scholarly journals One-Dimensional 13C NMR Is a Simple and Highly Quantitative Method for Enantiodiscrimination

Molecules ◽  
2018 ◽  
Vol 23 (7) ◽  
pp. 1785 ◽  
Author(s):  
Peter Lankhorst ◽  
Jozef van Rijn ◽  
Alexander Duchateau
Keyword(s):  
1H Nmr ◽  
13C Nmr ◽  
Quantitative Method ◽  
Enantiomeric Excess ◽  
Nmr Spectrum ◽  
One Dimensional ◽  
Nmr Method ◽  
Relative Standard ◽  
Excess Value ◽  
Chiral Solvating Agent

The discrimination of enantiomers of mandelonitrile by means of 1D 13C NMR and with the aid of the chiral solvating agent (S)-(+)-1-(9-anthryl)-2,2,2-trifluoroethanol (TFAE) is presented. 1H NMR fails for this specific compound because proton signals either overlap with the signals of the chiral solvating agent or do not show separation between the (S)-enantiomer and the (R)-enantiomer. The 13C NMR method is validated by preparing artificial mixtures of the (R)-enantiomer and the racemate, and it is shown that with only 4 mg of mandelonitrile a detection limit of the minor enantiomer of 0.5% is obtained, corresponding to an enantiomeric excess value of 99%. Furthermore, the method shows high linearity, and has a small relative standard deviation of only 0.3% for the minor enantiomer when the relative abundance of this enantiomer is 20%. Therefore, the 13C NMR method is highly suitable for quantitative enantiodiscrimination. It is discussed that 13C NMR is preferred over 1H NMR in many situations, not only in molecules with more than one chiral center, resulting in complex mixtures of many stereoisomers, but also in the case of molecules with overlapping multiplets in the 1H NMR spectrum, and in the case of molecules with many quaternary carbon atoms, and therefore less abundant protons.

ChemInform Abstract: A 1H NMR Method for the Determination of Enantiomeric Excess and Absolute Configuration of cis-Dihydrodiol Metabolites of Polycyclic Arenes and Heteroarenes.

ChemInform ◽  
2010 ◽  
Vol 23 (40) ◽  
pp. no-no
Author(s):  
D. R. BOYD ◽  
N. D. SHARMA ◽  
R. BOYLE ◽  
R. A. S. MCMORDIE ◽  
J. CHIMA ◽  
...  
Keyword(s):  
1H Nmr ◽  
Absolute Configuration ◽  
Enantiomeric Excess ◽  
Nmr Method

ASSIGNMENT OF NMR SIGNALS FOR CHLOROPRENE RUBBER BY TWO-DIMENSIONAL NMR SPECTROSCOPY

2013 ◽  
Vol 86 (2) ◽  
pp. 250-260
Author(s):  
Takayuki Saito ◽  
Seiichi Kawahara ◽  
Yoshito Ohtake
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr ◽  
13C Nmr ◽  
Quantum Correlation ◽  
Multiple Bond ◽  
Multiple Quantum ◽  
Heteronuclear Multiple Bond Correlation ◽  
Nmr Spectrum ◽  
Chloroprene Rubber ◽  
Nmr Signals

ABSTRACT Various pulse techniques of NMR spectroscopy were applied to CR to assign some small signals in 13C and 1H NMR spectra for the rubber. First, the rubber was subjected to distortionless enhancement by polarization transfer and attached proton test. The small signals in the 13C NMR spectrum were assigned to secondary, tertiary, and quaternary carbons. Second, correlations between 13C and 1H were investigated by heteronuclear multiple quantum correlation, heteronuclear two bond correlation, and heteronuclear multiple bond correlation measurements to assign the small signals in the 13C NMR spectrum in detail. By using the resulting correlations between 13C and 1H, the small unassigned signals in 1H NMR spectrum were assigned to methylene and methine protons of the rubber.

One-dimensional 13C NMR and HPLC-1H NMR techniques for observing carbon-13 and deuterium labelling in biosynthetic studies

2003 ◽  
Vol 2 (1-2) ◽  
pp. 31-43 ◽  
Author(s):  
Bernd Schneider ◽  
Jonathan Gershenzon ◽  
Gerson Graser ◽  
Dirk Hölscher ◽  
Bettina Schmitt
Keyword(s):  
1H Nmr ◽  
13C Nmr ◽  
Deuterium Labelling ◽  
One Dimensional ◽  
Nmr Techniques ◽  
Biosynthetic Studies

scholarly journals Simple HNMR Spectroscopic Method for Assay of Salts of the Contrast Agent Diatrizoate in Commercial Solutions

1996 ◽  
Vol 79 (4) ◽  
pp. 833-838 ◽  
Author(s):  
George M Hanna ◽  
Cesar A Lau-Cam
Keyword(s):  
Standard Deviation ◽  
Contrast Agent ◽  
1H Nmr ◽  
Sodium Acetate ◽  
Spectroscopic Method ◽  
Internal Standard ◽  
Fixed Amount ◽  
Nmr Spectrum ◽  
Nmr Method ◽  
Molecular Components

Abstract A simple, accurate, and specific 1H NMR spectroscopic method was developed for the assay of diatrizoate meglumine or the combination diatrizoate meglumine and diatrizoate sodium in commercial solutions for injection. A mixture of injectable solution and sodium acetate, the internal standard, was diluted with D20 and the 1H NMR spectrum of the solution was obtained. Two approaches were used to calculate the drug content, based on the integral values for the -N-CO-CH3 protons of diatrizoic acid at 2.23 ppm, the N-CH3 protons of meglumine at 2.73 ppm, and the CH3-CO-protons of sodium acetate at 1.9 ppm. Recoveries (mean ± standard deviation) of diatrizoic acid and meglumine from 10 synthetic mixtures of various amounts of these compounds with a fixed amount of internal standard were 100.3 ±; 0.55% and 100.1 ± 0.98%, respectively. In addition to providing a direct means of simultaneously assaying diatrizoic acid and meglumine, the proposed NMR method can also be used to identify diatrizoate meglumine and each of its molecular components.

scholarly journals Synthesis and Characterization of a Butenafine Analogue

2018 ◽  
pp. 1-11
Author(s):  
M. A. Muhammad ◽  
A. M. Jimoh ◽  
A. Awwal
Keyword(s):  
1H Nmr ◽  
13C Nmr ◽  
Reductive Amination ◽  
Reducing Agent ◽  
Target Compound ◽  
Nmr Spectrum ◽  
Tertiary Butyl ◽  
Tert Butyl ◽  
Chloride Catalyst ◽  
Solvent Action

Aims: The study aims: (I) To synthesise N-(4-(tert-butyl) benzyl)-1-(4-tert-butyl) phenyl)-N-methyl methanaminium chloride, an  analogue  of butenafine from tertiary-butyl benzyl derivatives, (II) to compare the solvent actions of Tetrahydrofuran (THF), acetonitrile, methanol and 1,2-dichloroethane (DCE), and the reducing efficiencies of NaBH4 and sodium triacetoxyborohydride (STAB) during the synthesis. Study Design:  The study involved laboratory experiments leading to the synthesis of the target compound by varying the non-aqueous solvents used, the reducing agent and the temperature of the operations. Silica chloride catalyst was used to speed up the reaction in one of the syntheses and in each synthesis, Thin Layer Chromatography was used to monitor the progress of the reaction. The time taken by each reaction and the yield were used as the basis for determining the solvent action and the reducing efficiency.  Place and Duration of Study: M.Sc. Access controlled Teaching Laboratory, School of Chemistry, Newcastle University, New castle upon Tyne, United Kingdom from June to August 2012. Methodology: Reductive amination was carried out by reacting 4-tert-butylbenzaldehyde and 4-tert-butylbenzylamine, using the direct and then the indirect approaches. This was followed by methylation using the Eschweiler-Clarke reaction in each of the two approaches. The time taken by each reaction was monitored and the product of each approach was characterised by EIS-MS, 1H NMR, 13C NMR and FTIR. Results: 1,2-dichloroethane gave the best solvent action at 40°C (Yield: 75%) and NaBH4  gave the best-reducing action with silica chloride catalyst at 25°C (Yield: 50%). At the end of each synthesis,  in all obtained  products, 1H NMR spectrum gave a single peak of 18 hydrogen atoms at 1.3 -1.5 ppm for the existence of 6 methyl groups in the two tertiary-butyl substituents, the 13C NMR spectrum also showed a peak at  31-32 ppm for the six methyl carbon atoms in the two tertiary-butyl substituents, the FTIR spectrum showed  a strong band at  2460 cm-1 for the presence of a tertiary ammonium ion and finally the EIS-MS gave  a mass to charge ratio of 324.2693 as a confirmation of the relative molecular mass of the compound. Conclusion:  The target compound can be synthesised by both direct and the indirect approaches of reductive amination in any of the solvents tested with/without a catalyst at room or elevated temperature using NaBH4 or STAB as a reducing agent but the best solvent action can be achieved with DCE at 40°C and the best-reducing action can be achieved with NaBH4 in the presence of silica chloride.

A 1h-nmr method for the determination of enantiomeric excess and absolute configuration of cis-dihydrodiol metabolites of polycyclic arenes and heteroarenes

1992 ◽  
Vol 33 (9) ◽  
pp. 1241-1244 ◽  
Author(s):  
Derek R. Boyd ◽  
Narain D. Sharma ◽  
Rosemary Boyle ◽  
R.Austin S. McMordie ◽  
Jagdeep Chima ◽  
...  
Keyword(s):  
1H Nmr ◽  
Absolute Configuration ◽  
Enantiomeric Excess ◽  
Nmr Method

scholarly journals A Rapid and Feasible 1H-NMR Quantification Method of Ephedrine Alkaloids in Ephedra Herbal Preparations

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1599
Author(s):  
Hsin-Yi Hung ◽  
Shih-Min Lin ◽  
Chia-Ying Li ◽  
Sio-Hong Lam ◽  
Yu-Yi Chan ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
1H Nmr ◽  
Present Method ◽  
Internal Standard ◽  
Proton Nuclear Magnetic Resonance ◽  
Nmr Spectrum ◽  
Herbal Preparations ◽  
Nmr Method ◽  
Quantification Method ◽  
Preliminary Purification

A highly specific and sensitive proton nuclear magnetic resonance (1H-NMR) method has been developed for the quantification of ephedrine alkaloid derivatives in Ephedra herbal commercial prescriptions. At the region of δ 4.0 to 5.0 ppm in the 1H NMR spectrum, the characteristic signals are separated well from each other, and six analogues in total, methylephedrine (ME), ephedrine (EP), norephedrine (NE), norpseudoephedrine (NP), pseudoephedrine (PE), and methylpseudoephedrine (MP) could be identified. The quantities of these compounds are calculated by the relative ratio of the integral values of the target peak for each compound to the known concentrations of the internal standard anthracene. The present method allows for a rapid and simple quantification of ephedrine alkaloid derivatives in Ephedra-related commercial prescriptions without any preliminary purification steps and standard compounds, and accordingly it can be a powerful tool to verify different Ephedra species. In comparison to conventional chromatographic methods, the advantages of this method include the fact that no standard compounds are required, the quantification can be directly performed on the crude extracts, a better selectivity for various ephedrine alkaloid derivatives, and the fact that a very significant time-gain may be achieved.

Synthesis and Biological Evaluation of Various New Substituted 1,3,4-oxadiazole-2-thiols

2008 ◽  
Vol 59 (4) ◽  
Author(s):  
Gabriela Laura Almajan ◽  
Stefania Felicia Barbuceanu ◽  
Ioana Saramet ◽  
Mihaela Dinu ◽  
Cristian Vasile Doicin ◽  
...  
Keyword(s):  
Biological Activity ◽  
Plant Growth ◽  
1H Nmr ◽  
Elemental Analysis ◽  
13C Nmr ◽  
Biological Evaluation ◽  
Ethyl Chloroacetate ◽  
Low Concentrations ◽  
Synthesis And Biological Evaluation

5-[4-(4X-phenylsulfonyl)phenyl]-1,3,4-oxadiazole-2-thiols, X=H, Cl, Br, reacted with ethyl chloroacetate to give S-alkylated compounds. Aminomethylation of the thione form of oxadiazoles yielded N(3)-derivatives. All the products have been characterized by elemental analysis, IR, 1H-NMR and 13C-NMR. The plant-growth regulating effects of the title compounds were examined. From the biological activity results, we found that most compounds showed weak stimulatory activities at low concentrations.

Synthesis and Spectral Characterization of New S-Alkylated 1,2,4-Triazoles as Potential Biological Agents

2017 ◽  
Vol 68 (10) ◽  
pp. 2436-2439
Author(s):  
Stefania Felicia Barbuceanu ◽  
Laura Ileana Socea ◽  
Constantin Draghici ◽  
Elena Mihaela Pahontu ◽  
Theodora Venera Apostol ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Spectral Data ◽  
1H Nmr ◽  
Elemental Analysis ◽  
13C Nmr ◽  
Ethyl Bromide ◽  
Spectral Characterization ◽  
Basic Medium ◽  
Phenacyl Bromide

In the work we presented the behavior of 5-(4-(4-X-phenylsulfonyl)phenyl)-4-(n-propyl)-2H-1,2,4-triazole-3(4H)-thiones (X= Cl or Br) with some alkylation agents. Thus, new S-alkylated 1,2,4-triazole derivatives were synthesized by reaction of the corresponding 1,2,4-triazole-3-thione derivatives with different �-halogenated compounds (ethyl bromide, ethyl chloroacetate or phenacyl bromide), in basic medium. The structures of synthesized compounds were elucidated by spectral data (1H-NMR, 13C-NMR, mass spectrometry) and elemental analysis.

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