摘要:

AbstractTwo‐dimensional NMR techniques were used to obtain a complete proton spectral assignment of nervosin, a natural product with medicinal interest isolated from a Chinese herbal medicine. The full relaxation matrix analysis method was used to process the NOE matrix of nervosin. The three‐dimensional structure in solution was calculated by the combination of the WUPH and WUPH‐S methods, based on NMR experimental data, with molecular mechanics energy minimization calculation. The result indicated that the solution structure of nervosin is similar to the x‐ray st

ISSN:0749-1581    

DOI:10.1002/mrc.1260320202

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe efficiency of two‐dimensional homonuclear1H1H NOE spectroscopy in characterizing and fully assigning the1H NMR spectra of several isomers ofmeso‐ or ring‐substituted deuteroporphyrins is demonstrated. The carbon resonances of the skeleton and the substituents were fully assigned using two‐dimensional reverse heteronuclear shift correlation spe

ISSN:0749-1581    

DOI:10.1002/mrc.1260320203

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe conformations of the complexes formed by the ionophore nigericin with Na+and K+in CDCl3solution determined by ROESY NMR and distance geometry computations are in good agreement with the X‐ray crystallographic data. The structures with the Na+ion are more compact than those with the K+ion, as the latter have a wider cage for the io

ISSN:0749-1581    

DOI:10.1002/mrc.1260320204

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

Abstract1H and13C NMR studies were carried out on benzanthrone and 3‐, 4‐, 6‐, 8‐, 9‐, 10‐ and 11‐chlorobenzanthrone. Complete assignments of proton and carbon resonances were made with the aid of HH‐COSY, NOESY, CH‐COSY and HMBC techniques. Substitution effects of a chlorine atom are not large, but give a systematic change particularly in13C shift values. The anomalous downfield shift of the H‐1 signal in 11‐chlorobenzanthrone was explained by the electrostatic attraction between the electronegative Cl atom, based on the result of an

ISSN:0749-1581    

DOI:10.1002/mrc.1260320205

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

Abstract1H and13C NMR assignments of sodium chenodeoxycholate in aqueous solution were obtained for three different bile salt concentrations.1H and13C NMR chemical shifts of sodium chenodeoxycholate and deoxycholate show slight concentration dependence due to micelle formation. Opposite trends in chemical shifts changes for α‐ and β‐protons cause polarization of the steroid nu

ISSN:0749-1581    

DOI:10.1002/mrc.1260320206

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe C‐6‐methylene protons in the internal glucosyl unit of panose,D‐Glc‐α(1 → 6)‐D‐Glc‐α(1 → 4)‐D‐Glc(α,β), were stereospecifically assigned. The assignment strategy involved the measurement of the long‐range3J(C‐4, H‐6R) and3J(C‐4,H‐6S) coupling constants for this residue in panose, with natural13C isotope abundance, using a newly desig

ISSN:0749-1581    

DOI:10.1002/mrc.1260320207

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractDetailed analysis of the1H and13C NMR spectra of four diastereomers of the important geochemical biomarker (20R)‐5α‐dinosterane was completed using various two‐dimensional1H1H and1H13C correlation

ISSN:0749-1581    

DOI:10.1002/mrc.1260320208

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractMagnetic field gradients were incorporated into the selective COSY experiment. The new gradient‐selected experiment has the expected advantages of significantly improved spectral quality resulting from better artifact suppression and the capacity to acquire spectra using fewer scans. A sample of brucine was used to evaluate the experiment and the resulting spectra were of excellent quality. These experiments may be implemented on commercial instrumentatio

ISSN:0749-1581    

DOI:10.1002/mrc.1260320209

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

Abstract15N NMR spectra of phenylhydrazine and of 14para‐ andmeta‐substituted phenylhydrazines were measured at natural isotope abundance in DMSO‐d6solution. The substituent present exerts a larger influence on the chemical shift of the nitrogen atom directly bound to the aromatic ring (N‐1) than on the second one (N‐2), which shows an attenuated and inverted trend. The chemical shifts of N‐1 and N‐2 give a good cross correlation in both series of compounds ifp‐NO2andm‐F derivatives are excluded from the correlations ofpara‐ andmeta‐substituted phenylhydrazines, respectively. Moreover, N‐1 SCS values show good linear correlations with Hammett substituent constants, with SCSs of directly bound hydrogen (H‐1) and with aniline nitrogen SCSs. The results of dual substituent parameter analysis are also reported together with a comparison of13C and15N chemical shifts with those of monosubstituted benzenes

ISSN:0749-1581    

DOI:10.1002/mrc.1260320210

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractA combination of solid‐state13C CP/MAS NMR methods was used to study the rates of rotation of the phenyl group in 3,5‐dimethyl‐1‐phenylhex‐1‐yn‐3‐ol. The methods used wereT1ρmeasurements, lineshape analysis and 2D exchange spectroscopy over the temperature range 219–284 K. The rates of rotation obtained from the lineshape and 2D EXSY methods give an energy of activation of 58.6 ± 3.0 kJ mol−1. In good agreement with this, theT1ρmeasurements give an activation energy for the rotation of 58.7 ± 3.6 kJ mol−1. The two sets of data are shown to be compatible, within experimental error, with a calculated value for the dipolar carbon–hydrogen interaction (B) from an

ISSN:0749-1581    

DOI:10.1002/mrc.1260320211

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY