scholarly journals Stereochemical Investigations of Diastereomeric N-[2-(Aryl)-5-methyl-4-oxo-1,3-thiazolidine-3-yl]-pyridine-3-carboxamides by Nuclear Magnetic Resonance Spectroscopy (1D and 2D)

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Öznur Demir-Ordu ◽  
Hale Demir-Dündar ◽  
Sumru Ozkirimli
Keyword(s):  
High Performance ◽  
Mass Spectra ◽  
Chiral Stationary Phase ◽  
Coupling Constants ◽  
Resonance Spectroscopy ◽  
H Nmr ◽  
Nuclear Overhauser Enhancement ◽  
Stereogenic Centers ◽  
Noesy Experiment ◽  
Nuclear Overhauser

Some new N-[2-(aryl)-5-methyl-4-oxo-1,3-thiazolidine-3-yl]-pyridine-3-carboxamides were synthesized and their structures were investigated by IR, NMR (1H, 13C, and 2D), and mass spectra. The presence of C-2 and C-5 stereogenic centers on the thiazolidinone ring resulted in diastereoisomeric pairs. The configurations of two stereogenic centers were assigned based upon 1H NMR analysis of coupling constants and 2D nuclear overhauser enhancement spectroscopy (NOESY) experiment. Resolution of the diastereoisomers was performed by high performance liquid chromatography (HPLC) using a chiral stationary phase.

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.

Mapping the copper ligands of Cu,Zn superoxide dismutase by nuclear overhauser enhancement of the isotropically shifted 1 H-NMR lines of the Cu,Co derivative

FEBS Letters ◽  
1990 ◽  
Vol 261 (2) ◽  
pp. 231-236 ◽  
Author(s):  
Maurizio Paci ◽  
Alessandro Desideri ◽  
Marco Sete ◽  
Mattia Falconi ◽  
Giuseppe Rotilio
Keyword(s):  
Superoxide Dismutase ◽  
H Nmr ◽  
Nuclear Overhauser Enhancement ◽  
Nuclear Overhauser ◽  
Copper Ligands

scholarly journals Isomerization of antimalarial drug WR99210 explains its inactivity in a commercial stock

2020 ◽  
Author(s):  
T. Parks Remcho ◽  
Sravanthi D. Guggilapu ◽  
Phillip Cruz ◽  
Glenn A. Nardone ◽  
Gavin Heffernan ◽  
...  
Keyword(s):  
Active Site ◽  
Antimalarial Drug ◽  
High Performance ◽  
Mass Spectra ◽  
Drug Candidate ◽  
Resonance Spectroscopy ◽  
Computational Docking ◽  
Layer Chromatography ◽  
Commercial Stock ◽  
Selection Of

ABSTRACTWR99210, a former antimalarial drug candidate now widely used for the selection of Plasmodium transfectants, selectively targets the parasite dihydrofolate reductase thymidine synthase bifunctional enzyme (DHFR-TS) but not human DHFR, which is not fused with TS. Accordingly, WR99210 and plasmids expressing human dhfr have become valued tools for the genetic modification of parasites in the laboratory. Concerns over the ineffectiveness of WR99210 from some sources encouraged us to investigate the biological and chemical differences of supplies from two different companies (compounds 1 and 2). Compound 1 proved effective at low nanomolar concentrations against Plasmodium falciparum parasites, whereas compound 2 was ineffective even at micromolar concentrations. Intact and fragmented mass spectra indicated identical molecular formulae of the unprotonated (free base) structures of 1 and 2; however, the compounds displayed differences by thin layer chromatography, reverse phase high performance liquid chromatography, and ultraviolet-visible spectroscopy, indicating important isomeric differences. Structural evaluations by 1H, 13C, and 15N nuclear magnetic resonance spectroscopy confirmed 1 as WR99210 and 2 as an isomeric dihydrotriazine. Induced fit, computational docking models showed that 1 binds tightly and specifically in the P. falciparum DHFR active site whereas 2 fits poorly to the active site in loose and varied orientations. Stocks and concentrates of WR99210 should be monitored for the presence of isomer 2, particularly when they are not supplied as the hydrochloride salt or are exposed to basic conditions that can promote isomerization. Absorption spectroscopy may serve for assays of the unrearranged and rearranged triazines.

Conformational analysis of key disaccharide components of Brucella A and M antigens

1990 ◽  
Vol 68 (7) ◽  
pp. 979-988 ◽  
Author(s):  
Thomas Peters ◽  
Jean-Robert Brisson ◽  
David R. Bundle
Keyword(s):  
Conformational Analysis ◽  
Boltzmann Distribution ◽  
Coupling Constants ◽  
Resonance Spectroscopy ◽  
Structural Elements ◽  
Torsion Angles ◽  
Proton Proton ◽  
Vicinal Proton ◽  
Polysaccharide Antigens ◽  
Nuclear Overhauser

The synthetic α 1,2 and α 1,3 disaccharide methyl glycosides of 4-amino-4,6-dideoxy-D-mannose 1–6 that constitute key structural elements of Brucella A and M antigens were analyzed by 1H and 13C nuclear magnetic resonance spectroscopy. A detailed conformational analysis was performed for the N-acetylated derivatives 1 and 4 as well as for the amino derivatives 2 and 5. Potential energy calculations using the GESA program established the global minima for the disaccharides 1, 2, 4, and 5, and mapped the energy surface as a function of the glycosidic torsion angles [Formula: see text] and ψ. Ensemble averaged nuclear Overhauser enhancements, weighted according to the Boltzmann distribution function, were derived for each of the four disaccharides. This procedure improved the fit between experimentally and theoretically derived nOe values, when compared to interpretations based on a single conformer model. The Brucella A and M antigens are homopolymers of 4-formamido-4,6-dideoxy-D-mannose and, as.N-formyl groups (saccharides 3, 6, and 8) are essential for the binding of these antigens to their respective antibodies, amide conformation was analyzed by examination of the vicinal proton–proton and proton–carbon coupling constants of the model monosaccharide 8. The conformational properties of the model compounds 1–8 were used to model the Brucella A and M polysaccharide antigens. Keywords: conformational analysis, disaccharide conformation, nuclear Overhauser measurements, molecular modeling, Brucella antigen.

Conformational and Structural characterization of carbohydrates and their interactions studied by NMR

2021 ◽  
Vol 28 ◽  
Author(s):  
Francisco Javier Cañada ◽  
Ángeles Canales ◽  
Pablo Valverde ◽  
Beatriz Fernández de Toro ◽  
Mónica Martínez-Orts ◽  
...  
Keyword(s):  
Structural Information ◽  
Theoretical Calculations ◽  
Chemical Shifts ◽  
Structural Complexity ◽  
Coupling Constants ◽  
Resonance Spectroscopy ◽  
Additional Information ◽  
Nuclear Overhauser ◽  
Nuclear Overhauser Effects

: Carbohydrates, either free or as glycans conjugated with other biomolecules, participate in many essential biological processes. Their apparent simplicity in terms of chemical functionality hides an extraordinary diversity and structural complexity. Deeply deciphering at the atomic level their structures is essential to understand their biological function and activities, but it is still a challenging task in need of complementary approaches and no generalized procedures are available to address the study of such complex, natural glycans. The versatility of Nuclear Magnetic Resonance spectroscopy (NMR) often makes it the preferred choice to study glycans and carbohydrates in solution media. The most basic NMR parameters, namely chemical shifts, coupling constants and nuclear Overhauser effects, allow defining short or repetitive chain sequences and characterize their structures and local geometries either in the free state or when interacting with other biomolecules, rendering additional information on the molecular recognition processes. The increased accessibility to carbohydrate molecules extensively or selectively labeled with 13C boosts the resolution and detail that analyzed glycan structures can reach. In turn, structural information derived from NMR, complemented with molecular modeling and theoretical calculations can also provide dynamic information on the conformational flexibility of carbohydrate structures. Furthermore, using partially oriented media or paramagnetic perturbations, it has been possible to introduce additional long-range observables rendering structural information on longer and branched glycan chains. In this review, we provide examples of these studies and an overview of the recent and most relevant NMR applications in the glycobiology field.

scholarly journals 2′-Hydroxylated 3-Deoxyanthocyanin from the Flowers of Cosmos sulphureus Cultivars

2019 ◽  
Vol 14 (9) ◽  
pp. 1934578X1987621
Author(s):  
Tsukasa Iwashina ◽  
Kotarou Amamiya ◽  
Tsunashi Kamo ◽  
Junichi Kitajima ◽  
Takayuki Mizuno ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
Magnetic Resonance ◽  
High Performance ◽  
Mass Spectra ◽  
Chemical Structure ◽  
Resonance Spectroscopy ◽  
Spectroscopic Methods ◽  
Liquid Chromatograph

A new 3-deoxyanthocyanin was isolated from the orange flowers of Cosmos sulphureus cultivar “Diabolo,” together with known aurone, chalcone, flavone, flavonol, and flavanone. The chemical structure of 3-deoxyanthocyanin was established as 5,7,2′,4′-tetrahydroxyflavylium 4′- O-β-d-glucopyranoside by chemical and spectroscopic methods including UV, FAB MS, and 1H and 13C nuclear magnetic resonance spectroscopy (NMR), and named as cosmonidin 4′- O-glucoside (1a). Other known flavonoids were characterized as sulfuretin 6- O-glucoside (2), butein 4′- O-glucoside (3), quercetin 3- O-glucoside (4), luteolin 7- O-glucuronide (5), and eriodictyol 7- O-glucuronide (6) by UV, liquid chromatograph - mass spectra (LC-MS), NMR, and high performance liquid chromatography comparisons with authentic samples. Anthocyanin, which 2′-position is hydroxylated, has not been reported until now. Compound (1a) was also found in other 10 C. sulphureus cultivars “Lamala Lemon,” “Sunrise,” “Dwarf Yellow,” “Cosmic Yellow,” “Carpet Gold,” “Mandarin,” “Cosmic Orange,” “Orange Flare,” “Cosmic Red,” and “Sunset.”

scholarly journals New Antifungal Metabolites from the Mariana Trench Sediment-Associated Actinomycete Streptomyces sp. SY1965

Marine Drugs ◽  
2020 ◽  
Vol 18 (8) ◽  
pp. 385 ◽  
Author(s):  
Wenwen Yi ◽  
Le Qin ◽  
Xiao-Yuan Lian ◽  
Zhizhen Zhang
Keyword(s):  
High Performance ◽  
Nuclear Overhauser Effect ◽  
Ionization Mass ◽  
Mariana Trench ◽  
Streptomyces Sp ◽  
Antifungal Metabolites ◽  
Ionization Mass Spectroscopy ◽  
Noesy Experiment ◽  
Nuclear Overhauser ◽  
New Compounds

New streptothiazolidine A (1), streptodiketopiperazines A (2) and B (3), and (S)-1-(3-ethylphenyl)-1,2-ethanediol (4), together with eight known compounds (5–12), were isolated from the Mariana Trench sediment-associated actinomycete Streptomyces sp. SY1965. The racemic mixtures of (±)-streptodiketopiperazine (2 and 3) and (±)-1-(3-ethylphenyl)-1,2-ethanediol (4 and 5) were separated on a chiral high-performance liquid chromatography (HPLC) column. Structures of the new compounds were elucidated by their high-resolution electrospray ionization mass spectroscopy (HRESIMS) data and extensive nuclear magnetic resonance (NMR) spectroscopic analyses. Streptothiazolidine A is a novel salicylamide analogue with a unique thiazolidine-contained side chain and its absolute configuration was established by a combination of nuclear Overhauser effect spectroscopy (NOESY) experiment, electronic circular dichroism (ECD) and 13C NMR calculations. New streptothiazolidine A (1) and streptodiketopiperazines A (2) and B (3) showed antifungal activity against Candida albicans with MIC values of 47, 42, and 42 g/mL, respectively.

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