摘要:

AbstractCarbon‐13 resonance assignments of cerin acetate, 2α‐pyridine‐N‐oxyfriedelan‐3‐one,epi‐cerin and its acetate, 3α‐hydroxyfriedelan‐2‐one and its acetate, 3‐hydroxyfriedel‐3‐en‐2‐one and its acetate, friedelane‐3,7‐dione, 3β‐hydroxyfriedelan‐7‐one, canophyllol, friedelolactone and friedelolactone‐2α‐yl acetate, friedelane‐2α,3β‐diol and its diacetate, friedelane‐2β,3α‐diyl diacetate, pachysandiyl‐A diacetate and friedelane‐2β‐3β‐diyl diacetate have been made. The carbon signals of 3‐oxofriedelan‐29‐ol and its acetate, methyl 3‐oxofriedelan‐29‐oate, 3‐oxofriedelan‐30‐ol, maytenfoliol, maytensifolin‐A, maytensifolin‐B, pachysonol and pristimerin reported in the literature have also been considered for their specific resonance assignments. A few signal assignments of some friedelanes, viz. friedelan‐28‐ol, friedelan‐29‐ol, friedelan‐30‐ol, friedelan‐29‐al, 3

ISSN:0749-1581    

DOI:10.1002/mrc.1260250202

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractGas‐phase 200 MHz1H NMR spectra of nineteen primary and nine secondary aliphatic amines were obtained at total densities below 0.15 amagat at 148.6 °C. Theoretical predictions of1H chemical shifts of ammonia and methylamine are compared with the gas‐phase experimental values. The amino proton chemical shifts move downfield with increasing alkyl group size. For series of amines with similar structural geometry about the amino nitrogen, the1H amino proton chemical shifts correlate reasonably well with gas‐phase basicities as measured via ion cyclotron resonance spectroscopy (r= 0.95 for a linear fit of chemical shift to the gas‐phase basicity for the primary amines andr= 0.93 for the secondary amines). Gas‐phase1H NMR spectra for linear diamines, hydroxyamines, cyclic amines and substituted anilines were als

ISSN:0749-1581    

DOI:10.1002/mrc.1260250203

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractProton and13C NMR chemical shifts and coupling constants of 2‐aminothiazoles and 2‐iminothiazolines are reported. The one‐bond CH, vicinal H‐H, geminal CH and vicinal CH coupling constants of 2‐aminothiazoles and 2‐iminothiazolines are discussed in terms of tautomerism between amino forms and imino forms. The site of charge centered either on the ring nitrogen or the exocyclic nitrogen atom in the protonated 2‐aminothiazol

ISSN:0749-1581    

DOI:10.1002/mrc.1260250204

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractUnder strongly basic conditions (t‐BuO−/t‐BuOD at 185 °C), the 9,9‐dimethyltricyclo[5.2.1.02,6]‐ and ‐[5.2.1.01,5]decan. 8‐ones and the homologous [5.3.1.0]undecanones undergo multi‐site1H/2H exchange. The total2H uptake was monitored by mass spectrometry, while the individual sites of exchange were established by13C NMR spectroscopy. The relative rates and stereoselectivity of incorporation at each site were determined by2H NMR. These results extend our knowledge on the activating effect of the carbonyl group for proton abstraction at remote centres and are compared with earlier data for several related bi‐ and tricyclic systems. In addition, the13C spectra provide several examples of geminal and vicinal2H‐induced isotope shifts in tricyc

ISSN:0749-1581    

DOI:10.1002/mrc.1260250205

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

Abstract14N NQR frequencies of thiourea complexes with HCIO4, HCI and H2SO4obtained at 77 K are reported. Comparison of NQR data previously obtained in hexamethylenetetramine‐2thiourea showed that the perchloric acid complex was a hydrogen‐bonded complex. A similar comparison with uronium salts showed that the other complexes were thiouronium salts. The protonation site in thiouronium salts was shown to be the S atom. S protonation produced decreases of the N non‐bonding orbital occupation number and increases in those of the NN and NC sigma bonds. Changes in the N non‐bonding orbital produced by protonation were larger in thiourea t

ISSN:0749-1581    

DOI:10.1002/mrc.1260250206

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractHigh‐resolution13C NMR spectra of some proanthocyanidin polymers are presented. They were measured in acetone‐d6‐water (1:1,v/v) solution at 30 °C and at 62.5 MHz. The chemical shifts of selected resonances in these spectra were compared with those of structurally related monomers and oligomers. These comparisons enable certain deductions to be made regarding the stereochemistry and mode of linkage of the constituent flavanoid monomer units of these po

ISSN:0749-1581    

DOI:10.1002/mrc.1260250207

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractTwo‐dimensional chemical shift correlation experiments (COSY and DEPT) may be applied to the detection of small spin‐spin couplings. To increase the sensitivity of these techniques, careful optimization of the experimental parameters is required. Equations applicable to AX spin systems are given for the optimal choice of delay periods in the pulse sequences. Practical applications have been demonstrated for oligosaccharide sequenc

ISSN:0749-1581    

DOI:10.1002/mrc.1260250208

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractA linear relationship was observed between the77Se and125Te chemical shifts in 14 model heterocycles (including 17 new data). The line slope, 1.3, is discussed in terms of Jameson and Gutowski's expression for the Ramsey paramagnetic term, σP. The shifts are also compared with the17O chemical shifts in related compounds

ISSN:0749-1581    

DOI:10.1002/mrc.1260250209

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe13C NMR spectra of nineteen bromo derivatives of 5α‐cholestan‐3‐one, cholest‐4‐en‐3‐one and cholest‐5‐en‐3‐one have been recorded. The substituent effects are analysed and examined with respect to additivity. The more interesting γsynand γantieffects

ISSN:0749-1581    

DOI:10.1002/mrc.1260250210

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

Abstract13C nuclear magnetic resonance spin‐lattice relaxation times (T1) have been used to probe the motional behavior of diphenyl compounds of the type PhXPh (X = heteroatom or group of atoms). Analysis of the relaxation data by employing Woessnier's formalism has permitted an investigation of the influence of the bridge on the rotation of the phenyl groups and the calculation of potential barriers to phenyl rotation in solution, which otherwise are inaccessibl

ISSN:0749-1581    

DOI:10.1002/mrc.1260250211

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY