Boron trihalide adducts of 1,1-bis(piperidinyl)ethylene. 13C and 11B nmr studies of a model system for β-carbon donation in enamine adducts

1981 ◽  
Vol 59 (8) ◽  
pp. 1284-1289 ◽  
Author(s):  
J. Stephen Hartman ◽  
Eric C. Kelusky
Keyword(s):  
Model System ◽  
Nmr Studies ◽  
11B Nmr ◽  
Covalent Adducts ◽  
Peak Widths ◽  
C Nmr

1,1-Bis(piperidinyl)ethylene coordinates to the boron trihalides through the CH2 carbon, but the covalent adducts D.BX3 undergo rearrangement to give predominantly the ionic adducts D2BX2+.BX4−. Striking variations in 11B and 13C nmr peak widths support our proposed structures. The disappearance of peaks due to excessive broadening can be misleading in the interpretation of such systems.

scholarly journals Structural Investigations of C-Nitrosobenzenes. Part 3.1 Solid-state and Solution 13C NMR Studies, and Crystal Structure of E-(4-CIC6H4NO)2

1999 ◽  
Vol 23 (3) ◽  
pp. 202-203
Author(s):  
Daniel A. Fletcher ◽  
Brian G. Gowenlock ◽  
Keith G. Orrell ◽  
David C. Apperley ◽  
Michael B. Hursthouse ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
13C Nmr ◽  
Nmr Studies ◽  
Structural Investigations ◽  
Nmr Data ◽  
C Nmr

Solid-state and solution 13C NMR data for the monomers and dimers of 3- and 4-substituted nitrosobenzenes, and the crystal structure of E-(4-CIC6H4NO)2 are reported.

scholarly journals Structural differences between humic fractions from different soil types as determined by FT-IR and 13 C-NMR studies

1989 ◽  
Vol 81-82 ◽  
pp. 187-194 ◽  
Author(s):  
R. Fründ ◽  
H.-D. Lüdemann ◽  
F.J. Gonzalez-Vila ◽  
G. Almendros ◽  
J.C. del Rio ◽  
...  
Keyword(s):  
Soil Types ◽  
Nmr Studies ◽  
Structural Differences ◽  
Ft Ir ◽  
Humic Fractions ◽  
C Nmr

Solid state stereochemistry of crown ethers: X-ray crystal structure and 13C NMR studies of the LiNCS complex of 1,4,7,11-tetraoxacyclotetradecane

2000 ◽  
Vol 78 (3) ◽  
pp. 316-321
Author(s):  
G W Buchanan ◽  
A B Driega ◽  
G PA Yap
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Crown Ether ◽  
13C Nmr ◽  
Title Complex ◽  
Nmr Studies ◽  
Nmr Spectrum ◽  
X Ray ◽  
Large Amplitude Motion ◽  
C Nmr

The title complex is asymmetric in the crystal due to the spatial orientation of the NCS function. The space group has been determined to be P21 with a = 9.496(3), b = 8.736(3), c = 9.676(3) Å, β = 117.859(5)°, and Z = 2. The solid state 13C NMR spectrum is consistent with the lack of symmetry in the crystal and there is little evidence for large amplitude motion in the macrocycle as determined from the dipolar dephased spectrum.Key words: macrocyclic crown ether, lithium complex.

scholarly journals TEMPERATURE-DEPENDENT 11B NMR STUDIES OF B2O3 GLASS

1988 ◽  
Vol 37 (11) ◽  
pp. 1866
Author(s):  
XU SHU ◽  
PAN LIN-ZHANG ◽  
TIAN FEN ◽  
WU XUE-WEN
Keyword(s):  
Temperature Dependent ◽  
Nmr Studies ◽  
11B Nmr ◽  
B2o3 Glass

Platinum complexes of vitamin C. NMR studies on the solution chemistry of cis-platinum(diamine)(ascorbate) complexes

1987 ◽  
Vol 109 (12) ◽  
pp. 3596-3602 ◽  
Author(s):  
L. Steven Hollis ◽  
Eric W. Stern ◽  
Alan R. Amundsen ◽  
Arthur V. Miller ◽  
Sheryl L. Doran
Keyword(s):  
Vitamin C ◽  
Platinum Complexes ◽  
Solution Chemistry ◽  
Nmr Studies ◽  
Ascorbate Complexes ◽  
C Nmr

scholarly journals Dynamic aspect of bacteriorhodopsin as viewed from13C NMR: Conformational elucidation, surface dynamics and information transfer from the surface to inner residues

2002 ◽  
Vol 16 (3-4) ◽  
pp. 107-120 ◽  
Author(s):  
H. Saitô ◽  
R. Kawaminami ◽  
M. Tanio ◽  
T. Arakawa ◽  
S. Yamaguchi ◽  
...  
Keyword(s):  
Ambient Temperature ◽  
Information Transfer ◽  
Side Chain ◽  
Amino Acid Residues ◽  
Surface Dynamics ◽  
Transmembrane Helices ◽  
Nmr Studies ◽  
Specific Manner ◽  
Local Conformations ◽  
C Nmr

We demonstrate here how dynamic as well as conformational features of bacteriorhodopsin (bR) in purple membrane (PM) as a typical membrane protein are revealed by extensive13C NMR studies on [3-13C]-, [2-13C]-, [1-13C]Ala or [1-13C]Val-labeled bR and a variety of site-directed mutants. A number of13C NMR peaks were well-resolved for [3‒13C]Ala‒ and [1-13C]Val-bR under the condition of fully hydrated PM at ambient temperature and assigned to individual amino-acid residues, initially by regio-specific manner with reference to the data of the conformation-dependent displacements of peaks from model polypeptides and subsequently by site-specific manner with reference to the specifically reduced peak-intensities of site-directed mutant as compared with those of wild type. It is noticeable that the revealed bR structure at ambient temperature by13C NMR is not static as anticipated from the data of diffraction studies at cryo-temperature but is dynamically heterogeneous undergoing motional fluctuations with various frequencies (102–108Hz) depending upon the domains of interest. We further applied this approach to reveal how charged state of surface residues, especially at the side-chain of exracellular Glu residues (Glu 194 and 204), could be transmitted to the inner part of the helices such as Ala 53, 84, and 215 to alter their local conformations of transmembrane helices near at the Schiff base through side-chain interactions. We also analyzed how information of the protonation at Asp 85 from helix C is initially transmitted to helices B (Val 49) and G (Val 213) though modified helix‒helix interactions through the side-chains of Arg 82.

An unusual carbomethoxyl migration from nitrogen to carbon. Formation of a 2H-pyrrole from AlCl3-promoted reaction of 1-carbomethoxy-2,5-dimethylpyrrole with dimethyl acetylenedicarboxylate

1979 ◽  
Vol 57 (20) ◽  
pp. 2743-2746 ◽  
Author(s):  
R. A. F. Matheson ◽  
A. W. McCulloch ◽  
A. G. McInnes ◽  
D. G. Smith
Keyword(s):  
Dimethyl Acetylenedicarboxylate ◽  
Carbon Formation ◽  
Nmr Studies ◽  
C Nmr

The AlCl3-promoted reaction of methyl 2,5-dimethylpyrrole-1-carboxylate 1 with dimethyl acetylenedicarboxylate affords under certain conditions a low yield of 2,5-dimethyl-2-tricarbomethoxyvinyl-2H-pyrrole 3. The structure of the latter was established on the basis of detailed 1H and 13C nmr studies, and confirmed by conversion to dimethyl 5-methyl-5-(3-oxobutyl)-3-pyrrolin-2-one-3,4-dicarboxylate 4.

scholarly journals Characterization of Cerebral Glutamine Uptake from Blood in the Mouse Brain: Implications for Metabolic Modeling of 13C NMR Data

2014 ◽  
Vol 34 (10) ◽  
pp. 1666-1672 ◽  
Author(s):  
Puneet Bagga ◽  
Kevin L Behar ◽  
Graeme F Mason ◽  
Henk M De Feyter ◽  
Douglas L Rothman ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Metabolic Model ◽  
Synthesis Rate ◽  
Nmr Studies ◽  
Nmr Data ◽  
Glutamine Synthesis ◽  
Time Courses ◽  
Glutamine Uptake ◽  
C Nmr

13C Nuclear Magnetic Resonance (NMR) studies of rodent and human brain using [1-13C]/[1,6-13C2]glucose as labeled substrate have consistently found a lower enrichment (~25% to 30%) of glutamine-C4 compared with glutamate-C4 at isotopic steady state. The source of this isotope dilution has not been established experimentally but may potentially arise either from blood/brain exchange of glutamine or from metabolism of unlabeled substrates in astrocytes, where glutamine synthesis occurs. In this study, the contribution of the former was evaluated ex vivo using 1H-[13C]-NMR spectroscopy together with intravenous infusion of [U-13C5]glutamine for 3, 15, 30, and 60 minutes in mice. 13C labeling of brain glutamine was found to be saturated at plasma glutamine levels > 1.0 mmol/L. Fitting a blood–astrocyte–neuron metabolic model to the 13C enrichment time courses of glutamate and glutamine yielded the value of glutamine influx, VGln(in), 0.036 ± 0.002 μmol/g per minute for plasma glutamine of 1.8 mmol/L. For physiologic plasma glutamine level (~0.6 mmol/L), VGln(in) would be ~0.010 μmol/g per minute, which corresponds to ~6% of the glutamine synthesis rate and rises to ~11% for saturating blood glutamine concentrations. Thus, glutamine influx from blood contributes at most ~20% to the dilution of astroglial glutamine-C4 consistently seen in metabolic studies using [1-13C]glucose.

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