Two-dimensional NMR Methods Research Articles

Ethyl 12-Sulfamoyl-abieta-8,11,13-trien-18-oate

We synthesized the novel compound ethyl 12-sulfamoyl-abieta-8,11,13-trien-18-oate in good yield from ethyl 12-sulfo-abieta-8,11,13-trien-18-oate via a two-step protocol. The product was comprehensively characterized by one- and two-dimensional NMR methods, single-crystal X-ray diffraction, IR spectroscopy, and high-resolution mass spectrometry.

Organic selenium compounds determination in the complex matrix by the 1H-77Se HMBC method

The development of the organic Selenium (Se) speciation assay to evaluate Se-enriched yeasts (SeYs) with high selectivity and good sensitivity is highly desired. We investigated contents of three organic Se compounds with a proton-detected 1H-77Se multiple-bond correlation (1H-77Se HMBC) method in a complex yeast matrix. The method showed quantitative correlation peaks resulting by the long-range coupling (nJ(77Se,1H), n = 2, 3) between 1H and 77Se atoms. Broadband excitation and homonuclear coupling evolution suppression can be achieved by utilizing the shaped pulse in the 77Se dimension and the constant time period, respectively. Several NMR methods were compared to improve performances of the 1H-77Se HMBC method in sensitivity. The limit of quantifications (LOQs) were 0.10, 0.11, and 0.15 mmol/L for SeMet, MeSeCys and SeCys2, respectively. Furthermore, the method can greatly raise the resolution without any separation technique compared to other one- and two-dimensional NMR and chromatographic method. The validation of the methodology showed satisfactory specificity, accuracy, precision, and linearity. The method was suitable for routine analysis, quality control and market supervision of Se species in the enriched-Se yeast.

Synthesis of 2-Oxaadamantane Derivatives

1,3-Dichloroadamantanes in fuming nitric acid were converted to mixtures of 2-oxaadamantane derivatives whose structure was determined by two-dimensional NMR methods and X-ray analysis. The resulting compounds can be used in the design of highly complex molecules as subjects for studying biological activity.

Ultrafast transverse relaxation exchange NMR spectroscopy.

Molecular exchange between different physical or chemical environments occurs due to either diffusion or chemical transformation. Nuclear magnetic resonance (NMR) spectroscopy provides a means of understanding the molecular exchange in a noninvasive way and without tracers. Here, we introduce a novel two dimensional, single-scan ultrafast Laplace NMR (UF LNMR) method to monitor molecular exchange using transverse relaxation as a contrast. The UF T2-T2 relaxation exchange spectroscopy (REXSY) method shortens the experiment time by one to two orders of magnitude compared to its conventional counterpart. Contrary to the conventional EXSY, the exchanging sites are distinguished based on T2 relaxation times instead of chemical shifts, making the method especially useful for systems including physical exchange of molecules. Therefore, the UF REXSY method offers an efficient means for quantification of exchange processes in various fields such as cellular metabolism and ion transport in electrolytes. As a proof of principle, we studied a halogen-free orthoborate based ionic liquid system and followed molecular exchange between molecular aggregates and free molecules. The results are in good agreement with the conventional exchange studies. Due to the single-scan nature, the method potentially significantly facilitates the use of modern hyperpolarization techniques to boost the sensitivity by several orders of magnitude.

Flavonoids and steroids from roots of Millettia speciosa

Study on extracts of Millettia speciosa roots collected at Nghe An Province led to the isolation of two flavonoids, pterocarpine (1), quercetin-3-O-[-L-rhamnopyranosyl-(16)--D-glucopyranoside (2) and two steroids, -sitosterol (3), daucosterol (4). Their structure elucidation were determined on the basis of one and two-dimensional NMR and spectrometric methods in combination.

Chemical constituents of two Ecuadorian medicinal plants, Tagetes terniflora Kunth and Croton rivinifolius Kunth

Phytochemical study of two medicinal plants from Ecuador, Tagetes terniflora Kunth, and Croton rivinifolius Kunth, led to the isolation and characterization of the major constituents present in the organic extracts obtained from these plants: 5-(4-acetoxy-1-butynil)-2,2’-bi-thiophene (1), 5-methyl-2,2’:5’,2”- terthiophene (2), patuletin (3) from Tagetes terniflora, and isocorydine (4), sweroside (5), tiliroside (6) from Croton rivinifolius. The structures of these compounds were established by spectroscopic analysis including two-dimensional NMR methods, MS, and comparison with published spectral data. They are recognized as secondary metabolites that represent the chemotaxonomy of Tagetes and Croton genera and could be responsible for the recognized medicinal properties attributed to these species. This paper deals with the first report that shows the presence of these compounds in these plants.

Design, synthesis, DFT, molecular modelling studies and biological evaluation of novel 3-substituted (E)-5-(arylidene)-1-methyl-2-thioxoimidazolidin-4-ones with potent cytotoxic activities against breast MCF-7, liver HepG2, and lung A549

We report the synthesis of novel 3-substituted (E)-5-(arylidene)-1-methyl-2-thioxoimidazolidin-4-ones 6-11, and their biological evaluation. Based on structural and pharmacophore analyses of known inhibitors such as fluorouracil (5-FU), we envisioned interesting 2-thioxoimidazolidin-4-one compounds, 3-substituted (E)-5-(arylidene)-1-methyl-2-thioxoimidazolidin-4-ones 6-11 that would be expected to well match the structural features in 5-FU. Efficient synthesis of twenty-four target compounds 6-11 were achieved through the synthetic pathway of 5 → 6 → 7 → 10 → 11, established after consideration of several plausible synthetic pathways. A series of (E)-5-(arylidene)-1-methyl-2-thioxoimidazolidinoneones 5a-d were synthesized via the reaction of 1-methyl-2-thioxoimidazolidin-4-one (3), which in turn was prepared via the reaction of N-methyl glycine (2) with NH4SCN, followed by Knoevenagel condensation. N-alkylation and N-glycosylation were carried via the reaction of 5a-d with alkyl bromides and α-glycopyranosyl bromides 9a,b under alkaline and glycoside conditions, respectively. The N-alkylated and N-glycosylated structures have been selected for the products. Conformational analysis has been studied by homonuclear and heteronuclear two-dimensional NMR methods (DQF-COSY, HMQC, and HMBC). The N site of alkylation and glycosylation were determined from the 1H, 13C heteronuclear multiple-quantum coherence (HMQC) experiments. Molecular modelling and DFT calculations using B3LYP/6-31+G (d, p) level were performed to study the electronic and geometric properties obtained from the stable structure of the investigated compounds. A good correlation between the quantum chemical descriptors and experimental observations was found. The synthesized derivatives exhibited good binding interactions towards the cyclin-dependent kinase 2, especially compound 11b, which have better key interactions than the co-crystallized ligand. Additionally, it had potent cytotoxic activities with IC50 = 4.30, 5.53, 9.43 against MCF-7, HepG2, and A549, respectively.

Thermal degradation behavior of poly[(R)-3-hydroxybutyrate-co-4-hydroxybutyrate

The thermal degradation behavior of poly[(R)-3-hydroxybutyrate-co-16 mol%-4-hydroxybutyrate] (P(3HB-co-16 mol%-4HB)) was investigated based on spectroscopic analysis of its pyrolyzates and two kinetic modeling approaches. Pyrolyzate analysis revealed that trans-crotonic acid, cis-crotonic acid, γ-butyrolactone, and their oligomers (dimers and trimers) were produced following thermal degradation of P(3HB-co-16 mol%-4HB). The kinetic analyses confirmed that the thermal degradation behavior of this copolymer changed depending on the time and/or temperature parameters. Specifically, this degradation process proceeded in at least two steps, (i) initial random degradation and (ii) subsequent 0th-order weight loss, which indicated unzipping degradation of the 3HB units. Based on 13C NMR and two-dimensional NMR methods, it was determined that the unzipping degradation of 3HB units starting from the chain end may stop or volatilize an oligomer when the reaction reaches a 4HB unit randomly present in the copolymer.

Post Analysis of Proficiency Test Samples Using Nuclear Magnetic Resonance Spectroscopy

Paper describes the Post Nuclear Magnetic Resonance Spectroscopic analysis of proficiency test samples using Phosphorus NMR. In our study two-dimensional 1H-31P NMR method was optimized effectively for identification of Chemical weapon convention related scheduled organophosphorus compounds in the environmental samples provided by OPCW during proficiency test, while second report is on post analysis of proficiency test sample, carried out to reexamine the samples to observe the missed organophosphorus compounds and to investigate the causes of missing of organophosphorus chemicals during analysis.

TD-NMR studies of starches from different botanical origins: Hydrothermal and storage effects

The effects of starch origin on water migration and starch transformation were investigated using one- and two-dimensional Time-domain NMR (TD-NMR) methods. The quantification of T1 and especially of T2 relaxation times during thermal treatment enabled their interpretation relative to the sorption, gelatinization and retrogradation phenomena of starches in the presence of water, in a level close to that used for bread making (50%, wet basis). Comparison between native wheat, waxy corn and potato starches made possible to link relaxation variations to starch structure and properties as crystallinity, granule size, polymorphism, amylopectin content and water-binding capacity all along heating, cooling and storage processes.

CHEMICAL CONSTITUENTS FROM THE LEAVES OF Uvaria boniana Fin. & Gagnep IN VIETNAM

Abstract HCTN_12A phytochemical study of extracts of Uvaria boniana Fin. & Gagnep collected at Vũ Quang National park, Nghe An province leaves led to the isolation of five secondary metabolites, including uvaridacol G (1); 4-methyl-4-[(2Z)-3’-phenylprop-2’-en-1’-yl]cyclohex-2-en-1-one (2); 3,7- dimethoxy quercetin 4’- O- [α-L- rhamnopyranosyl-(12) -β-D- glucopyranoside (3); b-sitosterol (4) and stigmasterol (5). Their structure elucidation were determined on the basis of one and two-dimensional NMR and spectrometric methods in combination with molecular modeling. This is the first report on the chemical constituents of Vietnamese Uvaria boniana.

Synthesis, molecular modeling and anti-cancer evaluation of a series of quinazoline derivatives

Quinazolines were surveyed as biologically relevant moieties against different cancer cell lines, so in the present study, we analyzed novel derivatives as target-oriented chemotherapeutic anti-cancer drugs. A series of 3-substituted 2-thioxo-2,3-dihydro-1H-quinazolin-4-ones 4a-e were synthesized via the reaction of 2-aminobenzoic acid (1) with isothiocyanate derivatives 2a-e. S-alkylation and S-glycosylation were carried via the reaction of 4a-e with alkyl halides and α-glycopyranosyl bromides 7a,b under anhydrous alkaline and glycoside conditions, respectively. The S-alkylated and S-glycosylated structures, and not that of the N-alkylated and N-glycosylated isomers, have been selected for the products. Conformational analysis has been studied by homo- and heteronuclear two-dimensional NMR methods (DQF-COSY, HMQC, and HMBC). The S site of alkylation and glycosylation were determined from the 1H, 13C heteronuclear multiple-quantum coherence (HMQC) experiments. All derivatives were subjected to molecular docking calculations, which selected some derivatives (5n, 8c, 8g, 9c, and 9a) as promising ones based on their excellent binding affinities towards the EGFR tyrosine kinase molecular target. The in vitro cytotoxic activity against MCF-7 and HepG2 cell lines showed effective anti-proliferative activity of the analyzed derivatives with lower IC50 values especially 9a with IC50 = 2.09 and 2.08 μM against MCF-7 and HepG2, respectively, and their treatments were safe against the normal cell line Gingival mesenchymal stem cells (GMSC). Moreover, RT-PCR reaction investigated the apoptotic pathway for the compound 9a, which activated the P53 genes and its related genes. So, further work is recommended for developing it as a chemotherapeutic drug.

Characterization and cytotoxicity of ellagitannins from Stachyurus praecox fruit

This study aimed to characterize and evaluate the cytotoxicities of ellagitannins from S. praecox fruit. Fractionation of an acetone extract of the fruit led to isolation of five new ellagitannins—stachyuranin D (15), stachyuranin E (16), stachyuranin F (17), stachyugluconin (18), and stachyuglyconin (19)—along with seven ellagitannins previously isolated from S. praecox leaves and seven known ellagitannins isolated from Stachyuraceae for the first time. Two-dimensional NMR and other spectroscopic methods enabled complete elucidation of the structures of the new compounds. Structure of flavanoellagitannin (16) was confirmed by 1H NMR comparison with synthetic analogs. The configuration of stachyuglyconin (19) with a C8-aldonic acid core was established with the aid of density functional theory calculations. A MTT assay revealed 5-desgalloylpterocarinin A (11) and hippophaenin B (9) had the highest cytotoxicities among the compounds against HeLa (IC50 = 35.35 μM) and HepG2 (IC50 = 60.00 μM) cells, respectively.

Chemical constituents of the leaves of Uvaria boniana Fin. & Gagnep in Vietnam

A phytochemical study of extracts of Uvaria boniana Fin. & Gagnep collected at Pu Mat National Park, Nghe An Province leaves led to the isolation of three secondary metabolites, including 6-methoxyzeylenol (1), aristolactam AII (2), and stigmasta-4,22-dien-3-on (3). Their structure elucidation was determined on the basis of one and two-dimensional NMR and other spectrometric methods. This is the first report on the chemical constituents of Vietnamese Uvaria boniana.

A four-gene operon in Bacillus cereus produces two rare spore-decorating sugars

Bacterial glycan structures on cell surfaces are critical for cell-cell recognition and adhesion and in host-pathogen interactions. Accordingly, unraveling the sugar composition of bacterial cell surfaces can shed light on bacterial growth and pathogenesis. Here, we found that two rare sugars with a 3-C-methyl-6-deoxyhexose structure were linked to spore glycans in Bacillus cereus ATCC 14579 and ATCC 10876. Moreover, we identified a four-gene operon in B. cereus ATCC 14579 that encodes proteins with the following sequential enzyme activities as determined by mass spectrometry and one- and two-dimensional NMR methods: CTP:glucose-1-phosphate cytidylyltransferase, CDP-Glc 4,6-dehydratase, NADH-dependent SAM:C-methyltransferase, and NADPH-dependent CDP-3-C-methyl-6-deoxyhexose 4-reductase. The last enzyme predominantly yielded CDP-3-C-methyl-6-deoxygulose (CDP-cereose) and likely generated a 4-epimer CDP-3-C-methyl-6-deoxyallose (CDP-cillose). Some members of the B. cereus sensu lato group produce CDP-3-C-methyl-6-deoxy sugars for the formation of cereose-containing glycans on spores, whereas others such as Bacillus anthracis do not. Gene knockouts of the Bacillus C-methyltransferase and the 4-reductase confirmed their involvement in the formation of cereose-containing glycan on B. cereus spores. We also found that cereose represented 0.2-1% spore dry weight. Moreover, mutants lacking cereose germinated faster than the wild type, yet the mutants exhibited no changes in sporulation or spore resistance to heat. The findings reported here may provide new insights into the roles of the uncommon 3-C-methyl-6-deoxy sugars in cell-surface recognition and host-pathogen interactions of the genus Bacillus.

Precise Determination of Enantiomeric Excess by a Sensitivity Enhanced Two-Dimensional Band-Selective Pure-Shift NMR.

Unambiguous identification and precise quantification of enantiomers in chiral mixtures is crucial for enantiomer specific synthesis as well as chemical analysis. The task is often challenging for mixtures with high enantiomeric excess and for complex molecules with strong (1)H-(1)H scalar (J) coupling network. The recent advancements in (1)H-(1)H decoupling strategies to suppress the J-interactions offered new possibilities for NMR based unambiguous discrimination and quantification enantiomers. Herein, we discuss a high resolution two-dimensional pure-shift zCOSY NMR method with homonuclear band-selective decoupling in both the F1 and F2 dimensions (F1F2-HOBS-zCOSY). This advanced method shows a sharp improvement in resolution over the other COSY methods and also eliminates the problems associated with the overlapping decoupling sidebands. The efficacy of this method has been exploited for precise quantification of enantiomeric excess (ee) ratio (R/S) up to 99:1 in the presence of very low concentrations of chiral lanthanide shift reagents (CLSR) or chiral solvating agents (CSA). The F1F2-HOBS-zCOSY is simple and can be easily implemented on any modern NMR spectrometers, as a routine analytical tool.

13C-detection two-dimensional NMR approaches for cellulose derivatives

To demonstrate the effectiveness of 13C-detection two-dimensional NMR methods used for the characterization protein structures for the characterization of cellulose derivatives, 13C–13C COSY, 13C–13C INADEQUATE, and 13C–13C TOCSY experiments were applied to 13C-enriched sodium carboxymethyl cellulose and cellulose acetate. These samples were prepared from bacterial cellulose biosynthesized by Gluconacetobacter xylinus ATCC 53582 in medium containing 20 % uniformly 13C-labelled glucose in unlabeled glucose. The combination of 13C–13C COSY (or 13C–13C INADEQUATE) and 13C–13C TOCSY spectra of the cellulose derivatives facilitated the direct and precise assignment of all ring carbons of each anhydroglucose unit comprising the cellulose chain during the short experimental time. In addition, a short spin-lock time (~24 ms) in the 13C–13C TOCSY experiments was revealed to be preferable for achieving improved sensitivity and obtaining correlation signals between all carbons in the anhydroglucose units of the cellulose derivatives.

Generalized adaptive intelligent binning of multiway data

NMR metabolic fingerprinting methods almost exclusively rely upon the use of one-dimensional (1D) 1H NMR data to gain insights into chemical differences between two or more experimental classes. While 1D 1H NMR spectroscopy is a powerful, highly informative technique that can rapidly and nondestructively report details of complex metabolite mixtures, it suffers from significant signal overlap that hinders interpretation and quantification of individual analytes. Two-dimensional (2D) NMR methods that report heteronuclear connectivities can reduce spectral overlap, but their use in metabolic fingerprinting studies is limited. We describe a generalization of Adaptive Intelligent binning that enables its use on multidimensional datasets, allowing the direct use of nD NMR spectroscopic data in bilinear factorizations such as principal component analysis (PCA) and partial least squares (PLS).

13C, 2H NMR Studies of Structural and Dynamical Modifications of Glucose-Exposed Porcine Aortic Elastin

Elastin, the principal component of the elastic fiber of the extracellular matrix, imparts to vertebrate tissues remarkable resilience and longevity. This work focuses on elucidating dynamical and structural modifications of porcine aortic elastin exposed to glucose by solid-state NMR spectroscopic and relaxation methodologies. Results from macroscopic stress-strain tests are also presented and indicate that glucose-treated elastin is mechanically stiffer than the same tissue without glucose treatment. These measurements show a large hysteresis in the stress-strain behavior of glucose-treated elastin—a well-known signature of viscoelasticity. Two-dimensional relaxation NMR methods were used to investigate the correlation time, distribution, and population of water in these samples. Differences are observed between the relative populations of water, whereas the measured correlation times of tumbling motion of water across the samples were similar. 13C magic-angle-spinning NMR methods were applied to investigate structural and dynamical modifications after glucose treatment. Although some overall structure is preserved, the process of glucose exposure results in more heterogeneous structures and slower mobility. The correlation times of tumbling motion of the 13C-1H internuclear vectors in the glucose-treated sample are larger than in untreated samples, pointing to their more rigid structure. The 13C cross-polarization spectra reveal a notably increased α-helical character in the alanine motifs after glucose exposure. Results from molecular dynamics simulations are provided that add further insight into dynamical and structural changes of a short repeat, [VPGVG]5, an alanine pentamer, desmosine, and isodesmosine sites with and without glucose. The simulations point to changes in the entropic and energetic contributions in the retractive forces of VPGVG and AAAAA motifs. The most notable change is the increase of the energetic contribution in the retractive force due to peptide-glucose interactions of the VPGVG motif, which may play an important role in the observed stiffening in glucose-treated elastin.

Cinnarizine: Comprehensive Profile.

Cinnarizine is a piperazine derivative with antihistaminic, antiserotonergic, antidopaminergic, and calcium channel-blocking activities. A comprehensive profile was performed on cinnarizine including its description and the different methods of analysis. The 1H NMR and 13C one- and two-dimensional NMR methods were used. In addition, infrared and mass spectral analyses were performed which all confirmed the structure of cinnarizine.