scholarly journals Determination of the enantiomeric composition of chiral delta-2-thiazolines-1,3 by1H and19F NMR spectroscopy using chiral solvating agents

2006 ◽  
Vol 20 (3) ◽  
pp. 95-107 ◽  
Author(s):  
Bérangère Merelli ◽  
Laurence Menguy ◽  
Estelle Soubeyrand-Lenoir ◽  
Jean-Claude Cherton
Keyword(s):  
Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Enantiomeric Composition ◽  
Enantiomeric Discrimination

Studies of the perturbing effect of chiral solvating agents (CSAs) namely the fluoroalcohols5aand5bupon the NMR spectra of chiral Δ2-thiazolines1presenting interesting insecticidal properties demonstrated the ability of these CSAs to afford diastereomeric solvates from these substrates providing their enantiomeric discrimination. Thus, for five of the six tested Δ2-thiazolines1Aand1Bthere is at least one possibility to proceed to their enantiomeric discrimination either by1H or19F NMR using mostly5bas CSA.

Cytoplasmic Mg2+ concentration in platelets: implications for determination of Ca2+ with aequorin

1988 ◽  
Vol 255 (4) ◽  
pp. H855-H859
Author(s):  
J. A. Ware ◽  
M. Smith ◽  
E. T. Fossel ◽  
E. W. Salzman
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Nmr Spectroscopy ◽  
Nmr Spectra ◽  
31P Nmr ◽  
Cell Types ◽  
Human Platelets ◽  
Null Point ◽  
The Mean ◽  
Different Cell Types

The concentration of cytoplasmic ionized Mg2+ ([Mg2+]i) varies considerably among different cell types. It has not been measured in platelets. Incorrect estimates of this value could markedly affect many intracellular investigations, including calibration of measurements of platelet cytoplasmic ionized Ca2+ concentration ([Ca2+]i) with the photoprotein aequorin and other Ca2+-sensitive probes. [Mg2+]i was measured in washed, gel-filtered human platelets suspended in modified Tyrode buffer by two methods: 31P-nuclear magnetic resonance (NMR) spectroscopy of intact platelets and null-point titration in platelets selectively permeabilized with digitonin. The 31P-NMR spectra demonstrated that the [Mg2+]i, as calculated from the chemical shift values of ATP resonances, was 0.23 +/- 0.02 (SD) mM in unstimulated platelets. The mean [Mg2+]i as determined by null-point titration was 0.3 +/- 0.1 mM (range: 0.1-0.6 mM). When this [Mg2+]i value was used to construct a Ca2+-calibration curve for aequorin, the indicated [Ca2+]i values in resting and stimulated platelets were lower than those obtained from curves based on previously assumed values for [Mg2+]i (1.0-1.25 mM). This finding largely resolves the discrepancy between resting [Ca2+]i as determined by aequorin or by quin2, fura-2, and indo-1.

Determination of the Structure of Chlorobutyl and Bromobutyl Rubber by NMR Spectroscopy

1987 ◽  
Vol 60 (4) ◽  
pp. 636-646 ◽  
Author(s):  
Chia Yeh Chu ◽  
Kenneth Norman Watson ◽  
Rastko Vukov
Keyword(s):  
Nmr Spectroscopy ◽  
13C Nmr ◽  
Nmr Spectra ◽  
Broad Band ◽  
Type Structure ◽  
13C Nmr Spectra ◽  
Model Compounds ◽  
1H And 13C Nmr

Abstract An analysis of the 1H and 13C NMR spectra of the chlorobutyl and bromobutyl rubbers was performed. Peaks were assigned based on evidence from broad-band decoupled, off-resonance decoupled, selectively decoupled and J-modulated spectra, the known characterization of butyl rubber and halogenation studies on model compounds. The assignment of the minor peaks indicated that the exomethylene-type structure is predominant in both halogenated rubbers. They also contain some nonhalogenated isoprenyl units. Bromobutyl rubber also contains some α-bromomethyl-type structures resulting from rearrangement of the exomethylene structure. The presence of endo-type structures will require further study for confirmation.

1H—NMR-spektroskopische Bestimmung der diastereomeren Reinheit und der absoluten Konfiguration am Phosphoratom von tButyl-phenyl-phosphinsäure-(—)-menthylester / Determination of the Diastereomeric Purity and the Absolute Configuration at Phosphorus of tButyl-phenyl-phosphinic Acid (—)-Menthyl Ester by Means of 1H NMR Spectroscopy

1977 ◽  
Vol 32 (5) ◽  
pp. 589-593 ◽  
Author(s):  
Reiner Luckenbach ◽  
Hans-H. Bechtolsheimer
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr ◽  
Absolute Configuration ◽  
1H Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Phosphinic Acid ◽  
H Nmr ◽  
The Absolute ◽  
Diastereomeric Purity

The preparation and separation into diastereomers of tbutyl-phenyl-phosphinic acid (—)-menthyl ester (1a) is reported. The diastereomeric purity as well as the absolute configuration at phosphorus of 1 a can be deduced from the detailed analysis of the 1H NMR spectra of samples of 1a differing in their diastereomer ratios.

scholarly journals Modeling of Antioxidant Activity, Polyphenols and Macronutrients Content of Bee Pollen Applying Solid-State 13C NMR Spectra

Antioxidants ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1123
Author(s):  
Sylwester Mazurek ◽  
Roman Szostak ◽  
Mateusz Kondratowicz ◽  
Magdalena Węglińska ◽  
Agnieszka Kita ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Solid State ◽  
Nmr Spectroscopy ◽  
13C Nmr ◽  
Nmr Spectra ◽  
13C Nmr Spectra ◽  
Bee Pollen ◽  
Relative Standard ◽  
Solid State 13C Nmr

An application of solid 13C nuclear magnetic resonance (NMR) spectroscopy for the determination of macronutrients, total polyphenols content, antioxidant activity, N C S elements, and pH in commercially available bee pollens is reported herein. Solid-state 13C NMR spectra were recorded for homogenized pollen granules without chemical treatment or dissolution of samples. By combining spectral data with the results of reference analyses, partial least squares models were constructed and validated separately for each of the studied parameters. To characterize and compare the models’ quality, the relative standard errors of prediction (RSEP) were calculated for calibration and validation sets. In the case of the analysis of protein, fat and reducing sugars, these errors were in the 1.8–2.5% range. Modeling the elemental composition of bee pollen on the basis of 13C NMR spectra resulted in RSEPcal/RSEPval values of 0.3/0.6% for the sum of NHCS elements, 0.3/0.4% for C, 1.8/1.9% for N, and 4.2/6.1% for S quantification. Analyses of total phenolics and ABTS antioxidant activity resulted in RSEP values in the 2.7–3.5% and 2.8–3.8% ranges, respectively, whereas they were 1.4–2.1% for pH. The obtained results demonstrate the usefulness of 13C solid-state NMR spectroscopy for direct determination of various important physiochemical parameters of bee pollen.

scholarly journals Determination of Absolute Stereochemistry of Natural Alicyclic Glycosides by 1H NMR Spectroscopy without Application of Chiral Reagents – An Indication

2011 ◽  
Vol 6 (5) ◽  
pp. 1934578X1100600 ◽  
Author(s):  
Tatyana N. Makarieva ◽  
Larisa K. Shubina ◽  
Alla G. Guzii ◽  
Natalya V. Ivanchina ◽  
Vladimir A. Denisenko ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr ◽  
Absolute Configuration ◽  
1H Nmr Spectroscopy ◽  
Nmr Spectra ◽  
H Nmr ◽  
Steroid Glycosides ◽  
The Absolute ◽  
Absolute Stereochemistry

A study has been made of the 1H NMR spectra of peracetylated β-glucopyranosides and α-arabinopyranosides obtained by reaction of D- and L-glucoses, and L- and D-arabinoses with either ( R)- or ( S)-2-octanols. The obtained and literature data show that 1H NMR spectra may be used to determine the absolute configuration of the aglycone moieties of some alicyclic glycosides without the need to synthesize derivatives with chiral reagents, as long as the absolute configuration of their monosaccharide moiety is known or vice versa. Spectra of marine steroid glycosides and their acetates containing glycosylated side chains as alicyclic fragments were also examined. It was shown that analysis of 1H NMR spectra for the determination of the absolute configuration is more applicable in the cases when glycosides have the same substitution in the D-ring of the aglycone moiety.

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