摘要:

AbstractMeasuring double‐selective and single‐selective proton relaxation rates has been shown to provide directly the dipolar cross‐relaxation rate of any pair of protons in a ligand molecule. The same measurements for a ligand exchanging between a free and a macromolecule‐bound state yield the cross‐relaxation rate of the bound ligand provided that the rate of exchange is relatively fast, thus allowing one to obtain dynamic and conformational features of the bound ligand. As an example, rigid binding of sulphisomidine to bovine serum albumin has been dem

ISSN:0749-1581    

DOI:10.1002/mrc.1260300602

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractAn improved 1D pulse sequence for detecting heteronuclear NOEs on a qualitative level is described and demonstrated. It makes use of shaped selective pulses and takes advantage of sequential perturbation of several proton resonances during one experiment and correspondingly more efficient data accumulation schemes. The method is particularly suitable for assigning quaternary carbons and for establishing connectivities between assigned molecular fragments bound to these quaternary centres.

ISSN:0749-1581    

DOI:10.1002/mrc.1260300603

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

Abstract1‐Alkylcyclohepta[b]pyrrol‐2(1H)‐ones showed rotational isomerism around the CN bond. Two rotamers of the 1‐(2,4‐dimethyl‐3‐pentyl) derivative were isolable by high‐performance liquid chromatography at 0°C. The activation free energy, measured by the line‐shape analysis of the variable‐temperature NMR spectra, was 86.8 kJ mol−1at 25°C. In a bromo derivative, a positive buttre

ISSN:0749-1581    

DOI:10.1002/mrc.1260300604

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

Abstract195Pt NMR data are reported for a series of (η5‐cyclopentadienyl)trialkylplatinum(IV) complexes. Chemical shift differences are rationalized primarily on the basis of substituent electronic properties. Changes in solvent produce relatively modest changes in chemical shift, and the dependence of the chemical shift on temperature and concentration is sufficiently strong to warrant control of these variables for comparative measurements. An improved synthesis of [IPtMe3]4is also describ

ISSN:0749-1581    

DOI:10.1002/mrc.1260300605

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractFluorine‐induced shifts of neighbouring protons were studied by comparing the1H NMR data of 20 fluorinated retinal isomers and their non‐fluorinated counterparts. Concurrent19F NMR data of various isomers, analysed with respect to those of the all‐transfluorinated isomers, showed an interactive effect between the γ‐protons and F. Successful application of the observed trends in1H NMR and19F NMR chemical shifts to retinylidene Schiff bases and protonated Schiff bases demonstrates their importance as practical aids in assigning configuration and predicting relative1H NMR and19F NMR re

ISSN:0749-1581    

DOI:10.1002/mrc.1260300606

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

Abstract13C NMR analyses of substitutedo‐nitroanisoles andn‐butylo‐nitrophenyl ethers are rep

ISSN:0749-1581    

DOI:10.1002/mrc.1260300607

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractSpectroscopic analysis of a lanostane derivative, which was synthesized with a view to its application as an intermediate in chiral building block syntheses, is presented together with the conformational analysis of a secolanostane‐7‐8‐9,11‐t

ISSN:0749-1581    

DOI:10.1002/mrc.1260300608

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractSubstituted phenol–trimethylamineN‐oxide (TMAO) systems were studied. The1H chemical shift of the hydrogen‐bonded proton first increases with decreasing pKaof the phenols and, after a sharp maximum, it then decreases. Thus, the shielding of the hydrogen‐bonded proton by the O atom of the phenol first decreases, and this proton is most deshielded in the 3,4‐dinitronphenol–TMAO system. With a further decrease in the pKaof the phenol this proton becomes shielded again by the O atom of the TMAO molecule. This behaviour of the1H NMR signal is in very good agreement with the changes in the shape of the proton potential obtained from IR spectra. In the case of the strongest hydrogen bond, in the 3,4‐dinitrophenol‐TMAO system, the13C signals are considerably broadened, probably owing to the long lifetime of this bond. Δ14Values were calculated from the13C NMR signals, which should also reflect the changes in the nature of the phenol—TMAO hydrogen bonds. A small difference is obtained between the results obtained from the13C and1H NMR spectra. This difference is caused by the effects of the substituents on the13C NMR signals, which are not taken into account in the calculatio

ISSN:0749-1581    

DOI:10.1002/mrc.1260300609

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe configurations of anagyrine, thermopsine and two other anagyrine‐type quinolizidine alkaloids were revised using15N and 2D NMR in a 400 MHz NMR study. Their1H and13C NMR chemical shifts are given in detai

ISSN:0749-1581    

DOI:10.1002/mrc.1260300610

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractIn order to achieve a better suppression of signals arising from protons non‐bonded to the considered heteronucleus, two (π/4) proton pulses are used in the HMQC sequence: one, at the very beginning, replaces the classical (π/2) pulse and the other is at the end of the sequence. In addition, a spin‐lock purging period improves the elimination process. This novel sequence is shown to provide the conventional heteronuclear correlations and, in addition, relayed homonuclear (proton–proton) correlations. A simple methodology capable of sorting out both types of correlations is proposed. However, this procedure entails a sensitivity loss by a factor

ISSN:0749-1581    

DOI:10.1002/mrc.1260300611

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY