摘要:

AbstractThe complete assignments of the13C NMR resonances of 1‐acetyl‐, 1‐benzoyl‐, 1‐benzenesulphonyl‐, 1‐methanesulphonyl‐ and 1‐(2‐nitrobenzenesulphonyl)‐isatins and their ring‐opened glyoxylic derivatives are reported. The13C assignments of acylisatins were derived from isatin as a model, while assignments of glyoxylic derivatives were made by complete assignment of compound 8b together

ISSN:0749-1581    

DOI:10.1002/mrc.1260300102

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractIn the structure determination of the C2symmetrical tetrastilbene hopeaphenol, isolated fromCarex pumila, the elucidation of the C‐‐C connectivity between equivalent carbons was needed. From an isotopomeric point of view, three isotopomers,12C12C,12C13C and13C13C, are present with respect to the equivalent carbons connecting each other. Among them, the the12C12C species is undetectable and the13C13C species is excluded owing to its low natural abundance. Therefore, only the12C13C isotopomer is detected in13C NMR and this species is not symmetrical. In the H12C13H system, the separate detection of1J(CH) and2J(CH) was achieved by the INEPT‐LSPD, COLOC and HMBC methods to demonstrate the connectivity between the equivalent carbons from the viewpoint of

ISSN:0749-1581    

DOI:10.1002/mrc.1260300103

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe15N NMR spectra of eight aminoglycosides were interpreted. The effect of mixing 20 mol.% of various aminoglycosides with phosphatidylinositol in aqueous dispersion was studied by15N NMR, and correlations were found between the degree of interaction of the aminoglycoside for phosphatidylinositol and the calculated energy of interaction of the antibiotic with the negatively charged phospholipid and the inhibitory potency of the drug towards lysosomal phospholipase A1, a critical parameter in the nephrotoxic potential of aminoglycosides.

ISSN:0749-1581    

DOI:10.1002/mrc.1260300104

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe17O NMR chemical shift data for a series of substituted 10‐methyleneanthrones and related 10‐alkylanthrones in acetonitrile solution at 75°C are reported. The17O NMR chemical shift value of 10‐methyleneanthrone is shielded byca. 35 ppm compared with that of anthraquinone. The chemical shifts of the 10‐methyleneanthrones range from 493 ppm for 10‐bromomethyleneanthrone to 440 ppm for 10‐diethylaminomethyleneanthrone. A correlation of the17O NMR chemical shifts of the 10‐substituted methyleneanthrones with σ+con

ISSN:0749-1581    

DOI:10.1002/mrc.1260300105

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe analysis of high‐frequency1H and13C NMR spectra and both1H1H homonuclear and1H13C heteronuclear chemical shift correlation experiments indicate thatN‐propynlnormetazocine (NPMH+) is configurationally heterogeneous in solution, with the N‐equatorial isomer being more populated than the N‐axial isomer. The experimental proton–proton coupling constants measured for both diastereoisomers were in agreement with the calculated values for a chair conformation of the piperidine ring. AM1 and MM2 theoretical calculations both indicated the chair conformation as that preferred by the piperidine ring, and the N‐equatorial isomer as being energetically favoured with respect to the N‐axial form. The best fit of the13CT1relaxation time data and the related motional analysis of NPMH+was carried out using the anisotropic model of reorientation with superimposed internal motion. The results showed an increase of the rotational anisotropy of the molecule on passing from the gas phase to t

ISSN:0749-1581    

DOI:10.1002/mrc.1260300106

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe1H and13C NMR spectra of magainin 1, a sterilizing agent of the skin, were studied using two‐dimensional techniques. All the1H and13C NMR resonances were unambiguously determined from a combination of 2D homo‐ and heteronuclear NMR spectrosc

ISSN:0749-1581    

DOI:10.1002/mrc.1260300107

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

Abstract2H solid‐state NMR was employed to study the statio and dynamic properties of perdeuteriated bis(dimethoxythiophosphoryl) disulphide. It was found that sample preparation has a significant influence on the line shapes of the broad‐line solid‐state spectra. It was concluded from inversion–recovery experiments that the methyl groups are in the fast exchange regime, τc<10−ss. The three‐site jump model, with reorientation of the methyl group about aC3symmetry, was assumed as the best explanation of theT1anisotropy. The apparent activation energy calculated from an Arrhenius plot was found to be 5

ISSN:0749-1581    

DOI:10.1002/mrc.1260300108

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractA method is proposed which allows a simple Pake doublet due only to the directly bonded CH pair to be obtained by measuring the local field at the position adjacent to a13C nucleus under proton homonuclear decoupling. This approach allows precise determination of the CH distance even in compounds with high proton dens

ISSN:0749-1581    

DOI:10.1002/mrc.1260300109

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractPrincipal component (PC) or factor analysis was applied to13C substituent effects (literature SCS values) in α to δ positions of 47 aliphatic frameworks with 4–13 different substituents X. Two PC terms for each substituent X are sufficient to describe 99.3% of all C‐α shifts within<± 0.6 ppm, even in the largest data matrix containing 13 × 47 = 611 shifts; shifts in β. γ and δ positions require a third PC term for a similar percentage SCS accuracy. Scaling problems with the different order of magnitudes between α to δ SCS variations are avoided by analysing the corresponding data sets separately; this approach, together with the large data base, leads to a dominating first PC term for C‐α which unambiguously correlates with substituent electronegativities (EN), in contrast to an earlier factor analysis. The same result is obtained by direct comparison of α‐SCS with different EN scales, including for the first time group electronegativities. PCs for β to γ SCS indicate only less consistent trends, which again agree partially with results from direct correlations, butnotwith EN values. The present PC analysis did not include stereochemical descriptors, but furnishes clear distinctions between clusters of (pseudo‐) equatorially or axially substituted compounds. The PC loadings for C‐α also lead to the unambiguous distinction of primary, secondary, tertiary a

ISSN:0749-1581    

DOI:10.1002/mrc.1260300110

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe13C and19F (when appropriate) chemical shifts of a variety of di‐, tri‐ and tetrasubstituted methanes of the type CH2XCOOEt (I), CHXYCOOEt (II) and CXYZCOOEt (III), where the substituents X, Y and Z are F, Br, OEt, OPh, SEt, SPh and NO2, were determined. The prediction of the observed C‐α chemical shifts of I, II and III based on the simple additivity of substituent effects in monosubstituted methanes [MeX; SCS(IV)] is not satisfactory, although those of I are well correlated with SCS (IV). The C‐α chemical shifts of II and III can be correlated in terms of the multi‐parameter analysis of individual SCS (I), the difference between δ (CH2XCOOEt) and δ (CH3COOEt). The origin of the chemical shifts is discussed. The19F chemical shifts of I, II and III were also satisfactorily analysed in terms

ISSN:0749-1581    

DOI:10.1002/mrc.1260300111

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY