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  • 1
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Phytochemistry 35 (1994), S. 791-794 
    ISSN: 0031-9422
    Schlagwort(e): Ochna calodendron ; Ochnaceae ; biflavonoids ; calodenins. ; chalcone dimers ; lophirones ; stem bark
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Biologie , Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Phytochemistry 31 (1992), S. 981-984 
    ISSN: 0031-9422
    Schlagwort(e): Lophira alata ; Ochnaceae ; lophirochalcone ; lophiroflavan. ; stem bark ; tetraflavonoids
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Biologie , Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Phytochemistry 31 (1992), S. 981-984 
    ISSN: 0031-9422
    Schlagwort(e): Lophira alata ; Ochnaceae ; lophirochalcone ; lophiroflavan. ; stem bark ; tetraflavonoids
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Biologie , Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Phytochemistry 31 (1992), S. 3595-3599 
    ISSN: 0031-9422
    Schlagwort(e): Lophira alata ; Ochnaceae ; lophirochalcone ; lophiroflavan. ; tetraflavonoids
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Biologie , Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 34 (1992), S. 325-330 
    ISSN: 1612-1112
    Schlagwort(e): Field-flow fractionation ; Secondary chemical equilibria ; Colloidal systems ; Retention theory
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The application range of field-flow fractionation (FFF) can be extended to low molecular weight solutes, as demonstrated a few years ago by Berthod et al., by taking profit of secondary chemical equilibria (SCE) occurring between the bulk carrier and a retained carrier component. The theory of solute retention in this SCE-FFF method is developed for any value of the solute distribution coefficient and of the retention ratio of the retained carrier component, provided that the Brownian mode of retention applies for this component and that the flow velocity profile is parabolic. This removes some of the limitations of the model previously developed by Berthod and Armstrong and sheds light on the potentialities of the SCE-FFF method for physico-chemical studies about secondary chemical equilibria in colloidal systems. Remaining assumptions in the model are discussed.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 299-305 
    ISSN: 0887-624X
    Schlagwort(e): polygluconamides ; stereoregular polyamides ; stereoregular nylons ; chiral polyamides ; chiral nylons ; aminoaldonic acids ; sugar polyamides ; carbohydrate monomers ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Two stereoregular polygluconamides, one (3) of polypeptide-type and the other (16) being a polycaproamide containing four stereocenters in the main chain of the repeating unit, have been prepared from D-glucosamine and D-glucose, respectively. The new polyamides were characterized by elemental analysis, and IR, 1H- and 13C-NMR spectroscopies. The molecular weights for 3 and 16 were estimated as 25,000 and 67,000, respectively, on the basis of viscosimetric measurements. Both polyamides display high optical activity; they are highly hydrophilic and readily soluble in water as well as in a variety of organic solvents including chloroform. Polyamide 16 is highly crystalline and yields resistant films with spherulitic texture. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    ISSN: 0886-9383
    Schlagwort(e): Derivatization reaction ; Factorial design ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A number of nucleophiles have been successfully identified and quantified using the Kröhnke reaction with 2,3-diphenyl derivatives of quinolizinium salts. Optimization of the reaction conditions by means of a mathematical model involving analysis of the response surface has led to a better understanding of the factors exerting an influence on the above reaction.The parameters chosen were temperature, reaction time, base concentration, water concentration and nucleophile concentration. The reaction was developed in polar aprotic solvents (acetone, acetonitrile). To facilitate the nucleophilic attack, the presence of an organic base (triethylamine) was necessary, although concentrations in excess of 0·15M did not alter the development of the reaction. Since pharmaceutical solutions are often aqueous, the influence of water on the reaction was studied. Low water volumes have no significant influence on the opening of the quinolizinium ring by the nucleophilic reagent. However, when the water proportion exceeded that of the organic solvent, the fluorescence intensity was lower than expected. Development of the fluorescent reaction product was first detected 5 min after the reaction started. The fluorescence intensity reached its optimum value after 138 min.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 15 (1982), S. 426-432 
    ISSN: 1612-1112
    Schlagwort(e): Polymer analysis ; Molecular weight distribution ; Steric exclusion chromatography ; Field-flow fractionation ; Light scattering
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The classical method for the determination of the molecular weight distribution (MWD) curve of a polymer requires fractionation according to the molecular weight and prior calibration of the separator. It is shown that the use of a dual detection system which includes a molecular mass sensitive detector eliminates the need for prior calibration. The principles of operation of a low-angle light scattering photometer, working as such a detector, are presented, as well as the basic equations for determination of the MWD curve from the elution curve and of the average molecular weights. Then the performances of the light scattering photometer are discussed with special emphasis on the various sources of errors and unaccuracies in these determinations.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    ISSN: 1612-1112
    Schlagwort(e): Field-flow fractionation ; Three-dimensional flow velocity profile ; Rectangular cross-section channel
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The shape of the velocity profile established in a carrier liquid flowing in a duct of rectangular cross-section under conditions of isoviscous flow is well known and can be calculated by using an approximate or the exact solution of Navier-Stokes equation. The series evaluated when applying the exact solution were found to converge very rapidly. Consequently, computing can be substantially shortened without loss of accuracy by summing only the first three terms of the series. A fair agreement between the approximate solution of Takahashi and Gill and the exact solution was obtained for all practically applicable aspect ratios of the separation channels used in field-flow fractionation. This conclusion is of interest when calculating various separation parameters in three-dimensional channels for field-flow fractionation.
    Materialart: Digitale Medien
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  • 10
    ISSN: 0899-0042
    Schlagwort(e): Circular dichroism ; helicity rule ; X-ray structure determination ; ultraviolet spectra ; n - π* and π - π* bands ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Chiroptical properties of a series of 3 and/or 4-heterosubstituted 2(5H)-furanones were investigated with respect to correlation with absolute configuration. The n - π* and π - π* Cotton effects have been assigned on the basis of comparison with the UV spectra in solvents of varying polarity. It is demonstrated that the n - π* transition in 4-amino substituted 2(5H)-furanones appears at shorter wavelength with respect to the π - π* transition. With the exception of 4-pyrrolidino and 4-benzylamino substituted 2(5H)-furanones, other heterosubstituted 2(5H)-furanones follow the butenolide configurational rule (Gawronski et al. J. Org. Chem. 61:1513-1515, 1996). Absolute configuration of 2(5H)-furanone derivatives can also be assigned according to the sign of the Cotton effect (of unknown origin) at 200-230 nm. The structure of four representative sulfur and nitrogen substituted 2(5H)-furanones has been analyzed by X-ray diffraction. The results indicate planarity of the furanone ring and extended conjugation in 4-amino substituted 2(5H)-furanones. Chirality 9:537-544, 1997. © 1997 Wiley-Liss, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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