摘要:

AbstractAs phenalene is an alternant hydrocarbon it is oxidized very easily to phenalenone, which condenses with various nitrogen nucleophiles in the presence ofp‐toluenesulphonic acid. 2‐Methylindolylphenalene is obtained with 2‐ methylindole, together with other products. This product is a mixture of five tautomers in equilibrium, and these were analysed by homo‐ and heteronuclear two‐dimensional high‐field NMR (500 MHz) s

ISSN:0749-1581    

DOI:10.1002/mrc.1260300802

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe hydrolysis reactions of complexes of the type Pt(L)X2where L is ethylenediamine (en),N,N‐ dimethylenediamine (N,N‐Me2en),N,N‐dimethylenediamine (N,N′‐Me2en) andN,N,N′, N′‐tetramethylethylenediamine (Me4en) were studied. The halo ligands were removed by precipitation with AgNO3and the pH of the resulting filtrate, which was about 2, was adjusted to 5.8 (pD = 6.2). The study of the products formed was carried out by multinuclear NMR spectroscopy. The195Pt NMR spectra showed the presence of several hydrolysed products, especially with en. The hydroxo‐bridged dimer can be synthesized in a pure state with all the ligands except en. The results on the latter ligand contradict the published results on the synthesis of the en hydroxo‐bridged dimer whose biological properties were studied. When Pt(L)I2is used as starting material a small quantity of chloro species was always observed, indicating that the reactant contained a small quantity of Pt(L)ICI. The crystal structure of the [Pt(N,N‐Me2en)(μ‐OH)]2(NO3)2dimer was determined. The compound belongs to theP21/cspace group, with a = 8.262(5),b= 10.960(8),c= 11.405(8), β = 121.07(5)°,Z= 2 and ρcalc= 2.720 mg m−3. The results showed that this is thetransisomer with an inversion centre between the two Pt atoms. There is a considerable strain inside the four‐membered ring, as shown by the reduced internal angles OPtO

ISSN:0749-1581    

DOI:10.1002/mrc.1260300803

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe13C NMR spectra forL‐lysine hydrochloride dihydrate are reported for static samples and samples spinning at the magic angle, which provide resolution of each carbon resonance. The spectra and theT1s,T1pandT1relaxation times for the carbon atoms demonstrate that there is little motion of the side‐chain in this crystal environment. The carbon spin–lattice relaxation is approximately accounted for by rotational motions of the ammonium ions in the range 50–100 ns and motions of the water molecules in the region of 50 ps or 70 ns. The backbone motions are relatively unimportant for relaxation of the carbo

ISSN:0749-1581    

DOI:10.1002/mrc.1260300804

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractHomonuclear scalar coupling constants can be measured in HMQC experiments by increasing the resolution in theF2dimension; in addition, the CH chemical shift correlation can be obtained. This approach is illustrated using the experimental spectra of chenodeoxycholic acid (CDCA). The1H NMR spectrum for CDCA was completely assigned; theJ(H, H) and1J(C,H) values and the CH correlation were obtained from the 2D HMQC spect

ISSN:0749-1581    

DOI:10.1002/mrc.1260300805

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

Abstract14N NQR and NMR spectroscopy were used to show that, in the solid phase, the products of nitrosation of phosphorylacetaldehydes are a mixture of dimers of 1‐(dialkoxyphosphoryl)‐1‐nitrosoethen‐2‐ols and dialkoxyphosphorylacetaldnitrones. The stabilization of the nitrone form is probably made possible by a high degree of conjugation and by the way the dimeric molecules are packed in the crystal, which causes them to be held in fixed positions. When the dimeric 1‐(dialkoxyphosphoryl)‐1‐nitrosoethen‐2‐ols and dialkoxyphosphorylacetaldnitrones are dissolved, they undergo aldo‐enol, nitroso‐oxime and nitrone‐oxime tautomerism, converting gradually into monomeric aldehyde oximes which exist in E‐ and Z‐isomeric forms. The ratios of dimeric nitroso‐enol, nitrone‐enol and monomeric aldehyde oxime forms can be measured by NMR and depend on the solve

ISSN:0749-1581    

DOI:10.1002/mrc.1260300806

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe fluorinated calcium ion chelator 5F BAPTA [1,2‐bis(2‐amino‐5‐fluorophenoxy)ethane‐N,N,N′,N′‐tetra‐acctic acid] was used for the determination of cytosolic Ca2+ion levels in cells and tissues by19F NMR. The possibility of enhancing the sensitivity of these measurements by modifying the relaxation behavior of the chelator was evaluated. These strategies involved the design of a chelator with reducedT1 value viz. 5F RBAPTA {1,2‐bis [2‐amino‐4‐(1‐carboxy‐2‐methyl‐2‐propyl)‐5‐fluorophenoxy]ethane‐N,T,N′,N‐tetraacetic acid}, and the evaluation of chelator with slower exchange characteristics, viz 5F BenzEGTA [1‐(2‐amino‐5‐fluorophenoxy)‐2‐(2‐aminoethoxy)ethane‐N,N,N′,N′‐tetraacetic acid]. Both analogs exhibit chemical shift differences on calcium complexation which are similar to those of the parent compound, 5F BAPTA. In the case of BenzEGTA, a considerably greater pHdependence of the apparent calcium, dissociation constant, KD, also results from the presence of a tertiary amine with a pKvalue above the physioligical range. Additionally, the synthetic approach used for RBAPTA can lead to wide variety of

ISSN:0749-1581    

DOI:10.1002/mrc.1260300807

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractCarbon‐13 spin–lattice relaxation times and NOE factors are reported for a tetrasaccharide, lacto‐N‐neotetraose, in solution as a function of temperature and magnetic field. The data that are outside the extreme narrowing regime are analysed using the ‘model‐free’ approach of Lipari and Szabo. The global reorientation is assumed to be isotropic. The experimental data for the inner rings can be fitted very well using a simplified version of the equations, neglecting the local motion term in the spectral densities. The complete expression for the spectral densities is required for the outer rings, and three different fitting procedures

ISSN:0749-1581    

DOI:10.1002/mrc.1260300808

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

Abstract13C NMR chemical shifts of 22ortho‐substituted nitrobenzenes are reported. Except for those on C‐3 and C‐5, the effects of the interacting nitro group and the substituent are non‐additive. The chemical shifts of theipso,orthoandparacarbons in the spectra and those of monosubstituted benzenes are linearly dependent. Multiparameter correlation analysis shows a predominant field/inductive effect on theipsocompared with both theorthoandparacarbon chemical shifts. It shows that the Reynolds non‐electronic factors evaluate the substituent chemical shifts of theipsoandorthopositions much better than the Charton steric parameters. Moreover, both inortho‐ andpara‐substituted nitrobenzenes the substituent exerts almost the same shift on theipsocarbon atom. This suggests that the studied compounds, except those carrying very bulky groups, show a high tendency

ISSN:0749-1581    

DOI:10.1002/mrc.1260300809

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractOne‐ and two‐dimensional magnetization transfer NMR methods were used to characterize symmetrical and unsymmetrical thiol–disulfide interchange reactions in the glutathione‐cysteamine system. The chemical system consists of four symmetrical and two unsymmetrical thiol–disulfide interchange reactions. In terms of the magnetization transfer experiment, these reactions can be treated as two three‐site exchange networks, one for exchange of the cysteamine moiety among cysteamine, cystamine and the cysteamine part of the glutathione–cysteamine mixed disulfide and another for exchange of the glutathione moiety among glutathione, glutathione disulfide and the glutathione part of the mixed disulfide. Two‐dimensional13C{1H} EXSY NMR spectroscopy was used to identify specific exchange reactions which take place on the time scale of the magnetization transfer experiment at a given pD. The kinetics of the interchange reactions were quantitatively characterized using an overdetermined version of the one‐dimensional13C{1H} EXSY experiment and a13C{1H} selective inversion‐transfer experiment with a linear‐least‐squares analysis of the time course data. Second‐order rate constants were calculated for all six of the thiol–disulfide interchange reactions from the pseudo‐first‐order rate constants obtained from the sel

ISSN:0749-1581    

DOI:10.1002/mrc.1260300810

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractFour derivatives of 2, 6, 6‐trimethylbicyclo[3.1.1]hept‐2‐ene (α‐pinene) and four derivatives of 2‐methylene‐6, 6‐dimethylbicyclo[3.1.1]heptane (β‐pinene) were synthesized and their1H,13C and17O NMR spectra were measured, analysed and assigned. The1H NMR spectral parameters were obtained by computer‐aided analyses of the very complex multi‐spin, second‐order spectra. Some of the13C NMR chemical shift assignments of these compounds reported in the literature should be changed, based on these accurate1H NMR spectral analyses and carbon‐proton chemical shift correlated spectra (COSY). The new assignments are supported by the1J(C, H) values, which show a strong dependence on the bond angle and the steric strain of

ISSN:0749-1581    

DOI:10.1002/mrc.1260300811

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY