摘要:

Abstract1H NMR data for amphotericin B methoxycarbonylmethylamide extracted from DQF‐COSY, ROESY and 1D spectra were compared with x‐ray data for amphotericin B. The conformation of amphotericin B in solution was identical with that found by x‐ray analysis in the solid state. Most of the relay artifacts observed in the ROESY spectrum were recognized, and their pathways of formation were ass

ISSN:0749-1581    

DOI:10.1002/mrc.1260300402

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractA competitive solvation study of Al(III) in water–dimethylformamide (DMF) and water–urea mixtures was carried out by1H and27Al NMR spectroscopy. At temperatures low enough to slow proton and ligand exchange, separate1H resonance signals were observed for bulk and coordinated ligand molecules, and for27Al in different solvation complexes. The1H NMR data confirmed hexacoordination of Al(III) at all concentrations, monodentate binding at the oxygen atom of both DMF and urea, preferential solvation by both organic ligands, the presence of steric hindrance to complexation, particularly by DMF, and the identification of the complexes responsible for the27Al spectra. It also showed a non‐equivalence of the amido groups in urea, in both the complex and free states, presumably owing to hindered rotation about the carbon—oxygen bond. In contrast to previous reports, the27Al spectra for the water–DMF and water–urea solutions showed well resolved signals for the species [Al(H2O)n–6Ln]3+(n= 0–6; L = DMF or urea), including two isomers for one of the water–urea complexes. The27Al NMR data reflected the stronger preferential

ISSN:0749-1581    

DOI:10.1002/mrc.1260300403

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractSeveral different versions of the13C‐detected13C1H shift correlation sequence in phase sensitive mode with partial and full1H1H decoupling are described and evaluated. As expected, they show sensitivity advantages over their absolute value analogues. Further, it is possible partially to edit the 2D spectra since CH2peaks are inverted relative to CH and CH3

ISSN:0749-1581    

DOI:10.1002/mrc.1260300404

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractA tricyclic sesquiterpene ketone, patchoulenone, was isolated from the hexane extract of the root bark ofUvaria narumWall. (Annonaceae). Its structural elucidation was based on detailed 2D NMR spectroscopy, leading to the complete assignment of the1H and13C NMR spectra.

ISSN:0749-1581    

DOI:10.1002/mrc.1260300405

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe1H and13C NMR spectra ofendo‐tricyclo[5.2.1.02,6]deoane (1‐H),endo‐tricyclo[5.2.1.02,6]decan‐2‐ol (1‐OH) and 2‐endo‐tricyclo[5.2.1.02,6]decanyl acetate (1‐OAc) were assigned by the use of1H1H,1H13C and13C13C correlation spectra. The substituent chemical shifts were similar to those observed for the analogous norbornane derivatives.2The flip angle of the five‐membered ring and the conformational composition were estimated from the vicinal1H1H coupling constants. The results were compared with those from molecular mechanics calculations (MMPMI) and semi‐empirical molecular orbital calculations (MNDO). The geometries obtained from the NMR data were close to those from the MMPMI calculations, and the calculated and observed energy differences were within ± 2 kJ mol−1of each other. Theendoconformation of the five‐membered ring was found to be most stable for both 1‐OH and 1‐OAc. The MNDO calculation indicated a close to planar five‐membered ring to be the most stable. This result cou

ISSN:0749-1581    

DOI:10.1002/mrc.1260300406

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractN‐Trimethylsilylaminophosphorus compounds containing phosphorus in different oxidation states [P(III) and P(V)] and with different coordination numbers (2, 3 or 4) were studied by13C,14N,29Si and31P NMR, using a variety of one‐ and two‐dimensional (2D) techniques, including Hahn‐echo extended (HEED) pulse sequences. These techniques were demonstrated by the determination of the signs of all coupling constants involving the1H,13C,15N,29Si and31P nuclei in bis(trimethylsilyl)aminodimethylphosphane (1). Appropriate experiments, including inverse 2D1H{15N} correlations, were performed for the other compounds in order to determine the signs of the coupling constants. A geometric dependence of2J(31P, N,29Si) was proved for bis(trimethylsilyl)amino(tert‐butyl)chlorophosphane (2c), where large negative2J(31P,29Si) and a small positive2J(31P,29Si) values, indicatesynandantiorientations, respectively, of the NSi bond relative to the phosphorus lone pair of electrons. The HEED pulse sequences allow the rapid determination of isotope‐induced shifts,1δ15/14N(31P), as shown for 1, derivativ

ISSN:0749-1581    

DOI:10.1002/mrc.1260300407

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractWell resolved natural‐abundance17O NMR spectra of the eight 1,6‐anhydro‐β‐D‐hexopyranoses and three deoxy model compounds were recorded in aqueous solution at 90°C. The assignment of the resonances was obtained by chemical shift comparison,O‐acetylation, lanthanide shift reagents (Eu3+) and, more generally applicable, by a computational search for the minimum of the sum of the squared deviations between the observed and calculated shifts. The17O chemical shifts were evaluated depending on the orientation of the hydroxyl groups, expressed in terms of additive γ‐ and δ‐interactions between the hydroxyl and ring ether groups. The γ‐gaucheeffects were dominant in a range between −7 and −20 ppm. No appreciable effects have been detected ofanti‐periplanar hydroxyl groups on the17O chemical shifts. Thesyn‐diaxial δ‐interaction was deshielding between hydroxyl groups, but shielding between a hydroxyl group and the bridge‐ether oxygen. A new type of interaction, a δ‐effect between equatorial hydroxyl oxygens in a planar zig‐zag arrangement, was detected. Arguments are presented suggesting that γ‐gaucheeffects between ox

ISSN:0749-1581    

DOI:10.1002/mrc.1260300408

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe1H,13C and17O NMR spectra of several 4,1‐disubstituted naphthalenes, viz. 4‐substituted 1‐ acetylnaphthalenes (series 1), 4‐substituted 1‐nitronaphthalenes (series 2), 4‐substituted 1‐methoxynaphthalenes (series 3) and 4‐substituted 1‐naphthyl methyl sulphides (series 4), were measured. The17O and13C chemical shifts of these 4,1‐disubstituted naphthalenes were compared with those of the corresponding 4,1‐disubstituted benzenes and analysed using the dual substituted parameter (DSP) equation. It is concluded that in series 1, 2 and 4 the substituent effects from the 4‐substituent to the C‐1 carbon and the side‐chain atoms are transmitted more effectively than those in the corresponding 4,1‐disubstituted benzenes, whereas the transmission in series 3 is almost equal to that in the analogous benzene series, viz. 4‐substituted anisoles. The reverse substituent effects displayed by the H‐8 chemical shifts of series 1 and 2 and the existence of linear relationships between the chemical shifts of H‐8 and the17O chemical shifts of the oxygen of both the acetyl and nitro groups in series 1 and 2, respectively, are ascribed mainly to changes in the electron densities on the oxygen of the carbonyl and nitro groups affecting the

ISSN:0749-1581    

DOI:10.1002/mrc.1260300409

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe13C and1H NMR spectra of azithromycin in D2O and DMSO‐d6have been unambiguously assigned using a range of 1 and 2D NMR methods. Similarities to the spectra of azithromycin in CDCl3and of erythromycin A ketone in the same solvents are discusse

ISSN:0749-1581    

DOI:10.1002/mrc.1260300410

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe complexation of four 1,6‐anhydro‐β‐D‐hexopyranoses with europium(III) was studied in aqueous solution by natural abundance17O NMR. The paramagnetic ion induced contact shifts of individual hydroxy and ether resonances to low frequency. A clear indication of tridentate complexes was obtained, proving the involvement of the oxygen atom of the anhydro ring in talosan and mannosan and that of the pyranose ring in

ISSN:0749-1581    

DOI:10.1002/mrc.1260300411

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY