1H and 13C nuclear magnetic resonance assignment of fluorescent olefinic sterol derivatives for use as membrane probes

1987 ◽  
Vol 65 (8) ◽  
pp. 1784-1794 ◽  
Author(s):  
Jacinta Drew ◽  
Jean-Robert Brisson ◽  
Peter Morand ◽  
Arthur G. Szabo
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Nmr Spectroscopy ◽  
Chemical Shifts ◽  
Methyl Groups ◽  
Coupling Constant ◽  
13C Nuclear Magnetic Resonance ◽  
High Degree ◽  
Degree Of Similarity ◽  
C Nmr ◽  
Membrane Probes

A number of fluorescent steroids with unsaturated sidechains have been analyzed by high resolution 1H and 13C nmr spectroscopy. The geometry of the olefinic systems was assigned on the basis of 1H–1H shift-correlated spectra (COSY) and selected nOe difference experiments. For one of these compounds, a 13C–1H shift-correlated spectrum, a COSY spectrum, a 1H J-resolved spectrum as well as nOe experiments on the angular methyl groups permitted complete ring proton assignment and coupling constant analysis. The high degree of similarity of the ring carbon 13C chemical shifts of these steroids and cholesterol would indicate that the former have the potential for use as fluorescent probes of cholesterol domains in membranes.

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.

Solvent and α-substituent perturbations of the 2H/1H isotope shifts in the 13C nuclear magnetic resonance of toluene-α-d3

1987 ◽  
Vol 65 (3) ◽  
pp. 534-537 ◽  
Author(s):  
Ted Schaefer ◽  
James Peeling ◽  
Rudy Sebastian
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Refractive Index ◽  
Magnetic Resonance ◽  
Isotope Effect ◽  
Electron Donor ◽  
Chemical Shifts ◽  
Aromatic System ◽  
Expectation Value ◽  
13C Nuclear Magnetic Resonance ◽  
C Nmr

The 2H/1H isotope effect on 13C nmr chemical shifts, nΔ, n being the number of intervening bonds between 2H and 13C nuclei, in toluene-α-d3 is solvent dependent. For example, 1Δ ranges from 817 ppb in CD3OH to 869 ppb in acetone-d6 solutions, a positive number indicating increased shielding in the deuterated species. 1Δ is linearly dependent on a function of the refractive index, nD, of the solvent, allowing extrapolation to nD = 1. The hyperconjugative model, in which the C—D bond is a poorer electron donor to the aromatic system than is a C—H bond, is tested for the substituents CH2D, CHD2, CD3, CHDCH3, CD2CH3, CD(CH3)2, C6H5CHD, and (C6H5)2CD. For these substituents, the negative 5Δ is linearly related to the expectation value of sin2 θ; θ is the angle by which the C—D bond twists out of the benzene plane. The model fails quantitatively for C6H5CD2X (X = Cl, COOH, CN, OH). For X = OH, very large negative 5Δ and 3Δ values are observed. nΔ is also reported for 4-ethyltoluene-α-d3 and benzaldehyde-α-d1. For the latter, all nΔ values are positive other than 5Δ, which vanishes in acetone-d6 solution.

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.

The structures and reactions of stannylene acetals from carbohydrate-derived trans-diols. Part I. In the absence of added nucleophiles

1990 ◽  
Vol 68 (7) ◽  
pp. 1007-1019 ◽  
Author(s):  
T. Bruce Grindley ◽  
Rasiah Thangarasa
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Nmr Spectroscopy ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Chemical Shifts ◽  
The Other ◽  
Resonance Spectroscopy ◽  
Pyranose Ring ◽  
Regioselective Reactions ◽  
C Nmr

Di-n-butylstannylene acetals of benzyl 4,6-O-benzylidene-α- and -β-D-glucopyranoside and galactopyranoside have been prepared and studied in solution by 1H, 13C, and 119Sn nuclear magnetic resonance spectroscopy. The species present in solution have been identified from the 119Sn nmr spectral data, by comparison of the 13C nmr chemical shifts of the stannylene acetals and their precursor diols and also by analysis of the products of reactions performed without added nucleophiles. The orientations of the two substituents on the carbons in the pyranose ring attached to the carbons in the stannylene ring determine the structures adopted by the stannylene acetal in solution. If one substituent is axial and the other equatorial, the stannylene acetal exists as a single symmetrical dimer in which the two oxygen atoms in the two 1,3,2-dioxastannolane rings adjacent to the axial substituents are dicoordinate. A stannylene acetal with two adjacent equatorial substituents exists as a non-interconverting mixture of dimers; one with two adjacent axial substituents is present as a rapidly interconverting mixture of dimers, trimers, and tetramers. Benzoylation and benzylation of the latter two types of stannylene acetals have been performed and have been shown to be only slightly regioselective in contrast to the known highly regioselective reactions of the first type. Only when single dimers are present are regiospecific or highly regioselective reactions obtained. The causes of the variation in the species present and of the reaction regioselectivity for different stannylene acetals are discussed. Keywords: stannylene acetals, 1,3,2-dioxastannolanes, 119Sn NMR spectroscopy, regioselective reactions, carbohydrates.

Medium-sized cyclophanes. XX. 13C nuclear magnetic resonance of cyclophanes: p-orbital compression shift and orbital deformation

1976 ◽  
Vol 54 (21) ◽  
pp. 3412-3418 ◽  
Author(s):  
Tetsuo Takemura ◽  
Takeo Sato
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Molecular Geometry ◽  
Methylene Carbon ◽  
Upfield Shift ◽  
13C Nuclear Magnetic Resonance ◽  
Orbital Axis ◽  
C Nmr

The 13C nmr spectra of [2.2]meta-, metapara-, and paracyclophanes were determined. By comparing the chemical shifts with those of acyclic models two types of anomalies were revealed.(1) Bridging methylene carbon resonances for [2.2]metacyclophanes having an alkyl group ortho to the bridge were shifted upfield as a result of van der Waals' compression. The upfield shift is much larger (5–12 ppm) for cyclophanes than for models (2–4 ppm) reflecting the rigid nature of the molecular geometry of the former.(2) Interestingly, inner aryl carbon resonances in [2.2]metacyclophanes and protonated aryl carbon resonances in [2.2]paracyclophanes were shifted downfield by 6–7 ppm. The complementary upfield shift of uncompressed atoms, hydrogen or carbon, connected to those carbons was also noticed. The downfield shift of compressed sp2 carbon results from interaction between two p-orbitals along the same orbital axis, p-orbital compression, and is attributable to decreased electron density.

Carbon-13 nuclear magnetic resonance spectra of E-silyl-alkenes

1980 ◽  
Vol 58 (4) ◽  
pp. 361-368 ◽  
Author(s):  
Constantinos A. Tsipis ◽  
Constantinos A. Tsoleridis
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Quantitative Analysis ◽  
Nmr Spectroscopy ◽  
Carbon Atom ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
H Nmr ◽  
Nuclear Magnetic Resonance Spectra ◽  
C Nmr

Carbon-13 nmr chemical shifts of a number of E-silyl-alkenes containing the silyl substituent at an sp2 carbon atom are presented. Assignments of the chemical shifts have been made by noting systematic variations in the spectra with changes in substituents and by comparison of the chemical shifts to those of the corresponding unsubstituted alkenes. The substituent effects observed were explained on the basis of the π-acceptor ability of the silyl substituents and the structure of the molecules. Comparing the 13C nmr spectra of the E-silyl-alkenes and those of the corresponding unsubstituted alkenes, differential chemical shifts have been obtained which can be used as empirical substituent parameters for the prediction of the 13C nmr spectra of other E-silyl-alkenes not yet studied. It was also demonstrated that 13C nmr spectroscopy can be used without resorting to special techniques (gated decoupling and the addition of paramagnetics) as an alternative method to the 1H nmr for the quantitative analysis of mixtures of regio-isomer E-silyl-alkenes.

A stereochemical investigation of substituted ethylene sulfites via 13C nuclear magnetic resonance

1976 ◽  
Vol 54 (9) ◽  
pp. 1428-1432 ◽  
Author(s):  
Gerald W. Buchanan ◽  
Desmond G. Hellier
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Conformational Analysis ◽  
Sulfur Atom ◽  
Chemical Shifts ◽  
Nmr Chemical Shifts ◽  
13C Nuclear Magnetic Resonance ◽  
Ethylene Sulfite ◽  
C Nmr ◽  
Nuclear Magnetic

13C nmr chemical shifts for ethylene sulfite and 17 derivatives are presented. From the magnitudes of the γ shifts and the tenets of conformational analysis, support is gained for the existence of twist-envelope conformations in solution. Pseudorotational paths are suggested which do not involve inversion at the sulfur atom.

Trimethylene sulfite conformations: Effects of sterically demanding substituants at C-4,6 on ring geometry as assessed by 1H and 13C nuclear magnetic resonance

1978 ◽  
Vol 56 (15) ◽  
pp. 2019-2024 ◽  
Author(s):  
Gerald W. Buchanan ◽  
Catherine M. E. Cousineau ◽  
Thomas C. Mundell
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Computer Analysis ◽  
Chemical Shifts ◽  
Tert Butyl ◽  
Nmr Data ◽  
Ring Geometry ◽  
13C Nuclear Magnetic Resonance ◽  
Sterically Demanding ◽  
C Nmr

1H and 13C nmr data for eight phenyl, diphenyl- and di-tert-butyl-2-oxo-1,3,2-dioxathianes, substituted at C-4 and/or C-6 are presented. Vicinal couplings obtained from 1H spectra by iterative computer analysis indicate chair geometries for all materials except trans-4,6-disubstituted compounds. 13C chemical shifts are corroborative.

Cyclopentadienyl platinum(IV) complexes: 1H, 13C nuclear magnetic resonance and optically active shift reagent study

1980 ◽  
Vol 58 (19) ◽  
pp. 2011-2015 ◽  
Author(s):  
Gordon Hamer ◽  
Alan Shaver
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Shift Reagent ◽  
Optically Active ◽  
Methyl Groups ◽  
Nmr Parameters ◽  
Trans Influence ◽  
Chiral Shift Reagent ◽  
13C Nuclear Magnetic Resonance ◽  
C Nmr

The 1H and 13C nmr parameters for the recently reported complexes (η5-C5H5)PtR1R2R3 where R1, R2, and R3 are combinations of CH3, C2H5, and C(O)CH3 groups are reported and compared to those for known octahedral di- and trimethylplatinium (IV) complexes. The C5H5 group has a relatively weak nmr trans-influence. A chiral shift reagent study on complex 5 (R1 = C(O)CH3, R2 = CH3, and R3 = C2H5) resolved the peaks due to the enantiomers, consistent with its structure and establishing its stereochemical stability. The four groups attached to the platinum atom in 5 differed greatly in their sensitivity to the shift reagent. The methyl groups in complex 4 (R1 = C(O)CH3, and R2 = R3 = CH3) become diastereotopic in the presence of chiral shift reagent. The J(Pt—H) values for 5 were not affected by the shift reagent.

Sign in / Sign up

Export Citation Format

Share Document