An NMR study of the Lycopodium alkaloids, annotinine and annotine: verification of the annotine structure

1989 ◽  
Vol 67 (11) ◽  
pp. 1765-1773 ◽  
Author(s):  
Donald W. Hughes ◽  
Robert V. Gerard ◽  
David B. MacLean
Keyword(s):  
Chemical Shifts ◽  
Structural Data ◽  
Double Quantum ◽  
Difference Spectra ◽  
Nmr Data ◽  
Nmr Study ◽  
Lycopodium Alkaloids ◽  
Phase Sensitive ◽  
Nuclear Overhauser ◽  
C Nmr

The Lycopodium alkaloids, annotinine and annotine, were examined by 1H and 13C NMR spectroscopy. Proton spectra were assigned by the application of double-quantum filtered phase-sensitive COSY and nuclear Overhauser enhancement difference spectra. These and other data confirmed the structure previously assigned to annotine. The 13C chemical shifts were consistent with the structural data derived from the proton spectra. The NMR data showed a good correlation with structures determined from molecular mechanics (MMX) calculations. Keywords: Lycopodium alkaloids 1H and 13C NMR, annotinine, annotine, structure of Lycopodium alkaloids, NMR alkaloids.

Identification of acyl groups occurring in sesquiterpene lactones: Proton and carbon-13 NMR study

1987 ◽  
Vol 52 (2) ◽  
pp. 453-475 ◽  
Author(s):  
Miloš Buděšínský ◽  
David Šaman
Keyword(s):  
Chemical Shifts ◽  
Sesquiterpene Lactones ◽  
Nmr Chemical Shifts ◽  
H Nmr ◽  
Nmr Parameters ◽  
Nmr Data ◽  
Nmr Study ◽  
C Nmr

Characteristic 1H NMR parameters of 88 acyl groups, hitherto found as ester substituents in natural sesquiterpenic lactones, were determined from the measured spectra as well as literature data. Characteristic 13C NMR chemical shifts for 45 acyl groups were obtained in the same way; for the remaining acyls with hitherto unknown 13C NMR data the values were calculated on the basis of semiempirical relationships.

NMR-spektroskopische Untersuchungen an 1,1-Thiophendioxid und verwandten Verbindungen / NMR Spectroscopical Investigations of Thiophene 1,1-Dioxide and Related Compounds

1984 ◽  
Vol 39 (7) ◽  
pp. 915-920 ◽  
Author(s):  
Herbert Meier ◽  
Thomas Molz ◽  
Heinz Kolshorn
Keyword(s):  
Computer Simulation ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Multiple Resonance ◽  
Nmr Data ◽  
Cyclic Diene ◽  
Related Compounds ◽  
C Nmr

The 1H and 13C NMR data of thiophene 1,1-dioxide (3) and related compounds, especially of the precursor 2 and the consecutive product 5 are evaluated by computer simulation and multiple resonance. Chemical shifts and coupling constants reveal that 3 has the character of a cyclic diene. Diatropic or paratropic effects can be excluded.

Synthesis, X-ray crystal structure, and solid-state 13C NMR study of tris(9-crown-3)triphenylene

2001 ◽  
Vol 79 (2) ◽  
pp. 195-200 ◽  
Author(s):  
Gerald W Buchanan ◽  
Majid F Rastegar ◽  
Glenn PA Yap
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Crown Ether ◽  
Chemical Shifts ◽  
Aromatic Rings ◽  
X Ray ◽  
Nmr Study ◽  
Group A ◽  
C Nmr ◽  
Solid State 13C Nmr

Benzo-9-crown-3 ether trimerizes in the presence of FeCl3 and aqueous H2SO4 to produce tris(9-crown-3)triphenylene in 25.4% yield. This compound crystallizes in the monoclinic P21/c space group: a = 13.759(2) Å, b = 13.318(2) Å, c = 13.399(2) Å, β = 96.883(2)°, with Z = 4. The three 9-crown-3 ether units of the trimer possess different geometries and there is substantial deviation from coplanarity in the three aromatic rings. 13C NMR chemical shifts in the solid state are consistent with this lack of symmetry and are discussed in terms of the X-ray crystal-structure data.Key words: crown ether, trimerization, stereochemistry.

scholarly journals A multinuclear NMR study of some cyclic phosphonic diamides

1994 ◽  
Vol 12 (1) ◽  
pp. 31-34
Author(s):  
Wojciech Bocian ◽  
Lech Stefaniak ◽  
Graham A. Webb
Keyword(s):  
Molecular Structure ◽  
Chemical Shifts ◽  
Multinuclear Nmr ◽  
Nmr Data ◽  
Nmr Study ◽  
Sensitive Parameters

1H,13C,15N and31p NMR data are presented for four cyclic phosphonic diamides. In tenns of useful structural infonnation it is found that the31p chemical shifts and1J(31P_15N) couplings are the most sensitive parameters to variations in molecular structure.

Crystal and molecular structure of Z- and E-1,2-dichloro-1,2-bis(2-chlorophenyl)ethylene. An X-ray and NMR study

1995 ◽  
Vol 73 (9) ◽  
pp. 1520-1525
Author(s):  
Luciano Antolini ◽  
Ugo Folli ◽  
Dario Iarossi ◽  
Adele Mucci ◽  
Silvia Sbardellati ◽  
...  
Keyword(s):  
Chemical Shifts ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray ◽  
Nmr Study ◽  
Phenyl Rings ◽  
A Cell ◽  
C Nmr

The crystal structures of the title compounds were determined by single crystal X-ray diffraction techniques. The molecule of the Z isomer, which crystallizes in the monoclinic space group C2/c with Z = 4 in a cell of dimensions a = 14.891 (2), b = 10.780(2), c = 8.769(1) Å, β = 97.47(2)°, V = 1395.7(7) Å3 has crystallographic twofold symmetry. The E form crystallizes in the orthorhombic space group Pbca with a = 11.730(1), b = 6.932(1), c = 16.841(1) Å, V = 1369.4(2) Å3 and Z = 4. Its molecules have crystallographically dictated [Formula: see text] symmetry. In both isomers the phenyl rings are roughly perpendicular to the average ethylene plane. The atoms characterizing this plane show significant deviations from planarity in the Z isomer. Marked bond-angle distortions at the ethene carbons of both structures are observed. The 1H and 13C NMR spectra of the compounds were measured and, particularly in the case of the 1H chemical shifts, fall into two quite separate spectral regions. At low temperature, two conformational isomers, those with different relative orientation of the C—Cl bonds of the phenyl rings, are observed in the spectrum of each compound. Keywords: chlorostilbenes, overcrowded molecules. X-ray structure, conformations, NMR spectroscopy.

Characterization of the 2,2′-bipyridine chelates of lanthanum(III) in acetonitrile. A 1H, 13C, 17O, and 139La NMR study

1993 ◽  
Vol 71 (3) ◽  
pp. 377-383 ◽  
Author(s):  
Monique Fréchette
Keyword(s):  
Coordination Sphere ◽  
Chemical Shifts ◽  
Complexation Reaction ◽  
Complex Species ◽  
H Nmr ◽  
Nmr Data ◽  
Nmr Study ◽  
Close Proximity ◽  
Coordinated Water

We have investigated the reaction between La(NO3)3•6H2O and 2,2′-bipyridine (bipy) in acetonitrile by means of 139La, 17O, 13C, and 1H NMR spectroscopy. The 139La spectra show up to three different sites with variable intensities attributed to solvated La(III) ions and to two complex species with one or two bipy moieties in the La(III) coordination sphere. 17O NMR indicates that during the complexation reaction, the coordinated water is totally displaced from the coordination sphere whereas the nitrate groups remain coordinated. Proton NMR data confirm the water expulsion. In addition, the proton chemical shifts of bipy, in comparison with the 13C NMR data, clearly show an anisotropic shielding when two bipy are coordinated to La(III). Therefore, the two bipy molecules are in close proximity in the coordination sphere. From the NMR results it has been shown that, during the complexation process, five different La(III) species are formed: [La(NO3)3(CH3CN)4], [La(NO3)3(CH3CN)3(H2O)], [La(NO3)3(bipy)(CH3CN)2], [La(NO3)3(bipy)(CH3CN)-(H2O)], and [La(NO3)3(bipy)2]. Each La(III) complex has a coordination member of 10, with NO3− and bipy acting as chelating ligands. Furthermore, the structure of the La(NO3)3(bipy)2 complex in solution shows similarities with the solid state compound. Finally, comparisons are made with the La(III) complexes previously obtained with 1,10-phenanthroline.

scholarly journals Carbon-13 NMR Chemical Shift of Methyl Group: A Useful Parameter for Structural Analysis of C-Methylated Flavonoids

2006 ◽  
Vol 1 (11) ◽  
pp. 1934578X0600101
Author(s):  
Pawan K. Agrawal ◽  
Chandan Agrawal ◽  
Shravan Agrawal
Keyword(s):  
Structural Analysis ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Nmr Chemical Shift ◽  
Methyl Group ◽  
Nmr Chemical Shifts ◽  
Nmr Study ◽  
Pterocarpus Santalinus ◽  
Group A ◽  
C Nmr

The 13C NMR resonances corresponding to the C-Me group of C-6 and/or C-8 C-methylated-flavonoids absorb between 6.7–10.0 ppm and typically between 6.7–8.7 ppm. A comparative 13C NMR study reflects that the 13C NMR chemical shifts reported for 6-hydroxy-5-methyl-3′,4′,5′-trimethoxyaurone-4-O-α-L-rhamnoside from Pterocarpus santalinus and 8-C-methyl-5,7,2′,4′- tetramethoxyflavanone from Terminalia alata are inconsistent with the assigned structures, and therefore need reconsideration.

The conformational equilibrium in [13C-1-methyl]-cis-1,4-dimethylcyclohexane

1980 ◽  
Vol 58 (23) ◽  
pp. 2709-2713 ◽  
Author(s):  
Harold Booth ◽  
Jeremy Ramsey Everett
Keyword(s):  
Conformational Equilibrium ◽  
Chemical Shifts ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Coupling Constants ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Nuclear Overhauser ◽  
In Cis ◽  
C Nmr

The conformational equilibrium in [13C-1-methyl]-cis-1,4-dimethylcyclohexane has been assessed by (a) direct integration of signals due to equatorial and axial methyl carbons in the 13C nmr spectrum at 172 K and (b) by measurement of the 13C chemical shifts of C-1 and C-4 in the spectrum at 300 K. It is concluded that a 13C isotope effect on the position of the degenerate equilibrium in cis-1,4-dimethylcyclohexane is either nonexistent, or is too small to be detected by methods of analyses employed. The 13C nmr data incidental to the study (chemical shifts, coupling constants, spin–lattice relaxation times, nuclear Overhauser enhancements, and 1-bond isotope shifts) are recorded for the title compound and its trans-isomer.

N.M.R. studies of myelin basic protein. VI. Proton spectra in aqueous solutions of proteins from mammalian and avian species

1982 ◽  
Vol 35 (10) ◽  
pp. 1979 ◽  
Author(s):  
GL Mendz ◽  
WJ Moore ◽  
PR Carnegie
Keyword(s):  
Aqueous Solution ◽  
Primary Structure ◽  
Chemical Shifts ◽  
Side Chains ◽  
Amino Acid Residues ◽  
Difference Spectra ◽  
Effects Of Ph ◽  
Central Nervous Systems ◽  
Species Comparisons ◽  
Nuclear Overhauser

Myelin basic proteins from human, cow, pig, rabbit and chicken central nervous systems were studied in aqueous solution by proton n.m.r. at 400 MHz. Species comparisons and other techniques led to the assignment of resonances of 23 specific amino acid residues in the primary structure. Resonances from side chains of polar amino acids adjacent to aspartic residues could be assigned by anomalous effects of pH on the chemical shifts. The pK values of histidine side chains all fall in the range 6.0-6.9, and four specific histidine residues were assigned. The conformation of the protein in aqueous solution is that of an extended non-random polypeptide chain with regions of localized structure. Nuclear Overhauser difference spectra showed that a reverse turn similar to that previously suggested for an encephalitogenic nonapeptide isolated from the protein (guinea pig determinant) occurs also in the protein itself, thus supporting the concept of special low-energy conformations responsible for biological activity. Upfield chemical shifts of some side chain methyl groups from the central region of the primary structure suggest ring-current shifts due to higher-order structuring.

Résonance magnétique nucléaire 13C des dérivés allyliques de la colonne IV-A, de type (C6H5)3ECH2CH=CH—CH3. Effets électroniques du substituant du noyau aromatique

1984 ◽  
Vol 62 (1) ◽  
pp. 133-135 ◽  
Author(s):  
E. Matarasso-Tchiroukhine
Keyword(s):  
Excitation Energy ◽  
Electronic Excitation ◽  
Inductive Effect ◽  
Chemical Shifts ◽  
Aromatic Nucleus ◽  
Electronic Excitation Energy ◽  
Nmr Study ◽  
Résonance Magnétique ◽  
The Mean ◽  
C Nmr

The 13C nmr study of the series (C6H5)3ECH2CH=CH—CH31E shows, for the aromatic nucleus, a polarization consistent with a mesomeric electron withdrawing effect of the substituent in the case of E = Si, Ge, Sn; inversely, a mesomeric donating effect, in the case E = Pb, involving a higher electronegativity for Pb; and a donating π inductive effect, in the case E = C. The mean electronic excitation energy seems to dominate the chemical shifts of the aromatic carbons Cipso and Cortho, as well as the coupling 0J(13C—207Pb).

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