Magnetic Resonance in Chemistry

doi: 10.1002/mrc.1260320201pmid: N/A

Yang, Yanwu; Xu, Xiaolong; Wang, Dehua; Qian, Baogong

doi: 10.1002/mrc.1260320202pmid: N/A

Two‐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 structure.

Bondon, Arnaud; Autret, Marie; Simonneaux, Gérard

doi: 10.1002/mrc.1260320203pmid: N/A

The efficiency of two‐dimensional homonuclear 1H1H NOE spectroscopy in characterizing and fully assigning the 1H NMR spectra of several isomers of meso‐ 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 spectroscopy.

Beloeil, Jean‐Claude; Biou, Valérie; Dauphin, Gérard; Garnier, Jean; Morellet, Nelly; Vaufrey, Françoise

doi: 10.1002/mrc.1260320204pmid: N/A

The conformations of the complexes formed by the ionophore nigericin with Na+ and K+ in CDCl3 solution 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 ion.

Takekawa, Minoru; Aoki, Junji; Iwashima, Satoshi; Ueda, Toyotoshi

doi: 10.1002/mrc.1260320205pmid: N/A

1H and 13C 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 in 13C 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 MNDO‐PM3 calculation.

Zakrzewska, J.; Okon, M.; Vučelić, D.

doi: 10.1002/mrc.1260320206pmid: N/A

1H and 13C NMR assignments of sodium chenodeoxycholate in aqueous solution were obtained for three different bile salt concentrations. 1H and 13C 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 nucleus.

Poppe, Leszek; Sheng, Shuqun; van Halbeek, Herman

doi: 10.1002/mrc.1260320207pmid: N/A

The 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‐range 3J(C‐4, H‐6R) and 3J(C‐4,H‐6S) coupling constants for this residue in panose, with natural 13C isotope abundance, using a newly designed 13C‐filtered 1D TOCSY experiment.

Stoilov, Ivan; Smith, Stanford L.; Watt, David S.; Carlson, Robert M. K.; Fago, Frederick J.; Moldowan, J. Michael

doi: 10.1002/mrc.1260320208pmid: N/A

Detailed analysis of the 1H and 13C NMR spectra of four diastereomers of the important geochemical biomarker (20R)‐5α‐dinosterane was completed using various two‐dimensional 1H1H and 1H13C correlation techniques.

Bernstein, Michael A.; Trimble, Laird A.

doi: 10.1002/mrc.1260320209pmid: N/A

Magnetic 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 instrumentation.

Mezzina, Elisabetta; Ferroni, Fiammetta; Spinelli, Domenico; Chimichi, Stefano; Frenna, Vincenzo

doi: 10.1002/mrc.1260320210pmid: N/A

15N NMR spectra of phenylhydrazine and of 14 para‐ and meta‐substituted phenylhydrazines were measured at natural isotope abundance in DMSO‐d6 solution. 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 if p‐NO2 and m‐F derivatives are excluded from the correlations of para‐ and meta‐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 of 13C and 15N chemical shifts with those of monosubstituted benzenes and substituted anilines.