scholarly journals A simple and facile NMR method for the determination of hydrogen bonding by amide N–H protons in protein models and other compounds

2017 ◽  
Vol 41 (14) ◽  
pp. 6064-6066 ◽  
Author(s):  
Michael H. Abraham ◽  
Raymond J. Abraham
Keyword(s):  
Hydrogen Bonding ◽  
Chemical Shifts ◽  
Amide Group ◽  
Nmr Method ◽  
Protein Models

It is shown that measurements of the 1H chemical shifts of amide N–H protons in chloroform and in DMSO solvents are sufficient to determine the extent of hydrogen bonding of the N–H protons in a variety of compounds containing the amide group.

Revision of the structure of 3-methoxy-14α-hydroxy-D-homo-1,3,5-(10)-estratrien-17a-one. A simple 1H NMR method for the determination of configuration of hydroxy group in position 5 and/or 14 of the D-homo-steroid skeleton

1991 ◽  
Vol 56 (7) ◽  
pp. 1512-1524 ◽  
Author(s):  
Miloš Buděšínský ◽  
Alexander Kasal ◽  
Želimír Procházka ◽  
Huynh Kim Thoa ◽  
Soňa Vašíčková ◽  
...  
Keyword(s):  
Hydroxy Group ◽  
Chemical Shifts ◽  
Cotton Effect ◽  
Hydroxyl Group ◽  
H Nmr ◽  
Nmr Method ◽  
Synthetic Models ◽  
Steroid Skeleton

Eignerova and Prochazka found in 1974 the Cotton effect value for 3-methoxy-14α-hydroxy-D-homo-1,3,5(10)-estratrien-17a-one (Ia) to be Δε – 2.76.Calculation of the Δε value for this compound led, however, to a substantially lower value, which suggested the hypothesis that the compound was in fact rather an epimer with the hydroxy group in position 14β. This hypothesis was studied by means of 1H NMR spectra of synthetic models, using the changes of the chemical shifts of angular methyls, induced by in situ acylation of the angular hydroxyl with an α- or β-configuration with trichloroacetyl isocyanate (TAI). The observed TAI-acylation shifts on model compounds indicated the structure Ib with a 14b-configuration of the hydroxyl group. Indenpendent proof has been given by the synthesis of both 14-hydroxy epimers, Ia and Ib. A simple 1H NMR method is proposed for the determination of configuration of the hydroxyl in position 5 or 14 of D-homo-steroid skeleton.

Gradient-Enhanced Inverse-Detected NMR Techniquesfor Determination of 1H-15N Coupling Constants in 2,2-Dimethylpenta-3,4-dienal Derivatives

1997 ◽  
Vol 62 (11) ◽  
pp. 1747-1753 ◽  
Author(s):  
Radek Marek
Keyword(s):  
Double Bond ◽  
Chemical Shifts ◽  
Multiple Bond ◽  
Coupling Constants ◽  
Single Quantum ◽  
Nmr Techniques ◽  
Phase Sensitive ◽  
Heteronuclear Coupling

Determination of 15N chemical shifts and heteronuclear coupling constants of substituted 2,2-dimethylpenta-3,4-dienal hydrazones is presented. The chemical shifts were determined by gradient-enhanced inverse-detected NMR techniques and 1H-15N coupling constants were extracted from phase-sensitive gradient-enhanced single-quantum multiple bond correlation experiments. Stereospecific behaviour of the coupling constants 2J(1H,15N) and 1J(1H,13C) has been used to determine the configuration on a C=N double bond. The above-mentioned compounds exist predominantly as E isomers in deuteriochloroform.

Sequential injection analysis coupled to on-line benchtop proton NMR: Method development and application to the determination of synthetic cathinones in seized drug samples

Talanta ◽  
2021 ◽  
Vol 231 ◽  
pp. 122355
Author(s):  
Timothy J. Trinklein ◽  
Malati Thapa ◽  
Lexie A. Lanphere ◽  
John A. Frost ◽  
Sandra M. Koresch ◽  
...  
Keyword(s):  
Method Development ◽  
Proton Nmr ◽  
Synthetic Cathinones ◽  
Sequential Injection Analysis ◽  
Sequential Injection ◽  
Nmr Method ◽  
On Line

scholarly journals NMR of Natural Products as Potential Drugs

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3763
Author(s):  
Poul Erik Hansen
Keyword(s):  
Natural Products ◽  
Hydrogen Bonding ◽  
Density Functional ◽  
Chemical Shifts ◽  
Isotope Effects ◽  
Density Functional Theory Calculations ◽  
Intramolecular Hydrogen Bonding ◽  
Chemical Equilibria ◽  
Nmr Techniques ◽  
Intramolecular Hydrogen

This review outlines methods to investigate the structure of natural products with emphasis on intramolecular hydrogen bonding, tautomerism and ionic structures using NMR techniques. The focus is on 1H chemical shifts, isotope effects on chemical shifts and diffusion ordered spectroscopy. In addition, density functional theory calculations are performed to support NMR results. The review demonstrates how hydrogen bonding may lead to specific structures and how chemical equilibria, as well as tautomeric equilibria and ionic structures, can be detected. All these features are important for biological activity and a prerequisite for correct docking experiments and future use as drugs.

Synthesis and characterization of 19F NMR chelators for measurement of cytosolic free Ca

1987 ◽  
Vol 252 (4) ◽  
pp. C441-C449 ◽  
Author(s):  
L. A. Levy ◽  
E. Murphy ◽  
R. E. London
Keyword(s):  
Chemical Shifts ◽  
Cell Types ◽  
Free Calcium ◽  
Tetraacetic Acid ◽  
Nmr Studies ◽  
Cytosolic Free Calcium ◽  
Fluorine Nmr ◽  
Dissociation Constant Kd

Fluorine 19 nuclear magnetic resonance (NMR) studies of intracellular fluorinated calcium chelators provide a useful strategy for the determination of cytosolic free calcium levels in cells and perfused organs. However, the fluorinated chelator with the highest affinity for calcium ions which has been described to date. 1,2-bis-(2-amino-5-fluorophenoxy)ethane-N,N,N',N'-tetraacetic acid (5FBAPTA), exhibits a dissociation constant (Kd) value 5- to 10-fold greater than the intracellular calcium concentration levels in most cell types, thus limiting the ability of fluorine NMR to report these concentrations reliably. We have consequently designed and synthesized several fluorinated calcium chelators with higher affinity for calcium. The best of these, 2-(2-amino-4-methyl-5-fluorophenoxy)-methyl-8 aminoquinidine-N,N,N',N'-tetraacetic acid (quinMF), has a Kd value approximately 10 times lower than that of 5FBAPTA. Several of the newly synthesized indicators have different chemical shifts for the calcium complexed and uncomplexed chelators to allow the simultaneous use of two indicators. In addition to providing information about the level of cytosolic free calcium, chelators containing a quinoline ring exhibit considerable sensitivity to magnesium levels and hence have potential application for the determination of cytosolic-magnesium concentrations. Application of these chelators is illustrated by determination of the cytosolic-free calcium level in erythrocytes. Use of quinMF, the chelator with the lowest Kd value, gives a calcium value of 25-30 nM.

Determination of the structure of certain 1,3-dioxane derivatives of furan by the NMR method

1969 ◽  
Vol 10 (2) ◽  
pp. 220-224
Author(s):  
Yu. Yu. Samitov ◽  
Z. I. Zelikman ◽  
V. G. Kul'nevich
Keyword(s):  
Nmr Method ◽  
Derivatives Of

17O NMR spectra of the 1,6-anhydro-β-D-hexopyranoses and related-compounds. Determination of configurational effects on the chemical shifts

1992 ◽  
Vol 30 (4) ◽  
pp. 312-319 ◽  
Author(s):  
Jürgen Lauterwein ◽  
Jürgen Schulte ◽  
Martin Schumacher ◽  
Miloslav Černý
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
17O Nmr ◽  
Related Compounds

scholarly journals X-RAY DETERMINATION OF THE STRUCTURE OF ANHYDROUS DIPHENYLCYCLOPROPENONE. VARIATIONS OF THE MOLECULAR GEOMETRY DUE TO HYDROGEN BONDING

1974 ◽  
Vol 3 (6) ◽  
pp. 639-642 ◽  
Author(s):  
Harumichi Tsukada ◽  
Hirotaka Shimanouchi ◽  
Yoshio Sasada
Keyword(s):  
Hydrogen Bonding ◽  
Molecular Geometry ◽  
X Ray
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