ISSN:0749-1581    

DOI:10.1002/mrc.1260261002

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

ISSN:0749-1581    

DOI:10.1002/mrc.1260261003

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractAn alternative pulse scheme which simplifies and improves the recently proposed P.E.COSY experiment is suggested for the retention of connected or unconnected transitions in a coupled spin system. An important feature of the proposed pulse scheme is the improved phase characteristics of the diagonal peaks. A comparison of various experiments designed for this purpose, namely COSY‐45, E.COSY, P.E.COSY and the present scheme (A.E.COSY), is also presented. The suppression of unconnected transitions and the measurement of scalar coupling constants and their relative signs are illustrated from A.E.COSY spectra of 2,3‐dibromopropionic acid and 2‐(2‐thienyl)p

ISSN:0749-1581    

DOI:10.1002/mrc.1260261004

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

摘要:

Abstract6Li,1H HOESY was used both for the detection of short lithium–proton distances and for proton spectral assignments of 1,8‐dilithio‐1,2‐diphenylhex‐1‐ene, which exists as a monomer–dimer equilibrium mixture in tetrahydrofuran (THF‐d8). Experiments using magnitude mode, pure absorption and pseudo‐steady‐state mode representations are described. Pure absorption6Li,1H HOESY proved to be

ISSN:0749-1581    

DOI:10.1002/mrc.1260261005

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe relative orientation of substituents in the opposite rings of one of the isomeric 4,7‐Dichloro‐5,8,12,15‐tetramethoxy‐13,6‐bis[4‐(2‐methoxycarbonylphenyl) butyl][2.2]paracyclophanes was determined by establishing by NOE their orientation relative to the bridge protons, which thus served as ‘space‐spy nuclei’. The mutual orientation of these bridge protons was ascertained by the analysis of their coupling constants, obtained from a phasesensitive COSY spectrum. The1H and13C resonances were assigned with the aid of1H COSY and1H/13C inversely

ISSN:0749-1581    

DOI:10.1002/mrc.1260261006

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe1H‐ and13C‐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 appl

ISSN:0749-1581    

DOI:10.1002/mrc.1260261007

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractA novel algorithm based on a two‐dimensional feature match is presented which compares the local features of the region containing a data point with the characteristics of the symmetry‐related area. The proposed method results in a very effective suppression of artifacts andt1noise ridges, equal to the quality obtained by conventional spectral symmetrization. It is superior to conventional techniques because peak shapes are less distorted, it does not create spurious peaks (at the crossing of ridges), does not remove real cross‐peaks when the symmetry‐related cross‐peak is very weak and retains some of the global spectral asymmetry as important information for computerized evaluation p

ISSN:0749-1581    

DOI:10.1002/mrc.1260261008

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractBoth negative, indirect heteronuclear NOE and 2D1H13C relayed incoherent transfer spectroscopy are shown to be useful in oligosaccharide sequencing. The one‐ and two‐dimensional manifestation of the former effect allows the experimental determination of the average carbon–proton distances along the non‐rigid glycosidic bond. However, these preliminary attempts must be further improved for predicting the accurate weights of the preferred c

ISSN:0749-1581    

DOI:10.1002/mrc.1260261009

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractExperimental procedures are presented for the extraction of1H1H and1H13C dipolar couplings from molecules oriented in high magnetic fields without a requirement for high field homogeneity. These couplings impose restrictions on structure in a manner similar to NOE distances and can serve as useful additional constraints for defining structure. The experimental procedures involve pulse sequences which refocus the effects of magnetic field inhomogeneities but which retain dipolar couplings, scalar couplings and, in cases of chemically distinct groups, chemical shift differences. The methods are important for the extension of experiments to higher fields and more complex media where field homogeneity is hard to maintain. The experiments are illustrated using samples containing sodium acetate‐99%13C2or alanine‐99%13C3dissolved in a nematic liquid crystal and oriented in an inhomogeneous magnetic field. Coupling constants obtained from the studies are in good agreement with couplings extracted from one‐dimensional spectra obtained in homogeneo

ISSN:0749-1581    

DOI:10.1002/mrc.1260261010

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe practical aspects of proton‐detected heteronuclear shift correlation spectroscopy are described in detail, with emphasis on the precautions necessary to obtain efficient suppression of signals from protons that are not coupled to13C. The experiment has been used to assign the quaternary carbon signals of a porphyrin and to resolve the proton spectrum of the K3 serotype polysaccharid

ISSN:0749-1581    

DOI:10.1002/mrc.1260261011

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY