摘要:

AbstractThe13C NMR chemical shifts of 126 Steroidal sapogenins published between 1983 and 1993 are listed and critical spectral features and advances made in the NMR characterization of these compounds are discussed as a guide for the identification of the parent skeleton and the determination of substitution patterns. The NMR spectroscopic methods applicable to deduce the complete structure of the oligosaccharide moiety and its linkage to the sapogenin residue are also presented to elucidate the structure of steroidal saponins.

ISSN:0749-1581    

DOI:10.1002/mrc.1260331202

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe synthesis and characterization of hexacoordinated ruthenium complexes of etioporphyrin I (EP) of general formula [(EP)RuL2] (L = teriary phosphine) and of the pentacoordinated complex [(EP)Ru(PPh3)] are reported. The multiplicity observed in the1H NMR spectra of complexes is discussed on the basis of the steric interactions between the axial ligands and the macrocycle.

ISSN:0749-1581    

DOI:10.1002/mrc.1260331203

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractL‐Val‐L‐boroPro, a potent DP IV (CD26) inhibitor, and its non‐inhibitory diastereomerL‐Val‐D‐boroPro, were studied by 1D1H and11H NMR and by 2D1H NMR methods in aqueous solution. Complete 1D1H NMR fine structures were computer analyzed to obtain the1H chemical shifts and spin‐coupling constants. Dihedral angles were derived from coupling constants on the basis of the Altona equation (i.e. an improved Karplus equation). The structures and populations of proline ring conformations were determined with the aid of pseudo‐rotation analysis. Good agreement between the distances derived from NOESY data and dihedral angle‐constrained force‐field calculations was obtained. Structural analysis allowed the identification of the absolute stereochemistry of the α‐carbon of the proline residue, and showed that the active inhibitor is the diastereomer which is homochiral withL‐proline.L‐Val‐L‐boroPro exists largely in a single conformer, in contrast toL‐Val‐D‐boroPro, which adopts two proline conformations in a 2:1 ratio. Analysis of1H and11H NMR spectra proves that inactivation of the inhibitor at physiological pH results from a cyclization reaction in which the freeN‐terminal nitrogen at

ISSN:0749-1581    

DOI:10.1002/mrc.1260331204

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

Abstract31P chemical shift‐structure correlations were established from methyl and ethyl esters of simple phosphonocarboxylic acids. The influence of solvent, acidity, function and neighbourhood of phosphorus was studied. The correlations could be extended and led to the identification of esters obtained when a series of phosphonocarboxylic acids were reacted with alcohols—reactions which were designed as models of cellulose cross‐linking by these

ISSN:0749-1581    

DOI:10.1002/mrc.1260331205

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe total assignment of the1H and13C NMR spectra of four fluoro‐substituted chromenes was deduced from the concerted application of homonuclear correlation (COSY),1H‐detected one‐bond heteronuclear multiple quantum coherence (HMQC) and long‐range (two and three bonds) heteronuclear multiple bond connectivity (HMBC) expe

ISSN:0749-1581    

DOI:10.1002/mrc.1260331206

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractA13C NMR study of a series of novel 2,4‐thio‐substituted 5‐trifluoromethylpoly‐chloropyridines was carried out. The carbon chemical shifts and external long‐range13C,19F NMR coupling constants between the pyridine ring carbons and the trifluoromethyl group are

ISSN:0749-1581    

DOI:10.1002/mrc.1260331207

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe additive behaviour generally observed for the substituent‐induced chemical shifts (SCS) for disubstituted benzenes was examined for a series of aryl 2‐N‐acetamido‐2‐deoxy‐β‐D‐glucopyranosides having a wide range ofparasubstituents with varying possible electronic contributions. The SCS values associated with non‐acetylated and peracetylated glucoside rings inpara‐substituted aryl 2‐N‐acetamido‐2‐deoxy‐β‐D‐glucopyranosides were calculated. The additive nature of SCS analysis forpara‐substituted systems was shown to hold for themetaandparapositions but the very small change in chemical shifts for theorthopositions precluded attempts at analysis of these data. The observation of a good correlation for theipsocarbons for the acetylated compounds compared with a poor correlation for the same site in the non‐acet

ISSN:0749-1581    

DOI:10.1002/mrc.1260331208

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe103Rh NMR chemical shifts of rhodoximes [Rh(dmgH)2(PPh3)X] (1) and organorhodoximes [Rh(dmgH)2(L)R] (2, L = PPh3;3, L = PMe3;4, L = P(OPh)3;5, L = SMe2;6, L = py) were measured with a wide range of anionic ligands X, organo groups R and axial ligands L. The chemical shifts δ(103Rh) in the halide complexes1show the ‘normal halogen dependence’ (Cl>Br>I). δ(103Rh) in2–6depends on the axial base L in the order py>SMe2>PPh3>P(OPh)3≈︁ PMe3and in2on the organo group R in the order Et ≈︁ Me

ISSN:0749-1581    

DOI:10.1002/mrc.1260331209

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractCarbon‐13 NMR signal assignments of some bicyclo[4.3.0]nonan‐4‐ones (hydrindanones) and bicyclo[4.4.0]decal‐4‐ones are

ISSN:0749-1581    

DOI:10.1002/mrc.1260331210

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

ISSN:0749-1581    

DOI:10.1002/mrc.1260331211

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY