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  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 21 (1983), S. 555-563 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1H NMR chemical shifts and the spin-spin coupling constants of the non-exchangeable protons of the N-terminal 13-residue C-peptide of ribonuclease A, obtained by cleavage of the enzyme with cyanogen bromide, have been measured in a 5 mM solution in D2O (pH 3.0, 24°C) at 360 MHz. The titration parameters for end groups (Lys-1 and homo-Ser-13) and side chains (Lys-1, Glu-2, Lys-7, Glu-9 and His-12) have been determined. The chemical shifts, their temperature coefficients and the vicinal coupling constants, 3J(HNCH-α), for the exchangeable NH protons have been measured in a 5 mM solution in D2O/H2O (1:9 v/v) at pH 3.0. An assignment of observed signals to individual residue protons based on characteristic shifts, standard double resonance experiments, spectral simulations and titration shifts is proposed. All experimental evidence indicates that under the conditions studied the C-peptide is in a random coil form.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 8 (1976), S. 49-55 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The complete analysis of the 1H NMR spectra of the six acetylated glycals as well as that of tetra-O-acetyl-2-hydroxy-D-glucal has been carried out. The conformation of these compounds, as determined from the proton couplings (±0.05Hz) obtained, has been interpreted in terms of a rapid interconversion equilibrium between the two possible dihydropyran half-chair conformations. A computer treatment of all observed couplings has been carried out to obtain optimized values for the populations and couplings characteristic of the two alternative half-chair conformations. The rotamer populations of the acetoxy-methyl group are discussed on the basis of the measured 5J16 and 5J36 couplings.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0749-1581
    Keywords: 13C NMR ; Diterpenes ; ent-Beyeranes ; ent-Beyer-15-enes ; Bicyclo[3.2.1]octanes ; Substituent effects ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A detailed analysis of the 13C NMR spectra of 39 isomeric ent-beyer-15-enes and ent-beyeranes functionalized at C-7, C-14, C-15 and C-16 has been performed. This diterpenic skeleton is a good example of a semirigid bicyclo[3.2.1]octane system. The sensitivity of 13C shielding to the stereochemical environment, particularly in polyfunctional compounds, has been confirmed. In some cases the ent-beyer-15-enes and ent-beyeranes show similar behaviour to that of similarly functionalized bicyclo[3.2.1]octane derivatives, but in other cases the shielding effects are very different. The compounds studied are a good model for the evaluation of shielding effects in exo/endo isomers of strained and rigid carbocyclic compounds.
    Additional Material: 12 Tab.
    Type of Medium: Electronic Resource
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