13C-Nuclear Magnetic Resonance Investigations of Xanthine and Some of its N-Methylated Derivatives

1974 ◽  
Vol 29 (9-10) ◽  
pp. 475-478 ◽  
Author(s):  
Claude Nicolau ◽  
Knut Hildenbrand
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Electron Densities ◽  
13C Chemical Shifts ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

Abstract The 13C-Nuclear Magnetic Resonance spectra of xanthine, 1,3-dimethyl-xanthine (theophylline), 3,7-dimethyl xanthine (theobromine) and 1,3,7-trimethylxanthine (caffeine) were obtained and the lines assigned. Protonation-and N-Methylation parameters are derived by comparison of the 13C-chemical shifts of the protonated cations with those of the neutral molecules and also with those of the xanthine cation. The shifts are discussed in terms of variations in the shielding at the different C-atoms induced by N-methylation and protonation. Approximate correlations are found between the 13C-chemical shifts and the π-electron densities at the C-atoms

13C nuclear magnetic resonance spectra of 3,6-disubstituted pyridazines

1991 ◽  
Vol 69 (6) ◽  
pp. 972-977 ◽  
Author(s):  
Gottfried Heinisch ◽  
Wolfgang Holzer
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Molecular Orbital Calculations ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The 13C nuclear magnetic resonance spectra of 17 3,6-disubstituted pyridazine derivatives have been systematically analyzed. Chemical shifts and various 13C, 1H coupling constants are reported. Attempts were made to correlate these data with results obtained from semiempirical molecular orbital calculations as well as with substituent electronegativities and Taft's substituent constants σI and σR0. Key words: 3,6-disubstituted pyridazines, 13C NMR spectroscopy, 13C, 1H spin coupling constants.

15N Nuclear Magnetic Resonance Spectra of Phenylacetanilides

1988 ◽  
Vol 41 (1) ◽  
pp. 1 ◽  
Author(s):  
C Yamagami ◽  
N Takao ◽  
Y Takeuchi
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Substituent Effect ◽  
Chemical Shifts ◽  
Substituted Anilines ◽  
13C Chemical Shifts ◽  
Meta Position ◽  
Nuclear Magnetic Resonance Spectra ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

15 N substituent chemical shifts (SCS) of a variety of anticonvulsant phenylacetanilides (1) and (2), with a substituent at the para or meta position of the aniline moiety, were analysed by means of DSP (dual substituent parameter) equations. For the sake of comparison, 15N scs of p-substituted anilines (3), and 13C chemical shifts of some ring carbons of (1) and (3) were also investigated. The similarity observed for the correlation of the carbon shifts para to the substituent for (1) and (3) indicates that the nitrogen shifts will be a better probe for the transmission of the substituent effect to nitrogen.

13C nuclear magnetic resonance spectra of some halosteroids, 6-ketosteroids, and related compounds

1979 ◽  
Vol 57 (23) ◽  
pp. 3069-3072 ◽  
Author(s):  
Herbert L. Holland ◽  
Everton M. Thomas
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Long Range ◽  
Chemical Shifts ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Related Compounds ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The 13Cmr spectra of 21-haloprogesterones have been assigned, and chemical shifts compared with those of simple α-haloketones. In addition, the 13Cmr spectra of some C-5α and C-6β halosteroids are presented, and long range 13C—19F coupling observed between C-19 and the C-6β fluorine in some cases. The spectra of several oxygenated analogues and of a series of 5α-hydroxy-6-ketosteroids are also discussed.

13C nuclear magnetic resonance spectra of steroids: the assignments of chemical shifts for C-15 and C-16 in 17β-acetyl steroids

1976 ◽  
Vol 54 (23) ◽  
pp. 3766-3768 ◽  
Author(s):  
Dong Je Kim ◽  
Lawrence D. Colebrook ◽  
T. J. Adley
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Chemical Shift Assignments ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

Previously reported 13C chemical shift assignments for C-15 and C-16 of a number of 17β-acetyl steroids related to progesterone have been shown to be reversed. Based on the revised assignment the effect of bromo- and hydroxy-substitution at C-17 on C-12, C-14, C-15, and C-16 is assessed.

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