scholarly journals Reactions of α-phenylglycinamide with some carbonyl compounds. Formation of 5,7-diisopropyl-8,8-dimethyl-2-oxo-3-phenylimidazolidino-[1,2-c]-tetrahydro-[1,3]-oxazine, and determination of structure and stereochemistry by nuclear Overhauser effect difference measurements

1989 ◽  
Vol 67 (10) ◽  
pp. 1560-1564 ◽  
Author(s):  
Ning Qing ◽  
Lawrence D. Colebrook ◽  
John T. Edward ◽  
Allan Kon ◽  
Francis L. Chubb
Keyword(s):  
Schiff Base ◽  
Molecular Mechanics ◽  
Carbonyl Compounds ◽  
Nuclear Overhauser Effect ◽  
Molecular Mechanics Calculations ◽  
Overhauser Effect ◽  
Effect Difference ◽  
Nuclear Overhauser

α-Phenylglycinamide 5 reacts with ketones to give either the Schiff base 3 or the 4-imidazolidone 4, but reacts with boiling isobutyraldehyde to give the bicyclic compond 6. The structure and stereochemistry of 6 have been established by 1H nuclear Overhauser effect difference measurements, supported by molecular mechanics calculations. Keywords: structure, stereochemistry, nuclear Overhauser effect, molecular mechanics, α-phenylglycinamide reactions.

Determination of configuration and conformation of isoxazolidines by nuclear Overhauser effect difference spectroscopy

1982 ◽  
Vol 47 (23) ◽  
pp. 4397-4403 ◽  
Author(s):  
Philip DeShong ◽  
C. Michael Dicken ◽  
Ronald R. Staib ◽  
Alan J. Freyer ◽  
Steven M. Weinreb
Keyword(s):  
Nuclear Overhauser Effect ◽  
Difference Spectroscopy ◽  
Overhauser Effect ◽  
Effect Difference ◽  
Nuclear Overhauser ◽  
Configuration And Conformation

Determination of the stereochemistry of isoxazolidinium salts by nuclear Overhauser effect difference spectroscopy

1988 ◽  
Vol 26 (11) ◽  
pp. 974-979 ◽  
Author(s):  
A. Liguori ◽  
R. Ottanà ◽  
G. Romeo ◽  
E. Rotondo ◽  
G. Sindona ◽  
...  
Keyword(s):  
Nuclear Overhauser Effect ◽  
Difference Spectroscopy ◽  
Overhauser Effect ◽  
Effect Difference ◽  
Nuclear Overhauser

The isolation, structure, and stereochemistry of traversiadiene. The precursor hydrocarbon of traversianal biosynthesis

1989 ◽  
Vol 67 (8) ◽  
pp. 1302-1304 ◽  
Author(s):  
Albert Stoessl ◽  
G. L. Rock ◽  
J. B. Stothers
Keyword(s):  
Magnetic Resonance ◽  
Biosynthetic Pathway ◽  
Nuclear Overhauser Effect ◽  
Difference Spectra ◽  
Heteronuclear Correlation ◽  
Magnetic Resonance Studies ◽  
Overhauser Effect ◽  
Effect Difference ◽  
Nuclear Overhauser ◽  
Magnetic Resonance Spectra

A tricyclic diene, traversiadiene, isolated from cultures of Cercosporatraversiana has been shown to have the structure and stereochemistry of the previously postulated hydrocarbon intermediate on the biosynthetic pathway to traversianal (1). Detailed:1H and 13C magnetic resonance studies, including homo- and heteronuclear correlation spectra, led to the gross structure, and the stereochemistry was established through a series of nuclear Overhauser effect difference spectra. Keywords: diterpene, traversiadiene, 1H and 13C magnetic resonance spectra.

Revised structure of a delta-aminolevulinic acid derivative

1993 ◽  
Vol 39 (9) ◽  
pp. 1867-1871 ◽  
Author(s):  
M Kajiwara ◽  
K Hara ◽  
K Takatori ◽  
K Matsumoto
Keyword(s):  
Aminolevulinic Acid ◽  
Nuclear Overhauser Effect ◽  
Correlation Spectroscopy ◽  
Molecular Formula ◽  
X Ray ◽  
Overhauser Effect ◽  
13C Nuclear Magnetic Resonance ◽  
Relative Arrangement ◽  
Effect Difference ◽  
Nuclear Overhauser

Abstract The structure of the fluorescent derivative formed in the method of Okayama et al. (Clin Chem 1990; 36:1494-7) for determining delta-aminolevulinic acid (ALA) concentrations was reinvestigated after esterification. The molecular ion peak at m/z 303.1473 corresponded to the molecular formula of C17H21NO4 (calcd 303.1470). The infrared spectrum showed the presence of carbonyl and carboxyl groups. This compound contained two acetyl groups, two methyl groups, and one methoxycarbonylethyl group, as revealed by 1H and 13C nuclear magnetic resonance and 13C-1H shift-correlated spectroscopy. Experiments with correlation spectroscopy via long-range coupling indicated that the main skeleton is 3H-pyrrolizine. The relative arrangement of functional groups was determined by means of nuclear Overhauser effect difference experiments. We were led to the conclusion that the methyl ester of the derivative is 2,6-diacetyl-1,5-dimethyl-7-(2-methoxycarbonylethyl)-3H-pyrrolizine. This structure was unequivocally confirmed by x-ray analysis; therefore, the structure of the derivative itself is 2,6-diacetyl-1,5-dimethyl-7-(2-carboxyethyl)-3H-pyrrolizine.

scholarly journals In Silico Modeling of Spirolides and Gymnodimines: Determination of S Configuration at Butenolide Ring Carbon C-4

Toxins ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 685
Author(s):  
Christian Zurhelle ◽  
Tilmann Harder ◽  
Urban Tillmann ◽  
Jan Tebben
Keyword(s):  
In Silico ◽  
Density Functional ◽  
Nuclear Overhauser Effect ◽  
Resonance Spectroscopy ◽  
Functional Theory ◽  
Relative Configuration ◽  
Overhauser Effect ◽  
In Silico Modeling ◽  
Nuclear Overhauser

Only few naturally occurring cyclic imines have been fully structurally elucidated or synthesized to date. The configuration at the C-4 carbon plays a pivotal role in the neurotoxicity of many of these metabolites, for example, gymnodomines (GYMs) and spirolides (SPXs). However, the stereochemistry at this position is not accessible by nuclear Overhauser effect—nuclear magnetic resonance spectroscopy (NOE-NMR) due to unconstrained rotation of the single carbon bond between C-4 and C-5. Consequently, the relative configuration of GYMs and SPXs at C-4 and its role in protein binding remains elusive. Here, we determined the stereochemical configuration at carbon C-4 in the butenolide ring of spirolide- and gymnodimine-phycotoxins by comparison of measured 13C NMR shifts with values obtained in silico using force field, semiempirical and density functional theory methods. This comparison demonstrated that modeled data support S configuration at C-4 for all studied SPXs and GYMs, suggesting a biosynthetically conserved relative configuration at carbon C-4 among these toxins.

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