SCOPE FOR THE DEVELOPMENT OF SPECTROSCOPIC METHODS IN DETERMINATION OF STEREOCHEMISTRY OF NATURAL PRODUCTS

INDIAN DRUGS ◽  
2012 ◽  
Vol 49 (02) ◽  
pp. 5-11
Author(s):  
S. R. Pattan ◽  
S. S. Kadam ◽  
S. A. Nirmal ◽  
D. K. Thakur ◽  
J. S. Pattan ◽  
...  
Keyword(s):  
Natural Products ◽  
Nuclear Overhauser Effect ◽  
Spectroscopic Studies ◽  
Spectral Studies ◽  
Spectroscopic Methods ◽  
Coupling Constant ◽  
Coupling System ◽  
Geminal Coupling ◽  
Nuclear Overhauser

India is a rich country in terms of biodiversity & natural products, but very little work is carried out on stereochemical & spectroscopic studies of natural products. Isomers of natural products are found to be active, but the detection of stereochemical/spectral data is not effectively achieved. There is tremendous scope for spectroscopic methods in the determination of stereochemistry of some novel natural products particularly on J based approach (coupling constant values) which reveals about configuration, conformation and reactivity. Coupling varies with the angle between bonds, ring size affects coupling, electronegative atom reduces coupling, ? system increases geminal coupling, proton attached to same carbon can be different (diastereotopic) and can couple to one another, and we have the Nuclear Overhauser Effect. With these connections stereochemistry of some novel natural products is explained by using coupling constant values (spectroscopic methods). The present review is aimed at highlighting the significance and need of stereochemical & spectral studies of natural products which can be explored as promising drugs of the future.

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.

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

Applications of the intermolecular nuclear Overhauser effect. I. Determination of differential solvent effects: the hydration of pyridine

1983 ◽  
Vol 36 (3) ◽  
pp. 493 ◽  
Author(s):  
GR Smith ◽  
B Ternai
Keyword(s):  
Nuclear Overhauser Effect ◽  
Water System ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Alternative Methods ◽  
Relaxation Rates ◽  
Overhauser Effect ◽  
Nuclear Overhauser ◽  
Intermolecular Relaxation

The intermolecular relaxation rates of the pyridine-water system have been obtained by the measurement of the total spin lattice relaxation rate and the intermolecular nuclear Overhauser effect between pyridine and water, for each pyridine proton. The advantages of this method for the determination of the intermolecular relaxation rates are discussed, and the method is compared with alternative methods. The results indicate that there is a varying degree of hydration about the pyridine molecule, with the nitrogen being the preferred site of water interaction. It is necessary to interpret the results in terms of solute-solute as well as solute-solvent interactions. A model is proposed which takes account of both types of interaction, and is considered in terms of previously proposed models of pyridine-water interactions.

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