Spatially Encoded Transfer of 1H Polarization to 13C for Uniform 1 JCH-Response in HSQC

10.26434/chemrxiv.13550399 ◽

2021 ◽

Author(s):

Bikash Baishya ◽

Rashmi Parihar ◽

Rajeev Verma

Keyword(s):

1H Nmr ◽

Magnetic Field Gradient ◽

Complex Mixture ◽

2D Nmr ◽

Polarization Transfer ◽

Quantitative Aspect ◽

Coherence Transfer ◽

One Dimensional ◽

Peak Intensity ◽

Dependent Polarization

Two dimensional (2D) NMR display better resolution than one-dimensional (1D) 1H NMR. However, 2D NMR does not display a straightforward quantitative aspect due to J-dependent polarization/coherence transfer. 1D 1H NMR is versatile for quantification; however, it displays significant spectral overlap in biological or organic complex mixtures, which forbids quantification of a large number of signals in 1D 1H NMR. The significant variations in 1H13C scalar couplings, T1, T2, and pulse imperfections are the main problems. Although T1, T2 can be suitably chosen to minimize their adverse effect on quantification, the large variations in 1H - 13C couplings lead to variations in cross peak intensity, which is more influenced by the amount of polarization transfer rather than the quantity of metabolites or amount of analytes in a complex mixture. In the present work, we show that spatial encoding of the polarization transfer periods can be executed in 1H13C HSQC using sweep frequency pulses in the presence of a magnetic field gradient. As a result, uniform transfer of polarization from 1H to 13C over a range of 1H - 13C couplings can be performed, subsequently improving the quantitative aspect of HSQC or improve the intensity of cross-peaks, which are mistuned in regular HSQC

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Solid state 1H NMR in one dimensional neutral complex: [PtCl2(en)][PtCl4(en)]

Solid State Communications ◽

10.1016/s0038-1098(97)00353-0 ◽

1997 ◽

Vol 104 (8) ◽

pp. 469-472 ◽

Cited By ~ 1

Author(s):

Ashutosh Ghosh ◽

Noriyoshi Kimura ◽

Shin'ichi Ishimaru ◽

Ryuichi Ikeda ◽

Akiko Takano ◽

...

Keyword(s):

Solid State ◽

1H Nmr ◽

Neutral Complex ◽

One Dimensional

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Benderamide A, a Cyclic Depsipeptide from a Singapore Collection of Marine Cyanobacterium cf. Lyngbya sp.

Marine Drugs ◽

10.3390/md16110409 ◽

2018 ◽

Vol 16 (11) ◽

pp. 409 ◽

Cited By ~ 3

Author(s):

Chi Ding ◽

Ji Ong ◽

Hui Goh ◽

Cynthia Coffill ◽

Lik Tan

Keyword(s):

Breast Cancer Cells ◽

Nuclear Overhauser Effect ◽

2D Nmr ◽

Marine Cyanobacterium ◽

One Dimensional ◽

Mechanistic Pathway ◽

Overhauser Effect ◽

Cyclic Depsipeptide ◽

Nuclear Overhauser ◽

Related Compounds

Benderamide A (1), a (S)-2,2-dimethyl-3-hydroxy-7-octynoic acid (S-Dhoya)-containing cyclic depsipeptide that belongs to the kulolide superfamily, was isolated from a Singapore collection of cf. Lyngbya sp. marine cyanobacterium using a bioassay-guided approach. While the planar structure of 1 was elucidated using a combination of 1D and 2D NMR experiments and MS analysis, the absolute configuration was subsequently achieved using the results obtained from Marfey’s analysis, comparative analysis of nuclear overhauser effect spectroscopy (NOESY) with the known compound 3, and one dimensional-nuclear overhauser effect (1D-NOE). Although 1 did not display antiproliferative activity against MCF7 breast cancer cells, the presence of an Ala instead of Gly suggests a possible mechanistic pathway to explain the consequential decrease in cytotoxicity compared to the closely related 2. In addition, results obtained from an LC–MS/MS-based molecular networking algorithm revealed two other closely related compounds encouraging further identification and isolation from the same marine cyanobacterium extract.

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

Molecules ◽

10.3390/molecules23071785 ◽

2018 ◽

Vol 23 (7) ◽

pp. 1785 ◽

Cited By ~ 5

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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tert-Butylphenolic Derivatives from Paenibacillus odorifer—A Case of Bioconversion

Molecules ◽

10.3390/molecules23081951 ◽

2018 ◽

Vol 23 (8) ◽

pp. 1951 ◽

Cited By ~ 2

Author(s):

Thi-Bach-Le Nguyen ◽

Olivier Delalande ◽

Isabelle Rouaud ◽

Solenn Ferron ◽

Laura Chaillot ◽

...

Keyword(s):

Bacterial Strain ◽

2D Nmr ◽

One Dimensional ◽

Spectroscopic Analyses ◽

Human Keratinocyte ◽

Rhizocarpon Geographicum ◽

Ionisation Mass Spectrometry ◽

Keratinocyte Cell ◽

Ic50 Values ◽

First Time

Two compounds (1) and (2) containing tert-butylphenol groups were, for the first time, produced during the culture of Paenibacillus odorifer, a bacterial strain associated with the crustose lichen, Rhizocarpon geographicum. Their entire structures were identified by one-dimensional (1D) and two-dimensional (2D) NMR and high-resolution electrospray ionisation mass spectrometry (HRESIMS) spectroscopic analyses. Among them, Compound 1 exhibited significant cytotoxicity against B16 murine melanoma and HaCaT human keratinocyte cell lines with micromolar half maximal inhibitory concentration (IC50) values. Furthermore, after supplementation studies, a putative biosynthesis pathway was proposed for Compound 1 throughout a bioconversion by this bacterial strain of butylated hydroxyanisole (BHA), an antioxidant polymer additive.

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Benzyl Furanones and Pyrones from the Marine-Derived Fungus Aspergillus terreus Induced by Chemical Epigenetic Modification

Molecules ◽

10.3390/molecules25173927 ◽

2020 ◽

Vol 25 (17) ◽

pp. 3927

Author(s):

Jing-Shuai Wu ◽

Xiao-Hui Shi ◽

Ya-Hui Zhang ◽

Chang-Lun Shao ◽

Xiu-Mei Fu ◽

...

Keyword(s):

Aspergillus Terreus ◽

Epigenetic Modification ◽

2D Nmr ◽

Etoac Extract ◽

One Dimensional ◽

X Ray ◽

Deacetylase Inhibitor ◽

Ic50 Values ◽

First Time ◽

Mic Value

Chemical epigenetic modification on a marine-derived fungus Aspergillus terreus RA2905 using a histone deacetylase inhibitor, suberoylanilide hydroxamic acid (SAHA), resulted in a significantly changed metabolic profile. A chemical investigation of its ethyl acetate (EtOAc) extract led to the isolation of a racemate of benzyl furanone racemate (±)-1, which further separated chirally as a pair of new enantiomers, (+)- and (−)-asperfuranone (1), together with two new benzyl pyrones, asperpyranones A (2) and B (3). Their structures were elucidated by analysis of the comprehensive spectroscopic data, including one-dimensional (1D) and two-dimensional (2D) NMR, and HRESIMS. The absolute configurations were determined by electronic circular dichroism (ECD) calculation and single-crystal X-ray crystallographic experiment. The structures with benzyl furanone or benzyl pyrone skeletons were discovered from natural products for the first time. Compounds (±)-1, (+)-1, (−)-1, and 2 displayed the antifungal activities against Candida albicans with MIC values of 32, 16, 64, and 64 μg/mL and PTP1B inhibitory activities with the IC50 values of 45.79, 17.32, 35.50, and 42.32 μM, respectively. Compound 2 exhibited antibacterial activity against Pseudomonas aeruginosa with the MIC value of 32 μg/mL.

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Unusual Polyhydroxylated Steroids from the Starfish Anthenoides laevigatus, Collected off the Coastal Waters of Vietnam

Molecules ◽

10.3390/molecules25061440 ◽

2020 ◽

Vol 25 (6) ◽

pp. 1440

Author(s):

Alla A. Kicha ◽

Dinh T. Ha ◽

Timofey V. Malyarenko ◽

Anatoly I. Kalinovsky ◽

Roman S. Popov ◽

...

Keyword(s):

Coastal Waters ◽

2D Nmr ◽

2D Nmr Spectroscopy ◽

Cytotoxic Effects ◽

One Dimensional ◽

The Common ◽

Polyhydroxylated Steroids ◽

New Compounds ◽

Ht 29 ◽

Inhibit Cell Proliferation

Four new polyhydroxylated steroids 1–4 were isolated along with two previously known related steroids 5 and 6 from the methanolic extract of the starfish Anthenoides laevigatus collected off the coastal waters of Vietnam. Structures of new compounds were substantially elucidated by one-dimensional (1D) and two-dimensional (2D) NMR spectroscopy and HRESIMS techniques. Heptaol 1 and hexaol 2 contain the common 5α-cholestane skeleton, while hexaol 3 and heptaol 4 have the rare among starfish steroid compounds 5β-cholestane skeleton. Compounds 1, 5, and 6 do not show cytotoxic effects against normal JB6 Cl41 and cancer HT-29 and MDA-MB-231 cells, however they inhibit cell proliferation and colony formation of cancer HT-29 and MDA-MB-231 cells.

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Demethylation of Alkali Lignin with Halogen Acids and Its Application to Phenolic Resins

Polymers ◽

10.3390/polym11111771 ◽

2019 ◽

Vol 11 (11) ◽

pp. 1771 ◽

Cited By ~ 8

Author(s):

Hao Wang ◽

Thomas L. Eberhardt ◽

Chunpeng Wang ◽

Shishuai Gao ◽

Hui Pan

Keyword(s):

1H Nmr ◽

Nucleophilic Reagent ◽

2D Nmr ◽

Hydroxyl Groups ◽

Chemical Processing ◽

Hydroxyl Content ◽

Phenolic Resins ◽

Alkali Lignin ◽

Ft Ir ◽

And Performance

Lignin, a byproduct from the chemical processing of lignocellulosic biomass, is a polyphenolic compound that has potential as a partial phenol substitute in phenolic adhesive formulations. In this study, HBr and HI were used as reagents to demethylate an alkali lignin (AL) to increase its hydroxyl content and thereby enhance its reactivity for the preparation of phenolic resins. Analyses by FT-IR, 1H-NMR and 2D-NMR(HSQC) demonstrated both a decrease in methoxyl groups and an increase in hydroxyl groups for each demethylated lignin (DL). In addition, the molar amounts of phenolic hydroxyls, determined by 1H-NMR, increased to 0.67 mmol/g for the HI-DL, and 0.64 mmol/g for the HBr-DL, from 0.52 mmol/g for the AL. These results showed that HI, a stronger nucleophilic reagent than HBr, provided a higher degree of AL demethylation. Lignin-containing resins, prepared by copolymerization, met the bonding strength standard for exterior plywood with DL used to replace as much as 50 wt.% of phenol. The increased hydroxyl contents resulting from the lignin demethylations also imparted faster cure times for the lignin-containing resins and lower formaldehyde emissions. Altogether, the stronger nucleophilicity of HI, compared to HBr, impacted the degree of lignin demethylation, and carried through to measurable differences the thermal properties and performance of the lignin-containing PF resins.

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