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  • 1990-1994  (1,673)
  • 1985-1989
  • 1992  (1,673)
  • Organic Chemistry  (916)
  • Engineering  (757)
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  • 1990-1994  (1,673)
  • 1985-1989
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Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Simulation of a class of multiprocessor machines (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 275-288 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper presents the simulation of a class of MIMD systems using discrete-event simulation enhanced by graphics-oriented reporting. MIMD systems can be specified, modelled and simulated using the package and in turn provide estimates of certain performance indices. A multiserver queueing model is constructed to describe the flow of data and instructions through the various elements of the system. The model is composed of P processors sharing M memory modules through a user-defined interconnection network. Graphical outputs allow the user to view the state of every processor/memory module over the simulation time with performance estimates such as the relative speedup, throughput, and utilization factor. Moreover, system performance graphs as a function of various system parameters are obtained to indicate the expected system behaviour for various loads and system configurations. The results section shows a case study of the influence of the memory modules' access time on the system performance. The purpose of the results is to aid in the analysis, understanding, design, and performance prediction of a class of MIMD systems in a user-friendly environment.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050408
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  • 2
    Electronic Resource
    Electronic Resource
    Computational models for laminated magnetic materials (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 83-92 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The permeability tensor of the homogeneous bulk material externally equivalent to a laminated packet of non-linear, anisotropic, non-hysteretic sheets is derived by symbolic computation. The composite permeability bears a surprisingly simple algebraic relationship to the local permeabilities of its component materials even in the general case. Several special cases of common interest, where the tensor permeability assumes symmetric or diagonal form, are examined. Results are presented both as algebraic expressions and as brief optimized Fortran subroutines suitable for fitting into field analysis programs.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050203
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  • 3
    Electronic Resource
    Electronic Resource
    Transient response of lossy transmission lines with arbitrary loads (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 111-120 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: In this paper, the method of transmission-line modelling is used to determine the transient response of a lossy transmission line. Non-linearity and frequency-dependent parameters (R and G) can be included without undue difficulty. Several numerical examples are described and are compared with exact and/or experimental results. In all cases good agreements are obtained.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050205
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  • 4
    Electronic Resource
    Electronic Resource
    The electromagnetic wave simulator - A dynamic visual electromagnetics laboratory based on the two-dimensional TLM method. W. J. R. Hoefer and P. P. M. So, John Wiley and Sons, 1991, 165 pp. Price £45. ISBN: 0 471 93075 X. (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 139-139 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050208
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  • 5
    Electronic Resource
    Electronic Resource
    Discrete modelling of transport processes in two spatial dimensions (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 121-127 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A random flight model of linear transport processes in two spatial dimensions is considered and solved exactly in closed algebraic form. Its one-dimensional version had been proposed by Taitel as a means to overcome the paradox of infinite speed of propagation within classical heat diffusion theory. The connection with hyperbolic diffusion theory is complemented here by deriving the discrete fluxes and their relaxation term. Moreover, such an approach circumvents the discretization of a continuum model for an intrinsically discrete process, when diffusion processes are to be solved numerically. Finite samples are treated by means of the reflection method. Some applications of these general results are mentioned.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050206
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  • 6
    Electronic Resource
    Electronic Resource
    Modeling in the time domain: Discrete and discreet - a Poem (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 143-144 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050303
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  • 7
    Electronic Resource
    Electronic Resource
    Radiation and scattering of transient electromagnetic fields (invited paper) (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 149-161 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Under wideband and especially ultrawideband (short pulse) excitation, the electromagnetic fields, after encounters with a propagation or scattering environment, reveal features which range from highly resolved spikes or dips to smooth oscillations at early and late observation times, respectively. Time-domain (TD) analytic modelling should be structured around wave objects which relate features (observables) in data to distinct features in the environment. A strategy to this end, named observable-based parametrization (OBP), is proposed here. The rules are learned from frequency- and time-domain asymptotics applies to spatial and spectral domain representations of tractable prototype problems. This leads to self-consistent hybrid combinations OBP-TD travelling (wavefront) and oscillatory (resonant) synthesizing basis fields; the latter include novel TD leaky modes for guiding wave channels and TD Bragg modes for periodic arrays. These concepts are illustrated by examples.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050305
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  • 8
    Electronic Resource
    Electronic Resource
    Multidimensional wave digital filters for discrete-time modelling of Maxwell's equations (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 183-201 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: An approach for numerically integrating the partial differential equations describing passive physical systems consists in modelling the continuous-domain physical system by means of a passive discrete-domain system. As has recently been shown, this can be achieved, in particular also for Maxwell's equations, by means of the same principles as known from multidimensional wave digital filters, which offers a number of important advantages. The present paper deals specifically with the application of the approach to Maxwell's equations and supplements corresponding results previously published.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050307
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  • 9
    Electronic Resource
    Electronic Resource
    Parallel implementation of cellular systems for numerical modelling (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 203-218 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: There is an increasing interest in the numerical modelling of physical and biological processes using cellular automata or cellular systems. One of the main advantages in using the concept of cellular systems is the inherent high degree of parallelism. The purpose of the contribution is to formally relate two different areas: time-domain modelling of physical processes using cellular systems and massive parallel implementations. At first, an overview of applications of cellular systems in computation theory and in modelling of physical systems and an overview of implementations of cellular systems is given. The subsequent sections address the following two questions: (1) Which class of algorithms can be interpreted as cellular systems. (2) Can cellular systems be efficiently simulated on a given parallel architecture. Results concerning these issues are presented.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050308
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  • 10
    Electronic Resource
    Electronic Resource
    Enantioselectivity of lipase-catalyzed hydrolysis of some 2-chloroethyl 2-arylpropanoates studied by chiral reversed-phase liquid chromatographySecond International Symposium on Chiral Discrimination, May 27 - 31, 1991, Rome, Italy. (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 98-102 
    Details
    ISSN: 0899-0042
    Keywords: enantioselective hydrolysis ; lipase ; 2-chloroethyl esters ; 2-arylpropanoic acids ; chiral liquid chromatography ; enantiomer separation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A technique based exclusively on chiral reversed-phase liquid chromatography has been shown to greatly facilitate studies of enantioselectivity in lipase-catalyzed hydrolysis of chiral organic esters. Only two sets of experimental data are needed to calculate the enantioselectivity (E) of a kinetically controlled enantiomer-differentiating reaction of this kind, viz. the enantiomeric excess of the product (eep) or substrate (ees), and the degree of substrate conversion (c). The product enantiomers are well separated on a BSA-based column, giving eep directly. In addition, separation of the (unresolved) ester substrate from the enantiomeric products gives c by integration. Via an optimization of the mobile phase used in the chiral chromatographic system, both these parameters can often be determined in a single run. Highly precise and detailed kinetic studies of the enzymatic reaction can thus be performed. In this way, E-values have been determined for a series of 2-chloroethyl 2-arylpropanoates hydrolyzed in the presence of a Candida cylindracea lipase at pH 6.0 and 7.1. Effects on the E-values from a partial purification and further processing of the lipase have also been studied.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040206
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  • 11
    Electronic Resource
    Electronic Resource
    Enzymatic resolutions of α- and β-hydroxypropionic acid esters (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 103-109 
    Details
    ISSN: 0899-0042
    Keywords: dihydrocinnamic acid derivatives ; hydroxy azido acids ; hydroxy amino acids ; enantioselective hydrolysis ; Pseudomonas fl. lipase ; Candida cyclindracea lipase ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of some acyloxy-methoxy-cinnamic acid derivatives, azidohydroxy butanoates, and azidohydroxy butanedioates in enantiomerically pure form is presented. Racemic diastereomerically pure educts were prepared in few steps. These racemates are resolved with lipases from Candida cylindracea (CC) and Pseudomonas fluorescens (P).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040207
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  • 12
    Electronic Resource
    Electronic Resource
    Optical resolution of β-lactams on 1-phenylethylcarbamates of cellulose and amylose (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 122-124 
    Details
    ISSN: 0899-0042
    Keywords: 4-acetoxy-2-azetidinone ; antibiotics ; carbapenem ; HPLC ; chiral stationary phases ; cellulose tris(1-phenylethylcarbamate) ; amylose tris(1-phenylethylcarbamate) ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optical resolution of six β-lactams was examined by HPLC using chiral stationary phases consisting of tris((R)-, (RS)-, and (S)-1-phenylethylcarbamate)s of cellulose and amylose. All β-lactams were optically resolved at least by one of the carbamates. Amylose tris((S)-1-phenylethylcarbamate) showed high optical resolving abilities for some β-lactams.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040210
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  • 13
    Electronic Resource
    Electronic Resource
    Cyclodextrin derivatives in GC separation of racemic mixtures of volatiles: Part IIISecond International Symposium on Chiral Discrimination, May 27 - 31, 1991, Rome, Italy. (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 125-131 
    Details
    ISSN: 0899-0042
    Keywords: capillary gas chromatography ; enantiomer resolution ; cyclodextrin derivatives ; chromatographic performance ; cyclodextrin/OV-1701 dilution ; operative temperature ; film thickness ; column length ; column conditioning ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The gas chromatographic performance of differently derivatized α-, β-, and γ-cyclodextrins in the separation of racemic mixtures of volatiles is investigated. The performances of 2,3,6-permethylated α-, β-, and γ;-cyclodextrins and 2,6-dimethyl-3-trifluoro-acetyl α-, β-, and γ-cyclodextrins mixed with different ratios of OV-1701 or OV-1701-OH terminated were tested with racemates with widely differing structures. The influence of the percentage of cyclodextrins in polysiloxane, of film thickness of the stationary phase, of the length of the column, of column conditioning, and of the operating temperatures in the separations of different racemates has been evaluated.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040211
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  • 14
    Electronic Resource
    Electronic Resource
    Stereoselective disposition and tissue distribution of carvedilol enantiomers in rats (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 148-154 
    Details
    ISSN: 0899-0042
    Keywords: carvedilol enantiomers ; kinetics ; tissue-to-blood partition coefficient ; plasma protein binding ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: After intravenous bolus injection of rac-carvedilol at 2 mg/kg to the rat, the (+)-(R)- and ( - )-(S)-enantiomer levels in the blood and tissues (liver, kidney, heart, muscle, spleen, and aorta) were measured by stereospecific HPLC assay. As compared with the (+)-(R), the ( - )-(S) had a larger Vdss (3.32 vs. 2.21 liter/kg), MRT (33.4 vs. 25.6 min), and CLtot (96.1 vs. 83.8 ml/min/kg). AUC comparison after iv and po administration showed systemic bioavailability of the ( - )-(S) to be about half that of its antipode, explained by the fact that the free fraction of the ( - )-(S) in blood was 1.65-fold greater than that of the (+)-(R). Tissue-to-blood partition coefficient values for the ( - )-(S) were 1.6- to 2.1-fold greater than those for the (+)-(R) in all tissues, showing that the ( - )-(S) accumulates more extensively in the tissues. These results were consistent with the greater Vdss for the ( - )-(S) estimated from systemic blood data. The stereoselective tissue distribution of carvedilol enantiomers results from an enantiomeric difference in plasma protein binding rather than in tissue binding. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040304
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  • 15
    Electronic Resource
    Electronic Resource
    Liquid chromatographic separation of chiral diarylcarbinolsSecond International Symposium on Chiral Discrimination, May 27-31, 1991, Rome, Italy. (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 170-173 
    Details
    ISSN: 0899-0042
    Keywords: chiral phases ; chiral recognition mechanism ; alcohols ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The direct HPLC separation of three chiral carbinols of general formula Mesityl-CH(OH)-Aryl has been achieved using Pirkle (R)-DNBPG ionic or covalent columns and, for Aryl = o-tolyl, on a Chiralpak OP(+) phase. It is apparent that steric hindrance and hydrogen bonding play important roles in chiral recognition. Two compounds structurally very similar but lacking the hydroxyl group were not resolved in their enantiomeric pairs. © 1992 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040307
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  • 16
    Electronic Resource
    Electronic Resource
    Masthead (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992) 
    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.530040401
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  • 17
    Electronic Resource
    Electronic Resource
    Spontaneous racemization of chlorthalidone: kinetics and activation parameters (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 222-226 
    Details
    ISSN: 0899-0042
    Keywords: 3-hydroxy-3-phenylphthalimidines ; inversion (of configuration) ; barrier to inversion ; rate constants (of inversion) ; enantiomer interconversion ; carbonium ion (intermediate in racemization) ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantiomers of chlorthalidone (CTD) and a minor, achiral dehydration product, δ2-CTD, are shown to exist in dynamic equilibrium in aqueous media through a carbonium ion intermediate. The barrier to inversion at carbon is low for an uncatalyzed system: ΔG
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040404
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  • 18
    Electronic Resource
    Electronic Resource
    Stereoselective binding of etodolac to human serum albuminPresented at the Second International Symposium on Chiral Discrimination, May 27-31, 1991, Rome, Italy. (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 240-246 
    Details
    ISSN: 0899-0042
    Keywords: NSAID ; chirality ; enantiomers ; protein binding ; equilibrium dialysis ; fluorescent specific markers ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The protein binding of etodolac enantiomers was studied in vitro by equilibrium dialysis in human serum albumin (HSA) of various concentrations varying from 1 to 40 g/liter, by addition of each enantiomer at increasing concentrations. In the 1 g/liter solution, at the lowest drug levels, the (R)-form is more bound than its antipode, the contrary being observed at the highest drug levels. For higher albumin concentrations, S was bound in a larger extent than R. Using the displacement of specific markers of HSA sites I and II, studied by spectrofluorimetry, it was suggested that R and S are both bound to site I, while only S is strongly bound to site II. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040407
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  • 19
    Electronic Resource
    Electronic Resource
    Resolution of terfenadine enantiomers by β-cyclodextrin chiral stationary phase high-performance liquid chromatography (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 268-272 
    Details
    ISSN: 0899-0042
    Keywords: HPLC ; chiral stationary phase ; optical isomers ; absolute configuration ; circular dichroism ; chiral ; enantiomers ; terfenadine ; cyclodextrin ; normal phase ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiomers of terfenadine were resolved by high-performance liquid chromatography (HPLC) using a chiral stationary phase (CSP) column packed with β-cyclodextrin (β-CD) covalently bound to silica. Separation was achieved in both the reverse phase and normal phase modes. Resolution of enantiomers was confirmed by ultraviolet-visible absorption, circular dichroism, and mass spectral analysis.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040411
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  • 20
    Electronic Resource
    Electronic Resource
    Obituary: professor goran schill (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 273-273 
    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.530040502
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  • 21
    Electronic Resource
    Electronic Resource
    Effects of the stereochemical orientation of phenethylamines and imidazolines on α-adrenergic receptor-mediated dna synthesis in primary cultured rat hepatocytes (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 279-285 
    Details
    ISSN: 0899-0042
    Keywords: stereochemistry ; catecholamines ; DNA synthesis ; liver regeneration ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hepatic α1-adrenergic receptor mediates a variety of hepatic functions including respiration, glycogenolysis, gluconeogenesis, and growth. We have utilized a rat primary hepatocyte culture system to show that the α1-adrenergic receptor can be activated in a stereoselective manner by a series of phenethylamines and catecholimidazolines resulting in the stimulation of DNA synthesis as determined by [3H]thymidine incorporation. The phenethylamines adhered to the Easson-Stedman hypothesis with a rank order of potency of (-)-(R)-norepinephrine (NE) 〉 (+)-(S)-NE 〉 the desoxy analog dopamine (DA) for the stimulation of DNA synthesis. However, the 2-substituted catecholimidazolines did not follow this trend and demonstrated an order of potency of the desoxy analog 3,4-dihydroxybenzyl imidazoline (DHT) ≥ (-)-(R)-2-(3,4,α-trihydroxybenzyl)imidazoline (TBI) 〉 (+)-(S)-TBI. 4-Substituted catecholimidazolines were less potent as inducers of DNA synthesis than the corresponding 2-substituted analogs with an order of potency of (+)-(R)-4-(3,4-dihydroxybenzyl)imidazoline (DBI) 〉 (+, -)-(R,S)-DBI 〉 (-)-(S)-DBI. When the β-hydroxyl moiety of NE is replaced with an amino group as in 3,4-dihydroxyphenylethylenediamine, the isomers are less active than the β-hydroxylated analogs and also demonstrate no stereoselectivity for the stimulation of DNA synthesis. These results demonstrate that the hepatic α1-adrenergic receptor can recognize various isomeric forms of these compounds and that hepatocellular growth can be modulated in a stereoselective manner by phenethylamines and imidazolines. © 1992 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040504
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  • 22
    Electronic Resource
    Electronic Resource
    Some mechanistic aspects on chiral discrimination of organic acids by immobilized bovine serum albumin (BSA) (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 24-29 
    Details
    ISSN: 0899-0042
    Keywords: organic acids ; enantiomers ; BSA ; chiral discrimination ; hydrophobic interaction ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Although chiral anionic compounds, notably a large number of organic acids, have been found to be readily separated into enantiomers on BSA-based columns, the structural requirements for an efficient enantiomer discrimination by the protein is still not very well known. Since it is often observed that very hydrophobic acids, like many of the antiinflammatory “profens,” can be resolved with large separation factors for the enantiomers, a systematic study of a series of racemic α-substituted alkanoic acids was made. The series of analytes was prepared from α-amino acids, RCH(NH2)CO2H (where R = C1-C6), by reaction with N-(chloroformyl)-carbazole. A rapid increase in the capacity ratios of both enantiomers was found with increasing length of R. The effect, however, was larger for the last eluted enantiomer, leading to a substantial increase in the separation factor; this being 7.3 for R = C6 in 20 mM phosphate buffer (pH 8.0) with 30% of acetonitrile. Further, the separation factor also increased with decreasing organic modifier content. Thus when the R = C6-analyte was run at a mobile phase concentration of 20% acetonitrile and a flow rate of 1.5 ml/min, the time difference between the two eluted enantiomers exceeded 20 hr.A reasonable interpretation of our results seems to be that enantioselectivity is promoted by increased hydrophobic interaction. Since the anionic charge of the analyte is also taking part in the retention mechanism, a tight binding of the analyte will result from simultaneous electrostatic and hydrophobic interaction. When the latter is increased, less conformational freedom will be left for the analyte and the steric configuration at the α-carbon atom will become more and more important. Steric hindrance by the α-substituent in the first eluted enantiomer will counteract the tight binding caused by the combined binding interactions and lead to a smaller increase in the capacity ratio.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040107
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    4',6-Dichloroflavan (BW683C): Enantiomeric separation by hplc/dad and antirhinovirus activity (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 65-67 
    Details
    ISSN: 0899-0042
    Keywords: optical resolution ; chiral HPLC ; chiral stationary phase ; 4',6-dichloroflavan ; circular dichroism ; antirhinovirus activity ; BW683C ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Racemic 4',6-dichloroflavan (BW683C), a highly effective inhibitor of rhinovirus serotype 1B in vitro, was resolved by high-performance liquid chromatography on a chiral stationary phase. The enantiomers were separately collected and circular dichroism curves were obtained, in order to determine the absolute configuration of the two enantiomers. The activity of the isomers was studied on human rhinovirus serotype 1B multiplication in HeLa cell cultures, by means of the plaque reduction assay. Both enantiomers were potent inhibitors of virus replication; by comparing the IC50 values, the S form was 3.5 times more effective than the R form.
    Additional Material: 3 Ill.
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    Erratum (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 71-71 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040116
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    Pulmonary inversion of 2-arylpropionic acids: Influence of protein binding (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 349-352 
    Details
    ISSN: 0899-0042
    Keywords: ibuprofen ; fenoprofen ; flurbiprofen ; rabbit lung ; first-pass ; presystemic ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The possible contribution of pulmonary metabolism to the putative first-pass metabolism of 2-arylpropionic acid nonsteroidal antiinflammatory drugs has not been documented. Isolated perfused rabbit lungs, perfused with 4.5% bovine serum albumin or 5% dextran, were used to study the pulmonary elimination of (R)- and rac-ibuprofen, fenoprofen, and flurbiprofen. In the absence of protein binding, ibuprofen was metabolized via inversion and other pathways, whereas fenoprofen metabolism was essentially restricted to inversion of the (R)-enantiomer; fraction inverted (± SE) was 0.37 ± 0.05 for (R)-ibuprofen and 0.85 ± 0.03 for (R)-fenoprofen. In the presence of protein, neither ibuprofen nor fenoprofen was metabolized. Flurbiprofen did not undergo pulmonary elimination under any condition studied. This study illustrates that even though a tissue is capable of metabolism, particularly inversion of 2-arylpropionics, the quantitative importance of such elimination pathways may be minimal in the presence of the high degree of protein binding that is characteristic of these drugs. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040604
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    Formation of glycine conjugate and (-)-(R)-enantiomer from (+)-(S)-2-phenylpropionic acid suggesting the formation of the coa thioester intermediate of (+)-(S)-enantiomer in dogs (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 342-348 
    Details
    ISSN: 0899-0042
    Keywords: arylpropionic acid ; 2-phenylpropionic acid ; glycine conjugation ; stereoselectivity ; chiral inversion ; reverse chiral inversion ; glycine N-acyl transferase ; dog hepatocytes ; chiral HPLC ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It has been proposed that the chiral inversion of the 2-arylpropionic acids is due to the stereospecific formation of the (-)-R-profenyl-CoA thioesters which are putative intermediates in the inversion. Accordingly, amino acid conjugation, for which the CoA thioesters are obligate intermediates, should be restricted to those optical forms which give rise to the (-)-R-profenyl-CoA, i.e., the racemates and the (-)-(R)-isomers. We have examined this problem in dogs with respect to 2-phenylpropionic acid(2-PPA). Regardless of the optical configuration of 2-phenylpropionic acid administered, the glycine conjugate was the major urinary metabolite and this was shown to be exclusively the (+)-(S)-enantiomer by chiral HPLC. Both (-)-(R)- and (+)-(S)-2-phenylpropionic acid were present in plasma after the administration of either antipode, and further evidence of the chiral inversion of both enantiomers was provided by the presence of some 25% of the opposite enantiomer in the free 2-phenylpropionic acid and its glucuronide excreted in urine after administration of (-)-(R)- and (+)-(S)-2-phenylpropionic acid. The (+)-(S)-enantiomer underwent chiral inversion to the (-)-(R)-antipode when incubated with dog hepatocytes. These data suggests that both enantiomers of 2-phenylpropionic acid are substrates for canine hepatic acyl CoA ligase(s) and thus undergo chiral inversion, but that the CoA thioester of only (+)-(S)-2-phenylpropionic acid is a substrate for the glycine N-acyl transferase. These studies are presently being extended to the structure and species specificity of the reverse inversion and amino acid conjugation of profen NSAIDs. © 1992 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040603
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    HPLC resolution of atropoisomeric compounds on a csp derived from (1R;2R)-diaminocyclohexane: Thermodynamic data from variable temperature chromatographyThis paper was presented at the Second International Symposium on Chiral Discrimination, May 27-31, 1991, Rome, Italy. (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 384-388 
    Details
    ISSN: 0899-0042
    Keywords: enantiomeric separations ; polymeric CSPs ; enthalpy ; entropy ; H-bonding ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation and a preliminary chromatographic evaluation of a novel polymeric chiral stationary phase (CSP) derived from (1R;2R)-diaminocyclohexane (DACH) are presented. A radical copolymerization process has been employed to generate a silica-based chiral sorbent, showing considerable high chemical and thermal stability and stereoselectivity toward racemic compounds capable of H-bonding (3-hydroxy-benzodiazepin-2-ones, chlorthalidone, atropoisomeric sulfur compounds, etc.); in the present paper we present the investigation on the resolution of racemic dihydroxy biarylic atropoisomers; the effects of eluent composition and of temperature on the separation ability of the CSP have been studied in order to elucidate the recognition mechanism operating in these chiral separations. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040609
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    Announcement (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 406-406 
    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.530040614
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    Masthead (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992) 
    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.530040701
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    Optical resolution of unusual amino acids using microbial proteases (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 427-431 
    Details
    ISSN: 0899-0042
    Keywords: enantioselective hydrolysis ; amino acid enantiomers ; Aspergillus oryzae protease ; Bacillus subtilis protease ; enantioselectivity ; enantiomeric purity determination ; HPLC ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have developed novel enzymatic methods for the optical resolution of unusual amino acids. In this work, we tried two microbial proteases, available inexpensively in a crude state, from Aspergillus oryzae and from Bacillus subtilis. The enantioselective hydrolysis of the methyl esters of the N-benzyloxycarbonyl (Z) derivatives of a number of amino acids, both aliphatic and aromatic, was examined using these microbial proteases. The enantiomeric purities of the resolved Z-amino acids were determined accurately by methods based on the reversed-phase HPLC separation of diastereomeric derivatives or the HPLC separation of enantiomeric derivatives on chiral stationary phases. In general, B. subtilis protease yielded better results than A. oryzae protease. Using the former protease, the amino acids bearing aliphatic side chains were resolved with good to excellent enantioselectivities and reasonable hydrolysis rates. The speed of hydrolysis was reduced significantly when the length of the side chain was longer than 5 carbon atoms. Phenylalanine, halogenated phenylalanines, and phenylalanine homologs were also resolved, generally with high enantiomeric purities, though the hydrolysis rates were not always reasonably fast. In all the cases examined, the L-enantiomers were preferentially hydrolyzed as in the lipase-catalyzed enantioselective hydrolysis reported previously. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040705
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    Resolution and adrenergic activities of the optical isomers of 4-[1-(1-Naphthyl)ethyl]-1H-imidazole (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 432-438 
    Details
    ISSN: 0899-0042
    Keywords: α-adrenergic ; imidayole analogs ; metetomidine ; enantiomers ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Recently we synthesized a naphthalene analog of medetomidine, 4-[1-(1-naphthyl)ethyl]-1H-imidazole hydrochloride (1), and found it to be highly potent in adrenergic systems. The separation of optical isomers of this naphthalene analog was achieved by using the isomers of tartaric acid. The optical purities of the isomers were determined by HPLC using a chiral column. Using X-ray analysis the (+)-isomer was determined to have the S absolute configuration. It has been reported that the (+)-isomer of medetomidine (2) is the most potent enantiomer on α2-adrenergic receptors. There were both qualitative and quantitative differences in biological activities of the optical isomers of 1 in α1- and α2-adrenergic receptor systems of guinea pig ileum and human platelets. (+)-(S)-1, but not ( - )-(R)-1 was a selective agonist of α2-mediated responses in ileum whereas ( - )-(R)-1 was more potent than (+)-(S)-1 as an inhibitor of α2-mediated platelet aggregation. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040706
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    Announcement (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 462-463 
    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.530040711
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    Optical stability of gossypol (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 216-221 
    Details
    ISSN: 0899-0042
    Keywords: atropisomerism ; gossypol stereochemistry ; molecular mechanics ; circular dichroism ; anhydrogossypol ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The optical stability of gossypol [1,1',6,6',7,7'-hexahydroxy-3,3'-dimetyl-5,5'-bis(1-methylethyl)-2,2'-binaphthalene-8,8'-dicarboxaldehyde], a natural product exhibiting profoundly enantiospecific antitumor and male antifertility action, was investigated by means of computational methods and thermal racemization experiments. The calculations on gossypol and several derivatives and model compounds were carried out using the MM2 force field; energies and geometries of minimum energy conformations, as well as structures along various inversion pathways, were calculated. According to the calculations, gossypol (the dialdehyde form) and its simple analogues are not thermally racemizable (energy barriers for rotational inversion above 50 kcal/mol). By contrast, the calculations suggest that the acetal tautomer of gossypol and its dehydration product (anhydrogossypol) are thermally racemizable, although the energy barriers are still relatively high (35-40 kcal/mol). Optically pure (+)-anhydrogossypol was prepared and characterized; its racemization became rapid only at high temperatures (180-200°C). When dehydration of gossypol was hindered (in aqueous solution), no racemization of gossypol was observed after prolonged heating at 90°C. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040403
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    Synthesis and pharmacological investigation of stereoisomeric muscarines (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 230-239 
    Details
    ISSN: 0899-0042
    Keywords: total synthesis ; chiral muscarines ; iodocyclization process ; muscarinic receptor subtypes M1, M2, and M3 ; affinity states ; eudismic ratio ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the eight stereoisomers of muscarine has been efficiently accomplished by utilizing the two enantiomers of lactic esters as starting material. The synthetic strategy is based on a SnCl4-catalyzed addition of allyltrimethylsilane to O-protected lactic aldehydes followed by an iodocyclization process. All the final derivatives possess an enantiomeric excess higher than 98%. The four pairs of enantiomers bound to M1, M2, and M3 muscarinic receptor subtypes in membranes from cerebral cortex, heart, and salivary glands, respectively, and recognized heterogeneous states of the receptors. Of the eight isomers, only natural muscarine (+)-1 recognized three affinity states of the M2 receptor. The compound was also the only one to show selectivity in the binding study, demonstrating 37- to 44-fold higher affinity for the M2 than for the M1 or M3 receptors. In addition, the compounds were tested in functional assays on isolated guinea pig atria (M2 receptors) and ileum (mixed population of M2 and M3 receptors) and their muscarinic potencies were determined. Among the eight isomers, again only (+)-1 enantiomer was found to be very active on both tissues. Its potency was more than two orders of magnitude higher than that of its enantiomer (-)-1 as well as the other six isomers. The eudismic ratios (E.R.) deduced from the two functional tests were 324 and 331. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040406
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    Discrimination in resolving systems: Ephedrine-mandelic acid (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 494-504 
    Details
    ISSN: 0899-0042
    Keywords: diastereomers ; crystal structures ; isosterism ; organic salts ; molecular recognition ; hydrogen bonding ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Resolution of mandelic acid with ( - )-(1R,2S)-ephedrine in water and ethanol produces intermediate diastereomeric salts with greatly disparate solubilities and melting points. Single crystal X-ray analysis of the less (L) and more (M) soluble ( - )-ephedrinium mandelates (I, II) shows crystal structures which are isosteric, each crystallizing in the monoclinic system, space group C2. Protonated ephedrines occupy the same relative positions in the L- and M-salts, and mandelates are in the same general locations. Hydrogen bonds link alternating protonated ephedrine nitrogens and mandelate carboxylate oxygens in each salt forming columns of ions. The helical H-bonded chain winds down the crystallographic 2-fold screw axis. Additional H-bonds form between 2-fold related mandelates in the L-salt. Mixed crystals, containing both mandelate isomers, (2R)- and (2S)-mandelates, are obtained from the resolving system partly depleted of the L-salt. A specimen with nearly equal amounts of the mandelates (III) is also isosteric with the commensurate structures. I (294K), L-salt: a = 18.160(7), b = 6.538(2), c = 13.898(4) Å, β = 92.02(3)°, V = 1649.1(9) Å3; IIa (294K), M-salt: a = 17.978(11), b = 7.164(4), c = 13.574(6)Å, β = 96.41(4)°, V = 1737.3(16) Å3; IIb (223K), M-salt: a = 17.805(8), b = 7.115(2), c = 13.50(5) Å, β = 96.89(3)°, V = 1697.9(15) Å3; III (294K), mixed-salt: a = 18.184(22), b = 6.792(7), c = 13.808(19) Å, β = 93.74(10)°, V = 1701.7(35) Å3. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040807
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    High enantiofacial selectivity in the OsO4 dihydroxylation of e-stilbene with a chiral biphenyl diamine catalyst (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 300-301 
    Details
    ISSN: 0899-0042
    Keywords: hydrobenzoin ; asymmetric oxidation ; osmium tetroxide ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chiral biphenyl-containing diamine 1 complexed with OsO4 oxidized trans-stilbene at -80°C to (+)-(1R;2R)-1,2-diphenyl-1,2-ethanediol in high enantiomeric excess. On the other hand, (R)- or (S)-2,2'-bis(dimethylamino)-6,6'-dimethylbiphenyl proved to be ineffective in promoting oxidation. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040507
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    Enantio- and regioselectivity in the epoxide-hydrolase-catalyzed ring opening of aliphatic oxiranes: Part II: Dialkyl- and trialkylsubstituted oxiranes (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 185-192 
    Details
    ISSN: 0899-0042
    Keywords: enantioselective hydrolysis ; regioselective hydrolysis ; epoxide hydrolase ; product enantioselectivity ; substrate enantioselectivity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The extent of substrate enantioselectivity and regioselectivity of a series of aliphatic 2,3-dialkyl- and trialkylsubstituted oxiranes in their in vitro epoxide-hydrolase-catalyzed hydrolysis depends on the size of the alkyl residues and on the substitution pattern of the oxirane ring. The enzyme-catalyzed hydrolysis of cis-oxiranes, containing at least one methyl substituent, shows complete or nearly complete substrate enantioselectivity and regioselectivity with nucleophilic attack by water occurring with inversion of configuration at the methylsubstituted ring carbon atom of (S)-configuration. In the hydrolysis of the isomeric trans-oxiranes, both enantiomers are metabolized with a higher rate for the (2S;3S)-enantiomer. The conversion of trimethyloxirane occurs with high substrate enantioselectivity in favor of the (S)-enantiomer and with complete regioselectivity at the monomethylsubstituted ring carbon atom. The differentiation of the enantiotopic ring carbon atoms (product enantioselectivity) in the smallest aliphatic meso-oxirane, cis-2,3-dimethyloxirane, leads to (2R;3R)-butane-2,3-diol with ee = 86%. cis-2-Ethyl-3-propyloxirane, possessing alkyl residues larger than methyl, represents an extremely poor substrate in the epoxide-hydrolase-catalyzed hydrolysis process. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040310
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    Structural characteristics of cyclodextrins in the solid state (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 205-215 
    Details
    ISSN: 0899-0042
    Keywords: cyclodextrins ; molecular mechanics ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A comparison of α-, β and γ-cyclodextrins in the solid state is made. Monomeric features analyzed include orientations of primary hydroxyl groups and pyran ring pucker. Macromolecular features examined include planarity of the oligomer, tilting of pyran rings, and, deviation from Cn symmetry where n = number of monomers. The mean values and standard deviations of these shape descriptors are given for cyclodextrins with and without guests embedded in their interiors. Molecular mechanics calculations using the MM2, AMBER, and CHARMM force fields show that most solid state cyclodextrins are trapped in high-energy conformations relative to the most stable forms found in this study. © 1992 Wiley-Liss, Inc.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040402
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    Enzymes in stereoselective pharmacokinetics of endogenous substancesPresented at the Second International Symposium on Chiral Discrimination, May 27-31, 1991, Rome, Italy. (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 247-251 
    Details
    ISSN: 0899-0042
    Keywords: radioenzyme assay ; stereospecific assay ; carnitine acetyl transferase ; L-carnitine family ; L-carnitine ; acetyl-L-carnitine ; propionyl-L-carnitine ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of enzymes to assay individual components of the L-carnitine family in pharmaceuticals, foodstuffs, and biological fluids with various forms of detection is reviewed. The most useful enzyme in the assay of compounds of the L-carnitine family is carnitine acetyl transferase (CAT), which catalyses the reversible interconversion of L-carnitine and its short-chain acyl esters. CAT can be used in one or more coupled reactions combined with U.V., or radiolabelled detection, or combined with HPLC, allowing, enantioselective, structurally specific, and, in the case of radiolabelled tracing, highly sensitive assays to be carried out. When compared with chromatographic separation of enantiomers or diastereoisomers, enantioselective enzyme mediated assays may be cheaper, more sensitive, and simpler, but they do not allow the nonpreferred isomer to be assayed. Consequently, they are appropriate for the specific assay of endogenous enantiomeric substrates of the enzyme concerned, in biological samples. The analysis of the other enantiomer in raw materials or in pharmaceuticals must be more properly approached by enantioselective chromatographic methods.
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    Direct enantiomeric separation of β-blockers on ChyRoSine-a by supercritical fluid chromatography: Supercritical carbon dioxide as transient in situ derivatizing agent (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 252-262 
    Details
    ISSN: 0899-0042
    Keywords: enantiomeric separations ; chiral stationary phases ; tyrosine chiral selector ; supercritical fluid chromatography ; 1,2-amino-alcohols ; β-blockers ; carbon dioxide ; 1H NMR ; ChyRoSine CSP ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The direct enantiomeric separation of a series of β-blockers has been carried out on two chiral stationary phases (CSPs) derived from 3,5-dinitrobenzoyl tyrosine: the commercially available ChyRoSine-A and a recent improved version of this CSP.Using supercritical fluid chromatography (SFC), facile separations are achieved (1.1 〈Rs 〈7) within short analysis times. The parameters affecting the enantioselectivity (temperature, pressure, mobile phase nature, solute structure) have been investigated. The optimal mobile phase consists in a mixture of carbon dioxide-methanol-propylamine at 25°C. The solute structure has a great influence on the enantioselectivity. For instance, both amine and hydroxyl protons are necessary for chiral discrimination to occur. Furthermore, the steroselectivity value is directly connected to the amine substituent steric bulkiness.Surprisingly, these solutes are poorly resolved using normal phase liquid chromatography (NPLC). Accordingly, the specific influence of carbon dioxide on the enantiomeric separation of 1,2-amino-alcohols has been investigated using various techniques such as nuclear magnetic resonance (NMR) or molecular modelisation. It has been shown that carbon dioxide acts as a complexing agent toward the amino-alcohol by setting up of a bridge with the hydroxyl and the amine protons of the solute. In that way, the resulting complex possesses lower acido-basic properties and a higher conformational rigidity, responsible for chiral discrimination.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040409
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    A proposal for the representation of the stereochemistry of quadrivalent centers (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 274-278 
    Details
    ISSN: 0899-0042
    Keywords: one-wedge diagram ; structure representation ; stereochemistry ; absolute configuration ; chiral center ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The broken wedge, broken line, solid bar, and broken bar are either not reasonable or can be replaced by only one type of solid wedge in the stereochemical formulation. A convention based on a one-wedge symbolization is proposed, where a or b is used instead of c, d, e, f, g, or h. © 1992 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040503
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    Asymmetric synthesis polymerization of meso oxiranes and thiiranesThis work is dedicated to the memory of Professor Piero Pino. (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 295-299 
    Details
    ISSN: 0899-0042
    Keywords: cis-dimethylthiirane ; cyclohexene sulfide ; cis-dimethyloxirane ; cyclohexene oxide ; chiral initiator system ; enantiogenic polymerization ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The asymmetric synthesis polymerization or “enantiogenic” polymerization of some meso oxiranes, cis-dimethyloxirane (cis-DMO) and cyclohexene oxide (CHO), and thiiranes, cis-dimethylthiirane (cis-DMT) and cyclohexene sulfide (CHS), initiated with different chiral systems was examined. Strong differences in behaviour were observed between oxiranes and thiiranes depending on the initiator used. The initiators based on ZnEt2 or CdMe2 and a chiral diol give optically active polymers from meso thiiranes but fail to induce an asymmetric polymer synthesis with meso oxiranes. A new chiral initiator based on ZnEt2 and (1S,2R)-ephedrine allowed us to prepare optically active poly CHOs, which can be fractionated into fractions exhibiting opposite optical activities. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Tab.
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    URL: http://dx.doi.org/10.1002/chir.530040506
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    Computer-Aided models for optimization of eluent parameters in chiral liquid chromatography (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 316-322 
    Details
    ISSN: 0899-0042
    Keywords: chiral LC ; drug enantiomers ; modelling ; central composite desire ; optimization ; β-cyclodextrin ; response surface ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of a central composite design to the enantiomeric separation of the antifungal drug tioconazole is investigated. The design involves application of a mathematical model to the data to model the response in regions of the factor space not investigated in the experimental design. The significance of the variable terms in the model is assessed statistically and those terms declared not significant are removed from the model. The statistical adequacy of these reduced models is discussed, together with an examination of the prediction errors of the models. Three-dimensional predicted response surfaces for the complete models are presented and the predictive performance assessed. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040510
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    Resolution of the enantiomers of drugs containing amino alcohol structure after derivatization with bromoacetic acid (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 333-337 
    Details
    ISSN: 0899-0042
    Keywords: chiral separation ; ligand exchange chromatography ; adrenergic drugs ; β-blockers ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The separation of the enantiomers of drugs containing an amino alcohol structure like adrenergic drugs or β-blockers is described. The compounds are resolved on chiral ligand-exchange chromatography phases after derivatization with bromoacetic acid. © 1992 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040512
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    Masthead (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992) 
    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.530040601
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  • 46
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    Optical isomers of a leukotriene b4 antagonist have differential effects on granulocyte diapedesis in the guinea pig dermis (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 353-355 
    Details
    ISSN: 0899-0042
    Keywords: leukotriene B4 ; SC-41930 ; dermis ; granulocyte ; stereoselectivity ; guinea pig ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Leukotriene B4 (LTB4) is a proinflammatory product of arachidonic acid metabolism that has been implicated in a number of inflammatory diseases. When injected intradermally into the guinea pig, LTB4 has been shown to elicit a dose-dependent infiltration of granulocytes as assessed by the level of the neutrophil marker enzyme myeloperoxidase. SC-41930 [7-[3-(4-acetyl-3-methoxy-2-propylphenoxy)propoxy]-3,4-dihydro-8-propyl-2H-1-benzopyran-2-carboxylic acid] is a potent LTB4 receptor antagonist. When compounds were coadministered along with LTB4 (35 ng) into the dermal site, racemic SC-41930, (+)-SC-41930, and (-)-SC-41930 each inhibited granulocyte accumulation with ED50 values of 340 ± 30, 98 ± 5.7, and 1000 ± 142 ng, respectively; when given intravenously inhibited with ED50 values of 0.5 ± 0.06, 0.3 ± 0.04, and 1.4 ± 0.19 mg/kg, respectively; and when given intragastrically inhibited with ED50 values of 1.7 ± 0.20, 1.4 ± 0.23, and 3.0 ± 0.41 mg/kg, respectively. © 1992 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040605
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  • 47
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    Stereoselective binding and activity of oxotremorine analogs at muscarinic receptors in rat brain (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 463-468 
    Details
    ISSN: 0899-0042
    Keywords: muscarinic receptors ; oxotremorine derivatives ; stereoselectivity ; adenylyl cyclase ; phosphoinositide metabolism ; receptor autoradiography ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The activities of the enantiomers of BM-5 were examined to measure muscarinic cholinergic selectivity in the central nervous system. Autoradiographic studies assessed the ability of each enantiomer to inhibit the binding of [3H]-(R)-quinuclidinyl benzilate ([3H]-(R)-QNB) to muscarinic receptors in the rat brain. (+)-(R)-BM-5 inhibited [3H]-(R)-QNB binding to rat brain sections at concentrations below 1.0 μM, while 100-fold higher concentrations of ( - )-(S)-BM-5 were required for comparable levels of inhibition. Analysis of the autoradiograms indicated that both stereoisomers had a similar distribution of high affinity binding sites. Each enantiomer displayed higher affinity for muscarinic receptors in the superior colliculi and lower affinity for receptors in the cerebral cortex and hippocampus. (+)-(R)-BM-5 and oxotremorine inhibited adenylyl cyclase activity in the cerebral cortex with efficacies comparable to that for acetylcholine. (+)-(R)-BM-5 was 26-fold more potent than ( - )-(S)-BM-5 in inhibiting adenylyl cyclase. Oxotremorine-M and carbamylcholine stimulated phosphoinositide turnover in the cerebral cortex. Oxotremorine had lower activity and (+)-(R)-BM-5 was essentially inactive at comparable concentrations. The difference in activity of the two enantiomers indicates a remarkable stereochemical selectivity for muscarinic receptors. The stereoselectivity index is comparable for both the autoradiographic assays (48) and measures of adenylyl cyclase activity (26) in the cerebral cortex. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040802
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  • 48
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    Measurement of the (R)- and (S)-isomers of warfarin in patients undergoing anticoagulant therapy (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 488-493 
    Details
    ISSN: 0899-0042
    Keywords: achiral/chiral coupled HPLC ; α1-acid glycoprotein column ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An achiral/chiral high-performance liquid chromatographic system for the analysis of total warfarin together with the (R)- and (S)-enantiomers in clinical samples has been developed. The achiral analysis is achieved using a C8 column, which is coupled to a chiral stationary phase, α1-acid glycoprotein (AGP), thereby allowing for analysis of warfarin isomers without interfering serum peaks. A 0.015 M phosphate buffer mobile phase with 15% v/v propan-2-ol (pH 7.0) was used on the C8/AGP system. UV analysis at 308 nm was used for quantitation of total warfarin on the C8 column and fluorescence (excitation 300 nm, emission 390 nm) detection was employed for isomer quantitation on the AGP. Retention time of total warfarin on the C8 column was 5.95 min, while that of the (S)- and (R)-warfarin on the AGP column was 10.38 and 12.69 min, respectively. Peak resolution of the warfarin isomers was 1.64. All serum samples were subjected to solid-phase extraction. Data from two patients in a single dose study indicate that a two-compartmental model could represent the warfarin concentration - time data with enterohepatic circulation. In some patients studied during steady state therapy, concentrations of (S)-warfarin were greater than (R)-warfarin indicating that the clearance of the former is slower in these patients. © 1992 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040806
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    Announcement (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 521-521 
    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.530040811
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  • 50
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    Resolution and stability of oxazepam enantiomers (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 443-446 
    Details
    ISSN: 0899-0042
    Keywords: oxazepam ; chiral stationary phases ; high-performance liquid chromatography ; enantiomer separation ; enantiomer stability ; racemization ; kinetics of racemization ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A solvent mixture containing dioxane, acetonitrile, and hexane was found to be suitable as a mobile phase to resolve oxazepam enantiomers by chiral stationary phase high performance liquid chromatography using covalent Pirkle columns. The resolved oxazepam enantiomers in this solvent mixture had a racemization half-life greater than 3 days at 23°C. When desiccated at 0°C as dried residue, OX enantiomers were stable for at least 50 days with less than 2% racemization. The conditions which stabilized OX enantiomers significantly facilitated the determination of racemization half-lives of OX enantiomers in a variety of aqueous and nonaqueous solvents and at different temperatures. © 1992 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040708
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    Masthead (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992) 
    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.530040801
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    Cytochrome p-455 nm complex formation in the metabolism of phenylalkylamines. XII. Enantioselectivity and temperature dependence in microsomes and reconstituted cytochrome p-450 systems from rat liver (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 469-477 
    Details
    ISSN: 0899-0042
    Keywords: metabolic intermediate (MI) complex ; amphetamine ; 1-phenyl-2-pentanamine ; N-hydroxyamphetamine ; 2-nitroso-1-phenylpropane ; P450 2B1 ; P450 2C11 ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Formation of metabolic intermediate (MI) complexes was studied with the enantiomers of amphetamine, 1-phenyl-2-pentanamine, N-hydroxyamphetamine, and 2-nitroso-1-phenylpropane (the C-nitroso analogue of amphetamine). Three different enzyme systems were used; liver microsomes from phenobarbital pretreated rats and two reconstituted systems containing the P450 2B1 and P450 2C11 forms of cytochrome P-450. Enantioselective complex formation in microsomes was shown for the amines and the nitroso compound, but not for the hydroxylamine. The highly purified P450 2B1 system formed the MI complex with all substrates tested, and the enantioselectivity observed with the microsomal system was reproduced. In the P450 2C11 system the nitroso compounds were completely inactive, whereas the enantiomers of N-hydroxyamphetamine still produced the complex at a high rate. Changes in temperature were shown to affect (R)-2-nitroso-1-phenylpropane more than its enantiomer. Both enantiomers showed biphasic Arrhenius plots for MI complex formation in microsomes (breaks around 22°C), but the activation energies of the (R)-isomer were about five times higher than those of the (S)-isomer. A theory is presented which suggests different modes of interaction with the active site of P-450 to account for the different behaviour of the various substrates. © 1992 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040803
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    Finite difference time-domain simulation of electromagnetic fields and microwave circuits (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 163-182 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: An overview is given on the application of finite difference time-domain analysis techniques to the simulation of electromagnetic wave phenomena and the design of planar microwave integrated circuits. In particular the application to the analysis of three-dimensional discontinuities in coplanar microwave circuits is described and numerical and experimental results are presented. Finally the design of planar microwave circuits containing non-linear active components using the finite difference time-domain method in combination with a harmonic balance technique is demonstrated using an example of a LUFET circuit.
    Additional Material: 17 Ill.
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    URL: http://dx.doi.org/10.1002/jnm.1660050306
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    Masthead (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992) 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050401
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    Editor'note (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. i 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050402
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    Implementation of timestep changes in transmission-line matrix diffusion modelling (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 251-257 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper details general expressions for implementing timestep transformations in transmission-line matrix (TLM) modelling of diffusion processes. The expressions can be conveniently incorporated into any TLM routine which models multidimensional problems using a variable meshing technique.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/jnm.1660050406
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    A companion macromodelling approach for the transient analysis of MOS large-scale integrated circuits (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 227-243 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Purpose of this work is to present a new macromodelling approach for the simulation at the device level of large MOS integrated circuits, requiring only marginal modifications to be implemented in the widely used circuit simulator SPICE. This method results in a substantial saving in computing time and guarantees the same accuracy of SPICE. A prototype simulator based on this method has been developed and used to analyse several significant circuits. In addition, since the method is particularly suitable to be implemented in parallel computers, some results obtained with the CRAY-YMP/432 computer are provided.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050404
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    Application of an efficient algorithm for solving the one-band effective mass equation self-consistently in the modelling of some low-dimensional structure devices (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 23-39 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: An efficient algorithm is presented for the self-consistent numerical solution of the single-band effective mass equation. This algorithm has a different form depending on whether the effective mass is modelled as continuous or piecewise continuous. Coupled with a Poisson solver, an established algorithm is applied for the attainment of self-consistency. The rate of convergence to a self-consistent solution is investigated, and the solvers are applied to three different structures to demonstrate its versatility and robustness. The first of these is a nominally undoped quantum well AlGaAs/GaAs heterostructure, the second a doubly δ-doped GaAs homostructure and lastly a quasi-square well modulation-doped field effect transistor. The algorithm is of sufficient efficiency so as to allow the software to run reasonably quickly on a modern microcomputer.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050105
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    Masthead (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992) 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050201
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    Masthead (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992) 
    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.530040101
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    Stereoselective aliphatic hydroxylation of 6-n-propylchromone-2-carboxylic acid by female Dutch rabbits (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 1-7 
    Details
    ISSN: 0899-0042
    Keywords: product enantioselectivity ; aliphatic hydroxylation ; 6-n-propylchromone carboxylic acid ; chiral HPLC ; chiral shift 1H-NMR ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 6-n-Alkylchromone-2-carboxylic acids are metabolized solely by aliphatic oxidation. In the rabbit, the 6-n-propyl congener (PCCA) undergoes ω-1 hydroxylation exclusively. Following administration of PCCA to female Dutch rabbits (500 μmol/kg), some 77% of the dose was excreted in the urine, 41% as PCCA and 36% as 6-(2'-hydroxy-n-propyl)chromone-2-carboxylic acid. Since this metabolite is chiral, we have examined the stereochemistry of the excreted material. Diastereoisomeric (as camphanate and α-methoxy-α-(trifluoromethyl)phenylacetate esters) and direct chiral HPLC and chiral lanthanide shift NMR have each shown the S:R ratio of the excreted metabolite to be 76:24. When rabbits were dosed with the racemic metabolite, excretion of the compound was not stereoselective. The regio- and stereo-selectivity of the aliphatic hydroxylation of PCCA are thus reflections of the selectivities of the enzyme systems responsible for its formation and suggest PCCA to be an appropriate probe compound for the study of prochiral-chiral hydroxylations.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040103
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  • 62
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    Enantiospecificity of kappa receptors: Comparison of racemic compounds and active enantiomers in two novel series of kappa agonist analgesics (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 8-15 
    Details
    ISSN: 0899-0042
    Keywords: opioids ; piperidines ; 1,2,3,4-tetrahydroisoquinolines ; antinociception ; binding affinity ; QSAR ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two novel series, Ia,b and IIa,b, of kappa opioid antinociceptive agents have recently been described. 2a,b,3a,b,c The biological activities of 16 racemic compounds and their corresponding (-) enantiomers are now compared in a battery of tests. Enantiomers of unsubstituted piperidines Ia were synthesized starting from S(-) pipecolic acid, whereas the enantiomerically pure substituted piperidines (Ib), tetrahydroisoquinolines (IIa), and thienopiperidines (IIb) were, in general, obtained after diastereomeric crystallization of the corresponding tartrate salts. The absolute stereochemistry of one representative enantiomer from series IIa was determined to be (1S) by X-ray crystallographic analysis. Antinociceptive activity in the mouse abdominal constriction and tail-flick tests following subcutaneous administration, and binding affinity for κ and μ receptors, were found to reside predominantly in the (-) enantiomers. Consequently, racemic compounds showed approximately half potency of the corresponding enantiomers. This potency difference was less clear after oral administration presumably due to small differences in bioavailability of the two corresponding enantiomers.For compounds with some affinity also for μ receptors (Ki 〈1,000 nM), the κ/μ selectivity was maintained within each enantiomeric pair, in contrast to results found for other κ agonists.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040104
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    Chiral discriminations with cinchona alkaloids (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 43-49 
    Details
    ISSN: 0899-0042
    Keywords: chiral discrimination ; enantiomeric separation ; chiral solvating agents ; asymmetric synthesis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040110
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    Enantioselective chromatography of the antimalarial agents chloroquine, mefloquine, and enpiroline on a α1 -acid glycoprotein chiral stationary phase: Evidence for a multiple-site chiral recognition mechanism (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 30-35 
    Details
    ISSN: 0899-0042
    Keywords: chiral liquid chromatography ; α1 -acid glycoprotein ; antimalarial agents ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of mobile phase pH and dimethyloctylamine (DMOA) on the retention (k') and stereoselectivity (α) of antimalarial agents mefloquine, enpiroline, and chloroquine on the α1-acid glycoprotein chiral stationary phase (AGP-CSP) was investigated. An increase of k' with increasing pH was observed while the effect on α was a function of the solute. The magnitude and direction of changes induced by DMOA depended on pH and the structure of the solute.The results of this study are consistent with a change of the conformation of the AGP between pH 5 and 7. At pH 7, the effect of DMOA on mefloquine was relatively well described by a competitive displacement from one enantioselective site. The effect on chloroquine and enpiroline suggests a multiple-site mechanism in which both competitive and allosteric interactions are involved.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040108
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    Preparation of α-substituted α-amino acids of high enantiomeric purity (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 302-307 
    Details
    ISSN: 0899-0042
    Keywords: hydantoin derivatives ; chiral isocyanates ; LC separation of diastereomers ; preparative LC separation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Racemic 5,5-dialkyl hydantoins derived from ketones are resolved by preparative liquid chromatography as the diastereomeric 1-carboxamide derivatives afforded by the reaction with optically pure configurationally known α-phenylethyl isocyanate. Hydrolysis of the resolved diastereomers affords α-substituted α-amino acids of high enantiomeric purity. The synthetic route is short, overall yields are high, and the absolute configuration of the amino acid enantiomers may be deduced from the chromatographic and NMR properties of the diastereomers. © 1992 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040508
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    Application of antibody-mediated extraction for the stereoselective determination of the active metabolite of loxoprofen in human and rat plasma (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 308-315 
    Details
    ISSN: 0899-0042
    Keywords: loxoprofen ; 2-arylpropionic acid ; active metabolite ; immobilized antibody column ; chiral hapten ; diastereomeric derivatization ; chiral inversion ; stereoselective ketone reduction ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Antibody-mediated extraction followed by chiral high-performance liquid chromatography (HPLC) was applied to stereoselective determination in human and rat plasma of the active metabolite [(2S,1]R,2[S)-trans-alcohol] with three chiral centers of Loxoprofen, a 2-arylpropionic acid antiinflammatory agent after oral administration. Antiserum against the (1'R,2'S)-cyclopentanol moiety was obtained from a rabbit immunized with bovine serum albumin conjugate linked to the propionic acid moiety, in which another chiral center is located. Then, the immunoglobulin G purified by a protein A column was coupled to BrCN-activated Sepharose 4B. Plasma samples were applied to the immobilized antibody column. After washing the column to remove unrequired stereoisomers, a mixture of two diastereomers whose configurations were 1'R,2'S in the cyclopentanol moiety was extracted with 95% methanol. The solvent was evaporated and the residue was derivatized with (+)-(R)-1-(1-naphthyl)ethylamine as a chiral reagent to separate the diastereomers by HPLC. This combined analytical method showed the stereoselective metabolism of Loxoprofen in human, that is, 64% of the total amount of four trans-alcohol stereoisomers was in the 2S, 1'R,2'S form, which is the active metabolite. This phenomenon was also observed in rats given Loxoprofen and its (2S)- and (2R)-isomers, and is explained by stereoselective ketone reduction of Loxoprofen to the (1'R,2'S)-trans-alcohol and inversion from 2R to 2S in the propionic acid moiety. Antibody-mediated extraction should be a selective and simple clean-up method for determining haptens with complicated structures, combined with an appropriate analytical method. © 1992 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040509
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    Editorial (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. i 
    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.530040102
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    Stereoselectivity at α-adrenoreceptor subtypes: observations with the enantiomers of WB 4101 separated through their amides of N-Tosyl-(S)-proline (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 16-20 
    Details
    ISSN: 0899-0042
    Keywords: optical resolution ; enantioselectivity ; chromatography ; dissociation constants ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We present a chromatographic method for the separation and determination of the optical purity of the enantiomers of WB 4101 [(±)-1], one of the most potent and selective α1-adrenoreceptor antagonists. (±)-1 was converted into the amide of N-tosyl-(S)-proline. The two diastereoisomers were separated on silica gel and analysed by HPLC reversed phase. The analytical method described is both accurate and sensitive and allows the optical purity to be determined at very low concentrations and to obtain WB 4101 enantiomers with a purity of more than 99.95%.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040105
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    Stereoselective effect of phenprocoumon enantiomers on the binding of benzodiazepines to human serum albumin (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 21-23 
    Details
    ISSN: 0899-0042
    Keywords: protein binding ; affinity chromatography ; resolution ; allosteric interaction ; increased enantioselectivity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of phenprocoumon enantiomers on the stereoselective binding of 3-substituted 1,4-benzodiazepines to human serum albumin (HSA) was studied by chromatography on HSA-Sepharose column. (S)-Phenprocoumon exerts stereoselective allosteric interaction on the binding of benzodiazepines. The structural requirements of enhanced stereoselectivities are similar to those found previously with (S)-warfarin.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040106
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    Improvement of the enantiorecognition ability of tyrosine-derived chiral stationary phases: Direct resolution of 1,2-amino-alcohols (β-blockers) (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 36-42 
    Details
    ISSN: 0899-0042
    Keywords: tyrosine chiral selector ; enantiomeric separations ; chiral stationary phases ; HPLC ; subFC ; β-blockers ; 1,2-amino-alcohols ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel chiral stationary phase (CSP) derived from tyrosine is evaluated with regard to the first generation commercially available (S)-ChyRoSine-A CSP, under normalphase or reversed-phase liquid chromatographic (NPLC or RPLC) and subcritical fluid chromatographic (SubFC) conditions. The complete scope of application of these CSPs is reviewed. The novel CSP, which bears a bulkier functional group, displays a higher enantiorecognition ability than previously described (S)-ChyRoSine-A toward about 15 families of racemates, whatever the mobile phase conditions.The direct enantiomeric separation of 1,2-amino-alcohols (β-blockers) is carried out on both CSPs. Facile separations are achieved within short analysis times using SubFC mode, whereas very poor separations are obtained using NPLC mode. These results disagree with previous theories (interchangeability between NPLC and SubFC modes).
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040109
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    Use of cyclodextrins in capillary zone electrophoresis for the separation of optical isomers: Resolution of racemic tryptophan derivatives (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 56-61 
    Details
    ISSN: 0899-0042
    Keywords: capillary zone electrophoresis ; enantiomers ; cyclodextrins ; tryptophan derivatives ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this study capillary zone electrophoresis has been used for the separation of racemic tryptophan derivatives in their enantiomers. The effect of cyclodextrins with different shape, added to the background electrolyte, on the migration time of 10 compounds, including methyl tryptophan, hydroxy tryptophan, and tryptophan ester derivatives, has been studied. Furthermore, the effect of cyclodextrins with different shape and that of the composition of the background electrolyte on the enantiomer resolution are discussed. Among different cyclodextrins used α-cyclodextrin and heptakis(2,6-di-O-methyl)-β-cyclodextrin were found to possess the best complexing capacity and thus the resolution power toward analysed compounds.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040112
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    Letter to the editors: Rootworm pheromones: The root of a stereochemical mixup (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 68-70 
    Details
    ISSN: 0899-0042
    Keywords: 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.530040115
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    The influence of aging on the stereoselective pharmacokinetics of propranolol in the rat (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 73-79 
    Details
    ISSN: 0899-0042
    Keywords: aging ; β-adrenergic blocking agent ; enantiomers ; propranolol ; protein binding ; stereoselective pharmacokinetics ; tissue binding ; tissue concentrations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of aging on the pharmacokinetics and the tissue distribution of (R)- and of (S)-propranolol was studied in 3-, 12-, and 24-month-old rats. After both iv and oral administration of rac-propranolol, the plasma concentrations were higher for the (R)- than for the (S)-enantiomer. For the tissue concentrations, the reverse was true. The free fraction of (S)-propranolol in plasma was about 4 times larger than that of (R)-propranolol, and this is the main factor responsible for the differences in kinetics between the two enantiomers. There was a suggestion for a difference in tissue binding between the two enantiomers. With aging, the plasma and tissue concentrations of both enantiomers increase, probably due to a decrease in blood clearance. Tissue binding did not change much with aging. Notwithstanding the marked differences between the kinetics of the propranolol enantiomers, the changes which occur with aging affect both enantiomers to the same degree.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040202
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    The disposition of venlafaxine enantiomers in dogs, rats, and humans receiving venlafaxine (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 84-90 
    Details
    ISSN: 0899-0042
    Keywords: high-performance liquid chromatography (HPLC) ; chiral assay ; naproxen chloride ; pharmacokinetics ; racemate ; stereoselective ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A stereospecific high-performance liquid chromatographic (HPLC) method was developed for the quantitation of the enantiomers of venlafaxine, an antidepressant, in dog, rat, and human plasma. The procedure involves derivatization of venlafaxine with the chiral reagent, (+)-S-naproxen chloride, and a postderivatization procedure. The method was linear in the range of 50 to 5,000 ng of each enantiomer per ml of plasma. No interference by endogenous substances or known metabolites of venlafaxine occurred. Studies to characterize the disposition of the enantiomers of venlafaxine were conducted in dog, rat, and human, following oral administration of venlafaxine. The Cmax, area under the curve (AUC) and (S)/(R) concentration ratios of the (R)- and (S)-enantiomers were compared. In rats, the mean plasma ratio of (S)-venlafaxine to that of (R)-venlafaxine over 0.5 to 6.0 h varied from 2.97 to 8.50 with a mean value of 5.51 ± 2.45. The Cmax, AUC0 - ∞, and t1/2 values of the (R)- and (S)-enantiomers in dogs were not significantly different from one another (P〉0.1). The mean ratios [(S)/(R)] of enantiomers of venlafaxine in human over a 2 to 6 h interval ranged from 1.33 to 1.35 with an overall ratio of 1.34 ± 0.26 (n = 12). These ratios of the enantiomers [(S)/(R)] were not statistically different from unity (P〉0.1) indicating that the disposition of venlafaxine enantiomers in humans is not stereoselective and is more similar to that in dogs than that in rats.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040204
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    Unusual amino acids I: Asymmetric synthesis of furylalanine derivatives (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 110-115 
    Details
    ISSN: 0899-0042
    Keywords: furyldehydroamino acid ; enantioselectivity ; hydrogenation ; chiral rhodium complexes ; amino-phosphine-phosphinite ; ligands enantiomers ; (R)- and (S)-isomers ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nonproteinogenic amino acids are valuable active compounds from their pharmacological and biochemical effects and also as novel building blocks for peptides. The preparation of furylalanine derivatives by asymmetric hydrogenation is described. Amino-phosphine-phosphinite-rhodium complexes catalyzed the hydrogenation of the prochiral dehydroamino acid precursors in high rate and with enantioselectivities of 70 - 90% ee. Substrate-catalyst ratios up to 2,000 can be used depending on the catalyst applied. The procedure turns out to be suitable for larger scale preparations.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/chir.530040208
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    Effective methods for enantioselective analysis of glycidol derivatives by liquid chromatography (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 132-135 
    Details
    ISSN: 0899-0042
    Keywords: sharpless asymmetric epoxidation ; chiral epoxide ; carbamate ; tin(IV) ; catalysis ; 4-hydroxy-2,3-epoxybutyrates ; Chiralcel OD ; Chiralcel® OB ; Zorbax® NH2 ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methodology for determination of the enantiomeric purity of sixteen 2,3-epoxy-1-propanols (glycidols) is delineated. Conversion of these epoxy alcohols and 1-naphthyl isocyanate (NIC) into the 1-naphthyl carbamates is catalyzed by dibutyltin diacetate. Enantiomers of these carbamates are resolved on a Chiralcel® OD column. Advantages of this method include mildness of reaction conditions, nonreliance on diastereomeric derivatization, and appendage of a UV-absorbing chromophore to the analyte.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040212
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    The effect of the enantiomers of ibuprofen and flurbiprofen on the β-oxidation of palmitate in the rat (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 137-141 
    Details
    ISSN: 0899-0042
    Keywords: 2-arylpropionic acids ; nonsteroidal antiinflammatory drugs ; stereoselective ; coenzyme A thioesters ; chiral inversion ; oxidative phosphorylation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of the enantiomers of ibuprofen (0.25 and 0.50 mmol/kg b.w.) and flurbiprofen (0.01, 0.03, and 0.06 mmol/kg b.w.) on the β-oxidation of palmitate were investigated in the rat. The mean cumulative exhalation of 14CO2 after ip administration of [U-14C]palmitic acid was significantly reduced over 6 h by ibuprofen at the higher dose but not at the lower dose for either enantiomer. There was no difference between the enantiomers, the reduction over 6 h being 31.3 and 33.0% for (R)- and (S)-ibuprofen, respectively. There was also a significant inhibition of β-oxidation by flurbiprofen at all 3 doses. Again, there was no stereoselectivity evident in this inhibition. Flurbiprofen was much more potent than ibuprofen in eliciting this effect, the 0.01mmol/kg dose giving a similar reduction in β-oxidation as observed for the 0.50 mmol/kg dose of ibuprofen. The data support the hypothesis that inhibition of the in vivo β-oxidation of palmitate by ibuprofen and flurbiprofen is primarily via a nonstereoselective noncoenzyme A-dependent mechanism. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040302
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    Enantioselective pharmacokinetics of ethotoin in humans following single oral doses of the racemate (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 142-147 
    Details
    ISSN: 0899-0042
    Keywords: anticonvulsants ; epilepsy ; stereoisomers ; hydantoins ; metabolism ; HPLC assay ; chiral columns ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Racemic ethotoin (1000 mg) was administered orally as a single dose to six healthy adult volunteers. Blood samples were collected at appropriate times for 120 h following the dose. Ethotoin was quantified enantioselectively in plasma using a novel chiral column HPLC procedure. One of the enantiomers of the chiral metabolite, 5-phenylhydantoin, was also quantified in the HPLC method. The Cmax and AUC0 - ∞ values for (+)-(S)-ethotoin were significantly greater than those for ( - )-(R)-ethotoin (ratio of mean AUC0 - ∞ values 0.88), but the elimination half-lives of the isomers were virtually identical [12.35 ± 5.15 h for ( - )-(R)-thotoin; 12.28 ± 5.34 h for (+)-(S)-ethotoin]. Parameters derived from AUC0 - ∞ (Cl0/F and Varea/F) also differed slightly between the isomers. The data were interpreted as indicating a small difference in the absorption of the two isomers; it seemed unlikely, in terms of the identical elimination rates, that their metabolic profiles would differ greatly. The 5-phenyl-hydantoin was eliminated with a significantly longer half-life (18.69 ± 6.11 h) than that of ethotoin. Enantioselectivity in the pharmacokinetics of ethotoin is therefore a minor issue. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040303
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    Chiroptical detection during liquid chromatographyPart 4. For Part 3, see Ref. 1.: Applications to stereoanalysis and stereodynamics (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 163-169 
    Details
    ISSN: 0899-0042
    Keywords: polarimetry ; circular dichroism spectra ; optical purity ; thermal interconversion of enantiomers ; optically active sorbents ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Qualitative and quantitative use of polarimetry at one wavelength for detection during liquid chromatography is briefly reviewed. Acquisition of circular dichroism spectra by stopped-flow and nonstop measurements has been further developed. Reasons are given why the angle of rotation, i.e., the polarimeter, is preferred for monochromatic use and differential absorbance, i.e., the dichrograph, for polychromatic requirements. Both methods are demonstrated by novel applications, mainly to enantiomers which interconvert thermally via intramolecular processes. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040306
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    Enantio- and regioselectivity in the epoxide-hydrolase-catalyzed ring opening of simple aliphatic oxiranes: Part I: Monoalkylsubstituted oxiranes (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 178-184 
    Details
    ISSN: 0899-0042
    Keywords: enantioselective hydrolysis ; regioselective hydrolysis ; epoxide hydrolase ; substrate enantioselectivity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The in vitro conversion of chiral aliphatic monoalkylsubstituted oxiranes into 1,2-diols catalyzed by epoxide hydrolase of rat liver microsomes occurs with substrate enantioselectivity and regioselectivity. Substrate enantioselectivity is generally low, and has the same sense, for methyloxirane, vinyloxirane, epichloro-, and epibromohydrin. In the hydrolysis of t-butyloxirane inhibitory effects are involved leading to a complex pattern of enantioselectivity. All investigated monosubstituted aliphatic oxiranes are hydrolyzed with high regioselectivity by nucleophilic attack of water at the unsubstituted ring carbon atom. The enantiomeric excess of the unreacted oxirane substrates and the diol metabolites formed were determined by complexation and inclusion gas chromatography. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530040309
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    Separation of enantiomeric amines and acids using chiral ion-pair chromatography on porous graphitic carbon (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 323-332 
    Details
    ISSN: 0899-0042
    Keywords: chiral separation ; chiral counterion ; ion-pair chromatography ; N-benzyloxycarbonylglycyl-L-proline ; quinine ; indirect detection ; porous graphitic carbon ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of porous graphitic carbon as adsorbing phase for direct separation of enantiomeric acids and amines using chiral ion-pair chromatography is described. The enantiomeric amines were separated as diastereomeric ion pairs with N-benzyloxycarbonylglycyl-L-proline, N-benzyloxycarbonylglycylglycyl-L-proline, or captopril as the chiral counterion. High enantioselectivities were obtained for amines having a hydrogen bonding function in the vicinity of the asymmetrical carbon atom. Quinine was the chiral counterion used to separate the enantiomeric acids. The strongly UV-absorbing quinine improved detection of solutes having low UV-absorbing properties, e.g., (R,S)-2-chloropropionic acid, by “indirect detection.” Retention and stereoselectivity of enanticmeric acids were regulated by the quinine concentration and by the addition of carboxylic acids as well as polar modifiers, e.g., methanol and 2-propanol, to the mobile phase. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/chir.530040511
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    Editorial: Chirality receives award from the association of american publishers (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 341-341 
    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.530040602
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    Chiral hplc-cd studies of the antituberculosis drug (+)-ethambutolPresented at the Second International Symposium on Chiral Discrimination, May 27-31, 1991, Rome, Italy. (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 227-229 
    Details
    ISSN: 0899-0042
    Keywords: circular dichroism ; exciton coupling ; derivatisation ; tetrabenzoylethambutol ; dibenzoyl-2-aminobutan-1-ol ; absolute stereochemistry ; Pirkle column ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Long standing errors in major pharmacopoeiae (BP,USP, and Eu.Ph.) concerning the absolute stereochemistry of the widely used antituberculosis drug (+)-ethambutol have been clarified by unambiguous synthesis and chiral HPLC. on a Pirkle, covalent D-phenylglycine column of perbenzoyl derivatives of each stereomer; the enantiomeric (-)-(R,R) and (+)-(S,S)-ethambutols together with the optically inactive (meso)-(R,S)-ethambutol. This paper describes how circular dichroism (CD) alone and combined with HPLC is used to demonstrate this chiral separation and also to confirm the absolute stereochemistry of each stereomer of ethambutol and its synthetic precursor 2-aminobutan-1-ol from studies of „exciton coupling.“ The strengths and weaknesses of these chiral techniques are discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040405
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  • 84
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    Masthead (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992) 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050101
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  • 85
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    Hydrodynamic simulation of electron heating in conventional and lightly-doped-drain MOSFETs with application to substrate current calculation (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 53-66 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper reviews the state of the art in hydrodynamic simulation of hot-carrier transport in semiconductor devices with application to MOSFET substrate current calculation. Hydrodynamic equations for semiconductors and derived and discretized expressions of these equations for device simulation are presented. Special attention has been given to the discretization of the input power term that appears in the energy conservation equation. A new discretization method for the input power term, based on power generation consideration, is proposed. Energy-based physical models for mobility and impact ionization are described for use in hydrodynamic simulation. Simulation results for both conventional and lightly-doped-drain MOSFETs are presented.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050107
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  • 86
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    A space-domain preconditioned spectral method for non-linear boundary value problems (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 67-81 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A novel spectral procedure for the numerical solution of non-linear boundary value problems is presented. The discrete spectral equations are solved by an iterative algorithm using space-domain preconditioning. The preconditioning operator is obtained by spatial weighting (or windowing) of the exact differential operator.Convergence behaviour of the iterative solution is investigated using an eigenvalue analysis. Theoretical estimates for the convergence rate and accuracy are compared with that achieved in a numerical application - a non-linear boundary value problem from semiconductor device modelling.The method combines the infinite-order exponential accuracy of spectral discretizations with the sparse structure of finite difference equations. This offers numerical advantages in comparison to previously developed Fourier-Galerkin algorithms, particularly important for physically ill-conditioned and strongly non-linear problems. The tradeoff of achievable accuracy versus computer time is easily controlled, thus making essential speed-ups possible for moderate accuracy requirements.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050202
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  • 87
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    Application of the TLM method to two-dimensional scattering problems (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 93-110 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: In this paper the application of the TLM method to electromagnetic scattering problems is investigated. To achieve the full computational benefits of using a time-domain numerical method, pulse excitation can be applied together with Fourier transformation of an output impulse response to yield frequency-domain results over a wide bandwidth. The configuration of the mesh is the same as that used in FD-TD scattering simulations (i.e., separation of the simulation space into total and scattered field regions). To terminate the exterior boundaries of the mesh, absorbing boundary conditions are applied to absorb the outward travelling waves. The effect of the absorbing boundaries on both time- and frequency-domain results is investigated. Frequency-domain scattered far-field patterns are presented for perfectly conducting square and circular cylinders illuminated by an incident plane wave (TM case). Forward and back scattering cross-section results obtained from a single TLM simulation indicate both the accuracy and efficiency of the method for calculating frequency-domain results over a wide bandwidth.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050204
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  • 88
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    An error parameter in TLM diffusion modelling (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 129-137 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper reports the results of a study of an error parameter, m, which has been proposed as a measure for determining the effects on accuracy of the basic assumptions upon which TLM modelling of diffusion and heat flow has been founded. The nature of the m parameter is studied in detail by using a two-dimensional thermal diffusion problem. The use of m in the implementation of automatic timestepping is discussed in a practical three-dimensional engineering problem.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050207
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  • 89
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    Masthead (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992) 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050301
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  • 90
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    Editorial (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 141-141 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050302
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  • 91
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    Panel discussion and open forum (closing session) summary report (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 145-147 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050304
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  • 92
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    TLM modelling of diffusion, drift and recombination of charge carriers in semiconductors (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 219-225 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The paper provides an extension to the one-dimensional TLM diffusion model. The extended diffusion node presented here models the exact transport equation with diffusion drift and recombination of charge carriers in semiconductors. A general algorithm for providing a numerical solution to the transport phenomena is also presented here. The analytical solution for infinitely long semiconductors is compared with the TLM numerical results.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050403
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  • 93
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    A note on the computational storage in the subsectional basis function approach to the method of moments (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 245-250 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: In order to efficiently store the information of a special class of matrices, a very useful algorithm has been derived and applied to the subsectional basis function approach to the method of moments. The algorithm represents a simple law of mapping and allows a reduction in the required computational storage by several orders of magnitude.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050405
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  • 94
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    Numerical analysis of waveguide apertures radiating into lossy media (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 259-274 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Three numerical methods are applied to the analysis of a rectangular waveguide-fed aperture radiating into a lossy media. A novel approach, the finite element method with an impedance boundary condition, and two established methods, the moment method and the mode-matching method, are presented. The methods are compared with respect to accuracy, execution time, memory requirement, and versatility. Four aperture geometries are chosen for detailed study: the full aperture of the rectangular waveguide, and three reduced apertures. The reflection coefficient of the aperture in contact with five known dielectrics is calculated in the frequency range 8·5-11·5 GHz. The theoretical results are validated by measurements performed on an HP8510 network analyser.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050407
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  • 95
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    The use of transmission-line modelling (TLM) for the solution of heat diffusion in electric fuses (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 289-295 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper describes an application of transmission-line modelling (TLM) for the solution of heat diffusion in a three-dimensional metallic structure, surrounded by a dielectric material. The example of heat propagation along an electric fuse embedded in granular silica is presented. Heat is generated by the flow of an electric current through the metallic element and results are shown for the variation of temperature with time and temperature distribution along the fuse element.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050409
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  • 96
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    Chirality evaluation in flavour and essential oil analysis (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 50-55 
    Details
    ISSN: 0899-0042
    Keywords: simultaneous stereodifferentiation of γ(δ)-lactones ; chiral monoterpenes ; stereoselective analysis ; modified cyclodextrins ; genuineness of flavours and essential oils ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The simultaneous stereodifferentiation of all aromarelevant 4(5) alkylsubstituted γ(δ)-lactones is described, using enantioselective multidimensional gas chromatography (MDG), and the column combination OV 1701/octakis(3-O-butyryl-2,6-di-O-pentyl)-γ-cyclodextrin. The method is applicated to the lactone flavour compounds of fruits, indicating the advance to the analytical differentiation between “natural” and “nature-identical” aromas. Modified cyclodextrins are also proved to be powerful tools in the chirospecific CGC analysis of monoterpenoid constituents of essential oils. Optical purity control is discussed as an indicator for their natural origin.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040111
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  • 97
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    Determination of the enantiomeric purity of (--) 2-(N-propyl-n-2-thienylethylamino)-5-hydroxytetralin (n-0923) by chiral stationary phase HPLC (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 62-64 
    Details
    ISSN: 0899-0042
    Keywords: dopamine agonist ; direct chiral separation ; cellulose carbamate stationary phase ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The determination of the enantiomeric impurity, i.e., the percentage of (+) N-0437 (= N-0924) in several batches of (--) N-0437 (= N-0923) by chiral HPLC is described. Enantiomeric impurities were calculated based on the peak areas of the two baseline separated enantiomers in the chromatogram. The enantiomeric impurities found in different batches ranged from 0.02% to 0.11%. Calibration curves of the two isomers of N-0437 (Fig. 1,) were made twice to study the reproducibility and linearity of the method. The absorbance ratio, N-0923/N-0924, was found to be 1.02 with a relative standard deviation (RSD) of 9% over the whole concentration range used for the calibration curves.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040113
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  • 98
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    Electronic Resource
    Masthead (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992) 
    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.530040201
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  • 99
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    Optically-Active compounds via biocatalytic methodsSecond International Symposium on Chiral Discrimination, May 27 - 31, 1991, Rome, Italy. (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 91-97 
    Details
    ISSN: 0899-0042
    Keywords: improving enantioselectivity ; lipase ; enantioselective biocatalysis ; enantiomerically pure compounds ; dihydropyridines ; enantioselective inhibition ; cis-3-hydroxy-6-acetoxy-cyclohex-1-ene ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Different approaches to improve the enantioselectivity of biocatalytic systems are presented. These methodologies have been successfully applied to the preparation of optically active dihydropyridine, calcium antagonists, and cis-3-hydroxy-6-acetoxy-cyclohex-1-ene, a valuable chiral building block for natural products synthesis. The phenomenon of enantioselective inhibition is described and several new heterocyclic amines have been shown to be effective enantioselective inhibitors in the Candida lipase system.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040205
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  • 100
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    Electronic Resource
    FDA'S policy statement for the development of new stereoisomeric drugs (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 338-340 
    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.530040513
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