scholarly journals Enantiomeric Variability of Distaminolyne A. Refinement of ECD and NMR Methods for Determining Optical Purity of 1-Amino-2-Alkanols

Molecules ◽  
2018 ◽  
Vol 24 (1) ◽  
pp. 90 ◽  
Author(s):  
A. Pearce ◽  
Brent Copp ◽  
Tadeusz Molinski
Keyword(s):  
New Zealand ◽  
1H Nmr ◽  
Geographic Distribution ◽  
Optical Purity ◽  
Nmr Analysis ◽  
Improved Method ◽  
Chiral Reagent ◽  
Nmr Method ◽  
Nmr Methods ◽  
Derivatives Of

Sample configurations of distaminolyne A (1a); isolated from the ascidians Pseudodistoma opacum and P. cereum, and collected at different sites in New Zealand, were investigated by two methods: Exciton coupled electronic circular dichroism (EC ECD) of the corresponding N,O-dibenzoyl derivative 1b; and chiral reagent derivatization of 1a with (S)- and (R)-α-methoxyphenylacetic acid (MPA), followed by 1H-NMR analysis. Configuration and optical purity of 1a (%ee) was found to vary depending on the geographic distribution of ascidian colonies. An improved method for preparing N,O-diarenoyl derivatives of 1a was optimized. The EC ECD method was found to be complementary to the MPA-NMR method at different ranges of %ee.

Polyhydroxyalkanoate quantification in organic wastes and pure cultures using a single-step extraction and 1H NMR analysis

2012 ◽  
Vol 66 (5) ◽  
pp. 1000-1006 ◽  
Author(s):  
Elisabeth Linton ◽  
Asif Rahman ◽  
Sridhar Viamajala ◽  
Ronald C. Sims ◽  
Charles D. Miller
Keyword(s):  
1H Nmr ◽  
Azotobacter Vinelandii ◽  
Nile Blue ◽  
Agricultural Waste ◽  
Accurate Method ◽  
Single Step ◽  
Proton Nuclear Magnetic Resonance ◽  
Copolymer Composition ◽  
Nmr Analysis ◽  
Nmr Method

In this study, a proton nuclear magnetic resonance (1H NMR) method was developed to quantitatively analyze polyhydroxyalkanoate (PHA) content in Cupriavidus necator H16, Azotobacter vinelandii AvOP, and mixed microbial cultures from the effluent of an agricultural waste treatment anaerobic digester. In contrast to previous methods, a single-step PHA extractive method using deuterated chloroform was established, thereby facilitating direct 1H NMR analysis. The accuracy of the method was verified through comparison with well-established gas chromatography (GC) methanolysis techniques. Nile blue fluorescence staining was also carried out to serve as an independent and qualitative indicator of intracellular PHA content. The results indicate that the 1H NMR method is appropriate for rapid and non-destructive quantification of overall PHA content and determination of PHA copolymer composition in a variety of cultures. Notably, this technique was effective in measuring PHA content in full-strength waste samples where high concentrations of background impurities and organic compounds are present. The straightforward procedures minimize error-introducing steps, require less time and materials, and result in an accurate method suitable for routine analyses.

1H NMR Spectral Simplification with Achiral and Chiral Lanthanide Shift Reagents. Part III:* Vinclozolin

1986 ◽  
Vol 40 (6) ◽  
pp. 743-745 ◽  
Author(s):  
Alexander Hatzis ◽  
Robert Rothchild
Keyword(s):  
1H Nmr ◽  
Nmr Spectra ◽  
Optical Purity ◽  
Molar Ratio ◽  
Molar Ratios ◽  
Chiral Reagent ◽  
H Nmr ◽  
Lanthanide Induced Shifts ◽  
Lanthanide Shift Reagents ◽  
Shift Reagents

The 60 MHz 1H NMR spectra of racemic vinclozolin, 1, have been studied at 28° in CDCI3 solution with the achiral reagent tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium(III), 2, and the chiral reagents tris[3-(trifluoromethylhydroxymethylene)- d-camphorato] europium(III), 3, and tris[3-(heptafluoropropylhydroxymethylene)- d-camphorato]europium(III), 4. Reagent 3 produced only small lanthanide-induced shifts and no observable enantiomeric shift differences, ΔΔδ, with 3:1 molar ratios as high as 1.40. In contrast, chiral reagent 4 produced substantial ΔΔδ for the proton, Hβ, at C-2 of the ethenyl group syn to the oxazolidinedione ring and smaller ΔΔδ for the anti proton, Hβ, at the above carbon and for the CH3. With a 4:1 molar ratio of 0.581, ΔΔδ of 7.0 Hz was seen for Hβ. A 4:1 ratio of about 0.41 should be optimum for optical purity determinations; as little as 5% of the minor enantiomer should be detectable.

Synthesis and solid state 13C and 1H NMR analysis of new oxamide derivatives of methyl 2-amino-2-deoxy-α-d-glucopyranoside and ester of amino acids or dipeptides

2003 ◽  
Vol 338 (2) ◽  
pp. 183-188 ◽  
Author(s):  
Andrzej Temeriusz ◽  
Magdalena Rowińska ◽  
Katarzyna Paradowska ◽  
Iwona Wawer
Keyword(s):  
Amino Acids ◽  
Solid State ◽  
1H Nmr ◽  
Nmr Analysis ◽  
Derivatives Of

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

Iridium-Catalyzed Triborylation of 3-Substituted Indoles

2015 ◽  
Vol 68 (12) ◽  
pp. 1810 ◽  
Author(s):  
Andrew S. Eastabrook ◽  
Jonathan Sperry
Keyword(s):  
1H Nmr ◽  
Nmr Analysis ◽  
One Pot ◽  
Substitution Pattern ◽  
The Third

Readily available 3-substituted indoles undergo a one-pot iridium-catalyzed triborylation at the C2, C5, and C7 sites. 1H NMR analysis indicates borylation at C2 and C7 occurs first (no monoborylated product is observed), with the third borylation occurring as a separate, distinct step that is sterically directed to C5 by a combination of the substituent at C3 and the boronate at C7. The resulting tetrasubstituted indoles possess a substitution pattern that is cumbersome to prepare using existing methods.

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

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.

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