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  • 1
    Digitale Medien
    Digitale Medien
    Effects of misoptimization of the BIRD pulse on one-bond modulation effects in long-range heteronuclear chemical shift correlation spectra (1989)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 27 (1989), S. 123-126 
    Details
    ISSN: 0749-1581
    Schlagwort(e): Long-range heteronuclear correlation ; 2D-NMR ; One-bond modulation ; BIRD pulse ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: BIRD pulses have been shown to provide an effective means of decoupling one-bond modulation of long-range response intensity. It is not possible to optimize the BIRD pulse effectively when there is a range of one-bond coupling constants. To examine the effects of misoptimization of the fixed delays (τ) in the BIRD pulse, the simple alkaloid norharmane was employed. Long-range heteronuclear correlation spectra were recorded using a modified pulse sequence containing a BIRD pulse midway through the Δ2 interval. The experiment was optimized for 10.3 and 11.1 Hz, which correspond to a valley and a peak in the response intensity curve when the experiment is performed without the BIRD pulse midway through Δ2. The delays in the BIRD pulse were variously optimized for values ranging from 80 to 175 Hz. The results suggest that the BIRD pulse is effective in decoupling one-bond modulations of response intensity even when the τ delays are grossly misoptimized for the one-bond coupling constantin question.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrc.1260270205
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  • 2
    Digitale Medien
    Digitale Medien
    Total assignment of the 1H and 13C NMR spectra of phenanthro[9,10-b]thiophene: Concerted use of two-dimensional NMR techniques (1989)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 27 (1989), S. 318-322 
    Details
    ISSN: 0749-1581
    Schlagwort(e): 2D NMR ; Heteronuclear chemical shift correlation ; Heteronuclear relayed coherence transfer ; Proton-detected long-range heteronuclear multiple quantum coherence ; HMBC ; Low-pass J-filtration ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The 1H and 13C NMR spectra of phenanthro[9,10-b]thiophene were totally assigned using a combination of twodimensional NMR techniques. Direct hetcronuclear correlations were established using heteronuclear chemical shift correlation with semi-selective proton decoupling. Two methods were employed to establish the identity of vicinal neighboring protons: heteronuclear relayed coherence transfer and low-pass J-filtered heteronuclear relayed coherence transfer. The versatilities of the two techniques were compared. Quaternary carbon resonance assignments and the orientations of individual spin systems relative to one another were accomplished using the proton-detected long-range heteronuclear multiple quantum coherence experiment (HMBC). Key long-range inter-ring proton homonuclear spin couplings served to confirm the orientations of the proton spin systems.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrc.1260270404
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  • 3
    Digitale Medien
    Digitale Medien
    Total assignment of the 1H- and 13C-NMR spectra of dinaphtho[1,2-b:1′,2′-d]thiophene through the concerted use of two-dimensional NMR techniques (1988)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 26 (1988), S. 839-847 
    Details
    ISSN: 0749-1581
    Schlagwort(e): 2D NMR ; heteronuclear chemical shift correlation ; COSY ; double quantum coherence ; zero quantum coherence ; relayed coherence transfer ; J-filtration ; long range heteronuclear shift correlation ; BIRD pulse ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The 1H- and 13C-NMR spectra of dinaphtho[1,2-b:1′2′-d]thiophene (1), a sulfur-containing polynuclear heteroaromatic, have been totally assigned using a combination of two-dimensional NMR techniques. Techniques applied were standard proton-proton COSY, proton zero-quantum coherence (ZQCOSY, optimized to 7 Hz and to 1.75 Hz), proton double quantum coherence (DQCOSY, optimized to 7 Hz), broad-band decoupled (both dimensions) proton-carbon chemical shift correlation, long-range proton-carbon chemical shift correlation, and proton-carbon heteronuclear relayed coherence transfer. A comparison of these methods on 1 showed the most useful information concerning connectivities to be obtained from the zero-quantum coherence and long-range heteronuclear correlation experiments. A detailed critique of each type of experiment is given in the context of applications to polynuclear aromatics.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrc.1260261007
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  • 4
    Digitale Medien
    Digitale Medien
    Modulation of methylene carbon response intensity in long-range heteronuclear 2D NMR chemical shift correlation spectra (1988)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 26 (1988), S. 24-27 
    Details
    ISSN: 0749-1581
    Schlagwort(e): two-dimensional NMR ; 2D-NMR ; long-range heteronuclear correlation ; response intensity modulation ; modulation decoupling ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Several recent papers have dealt with the modulation of protonated carbon response intensities in long-range heteronuclear 2D NMR chemical shift correlation spectra. Expressions describing the one-bond modulation of the response intensity of the C-3 methylene resonance of 6,7-dimethoxy-3,4-dihydroisoquinoline, and the decoupling of this modulation afforded by a BIRD pulse located midway through the Δ2 refocusing delay, are presented with experimental confirmation. Long-range response intensities are related to the conventional heteronuclear chemical shift correlation spectrum optimized for transfer from the directly attached proton.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrc.1260260107
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  • 5
    Digitale Medien
    Digitale Medien
    Elimination of direct responses and one-bond modulations in long-range heteronuclear chemical shift correlation spectra through the use of low-pass J filters and BIRD pulses (1988)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 26 (1988), S. 28-32 
    Details
    ISSN: 0749-1581
    Schlagwort(e): two-dimensional ; NMR ; 2D-NMR ; long-range heteronuclear chemical shift correlation ; bilinear rotational decoupling ; BIRD pulses ; low-pass J filtering ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Modified long-range heteronuclear chemical shift correlation pulse sequences which incorporate both BIRD pulses midway through the Δ2 magnetization transfer delay and low-pass J filters are described. The BIRD pulse provides the means of decoupling one-bond modulations of response intensity when magnetization is transferred to protonated carbons. The one- and three-step low-pass J filters utilized eliminate responses due to directly attached protons over a range of one-bond coupling constants.Results obtained by long-range optimization of the conventional heteronuclear chemical shift correlation pulse sequence, the previously reported pulse sequence containing only the BIRD pulse midway through Δ2 and the two new pulse sequences described in this work are compared using 2,3-dihydrofuran as a model compound.The low-pass J filters have no adverse effects on the ability of the BIRD pulse to decouple one-bond modulations. Modulation decoupling in the modified pulse sequences was confirmed using the 3J(C-3, H-1) coupling pathway of the simple alkaloid norharmane. The response intensities, however, were up to 10% lower with a one-step low-pass J filter when compared with the simpler pulse sequence containing only the BIRD pulse midway through Δ2.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrc.1260260108
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  • 6
    Digitale Medien
    Digitale Medien
    Synthesis and spectroscopic studies of 2-(1,1-dimethylhydrazono)propyl phosphonates (1988)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 26 (1988), S. 471-474 
    Details
    ISSN: 0749-1581
    Schlagwort(e): diethyl 2-(1,1-dimethylhydrazono)propyl phosphonate ; ethyl α-benzoyl-β-(1,1-dimethylhydrazino)crotonate ; 2D NMR ; heteronuclear chemical shift correlation ; HC-COSY ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The synthesis of diethyl 2-(1,1-dimethylhydrazono)propyl phosphonate (1) and its 1-benzoyl derivative (2) is described. The 1H and 13C NMR spectra of 1 and 2 have been completely assigned with the aid of two-dimensional 1H—13C correlation NMR spectroscopy. Spectral data for ethyl α-benzoyl-β-(1,1-dimethylhydrazino)crotonate (5) were also obtained.The results show that 1 exists predominantly in the E- and Z-isomeric forms in a ratio of ca 2:1, and 2 occurs almost exclusively in the E-form. Data for 5 indicate that this compound exists in the Z- and E-forms in a ratio of ca 3:1.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrc.1260260607
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