Discussion on 13C nuclear magnetic resonance spectra of structurally rigid cyclonucleosides. Violation of Karplus relationship between 3JC,H and dihedral angles

1984 ◽  
Vol 62 (8) ◽  
pp. 1555-1557 ◽  
Author(s):  
Jun Uzawa ◽  
Kentaro Anzai
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Coupling Constants ◽  
Dihedral Angles ◽  
Vicinal Coupling Constants ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Karplus Relationship ◽  
Derivatives Of ◽  
C Nmr

Using structurally rigid cyclonucleoside derivatives of adenosine, the effect of the oxygen functional groups on the vicinal coupling constants between carbon and hydrogen in, 13C nmr was investigated.

13C nuclear magnetic resonance spectra of the spirobenzylisoquinoline alkaloids and related model compounds

1977 ◽  
Vol 55 (18) ◽  
pp. 3304-3311 ◽  
Author(s):  
Donald W. Hughes ◽  
Bala C. Nalliah ◽  
Herbert L. Holland ◽  
David B. MacLean
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Isoquinoline Alkaloids ◽  
Model Compounds ◽  
Related Model ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
C Nmr ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The natural abundance 13C nuclear magnetic resonance spectra of a number of spirobenzylisoquinoline alkaloids and related model compounds have been recorded. The carbon resonances of the alkaloids were assigned by comparison with the spectra of other isoquinoline alkaloids and with those of the model compounds. It has been shown that 13C nmr spectroscopy may be used to differentiate between diastereomers in this series.

scholarly journals Carbon-13 nuclear magnetic resonance spectra of oxazoles

1979 ◽  
Vol 57 (23) ◽  
pp. 3168-3170 ◽  
Author(s):  
Henk Hiemstra ◽  
Hendrik A. Houwing ◽  
Okko Possel ◽  
Albert M. van Leusen
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Proton Coupling ◽  
Nuclear Magnetic Resonance Spectra ◽  
C Nmr ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The 13C nmr spectra of oxazole and eight mono- and disubstituted derivatives have been analyzed with regard to the chemical shifts and the various carbon–proton coupling constants of the ring carbons. The data of the parent oxazole are compared with thiazole and 1-methylimidazole.

Sporidesmins. XV, The 13C nuclear magnetic resonance spectra of sporidesmin and sporidesmin-D. The evidence in the spectra for strain imposed by an epidithio bridge

1976 ◽  
Vol 29 (10) ◽  
pp. 2307 ◽  
Author(s):  
JW Ronaldson
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Coupling Constants ◽  
Carbonyl Groups ◽  
Proton Resonance ◽  
Methyl Proton ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Electro Negativity ◽  
Magnetic Resonance Spectra

The proton-noise-decoupled 13C N.M.R. spectra of sporidesmin and sporidesmin-D are presented. The detailed assignments were worked out from the undecoupled spectrum of sporidesmin-D. The 3-methyl resonance moved downfield (by 7.3 ppm) upon cleavage of the -S-S- bridge in sporidesmin while the peaks of the two quaternary carbons to which the sulphurs are bound moved upfield (by 4.7 ppm). Lactam N-methyl and indoline N-methyl proton resonance decoupling showed that their p.m.r. assignments should be reversed. The electro-negativity of nitrogen, sulphur and carbonyl groups increased the coupling constants of the 3-CH3 by 7Hz and of the 11-CH by 10 Hz. The carbon of the lactam N-methyl was shielded by 14 ppm. There were six three-bond couplings, four HCN13C and two HCO13C, evident but no non-aromatic HCC13C couplings.

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.

Alkanes with multiple asymmetric centers: synthesis, identification, and 13C nuclear magnetic resonance spectra

1979 ◽  
Vol 57 (4) ◽  
pp. 367-376 ◽  
Author(s):  
Pierre Lachance ◽  
S. Brownstein ◽  
Arthur M. Eastham
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
Aliphatic Hydrocarbons ◽  
Capillary Chromatography ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Capillary Glc ◽  
C Nmr ◽  
Magnetic Resonance Spectra

The identification of aliphatic hydrocarbons containing multiple asymmetric centers can be difficult because of the complexity of the nmr spectra and because in capillary chromatography the diastereomers may be resolved to varying degrees. We suggest that the most effective method for identifying such hydrocarbons is through the pattern of retention times developed by the mixture of diastereomers on a suitable capillary glc column.This paper presents the results of some studies of a series of alkanes having the general form C2H5—(CH—CH3)n—R, where n = 1 to 4, and includes the syntheses and 13C nmr spectra of the compounds.

Nuclear magnetic resonance spectra of pyrrolizidine alkaloids. II. The pyrrolizidine nucleus in ester and non-ester alkaloids and their derivatives

1965 ◽  
Vol 18 (10) ◽  
pp. 1625 ◽  
Author(s):  
CCJ Culvenor ◽  
WG Woods
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Pyrrolizidine Alkaloids ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Vicinal Coupling Constants ◽  
Nuclear Magnetic Resonance Spectra ◽  
Saturated Ring ◽  
Magnetic Resonance Spectra

Chemical shifts and coupling constants are tabulated for the protons of the pyrrolizidine nucleus in 40 pyrrolizidine alkaloids and derivatives. The effect of acylation of hydroxyl substituents on C7 and C9 and the very large difference in chemical shift of the H9 protons in the macrocyclic diester alkaloids is discussed. The direction of buckling of the saturated ring can be ascertained from the H5,H6 vicinal coupling constants or from the width of the H7 multiplet if H7 bears an oxygen substituent. In general, retronecine derivatives are exo-buckled whereas heliotridine derivatives consist of interconverting exo- and endo-buckled forms.

13C nuclear magnetic resonance spectra of alkyl indoles including derivatives of hexahydroechinulin

1976 ◽  
Vol 54 (18) ◽  
pp. 2915-2918 ◽  
Author(s):  
Robert R. Fraser ◽  
Salvatore Passannanti ◽  
Franco Piozzi
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Original Data ◽  
Single Frequency ◽  
Methyl Groups ◽  
Methyl Substituent ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
A Site ◽  
Derivatives Of ◽  
C Nmr

Revised structures for 4-bromohexahydroechinulin and 6-nitrohexahydroechinulin have been established using 13C nmr spectroscopy. For this purpose the substituent parameter for the nitro group at a site flanked by two methyl groups has been measured. Inconsistencies in previous data on alkyl indoles in comparison with hexahydroechinulin suggested a reassignment of the C4 and C6 signals in 5-methylindole, which we have proven by single frequency spin-decoupling experiments. The original data on methyl indoles has been retabulated to include the above reassignments and others recently reported by Gribble et al. A more consistent and reliable set of methyl substituent parameters is thereby obtained.

An unlikely coincidence in coupled 13C nuclear magnetic resonance spectra. 2J(C,H) in 2,6-dichlorotoluene and related molecules

1988 ◽  
Vol 66 (1) ◽  
pp. 184-186
Author(s):  
Ted Schaefer ◽  
James Peeling
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Benzyl Bromide ◽  
Correct Choice ◽  
Theoretical Spectrum ◽  
Coupling Constant ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Derivatives Of ◽  
Nuclear Magnetic

Although as many as 13 peaks are observable in each half of the 13C nuclear magnetic resonance spectrum of C-4 in 2,6-dichlorotoluene at 22.6 MHz, the iterative analysis yields an incorrect value of 2J(C,H). Theoretical spectra for two values of this coupling constant are essentially identical under normal linewidth conditions. At 75.5 MHz, the 13C spectrum displays most of the 48 peaks expected for the X part of an AB2XR3 spectrum, yielding the correct choice for 2J(C,H). The theoretical spectrum at 125 MHz is similar to that at 22.6 MHz but only for the correct 2J(C,H). Correct values of 2J(C-4,H) are given for the 2,6-dichloro derivatives of toluene, ethylbenzene, benzyl alcohol, benzyl bromide, and chloride; these were given incorrectly previously.

Flavan derivatives. XXI. Nuclear magnetic resonance spectra, configuration, and conformation of flavan derivatives

1968 ◽  
Vol 21 (8) ◽  
pp. 2059 ◽  
Author(s):  
JW Clark-Lewis
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Heterocyclic Ring ◽  
Coupling Constants ◽  
Vicinal Coupling Constants ◽  
Nuclear Magnetic Resonance Spectra ◽  
Configuration And Conformation ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

Nuclear magnetic resonance spectra of 80 compounds belonging to several classes of flavan derivative have been analysed, and chemical shifts and coupling constants of heterocyclic ring protons and aromatic protons are tabulated and discussed. Compounds examined include flav-2-enes, flav-3-enes, 3-substituted flavanones and flavans, 2- and 4-substituted isoflavans, 3,4-disubstituted flavans, and flavan-4-ols. The geometrical configurations of substituents in the heterocyclic ring follow unequivocally from the magnitudes of the vicinal coupling constants.

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