A bisthiourea-based 1 H NMR chiral sensor for chiral discrimination of a variety of chiral compounds

Chiral total syntheses of both enantiomers of the anti-MRSA active plymuthipyranone B and all of the both enantiomers of three unnatural and synthetic analogues were performed. These two pairs of four chiral compounds are composed of the same 3-acyl-5,6-dihydro-2H-pyran-2-one structure. The starting synthetic step utilized a privileged asymmetric Mukaiyama aldol addition using Ti(OiPr)4/(S)-BINOL or Ti(OiPr)4/(R)-BINOL catalysis to afford the corresponding (R)- and (S)-δ-hydroxy-β-ketoesters, respectively, with highly enantiomeric excess (>98%). Conventional lactone formation and successive EDCI-mediated C-acylation produced the desired products, (R)- and (S)-plymuthipyranones B and three (R)- and (S)- synthetic analogues, with an overall yield of 42–56% with a highly enantiomeric excess (95–99%). A bioassay of the anti-MRSA activity against ATCC 43300 and 33591 revealed that (i) the MICs of the synthetic analogues against ATCC 43300 and ATCC 33591 were between 2 and 16 and 4 and 16 μg/mL, respectively, and those of vancomycin (reference) were 1 μg/mL. (ii) The natural (S)-plymuthipyranone B exhibited significantly higher activity than the unnatural (R)-antipode against both AACCs. (iii) The natural (R)-plymuthipyranone B and (R)-undecyl synthetic analogue at the C6 position exhibited the highest activity. The present work is the first investigation of the SAR between chiral R and S forms of this chemical class.

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Chiral Discrimination through 1 H NMR and Luminescence Spectroscopy: Dynamic Processes and Solid Strip for Chiral Recognition

Chemistry - A European Journal ◽

10.1002/chem.201704837 ◽

2017 ◽

Vol 23 (72) ◽

pp. 18303-18313 ◽

Cited By ~ 11

Author(s):

Monalisa Gangopadhyay ◽

Arunava Maity ◽

Ananta Dey ◽

P. R. Rajamohanan ◽

Sapna Ravindranathan ◽

...

Keyword(s):

Chiral Recognition ◽

Chiral Discrimination ◽

Luminescence Spectroscopy ◽

Dynamic Processes ◽

H Nmr

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Chiral discrimination of α-hydroxy acids and N-Ts-α-amino acids induced by tetraaza macrocyclic chiral solvating agents by using 1H NMR spectroscopy

Organic & Biomolecular Chemistry ◽

10.1039/c6ob02578a ◽

2017 ◽

Vol 15 (7) ◽

pp. 1642-1650 ◽

Cited By ~ 10

Author(s):

Caixia Lv ◽

Lei Feng ◽

Hongmei Zhao ◽

Guo Wang ◽

Pericles Stavropoulos ◽

...

Keyword(s):

Amino Acids ◽

Nmr Spectroscopy ◽

1H Nmr ◽

1H Nmr Spectroscopy ◽

Chiral Discrimination ◽

Hydroxy Acids ◽

H Nmr

Several α-hydroxy acids and N-Ts-α-amino acids were effectively discriminated in the presence of tetraaza macrocyclic chiral solvating agents (TAMCSAs) 1a–1d by 1H NMR spectroscopy.

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FTIR and1H-NMR studies of chiral (S)-(-)-2-methylbutyl 4′-(4″-hexyloxy-, (S)-(-)-2-methylbutyl 4′-(4″-(d13)-hexyloxy‒, (S)-(-)-2-methylbutyl 4′-(4″-octyloxy- and (S)-(-)-2-methylbutyl 4′-(4″-(d17)-octyloxyphenyl)benzoates

Spectroscopy An International Journal ◽

10.1155/2000/207089 ◽

2000 ◽

Vol 14 (3) ◽

pp. 93-98 ◽

Cited By ~ 2

Author(s):

Guan-Yeow Yeap ◽

Yoichi Takanishi ◽

Hideo Takezoe

Keyword(s):

Elemental Analysis ◽

Potassium Bromide ◽

Ftir Spectra ◽

Nmr Studies ◽

Chiral Compounds ◽

H Nmr ◽

First Time

Four organic chiral compounds (S)-(-)-2-methylbutyl 4′-(4″-hexyloxy-, (S)-(-)-2-methylbutyl 4′-(4″-(d13)- hexyloxy-, (S)-(-)-2-methylbutyl 4′-(4″-octyloxy- and (S)-(-)-2-methylbutyl 4′-(4″-(d17)-octyloxy-phenyl)benzoates were synthesized via generalized methods and characterized by elemental analysis, FTIR and1H NMR. A noticeable difference between the compounds which possess hydrogenated achiral substituent with the deuterated counterparts as exemplified from the FTIR spectra has been suggested for the first time to result from the afinity of the latter compounds towards hydroxylation induced by potassium bromide.

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Competition of Ester, Amide, Ether, Carbonate, Alcohol and Epoxide Ligands in the Dirhodium Experiment (Chiral Discrimination by NMR Spectroscopy) [1]

Natural Product Communications ◽

10.1177/1934578x1200700318 ◽

2012 ◽

Vol 7 (3) ◽

pp. 1934578X1200700 ◽

Cited By ~ 1

Author(s):

Jens T. Mattiza ◽

Vera Meyer ◽

Gülsüm Özüduru ◽

Tanja Heine ◽

Joerg Fohrer ◽

...

Keyword(s):

Chiral Discrimination ◽

Primary Alcohols ◽

Priority List ◽

H Nmr ◽

Rhodium Atom ◽

Polyfunctional Compounds ◽

Oxygen Groups ◽

Derivatives Of ◽

Epoxy Groups ◽

Ether Alcohol

Thirty-eight derivatives of 3-hydroxy-2-methylpropanoic acid, each with two different oxygen functionalities, were synthesized and subjected to the standard dirhodium experiment (1H NMR in the presence of an equimolar amount of the chiral dirhodium tetracarboxylate complex Rh*). Their structures represent ester, amide, carbonate, ether, alcohol and/or epoxy groups. Significant selectivity in the binding of those oxygen groups to the complex were determined. From these results, a priority list in binding to a rhodium atom of Rh* was established: epoxides > primary alcohols > ethers ≥ esters ≥ amides > carbonates > tertiary alcohols This sequence allows the prediction of the preferred binding site of oxygen-containing groups in polyfunctional compounds, which frequently occur among natural products, and, particularly, in asymmetric synthesis of such compounds. Differentiation of the enantiomers by the dirhodium experiment is easily accomplished due to numerous signal dispersions in nearly all cases.

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1 H NMR investigation of the hetero-association of aromatic molecules in aqueous solution: factors involved in the stabilization of complexes of daunomycin and acridine drugs

Molecular Physics ◽

10.1080/002689700750036971 ◽

2000 ◽

Vol 98 (23) ◽

pp. 1961-1971 ◽

Cited By ~ 1

Author(s):

David B. Davies, Dennis A. Veselkov, Veni

Keyword(s):

Aqueous Solution ◽

H Nmr ◽

Aromatic Molecules

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Das Verhalten der Körpermasse bei einem 81-jährigen Läufer an einem 100-km-Lauf

Praxis ◽

10.1024/1661-8157.98.3.143 ◽

2009 ◽

Vol 98 (3) ◽

pp. 143-149 ◽

Cited By ~ 3

Author(s):

Knechtle ◽

Wirth ◽

Knechtle ◽

Kohler

Keyword(s):

H Nmr

Ein 81-jähriger Läufer mit Status nach aortokoronarem Bypass bei bekannter koronarer Herzkrankheit hat einen 100-km-Lauf in 19 h und 45 min erfolgreich beendet. Vor und unmittelbar nach dem Lauf wurden Fett- und Muskelmasse nicht-invasiv sowohl mit der bioelektrischen Impedanzanalyse als auch mit der klassischen Hautfaltenmethode bestimmt. Zusätzlich wurden Blut- und Urinproben zur Beurteilung des Flüssigkeitshaushaltes genommen und eine ¹H-NMR-Spektroskopie des Urins zum Nachweis eines erhöhten Kohlenhydrat-, Fett- oder Eiweissstoffwechsels durchgeführt. Das Körpergewicht nahm um 1.9 kg ab. Während die errechnete Muskelmasse um 0.1 kg zunahm, nahm die errechnete Fettmasse um 0.2 kg (anthropometrische Methode) resp. 3.1 kg (BIA) ab. Das errechnete Körperwasser nahm um 1.2 l zu. Während Hämatokrit, Harnstoff und spezifisches Gewicht des Urins zunahmen, sank das Natrium im Blut ab. Das Plasmavolumen nahm um 19% ab. Die ¹H-NMR-Spektroskopie des Urins zeigte nach der Belastung einen Anstieg der Ketonkörper. Um einen Abbau der Muskelmasse objektivieren zu können, muss der Ausgangswert des Körperwassers abgewartet werden, um keine Fehlinterpretation aufgrund der Methoden zu machen. Unklar bleibt, wieso es zu einer Einlagerung von Wasser kam. In weiteren Untersuchungen könnten zusätzliche Methoden wie DEXA, Muskelbiopsien und Bestimmung von weiteren Blut- und Urinparametern Auskunft geben, ob effektiv und wie viel Muskelmasse abgebaut wird und ob Abbauprodukte der Muskulatur die Nierenfunktion einschränken und somit zu einer Wasserretention führen.

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H NMR Evidence for a Change in The Local Hydrogen Environment of Sites Associated with the Staebler-Wronski Effect in a-Si:H

MRS Proceedings ◽

10.1557/proc-715-a11.2 ◽

2002 ◽

Vol 715 ◽

Author(s):

T. Su ◽

Robin Plachy ◽

P. C. Taylor ◽

S. Stone ◽

G. Ganguly ◽

...

Keyword(s):

Line Shape ◽

Defect Density ◽

Hydrogen Atoms ◽

Hydrogen Environment ◽

H Nmr ◽

Line Shapes ◽

Different Temperatures ◽

Staebler Wronski Effect

AbstractWe study the H NMR line shapes of a sample of a-Si:H under several conditions: 1) as grown, 2) light-soaked for 600 hours, and 3) light-soaked followed by annealing at different temperatures. At T = 7 K, the NMR line shape of the sample after light soaking exhibits an additional doublet compared to that of the sample as-grown. This doublet is an indication of a closely separated hydrogen pair. The distance between the two hydrogen atoms is estimated to be about (2.3 ± 0.2) Å. The concentration of these hydrogen sites is estimated to be between 1017 and 1018 cm-3 consistent with ESR measurements of the defect density after light soaking. This doublet disappears after the sample is annealed at 200°C for 4 hours.

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Room Temperature Flow Electrochemistry as a Means of Retaining the “Memory of Chirality” via Hofer Moest Type Reaction

10.26434/chemrxiv.11516967.v2 ◽

2020 ◽

Author(s):

Tomas Hardwick ◽

Rossana Cicala ◽

Nisar Ahmed

Keyword(s):

Continuous Flow ◽

Room Temperature ◽

Biological Activities ◽

Supporting Electrolyte ◽

Enantiomeric Excess ◽

Flow Chemistry ◽

Batch Processes ◽

Enabling Technology ◽

Chiral Compounds ◽

Memory Of Chirality

Many chiral compounds have become of great interest to the pharmaceutical industry as they possess various biological activities. Concurrently, the concept of “memory of chirality” has been proven as a powerful tool in asymmetric synthesis, while flow chemistry has begun its rise as a new enabling technology to add to the ever increasing arsenal of techniques available to the modern day chemist. Here, we have employed a new simple electrochemical microreactor design to oxidise an L-proline derivative at room temperature in continuous flow. Flow performed in microreactors offers up a number of benefits allowing reactions to be performed in a more convenient and safer manner, and even allow electrochemical reactions to take place without a supporting electrolyte due to a very short interelectrode distance. By the comparison of electrochemical oxidations in batch and flow we have found that continuous flow is able to outperform its batch counterpart, producing a good yield (71%) and a better enantiomeric excess (64%) than batch with a 98% conversion. We have, therefore, provided evidence that continuous flow chemistry has the potential to act as a new enabling technology to replace some aspects of conventional batch processes.

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Solvent-Ligand Interactions in Colloidal Nanocrystals

10.26434/chemrxiv.6447884 ◽

2018 ◽

Author(s):

Jonathan De Roo ◽

Nuri Yazdani ◽

Emile Drijvers ◽

Alessandro Lauria ◽

Jorick Maes ◽

...

Keyword(s):

Direct Method ◽

Line Broadening ◽

H Nmr ◽

Size Dependent ◽

Line Shape Analysis ◽

Wide Range ◽

Nanocrystal Synthesis ◽

Ligand Interactions ◽

Indispensable Tool ◽

Theoretical Evidence

Although solvent-ligand interactions play a major role in nanocrystal synthesis, dispersion formulation and assembly, there is currently no direct method to study this. Here we examine the broadening of 1H NMR resonances associated with bound ligands, and turn this poorly understood descriptor into a tool to assess solvent-ligand interactions. We show that the line broadening has both a homogeneous and a heterogeneous component. The former is nanocrystal-size dependent and the latter results from solvent-ligand interactions. Our model is supported by experimental and theoretical evidence that correlates broad NMR lines with poor ligand solvation. This correlation is found across a wide range of solvents, extending from water to hexane, for both hydrophobic and hydrophilic ligand types, and for a multitude of oxide, sulfide and selenide nanocrystals. Our findings thus put forward NMR line shape analysis as an indispensable tool to form, investigate and manipulate nanocolloids.

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