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  • Organic Chemistry  (4)
  • Wiley-Blackwell  (4)
  • American Chemical Society
  • American Institute of Physics (AIP)
  • 1995-1999  (4)
  • 1950-1954
  • 1945-1949
  • 1880-1889
  • 1995  (4)
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Verlag/Herausgeber
  • Wiley-Blackwell  (4)
  • American Chemical Society
  • American Institute of Physics (AIP)
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  • 1995-1999  (4)
  • 1950-1954
  • 1945-1949
  • 1880-1889
Jahr
  • 1
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A procedure was developed for the biosynthetic preparation of 15N-labelled guanosine and inosine through the action of a mutant Bacillus subtilis strain. Crude [N2,1,3,7,9-15N]guanosine and [1,3,7,9-15N]inosine were isolated from the culture filtrate by precipitation and anion-exchange chromatography (Scheme 1). No cell lysis and no enzymatic degradation was necessary. The per-isobutyrylated derivatives 1 and 2 were isolated from a complex mixture, purified by virtue of their different lipophilicity, and separated in three steps involving normal-and reversed-phase silica-gel chromatography. One litre of complex nutrient medium yielded 8.44 mmol of guanosine derivative and 2.84 mmol of inosine derivative with high average 15N enrichment (83.5 and 91.9 atom-%, resp.). [N6,1,3,7,9-15N]Adenosine (4) was obtained from 2′,3′,5′-tri-O-isobutyryl[1,3,7,9-15N]inosine (1) through the ammonolysis of its 1,2,4-triazolyl derivative with aqueous 15NH3 (Scheme 2).
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 567-571 
    ISSN: 0899-0042
    Schlagwort(e): enantiomer separation ; chromatographic resolution ; peak integration ; peak size ratio ; calibration curve ; determination of optical purity ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The chromatographic quantitation of very low amounts of an enantiomer in the presence of its antipode can be an extraordinary challenge. If resolution of the peaks is not complete even at extreme mass ratios an integrator will yield inaccurate results due to geometric effects. A given resolution can be adequate for peaks of similar size but result in severe overlap if one of the signals is markedly smaller. If tailing occurs, which is more the rule than the exception, the problem is especially severe for last eluted small peaks. Additional obstacles are detector nonlinearity and other sources of unsatisfactory calibration curves, overloading phenomena, and the possible lack of standards of highest optical purity. These problems have been studied by computer simulations and the liquid chromatographic separation of (R,S)-phenylethyl naphthoic acid amide on a chiral stationary phase. © 1995 Wiley-Liss, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    ISSN: 0947-3440
    Schlagwort(e): Antibiotics ; Sorangium cellulosum ; Macrolides ; Mass spectrometry ; X-ray structure analysis ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Two novel metabolites, sorangiolide A (1) and B (2), were isolated from the mother liquors and side fractions of the sorangicin A pilot-scale production. Their structures were elucidated by 2D-NMR spectroscopy and mass spectrometry as 18-membered macrolactones with a C11-carboxylic acid side chain. Sorangiolide B (2) differs from A (1) by an additional hydroxyl group at C-6 in the side chain. The absolute configuration of sorangiolide A (1) was established by X-ray structure analysis. The sorangiolides show a weak antibiotic activity against Gram-positive bacteria.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    ISSN: 0947-3440
    Schlagwort(e): 4H-Pyrazole synthesis ; Dimethoxycarbene ; Diels-Alder reactions, „inverse“ ; Isopyrazolium ketal cations ; Phthalazinecarboxylates ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 3,6-Diphenyl-1,2,4,5-tetrazine (6) reacts with dimethoxycarbene (7), generated from the 1,3,4-oxadiazoline 8, to yield the 4H-pyrazole 10. This is alkylated to the N-methyl-4H-pyrazolium tetrafluoroborate 12 in high yield. The alkylated, cationic azine system of 12 serves as electron-deficient diene in a [4+ + 2] cycloaddition with inverse electron demand and reacts diastereoselectively with several cyclic olefins as electron-rich dienophiles. The initially formed cationic [4+ + 2] adduct, e.g. 15, is unstable and rearranges probably via 16 to a racemic phthalazinecarboxylic ester of type 17. The crystal structures of the epoxyphthalazinecarboxylic ester 25 and of the trans-annulated cycloocta[d]pyridazine 27 were determined by X-ray diffraction. In contrast to the cyclic olefins, cyclooctyne (28) reacts with the pyrazolium cation 12 to yield the cyclooctapyridiazinium tetrafluoroborate 30 via the cycloadduct 29.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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