摘要:

AbstractA series ofO,O′‐dialkyldithiophosphoric acids have been studied by31P NMR, and a four‐bond31P‐1H scalar coupling has been detected. This coupling is unusual because it is observed between phosphorus and only one of two available protons located on the same carbon, even when the alkyl fragment is simply an alkane that should not show any conformational preference. Variation of the structural features of the alkyl group showed that this coupling involved a “W

ISSN:0749-1581    

DOI:10.1002/mrc.1260251102

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractCorrelation of the nucleic acid base conformation in 43 purine nucleosides with high‐field13C NMR data is described. A key to the correlation is the chemical shift difference between C‐2′ and

ISSN:0749-1581    

DOI:10.1002/mrc.1260251103

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractProton lanthanide‐induced shifts (LIS) were measured for Yb(fod)3‐dibucaine complexes in CDCl3solution. The data were used in conjunction with empirical energy calculations to determine the preferred conformations of dibucaine. The energy calculations and the LIS analysis were in agreement in showing that the plane of the amide group makes an angle of approximately 60° with the plane of the quinoline ring, and also that the two carbon‐carbon bonds between the amide group and the tertiary amine nitrogen are both ingaucheconfigurations. Energy calculations showed that the diethyl tertiary zmine group has very restricted conformational freedom owing to internal steric constraints. The butyl ether group has considerable flexibility but is forced out of the plane of the quinoline ring by steric e

ISSN:0749-1581    

DOI:10.1002/mrc.1260251104

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe13C NMR spectrum of erythromycin A (1) has been unambiguously assigned by use of the 2D INADEQUATE technique in conjunction with DEPT. Previously reported assignments were found to be in error. The effect of solvent, which semms to be negligible on the conformation, was also investigated.

ISSN:0749-1581    

DOI:10.1002/mrc.1260251105

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractNumerous areneselenenamides derived from ammonia, primary and secondary amines and twoN,N‐bis(arylseleno)alkylamines have been studied. The selenenamides bearing an electron‐withdrawing substituent on the aromatic moiety are stable. The1H,13C and77Se chemical shifts and some coupling constants are reported.ForN.N‐dialkyl‐o‐nitrobenzeneselenenamides, the77Se NMR and the17O NMR give evidence of an Se‐O interaction. InN‐alkyl derivatives, a hydrogen bond between the amine group and theortho‐substituent is proposed to explain the deshielding of the s

ISSN:0749-1581    

DOI:10.1002/mrc.1260251106

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractCondensation of substituted cyclohexanones with cinnamaldehydes and morpholine in the presence of anhydrous cerium(III) chloride was carried out. The stereochemistry of the condensed products, variously substituted 2‐morpholino‐4‐phenylbicyclo[3.3.1]nonan‐9‐ones, was deduced by using the1H NMR COSY technique and13C NMR data. In order to draw a general conclusion, the stereochemistry of the sterically comparable 2,4‐diphenylbicyclo[3.3.1]nonan‐9‐one was also studied in detail, using1H NMR COSY and13C NMR data. A general conclusion regarding the boat‐chair conformational preference for such sterically comparablecis‐2,4‐disubstituted bicyclo[3.3.1]nonan‐9‐ones has been deduced, with the substituted ring in the boat form and a diequatorial dispositio

ISSN:0749-1581    

DOI:10.1002/mrc.1260251107

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractCarbon‐13 NMR chemical shifts of sixteen 1‐X,2‐Y,4‐Z‐3,5‐dimethylbenzenes are presented. It is suggested that the conformational changes of the substituents are significant in determining the chemical shifts of these compounds. The deviation from the additivity rule i

ISSN:0749-1581    

DOI:10.1002/mrc.1260251108

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

Abstract13C and1H NMR parameters were measured for isoproterenol in solution. Spin‐lattice relaxation rates were considered and C‐H and H‐HJcouplings were determined. Thetrotamer was shown to occur in a much greater abundance than the twogrotamers. Dynamics in solution were interpreted in terms of a nearly isotropic motion of the α‐hydroxyphenethyl moiety and of a high degree of flexibility of the isopropyl moiety, Relevant distances and dipolar connectivities were measured and used to build up a Dreiding model of the most probable conf

ISSN:0749-1581    

DOI:10.1002/mrc.1260251109

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe carbon and proton spectra for zearalenone and its two C‐6′ alcohol derivatives have been assigned using 2D techniques along with NOE difference spectra and the LIS of the dimethoxy derivative of the β‐alcohol. Low temperature and relaxation time studies on the latter compound support the existence of only one solution conformer for each molecule. Molecular mechanics calculations for each molecule predict the existence of several low energy conformers which differ in energy by less than 3 kcal/mol; however, barriers to conformational interchange could not be estimated. Partial analysis of the proton spectra allows a comparison of the NMR parameters with the MM derived conformations and with x‐ray structural data. The solution conformations of zearalenone and α‐zearalenol are closely related to the solid state co

ISSN:0749-1581    

DOI:10.1002/mrc.1260251110

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractA series of highly substituted biphenyls andm‐quaterphenyls have been synthesized and carbon and proton NMR spectra have been assigned by a combination of 1D and 2D techniques. The XCORFE variation of the long range heteronuclear correlation experiment was found to be particularly valuable in making assignments via H‐C‐C‐13C corre

ISSN:0749-1581    

DOI:10.1002/mrc.1260251111

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY