The use of shift reagents and 13C nuclear magnetic resonance for assignment of stereochemistry to oximes

1983 ◽  
Vol 61 (11) ◽  
pp. 2616-2620 ◽  
Author(s):  
Robert R. Fraser ◽  
Raj Capoor ◽  
John W. Bovenkamp ◽  
Benoit V. Lacroix ◽  
Jack Pagotto
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
The Past ◽  
Configurational Assignment ◽  
13C Nuclear Magnetic Resonance ◽  
Proton Data ◽  
Shift Reagents ◽  
C Nmr ◽  
Nuclear Magnetic

The effects of the shift reagents Eu(dpm)3 and Eu(fod)3 on the 1H and 13C nmr spectra of twelve oximes of diverse structure were examined. The proton data show that the use of proton shifts to assign oxime stereochemistry, as has been done in the past, is unreliable. In contrast, Eu(dpm)3 causes LIS values for the 13C signals of α carbons which are strongly dependent on stereochemistry. Signals for all α carbons anti to the oxime oxygen experience large downfield shifts while all syn carbons are either unaffected or shifted upfield. Thus the effects of Eu(dpm)3 on these 13C signals provides an unambiguous method of configurational assignment to oximes. The effects of Eu(fod)3, though similar to Eu(dpm)3, were less consistent and thus less promising for making configurational assignments.

13C nuclear magnetic resonance studies. 58. 13C spectra of a variety of bicyclo[2.2.2]octane derivatives. Further definition of the deshielding δ effect

1976 ◽  
Vol 54 (6) ◽  
pp. 917-925 ◽  
Author(s):  
J. B. Stothers ◽  
C. T. Tan
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
Magnetic Resonance Studies ◽  
13C Nuclear Magnetic Resonance ◽  
Definition Of ◽  
C Nmr ◽  
Nuclear Magnetic

The 13C nmr spectra of 35 bicyclo[2.2.2]octane and -octene derivatives have been determined to extend our examinations of the effects of stereochemistry on the shieldings of closely neighboring carbons. This series includes a variety of methyl substituted bicyclooctanols and -octenols as well as the corresponding hydrocarbons and some bicyclooctanones. With the bicyclo[2.2.2]octane skeleton it is possible to examine an array of systems having substituents separated by three and four bonds in a variety of orientations. The interactions, termed γ and δ effects, respectively, produce distinctive shielding variations which are useful for stereochemical elucidations. Particularly interesting are the pronounced shifts observed for the carbons bearing closely neighboring substituents. Characteristically, for vicinal substituents, these carbons are shielded while for syn-axial δ interactions, these carbons are deshielded by as much as 8.6 ppm. The results are compared with the trends found in other sterically crowded Systems.

13C nuclear magnetic resonance spectra of some C19-diterpenoid alkaloids and their derivatives

1979 ◽  
Vol 57 (13) ◽  
pp. 1652-1655 ◽  
Author(s):  
S. William Pelletier ◽  
Naresh V. Mody ◽  
Rajinder S. Sawhney
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Conformational Changes ◽  
Nmr Spectra ◽  
Diterpenoid Alkaloids ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
C Nmr ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The natural abundance carbon-13 nuclear magnetic resonance spectra of some C19-diterpenoid alkaloids and their alkamines (lappaconitine, lappaconine, lapaconidine, ranaconine, 14-dehydrobrowniine, aconine, pseudoaconine, deoxyaconine, and hypaconine) have been determined at 15.03 MHz. With the aid of proton decoupling techniques, additivity relationships, and comparison with spectra of related alkaloids, self-consistent and unambiguous assignments of nearly all carbon resonances for these alkaloids have been made. Some important chemical shift trends have been observed, which are useful for identifying the basic C19-diterpenoid alkaloid skeleton and the hydroxy and methoxy group substitution patterns in these alkaloids. On the basis of 13C nmr spectra of lappaconitine and lappaconine, the anthranoyl ester moiety is assigned to the C-4 position in lappaconitine. The 13C nmr spectra of lapaconidine, aconine, and pseudoaconine taken in pyridine and chloroform have been compared to determine the conformational changes of the ring A hydroxy groups in these alkaloids.

13C nuclear magnetic resonance studies. 55. A comparison of the stereochemical dependence of γ- and δ-substituent effects on 13C shieldings in several norbornanols and norbornenols

1976 ◽  
Vol 54 (8) ◽  
pp. 1211-1221 ◽  
Author(s):  
J. B. Stothers ◽  
C. T. Tan ◽  
K. C. Teo
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
Substituent Effects ◽  
Magnetic Resonance Studies ◽  
Considerable Potential ◽  
13C Nuclear Magnetic Resonance ◽  
Insight Into ◽  
C Nmr ◽  
Nuclear Magnetic

The 13C nmr spectra of a series of 50 methyl substituted norbornanols have been determined to gain further insight into the nature of stereochemical effects on the shieldings of carbons having closely neighboring substituents. The relatively rigid norbornyl skeleton permits examination of a variety of orientations of substituents separated by three and four bonds, the γ and δ interactions, respectively. While methyl carbons close to γ substituents exhibit upfield shifts, as is well established, methyl carbons close to δ substituents are significantly deshielded. Even more striking shifts are found for the carbons bearing these closely lying groups. The penultimate carbons in a fragment having a δ interaction between terminal groups show deviations of up to +11 ppm from the shieldings predicted by simple additivity. For fragments having a corresponding γ interaction, the penultimate carbons absorb as much as −10 ppm from the values expected by additivity. These deviations have considerable potential for stereochemical assignments and offer a challenge for theoretical interpretation.Some norbornenols and the acetates of several of the norbornanols were also included in this series and the latter shieldings are compared briefly with those observed for the parent alcohols.

Nuphar thiaspirane sulfoxides. 13C nuclear magnetic resonance determined configuration and utilization in the interconversion of thiaspirane stereochemical types

1978 ◽  
Vol 56 (1) ◽  
pp. 56-61 ◽  
Author(s):  
R. T. LaLonde ◽  
C. F. Wong
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Subsequent Reduction ◽  
13C Nuclear Magnetic Resonance ◽  
Sodium Borodeuteride ◽  
C Nmr ◽  
Nuclear Magnetic

The configuration of the sulfoxide oxygen in syn- and anti-thiobinupharidine sulfoxide was determined by employing the 13C nmr sulfoxidation increments of C-6. Establishment of the 13C nmr line assignments for C-6 included the study of the C-6 and C-6′ deuterated thiobinupharidine and the corresponding sulfoxides. Thermolysis of syn-thiobinupharidine sulfoxide in DMSO and subsequent reduction with sodium borodeuteride in methanol yielded thiobinupharidine, labelled with deuterium only at C-6, and thionuphlutine B, labelled with deuterium at both C-6 and C-6′. Treatment of the anti sulfoxide in xylene or DMSO resulted in no thiobinupharidine or thionuphlutine B. Similarly, syn-neothiobinupharidine sulfoxide gave neothiobinupharidine and a new thiaspirane, thionuphlutine C. These two compounds were not produced from anti-neothiobinupharidine sulfoxide heated in xylene.

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.

15N and 13C nuclear magnetic resonance of deoxydinucleotide monophosphates. II. Protonation of the homo dimers deoxycytidylyl-(3′,5′)-deoxycytidine, thymidylyl-(3′,5′)-thymidine, and deoxyadenylyl-(3′,5′)-deoxyadenosine in dimethyl sulfoxide

1990 ◽  
Vol 68 (11) ◽  
pp. 2033-2038 ◽  
Author(s):  
Giovanna Barbarella ◽  
Massimo Luigi Capobianco ◽  
Luisa Tondelli ◽  
Vitaliano Tugnoli
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Dimethyl Sulfoxide ◽  
Phosphate Group ◽  
Nmr Data ◽  
13C Nuclear Magnetic Resonance ◽  
C Nmr ◽  
Nuclear Magnetic

The preferential protonation sites of the homo dimers deoxycytidylyl-(3′,5′)-deoxycytidine, thymidylyl-(3′,5′)-thymidine, and deoxyadenylyl-(3′,5′)-deoxyadenosine were established by nitrogen-15 and carbon-13 NMR in dimethyl sulfoxide, in the presence of varying amounts of CF3COOH. The nitrogen-15 NMR data show that in d(CpC) the capability of the two N3 nitrogens to accept the proton is slightly different. In d(TpT) and d(ApA) the protonation of the phosphate group leads to significant variations of the chemical shift of the carbons adjacent to phosphorus. Keywords: deoxydinucleotides, protonation, 15N and 13C NMR.

13C nuclear magnetic resonance and Raman investigations of aqueous carbon dioxide systems

1982 ◽  
Vol 60 (8) ◽  
pp. 1000-1006 ◽  
Author(s):  
Theresa M. Abbott ◽  
Gerald W. Buchanan ◽  
Peeter Kruus ◽  
Keith C. Lee
Keyword(s):  
Carbon Dioxide ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Linear Relationship ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Carbonate Ion ◽  
13C Nuclear Magnetic Resonance ◽  
Wide Range ◽  
C Nmr

13C-nmr spectra of carbon dioxide in water are reported for a wide range in pH. Chemical shifts were determined for the following species: CO2(g), CO2(aq), HCO3−(aq), CO32−(aq). A linear relationship was found between the shift of the 13C line and the fraction of carbonate ion calculated to be present, as well as between the ratio of the area under the 1067 cm−1 (carbonate) Raman peak to the sum of the area under the 1067 cm−1 and 1017 cm−1 (bicarbonate) peaks and the fraction carbonate.

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.

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.

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