Comparison of the conformation and dynamics of a polysaccharide and of its isolated heptasaccharide repeating unit on the basis of nuclear Overhauser effect, long-range C-C and C-H coupling constants, and NMR relaxation data

Biopolymers ◽  
2000 ◽  
Vol 54 (4) ◽  
pp. 235-248 ◽  
Author(s):  
Manuel Martin-Pastor ◽  
C. Allen Bush
Keyword(s):  
Long Range ◽  
Nuclear Overhauser Effect ◽  
Nmr Relaxation ◽  
Coupling Constants ◽  
Relaxation Data ◽  
Overhauser Effect ◽  
Nuclear Overhauser

Beiträge zur Chemie des Silieiums und Germaniums, XXIX [1] 29Si-NMR-spektroskopische Untersuchungen von geradkettigen und verzweigten Silanen / Contributions to the Chemistry of Silicon and Germanium, XXIX [1] 29Si NMR Spectroscopic Investigations on Straight and Branched Silanes

1980 ◽  
Vol 35 (3) ◽  
pp. 282-296 ◽  
Author(s):  
Josef Hahn
Keyword(s):  
Nuclear Overhauser Effect ◽  
Empirical Relationship ◽  
Spin Systems ◽  
Coupling Constants ◽  
Complete Analysis ◽  
29Si Nmr ◽  
Overhauser Effect ◽  
Coupling Parameters ◽  
Nuclear Overhauser ◽  
Silicon And Germanium

,The structure of the straight silanes SinH2n+2 (1 ≤ n ≤ 7) and of the branched isomers isotetrasilane, iso- and neopentasilane, 2-silyl- and 3-silylpentasilane, 2,3-disilyltetrasilane as well as 2-silyl- and 3-silylhexasilane could be unambiguously elucidated by 29Si NMR spectroscopy. Systematic trends in the chemical shift and coupling parameters were observed and an empirical relationship between δ(29Si) of a 29Si nucleus and the number of the neighbouring silicon atoms in αβor γposition is given. In 1H decoupled spectra the nuclear Overhauser effect on the 29Si resonance was found to increase with increasing distance of the 29Si nucleus from the end of the chain. A complete analysis of the multi spin systems of disilane, trisilane and isotetrasilane was performed and the signs of the 29Si,H- and H,H-long range coupling constants were determined with regard to the negative sign of 1J(29SiH).

A proton magnetic resonance nuclear Overhauser enhancement study. Application to vitamin D derivatives D2 and D3

1980 ◽  
Vol 58 (12) ◽  
pp. 1206-1210 ◽  
Author(s):  
George Kotovych ◽  
Gerdy H. M. Aarts ◽  
Klaus Bock
Keyword(s):  
Conformational Equilibrium ◽  
Nuclear Overhauser Effect ◽  
Coupling Constants ◽  
Nuclear Overhauser Enhancement ◽  
Conformational Interconversion ◽  
Overhauser Effect ◽  
Effect Difference ◽  
Nuclear Overhauser ◽  
Unambiguous Assignment ◽  
Study Application

Nuclear Overhauser effect difference experiments on vitamins D2 and D3 at 400 MHz allow an unambiguous assignment to be made for the HE and HZ protons bonded to the C-19 carbon. This assignment is especially important since the A ring, and hence the C-19 atom, undergoes a conformational interconversion. The results indicate the importance of proton nOe difference experiments in determining points of configuration and they indicate that the assignment of resonances based on allylic coupling constants in a molecule undergoing a conformational equilibrium can be incorrect.

A nuclear Overhauser effect difference study of the solution conformation of (6R)-prostaglandin I1

1980 ◽  
Vol 58 (23) ◽  
pp. 2649-2659 ◽  
Author(s):  
George Kotovych ◽  
Gerdy H. M. Aarts
Keyword(s):  
Proton Magnetic Resonance ◽  
Nuclear Overhauser Effect ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Solution Conformation ◽  
Magnetic Resonance Studies ◽  
Overhauser Effect ◽  
Complete Assignment ◽  
Effect Difference ◽  
Nuclear Overhauser

Proton magnetic resonance studies at 400 MHz allowed the complete assignment of the spectra for (6R)-prostaglandin I1 in phosphate buffer and in CDCl3 solutions. The spectral analysis was based on the nuclear Overhauser effect difference measurements, which also provide accurate chemical shifts and coupling constants. Conformational differences in the two solvents for the ring portion of the molecule are indicated.

The synthesis and the nuclear magnetic resonance study of β-lactam derivatives of 1,5-benzothiazepines

1988 ◽  
Vol 66 (2) ◽  
pp. 279-282 ◽  
Author(s):  
Aron Szöllösy ◽  
George Kotovych ◽  
Gábor Tóth ◽  
Albert Lévai
Keyword(s):  
Nuclear Overhauser Effect ◽  
Nuclear Magnetic Resonance Study ◽  
Coupling Constants ◽  
Magnetic Resonance Study ◽  
Proton Proton ◽  
Proton Coupling ◽  
Overhauser Effect ◽  
Vicinal Proton ◽  
Nuclear Overhauser ◽  
Derivatives Of

The synthesis and stereochemistry of seven β-lactam derivatives of 1,5-benzothiazepines are presented. The configurational and conformational analysis is based on nuclear Overhauser effect experiments, together with analysis of the vicinal proton–proton coupling constants. In the preferred conformation, the seven-membered ring is in a half-chair. Only for one compound, 2-aza-4-bromo-4-methyl-5,7-diphenyl-8-thiatricyclo[7.4.0.02,5]trideca-Δ1,9,10,12-trien-3-one, were two diastereomers isolated (compounds 6a and 6b). Six of the compounds have the 4S*, 5R*, 7R* configuration while compound 6b has the 4R*, 5R*,7R* configuration.

Stereochemical course of the reaction of 2-haloethyl isothiocyanates with nucleophiles. Stereospecific route to 4,5-disubstituted Δ2-thiazolines and thiazolidine-2-thiones

1981 ◽  
Vol 46 (3) ◽  
pp. 717-728 ◽  
Author(s):  
Ladislav Kniežo ◽  
Pavol Kristian ◽  
Miloš Buděšínský ◽  
Katarína Havrilová
Keyword(s):  
Nuclear Overhauser Effect ◽  
Coupling Constants ◽  
Overhauser Effect ◽  
Nuclear Overhauser

Diastereoisomeric 1-chloro-1-phenyl-2-isothiocyanatopropanes have been prepared. They reacted stereospecifically with CH3Ona, diethylamine, aniline and NaSH to give pure cis or trans-4,5-disubstituted Δ2-thiazolines and thiazolidine-2-thiones whose configuration was determined using the nuclear Overhauser effect. The preponderant conformation of diastereoisomeric 1-chloro-1-phenyl-2-isothiocyanatopropanes was estimated on the basis of coupling constants of vicinal protons.

The conformational analysis of leukotriene D4 in aqueous solution based on high-field nuclear magnetic resonance measurements

1984 ◽  
Vol 62 (8) ◽  
pp. 1640-1645 ◽  
Author(s):  
Makiko Sugiura ◽  
Helmut Beierbeck ◽  
George Kotovych ◽  
Patrice C. Bélanger
Keyword(s):  
Conformational Analysis ◽  
Nuclear Overhauser Effect ◽  
Relaxation Times ◽  
Coupling Constants ◽  
Leukotriene D4 ◽  
Proton Proton ◽  
Proton Coupling ◽  
Overhauser Effect ◽  
Vicinal Proton ◽  
Nuclear Overhauser

The conformational analysis of LTD4 in D2O was carried out based on the analysis of vicinal proton–proton coupling constants, nonselective proton longitudinal relaxation times, and nuclear Overhauser effect data. The H6—C6 to C12 region of the molecule is transoid, the predominant rotamer about C5—C6 is gauche, and two rotamers can be used to describe the rotation about C12—C13. There are three rotamers that can be used to describe the rotation about the C21—C22 bond of cysteine. Finally, chelation between an Yb3+, shift reagents and LTD4 was not observed.

A nuclear Overhauser effect difference study and a two-dimensional J proton magnetic resonance study of (6S)-prostaglandin I1

1981 ◽  
Vol 59 (10) ◽  
pp. 1449-1454 ◽  
Author(s):  
George Kotovych ◽  
Gerdy H. M. Aarts ◽  
Tom T. Nakashima
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Nuclear Overhauser Effect ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Two Dimensional ◽  
Overhauser Effect ◽  
Effect Difference ◽  
Proton Resonances ◽  
Nuclear Overhauser

High-field nuclear Overhauser effect difference measurements allowed the assignment of the proton resonances for (6S)-prostaglandin I1 in phosphate buffer solutions. The two-dimensional J proton magnetic resonance experiments complemented these studies, as they also allowed the structure of several multiplets to be obtained when these multiplets are hidden by nearby resonances in a normal spectrum. The chemical shifts and coupling constants are compared with the data obtained previously for (6R)-prostaglandin I1.

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