, efficient, and predictable chiral capillary electrophoresis separation methods development based on a new and systematic theory. Optimized separations and their parameters are presented for several enantiomeric acids and bases. All the three possible cases, such as the use of low and high pH, as well as pH = pK buffer systems are thoroughly discussed. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070605
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  • 84
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    Chiral separation based on immobilized intact and fragmented cellobiohydrolase II (CBH II): A comparison with cellobiohydrolase I (CBH I) (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 415-424 
    Details
    ISSN: 0899-0042
    Keywords: cellulase ; cellobiohydrolase I ; cellobiohydrolase II ; Trichoderma reesei ; chiral stationary phase ; chiral separation ; enantiomer ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Intact and fragmented cellobiohydrolase II (CBH II) were immobilized to silica and used as chiral stationary phases (CSPs) for liquid chromatographic separations of enantiomers. Both acidic and basic chiral compounds could be resolved into their enantiomers on these phases. The enantioselectivities obtained on intact CBH II and its core were almost equivalent. Comparisons were also made with CBH I silica. It was found that the new materials show quite different chiral and chromatographic properties. The enzymatic activity of the CBH II in free solution was influenced by alprenolol and mexiletine, both separated on the corresponding CSP. It indicates that the sites for catalysis and for chiral recognition overlap. © 1995 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070606
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  • 85
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    GABAA agonists: Resolution and pharmacology of (+)- and (-)-isoguvacine oxide (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 434-438 
    Details
    ISSN: 0899-0042
    Keywords: chiral HPLC ; resolution ; enantiomeric purity ; GABAA receptor affinity ; GABAA agonist ; benzodiazepine stimulation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (3SR,4RS)-3,4-Epoxypiperidine-4-carboxylic acid (isoguvacine oxide) is a potent and specific GABAA receptor agonist. Isoguvacine oxide, originally designed as a potentially alkylating agonist, turned out to interact with the GABAA receptor in a fully reversible manner. The protected form of isoguvacine oxide, benzyl (3SR,4RS)-1-(benzyloxycarbonyl)-3,4-epoxypiperidine-4-carboxylate (1) (Scheme 1), has now been resolved by chiral chromatography using cellulose triacetate as a chiral stationary phase. The enantiomers of 1 (ee ≥ 98.8%) were subsequently deprotected by hydrogenolysis. Whereas both enantiomers of isoguvacine oxide were inactive as inhibitors of the binding of [3H]GABA to GABAB receptor sites (IC50 〉 100 μM), (+)-isoguvacine oxide (IC50 = 0.20 ± 0.03 μM) and (-)-isoguvacine oxide (IC50 = 0.32 ± 0.05 μM) showed comparable potencies as inhibitors of the binding of [3H]GABA to GABAA receptor sites. Furthermore, (+)-isoguvacine oxide (EC50 = 6 μM; 33% relative efficacy) and (-)-isoguvacine oxide (EC50 = 5 μM; 38% efficacy relative to 10 μM muscimol) were approximately equipotent and equiefficacious as stimulators of the binding of [3H]diazepam to the GABAA receptor-associated benzodiazepine site. This latter effect is an in vitro estimate of GABAA agonist efficacy. These pharmacological data for isoguvacine oxide and its enantiomers do not seem to support our earlier conception of the topography of the GABAA recognition site(s), derived from extensive structure - activity studies on GABAA agonists. Thus, the model of the GABAA recognition site(s) comprising a narrow cleft or pocket, in which the anionic moiety of the zwitterionic GABAA agonists is assumed to be embedded during receptor activation, may have to be revised. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070608
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  • 86
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    Low configurational stability of amfepramone and cathinone: Mechanism and kinetics of chiral inversion (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 469-473 
    Details
    ISSN: 0899-0042
    Keywords: aminoketones ; anorectics ; general-base catalysis ; labile chiral centres ; proton - deuterium substitution ; 1H-NMR ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The low configurational stability of two model compounds, the anorectic drug amfepramone and one of its basic metabolites, rac-cathinone, was examined for its mechanism and kinetics. Assuming a common intermediate for chiral inversion and deuteration, the rates of racemization were determined by the indirect method of proton-deuterium substitution monitored by 1H-NMR. The rate of racemization increased linearily with increasing pD. At a pD of 7.4, the rate of racemization of both aminoketones was markedly dependent on buffer concentration, indicating a mechanism of general-base catalysis. The reactions were some five to six times faster in phosphate buffers than in hydroxylamine buffers of identical molarity. Amfepramone racemized about five times faster than the primary amine cathinone. One implication of these findings is that amfepramone and cathinone may be subject in vivo to chiral inversion catalyzed by numerous endogenous bases. As a result, it will be misleading to extrapolate rates of inversion expected in plasma from those measured in buffer solutions. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070613
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  • 87
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    In vitro fenoprofenyl-coenzyme a thioester formation: Interspecies variations (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 534-540 
    Details
    ISSN: 0899-0042
    Keywords: thioesterification ; enantiomer ; long chain fatty acid CoA synthetase (EC 6.2.1.3) ; fenoprofen ; palmitic acid ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In vitro coenzyme A thioester formation from (-)-(R)-fenoprofen (FPF) and palmitic acid has been studied using liver microsomes from rat, guinea pig, sheep, and dog. In every species with both palmitic acid or (-)-(R)-fenoprofen, the Lineweaver-Burk plot was linear in the substrate concentration range used and as a consequence agrees with the involvement of only one isoenzyme (or different isoenzymes of similar Km values). The Vmax values for the thioesterification of (-)-(R)-fenoprofen present large species variations from 2.1 ± 1.0 with sheep liver microsomes to 60.6 ± 11 nmol/min/mg with dog liver microsomes. These values statistically significantly correlate (r = 0.94) to the Vmax values observed when palmitic acid was used as a substrate. Furthermore palmitic acid inhibited (-)-(R)-fenoprofen-CoA formation in the same extent in all animal species. The stereoselectivity of the thioesterification was also species dependent. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530070707
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  • 88
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    Nonlinear model-based feedforward control of distillation columnsPaper presented by J. Broll at the “Jahrestagung der Verfahrensingenieure”, Nürnberg, September 29 to October 1, 1993. (1995)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 18 (1995), S. 178-182 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An approach to feedforward distillation control based on inverse computation of nonlinear stage models is presented. The feedforward model calculates dynamic trajectories of manipulated variables from measured disturbances and product purity set points independently of the control configuration. Because the model includes the dominant dynamics and nonlinearities of the column, dynamic decoupling of the control loops is achieved. A superimposed linear controller only has to compensate model uncertainties and disturbances that cannot be measured. The proposed approach improves the control performance. Simulation studies show the applicability of the method to multicomponent distillation as well as to distillation trains. Experiments on a pilot plant scale binary distillation column verify the simulation results.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/ceat.270180306
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  • 89
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    An improved system for automated peptide synthesis (1995)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 18 (1995), S. 210-215 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper describes an original system for automated solid-phase peptide synthesis (SPPS) that was developed in our laboratories. The synthesizer is equipped with separate activator and batch reactors, and was designed to operate under either manual or computer control. Two metering pumps, which constitute the core of the entire apparatus, provide for the delivery and transfer of reagents and solvents in the appropriate quantities and in the correct sequence, and permit simultaneous condensation and activation operations that result in considerable time saving. Various applications to the synthesis of biologically important peptides, utilizing the most widely used strategies in SPPS, are presented as examples of this improved technology.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270180310
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  • 90
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    Interfacial area of mellapak packing: Absorption of 1,1,1-trichloroethane by Genosorb 300 (1995)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 18 (1995), S. 248-255 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this work a Sulzer structured packing, Mellapak 250Y, was studied for applications in the field of absorption. A new model was proposed which makes it possible to estimate the packing surface that actually takes part in the process. In the course of these studies, new experimental data were obtained relating to the absorption of 1,1,1-trichloroethane using Genosorb 300, a mixture of polyethylene glycol dimethyl ethers produced by Hoechst S.p.A., as absorption liquid. The results obtained with the proposed model are in agreement both with the experimental measurements made in the course of the work and with experimental absorption measurements reported by other authors on water systems.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270180405
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  • 91
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    Deactivation kinetics and modelling of coke removal under supercritical conditions for the example of ethylbenzene disproportionation (1995)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 18 (1995), S. 278-283 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Deactivation kinetics and coke removal kinetics were derived from experimental studies on the disproportionation of ethylbenzene with a protonated Y-faujasite (Z-14) in a loop reactor under supercritical conditions. Derivation of the steady state kinetics of ethylbenzene disproportionation permitted determination of the catalyst activity. At small educt mole fractions of ethylbenzene, owing to the modest removal of coke the deactivation kinetics can be described by a power relationship. The rate of coke removal can be correlated with the activity and the deactivation rate of the catalyst.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270180409
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  • 92
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    Masthead (1995)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 18 (1995) 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270180501
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    Modelling of agglomeration in industrial crystallization from solution (1995)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 18 (1995), S. 302-309 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A phenomenological approach to evaluating the agglomeration rate of growing crystals is presented. Crystals larger than the Kolmogoroff microscale collide because of the fluctuating velocity field. Bridges between the crystals form as a result of competition between crystalline growth and the turbulent velocity fluctuations on the opposite sides of the agglomerate.Crystals smaller than the Kolmogoroff microscale collide because of viscous laminar microshear stresses within the same turbulent eddy, are kept close together by Van der Waals forces and are joined together by crystalline bridges that grow between them. The strength of these bridges depends on the supersaturation level during the moments following the collision.These two sets of phenomena lead to two different preferential generation mechanisms for agglomerates. One example involving important agglomeration effects is developed for each case: the crystallization of adipic acid belongs to the first group (large crystals), whereas the precipitation of calcium oxalate monohydrate is typical of the second case (small crystals).
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/ceat.270180503
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    Modelling of a woodchip refiner using artificial neural network (1995)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 18 (1995), S. 337-342 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Neural networks can be an attractive alternative to mathematical modelling of complex and poorly understood processes if input/output data can easily be obtained. Woodchip refining falls into this category. The mechanism of the refining process is still being studied and no thorough models have yet been developed. A feed-forward neural network is proposed for modelling of woodchip refiners. The outputs predicted by the neural network are compared with industrial refiner data. It is also shown that a modified neural network structure can be used to optimize refiner operation and product quality. The advantages and disadvantages of neural network model application in simulation and optimization of industrial processes are discussed.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/ceat.270180508
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  • 95
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    Air stripping - a method for treatment of wastewaterPoster presented at the “GVC-Jahrestagung für Verfahrensingenieure”, Nürnberg, Germany, September 30 to October 1, 1993. (1995)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 18 (1995), S. 149-155 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: During recent years the air stripping process has been increasingly applied to the cleaning of water contaminated by volatile organic compounds (VOC). The present contribution compares various methods of treating VOC-contaminated water, with a special focus on removal efficiency and economic aspects. In particular, air stripping, a universally used cleaning method, is described in greater detail. Design and operational aspects are worked out for packed stripping towers for the special case of water contaminated with chlorinated hydrocarbons. Experimental results substantiate predictions of various operating conditions, packing types and scale-up effects.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270180302
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  • 96
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    Performance of a venturi jet scrubber for H2S removal by iron-complex solution (1995)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 18 (1995), S. 166-170 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Venturi jet scrubbers are widely used in chemical industries as an efficient gas-liquid contacting equipment. They are simple in design, have no moving parts, operate with circulating liquid and are reliable in service. Moreover, due to high relative velocity of liquid and gas, considerable overall mass transfer can be produced. In spite of their wide application, readily usable design data are not available in literature, particularly for units producing a gas flow by their own pumping action. The purpose of this paper is to introduce the equipment and its application for H2S removal. The effects of various parameters such as gas and liquid flow rates as well as pressure on hydrodynamics and mass transfer performance of the equipment are investigated. Results of experiments have been shown graphically.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/ceat.270180304
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    The vapour-liquid equilibria of several binary systems of fluorocarbons and hydrocarbons, part II (1995)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 18 (1995), S. 193-202 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The vapour-liquid equilibria of the binary systems perfluoromethylcyclohexane-pentafluorobenzene, benzene-pentafluorobenzene, benzene-methylperfluorobutanoate and perfluoromethylcyclohexane-methylperfluorobutanoate have been measured at 333.07 K and 343.12 K using a dynamic circulation still of the Sieg-Röck type. The thermodynamic consistency of the measurements was tested by two different methods. New UNIFAC interaction parameters [1] were calculated for the following groups: ACH-ACF, ACF-CF2, CF2-COO, ACCH2-ACF, ACH-CF2. The abbreviations stand for the following increments: ACH = aromatic CH group, ACF = aromatic CF group, CF2 = aliphatic CF2 group, COO = ester group and ACCH2 = side chain CH group.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/ceat.270180308
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    Kinetic modelling of the oxidative coupling of methane over lanthanum oxide in connection with mechanistic studiesDedicated to Prof. Dr. Manfred Baerns on the Occasion of his 60th Birthday (1995)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 18 (1995), S. 216-223 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A kinetic model of the oxidative coupling of methane (OCM) over lanthanum oxide is developed on the basis of mechanistic conclusions obtained elsewhere. A reaction scheme is proposed, and the kinetic parameters corresponding to the different kinetic equation are optimized. Experimental and calculated reaction rates are compared with the aim of testing the proposed scheme and validating the basic mechanistic assumptions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270180311
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    Modeling of sulphur retention in atmospheric fluidized bed combustors. Sensitivity analysis and simulation (1995)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 18 (1995), S. 229-242 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: For the design, simulation and optimization of sulphur retention in atmospheric fluidized bed coal combustors, a mathematical model is needed that would be able to predict the behaviour of the combustor in a wide range of operating conditions. In this work, a sensitivity analysis of the sulphur retention predictions of the different hypotheses, equations and parameters, which define the different submodels and phenomena occurring in the combustor, has been carried out. It has been found that the hypotheses related to the gas flow, devolatilization type and sulphur distribution in the pyrolysis products imply an important division among models. The greatest effect on sulphur retention predictions is exercised by the parameters defining the fines elutriation and sorbent sulphation capacity. However, those corresponding to the bed hydrodynamics (minimum fluidization velocity and bed expansion) do not have a significant effect on the sulphur retention predictions.The sulphur retentions obtained in the combustion of high sulphur lignites with eight different limestones were used for model validation. A good fit of the experimental sulphur retentions was found, without using any adjustable parameter. Finally, a simulation of the process was made. The great effect of the bed height, air velocity and the particle size distribution of the limestone must be pointed out, as well as the effect of its reactivity through the maximum conversion attainable by each particle size.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270180403
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  • 100
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    Mass transfer effects on kinetics of nonideal liquid phase ethyl tert-butyl ether formationDedicated to Professor Dr. Manfred Baerns on the Occasion of his 60th Birthday (1995)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 18 (1995), S. 269-277 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Ethyl tert-butyl ether (ETBE) is an alternative fuel oxygenate that can be produced in the liquid phase by addition of ethanol to isobutene catalyzed by sulfonic acid ion exchange resins. A generalized Langmuir-Hinshelwood rate expression is formulated in terms of the liquid phase activities of the reactants that is quasi-autocatalytic due to ethanol. This microkinetic model is combined with the generalized Maxwell-Stefan equations for a detailed investigation of the influence of multicomponent mass transfer limitations inside the macropores of the heterogeneous catalyst. The model is used for revision of experimental rate data for ETBE synthesis in the literature. The analysis reveals that reverse diffusion of isobutene can occur by strong interaction with ethanol and the catalyst effectiveness factor can exceed unity.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270180408
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