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  • 1
    Electronic Resource
    Electronic Resource
    Estimation of the number of enantioselective sites of bovine serum albumin using frontal chromatography (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. 513-515 
    Details
    ISSN: 0899-0042
    Keywords: enantioselective retention ; albumin ; bilangmuir adsorption model ; frontal analysis ; saturation capacity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On a column with bovine serum albumin (BSA) immobilized covalently to silica, the adsorption isotherms of the enantiomers of mandelic acid, tryptophan, 2-phenylbutyric acid, and N-benzoylalanine are measured using a buffered mobile phase. Knowing the amount of BSA immobilized on the column (36 mg), the ratio of the number of enantiomer molecules needed to saturate the enantioselective retention mechanism to the number of BSA molecules is determined. The mean of the set of eight enantiomers is 0.28. These data confirm that at most one enantioselective site exists for each BSA molecule for the kind of enantiomers studied. © 1993 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530050707
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  • 2
    Electronic Resource
    Electronic Resource
    Chloroperoxidase-induced asymmetric sulfoxidation of some conformationally restricted sulfides (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 246-252 
    Details
    ISSN: 0899-0042
    Keywords: sulfoxides ; chloroperoxidase ; asymmetric oxidation ; enantioselective ; episulfide ; gas chromatography ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Asymmetric sulfoxidation by means of a chloroperoxidase from Caldariomyces fumago and hydrogen peroxide as the oxygen source was studied for a series of sterically well-defined substrates. The stereochemistry of the sulfoxidation was the same for all substrates studied. While 2,3-dihydrobenzo[b]thiophene (1) is an excellent substrate (giving 99.5% yield and 99% e.e. of the (R)-sulfoxide), replacement of a methylene group by either a more sterically demanding group or a heteroatom caused a substantial decrease in reactivity or in reactivity as well as enantioselectivity. A further investigation of the lowered catalytic efficiency of chloroperoxidase with these substrates has been carried out in a series of competitive reactions. Thus, benzo[1,3]oxathiole (5) acted as a competitive inhibitor of the enzyme, whereas 1-thiochroman (2) and 1-thiochroman-4-one (3) were shown to be too sterically demanding to significantly compete for the active site. For the oxidation of 2, 3, and 5, it was found that in the low CPO concentration range the chemical yield after 60 min reaction time increased almost linearly with the amount of CPO used. The products from 2 and 3 could be obtained in over 80% yield with an e.e. exceeding 96%. Chloroperoxidase was also found to be an effective catalyst in the oxidation of labile episulfides, yielding the corresponding anti-sulfoxides quantitatively and giving 12% e.e. of (1R, 2R)-sulfoxide in the oxidation of propylene sulfide. Chirality 10:246-252, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Liquid chromatographic resolution of cyclic sulfoximides and their sulfoxide precursors on an N,N′-diallyl-L-tartardiamide-based chiral stationary phase (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 167-172 
    Details
    ISSN: 0899-0042
    Keywords: chromatographic resolution ; enantiomers ; sulfoximide ; sulfoximine ; sulfoxide ; hydrogen bonding ; DATD-based CSP ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two O,O′-diaroyl derivatives of an N,N′-diallyl-L-tartardiamide-based CSP, 3,5-dimethylbenzoyl (CSP I) and 4-tert-butylbenzoyl (CSP II), have been investigated and compared with respect to retention behaviour and resolving capabilities of a series of endocyclic sulfoximides of the 1-R-3-oxo-benzo[d]-isothia (IV)-azole 1-oxide type (R = methyl, octyl, 2′-carboxyphenyl, and 2′-carbethoxyphenyl) and their corresponding sulfoxide precursors. For the sulfoximides, selectivities of 1.44, 1.27, 1.28, and 1.20, respectively, were found on CSP II when eluted with 15% 2-propanol in hexane. Both the sulfoximide compounds and their sulfoxide precursors are well resolved by CSPs I and II. The retention was larger on the former phase, indicating that the molecular skeletons of the analytes studied interact, through hydrogen bonding, more strongly with CSP I than CSP II. Chirality 9:167-172, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    A new class of network-polymeric chiral stationary phases (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 248-256 
    Details
    ISSN: 0899-0042
    Keywords: chiral discrimination ; chiral stationary phase ; network polymer ; DATD ; hydrogen bonding ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A strategy based on the use of homo bi- and multifunctional building blocks for the synthesis of a new class of network-polymeric chiral stationary phases has been evaluated. The key steps comprise acylation of N,N′-diallyl-L-tartardiamide (DATD) and reaction with a multifunctional hydrosilane, yielding a network polymer incorporating the bifunctional C2-symmetric chiral selector. Covalent bonding to a functionalized silica takes place during the latter process. Many of these chiral sorbents show interesting enantioselective properties toward a wide variety of racemic solutes under normal-phase (hexane-based) conditions. The retention is mainly caused by the hydrogen-bonding ability of the analyte, which is regulated by mobile phase additives like alcohol or ether cosolvents. The most interesting chiral stationary phases, in terms of broad enantioselectivity, were obtained from O,O′-diaryol-DATD-derivatives, particularly those containing the 3,5-dimethylbenzoyl and the 4-(tert-butyl)benzoyl moieties. Since high column efficiencies can be obtained with these chiral sorbents, an α-value of ca. 1.2 is usually sufficient to produce baseline separation. A large number of neutral as well as acidic or basic drug racemates are resolved without derivatization. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070411
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