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  • Wiley-Blackwell  (2)
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  • Wiley-Blackwell  (2)
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  • 1
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The simple combination of thin-layer chromatography on polyamide with subsequent mass spectrometry of the separated compounds together with the carrier material has been employed for unambiguous identification of individual dipeptides in a mixture. The dipeptides were analysed in the form of their dansyl methyl ester derivatives. The appearance of molecular ions in the electron impact mass spectra simultaneously with the ions dans-NH=CHR⌝+ indicating the corresponding N-terminal amino acid residue enables a rapid and sensitive structure elucidation of the dipeptides. The chromatography and mass spectrometry can be performed with 0.2-0.3 nmol dipeptide.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Symmetrical carbonates were formed when the corresponding carbonochloridates containing electron-withdrawing groups were converted with tertiary amines in dry solvents at room temperature. 5-Norbornene-2,3-dicarboximido carbonochloridate (1) and bis(5-norbornene-2,3-dicarboximido) carbonate (5) were used for acylation of OH groups in polymers in the presence of tertiary amines under anhydrous conditions. The influence of the amounts of 1 and 5, the kind and amount of amines, the organic solvent, the reaction time and temperature on the yield of the active carbonate 7 was investigated using bead cellulose as polymer. The reaction based on the catalysis by strongly nucleophilic amines such as 4-dimethylaminopyridine (DMAP) was optimized for preparation of acylated polymers. The formation of cross-linking and cyclic carbonates 9 and 10, respectively, was observed as a side reaction. It was shown that carbonates 9 and 10 can also be obtained as the main products of acylation. The preparation of 9 was also carried out by treating 7 with an excess of DMAP. Examples are presented for the transesterification of 7 with compounds containing OH groups. The acylated polymers were characterized by a specific titration method, UV/VIS and IR spectroscopy. The mechanism of the DMAP-catalyzed acylation of polymers is discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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