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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 233-237 
    ISSN: 0899-0042
    Keywords: non-covalent molecular imprinting ; Scatchard plot ; batch rebinding ; site specificity ; boc-amino acids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A potential problem associated with molecularly imprinted polymer (MIP) sorbents is that of cross-reactivity. In this study three MIPs (imprinted with Boc-L-phenylalanine, Boc-L-alanine, Boc-L-glutamic acid) plus a non-imprinted control were prepared and examined for their ability to bind differentially the enantiomers of boc-protected phenylalanine in an effort to quantify cross-reactivity and to develop a predictive model. Batch rebinding studies showed a degree of predictability for a number of MIP-ligand pairs, but other combinations showed unexpectedly high levels of cross-reactivity. Despite the general acceptance of heterogeneity of MIP binding sites, many previous studies report linear Scatchard plots, which is indicative of binding site homogeneity. The data from this study produced curves, clearly demonstrating heterogeneity. The theoretical and practical implications of this heterogeneity are discussed. Chirality 9:233-237, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 238-242 
    ISSN: 0899-0042
    Keywords: non-covalent molecular imprinting ; hydrogen bonding parameters ; solvent properties ; chiral separation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The aim of this study was to rationalise retention behaviour of a chiral solute on molecularly imprinted polymer (MIP) HPLC stationary phases in terms of variation of the mobile phase. It is generally held that the most important interaction governing the separation of enantiomers on such materials is H-bonding, and that retention times increase with decreasing H-bonding potential of the mobile phase. Previous studies have largely concerned mobile phases containing chloroform with acetic acid as a polar modifier. Boc-L-Phenylalanine (Boc-L-Phe-OH) MIPs were prepared, processed, and packed into HPLC columns, which were then used to investigate the retention characteristics of Boc-L-Phe-OH and Boc-D-Phe-OH with a range of mobile phases. The main observations were as follows: (1) in chloroform-based mobile phases there was generally a linear relationship between the H-bond donator factor of the polar modifier and capacity (K′). Results also indicated a hydrogen bond donor parameter value for a polar modifier at which retention became concentration independent; (2) For given values of K′L, K′D varied depending on the polar modifier, indicating that enantiomer resolution was solvent dependent; (3) Using mobile phases based on solvents of lower polarity/H-bonding potential than chloroform, substantial increases in K′ were observed, although enantioselectivity was greatly reduced. Chirality 9:238-242, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0947-3440
    Keywords: Biscalix[4]arene ; Lanthanide ions ; Energy transfer ; Luminescence ; Dinuclear complexes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three types of lower-lower rim linked biscalix[4]arenes that contain carboxylic ester (1) and/or amide functions (2 and 3) at their remaining phenolic oxygen atoms were synthesized. The homo- and heterodinuclear lanthanide ion complexes based on these ligands were used to study the energy transfer between different lanthanide ions. Photophysical studies comparing the luminescence properties of the homodinuclear Eu3+ complex and the heterodinuclear Eu3+-Nd3+ complex of 2 indicated that energy transfer is likely to occur from Eu3+ to Nd3+ with an efficiency of 〉 50%. The luminescence properties turned out to be strongly solvent dependent, which is attributed to structural changes leading to different positions of the lanthanide ions in the cavities provided by the biscalix[4]arene.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0947-3440
    Keywords: Host-guest chemistry ; Calix[4]arenes ; Resorcin[4]arenes ; Dimerization ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Receptor molecules with a preorganized cavity were synthesized by combining two resorcin[4]arene and one calix[4]-arene building block. Based on predictions from a computational study which matches hosts and guests, several steroids, sugar derivatives, and alkaloids were selected for complexation studies. Experimentally the complexation of such guests by these receptor molecules was proven by 1H-NMR spectroscopy (association constants of 1.0-6.0 × 102 M-1 in CDCl3). One of these receptors with four hydroxyl groups forms a dimeric capsule (Kdimer = 11 M-1 in CDCl3). Evidence for this dimerization comes from 1H-NMR, FAB MS spectroscopy, and molecular mechanics and dynamics calculations.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 6 (1835), S. 92-96 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 15 (1838), S. 465-480 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 34 (1886), S. 378-394 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 36 (1887), S. 481-498 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 41 (1889), S. 91-96 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 117-130 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Gas phase ion/molecule reactions have been used to probe the structure of ions obtained by electron impact upon 1-(diphenylmethylene)cyclopropane and 2,2-diphenyl-1-methylenecyclopropane. The resulting ions of molecular composition C16H14 (m/z 206+) were reacted with charge transfer reagents (6·9 〈 IP 〈 8·8eV), giving evidence for the presence of isomeric ions with different reactivities. The less reactive ion is identified as a trimethylenemethane species (TMM+) in which one cyclopropane bond is broken; the more reactive ions are assigned as vertical ions in which the cyclopropane ring is unaffected. The vertical ions have recombination energies of 8·44 ± 0·05eV, whereas TMM+ has one of 7·41±0·05eV. The TMM+ fraction is not constant; it increases with increasing IP of the reagent. This is attributed to a reagent-catalyzed isomerization of the vertical ion to TMM+. In addition, the reagent ions are observed to undergo a unique reaction with the neutral methylenecyclopropane derivatives: electron transfer and ring opening to yield TMM+. These findings limit the application of the customary equilibrium measurements as a method to determine the substrate IP.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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