Search results

1

New serinolic amino-s-triazines by chemoselective amination of cyanuric chloride and their (pro)diastereomerism in restricted rotational phenomena

100%

Moldovan O., Lameiras P., Henon E., Popa F., Martinez A., Harakat D., Sacalis C., Ramondenc Y., Darabantu M.

Open Chemistry

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2012

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vol. 10

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issue 4

1119-1136

EN

The highly chemoselective preparation of new elaborated N-unsymmetrically substituted chlorodiamino-s-triazines and melamines, seen as building-blocks for iterative synthesis, is reported. It consisted of amination of cyanuric chloride with commercial C-2-substituted 2-aminopropane-1,3-diols (“serinols”), playing the role as “open-chain” unit and enantiopure (1S,2S)-2-amino-1-(4-nitrophenyl)propane-1,3-diols (“p-nitrophenylserinols”) based amino-1,3-dioxanes (“closed-chain” unit). Issued from the restricted rotation about C(s-triazine)-N(exocyclic) partial double bonds, seen as axes of (pro)diastereomerism, a global four-component rotational equilibrium involving the title compounds is discussed based on DFT computation and (VT) NMR data. Depending on π-deficiency of the s-triazine core, an (un)synchronised deblocking of the generated rotational diastereomers was observed. They are discussed as influence of intra-vs. intermolecular NH...OH (dynamic) interactions occurring in the “open-chain” unit and the anancomeric, axial vs. equatorial, amino-anchorage of the “closed-chain” unit. [...]

2

Identification of 2-[2-nitro-4-(trifluoromethyl)benzoyl]- cyclohexane-1,3-dione metabolites in urine of patients suffering from tyrosinemia type I with the use of 1H and 19F NMR spectroscopy

100%

Szczeciński P., Lamparska D., Gryff-Keller A., Gradowska W.

Acta Biochimica Polonica

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2008

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vol. 55

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issue 4

749-752

EN

Organic extracts of six urine samples from children treated with nitisinone, a medicine against tyrosinemia type I, were investigated by 1H and 19F NMR spectroscopy. The presence of unchanged 2-[2-nitro-4-(trifluoromethyl)benzoyl]cyclohexane-1,3-dione (NTBC), 6-hydroxy-2-[2-nitro-4-(trifluoromethyl)benzoyl]cyclohexane-1,3-dione (NTBC-OH) and 2-nitro-4-trifluoromethylbenzoic acid (NTFA) as well as a few other unidentified compounds containing CF3 group was documented.

3

Complexation of [2.2]paracyclophane with β- and γ-cyclodextrins studied by HPLC and NMR

100%

Dodziuk H., Bielejewska A., Schilf W., Ueda H.

Open Chemistry

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2011

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vol. 9

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issue 6

1056-1061

EN

The NMR spectra of [2.2]paracyclophane with β- or γ-cyclodextrin in DMF-d7 at room temperature do not show significant complexation, while HPLC of the complexes in mixed H2O:alcohol solvents demonstrate complexation with different stoichiometries. At 243 K in DMF solution the H3 and H5 NMR signals of γ-cyclodextrin (but not β) exhibit complexation-induced chemical shifts denoting complex formation. According to HPLC, at room temperature the [2.2]paracyclophane complex with β-cyclodextrin in 20% H2O:EtOH exhibits 1:2 stoichiometry with K 1 = 1×102 ± 2, K 2 = 9.0×104 ± 2×103 (K = 9×106) while that with γ-cyclodextrin in 50% H2O:MeOH exhibits 1:1 stoichiometry with K 1 = 4×103 ± 150 M−1. Thermodynamic parameters for both complexes have been estimated from the retention time temperature dependence. For the β-cyclodextrin complexation at 25°C ΔG 0CD is −39.7 kJ mol−1 while ΔH 0CD and ΔS 0CD are −88.2 kJ mol−1 and −0.16 kJ mol−1 K−1. For γ-cyclodextrin, the corresponding values are ΔG 0CD = −20.5 kJ mol−1, ΔH 0CD = −33.5 kJ mol−1 and ΔS 0CD = −0.04 kJ mol−1 K−1. [...]

4

Direct determination of enantiomeric enrichment of chiral, underivatized aminophosphonic acids - useful for enantioselective bioconversion results evaluation

100%

Kozyra K., Klimek-Ochab M., Brzezińska-Rodak M., Żymańczyk-Duda E.

Open Chemistry

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2013

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vol. 11

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issue 9

1542-1547

EN

Abstract The possibility of applying 31P NMR spectroscopy for the determination of the enantiomeric excess of the racemic mixture of non-derivatized aminophosphonic acids with small side chains has been investigated. It is proven, that the effectiveness of the application of a chiral solvating agent strongly depends on the concentration of applied shift reagent and on the pH of the particular experiment. Effectual resolution protocols are elaborated for following phosphonic acids: 1-aminoethanephosphonic acid, 1-amino-2-methylpropanephosphonic acid, 1-aminophenylmethanephosphonic acid, 1-aminophenylmethane-phosphonic acid and 1-amino-2-phenylethanephosphonic acid. Graphical abstract [...]

5

Nuclear magnetic resonance spectroscopic studies of the trihexyl (tetradecyl) phosphonium chloride ionic liquid mixtures with water

100%

Dwan J., Durant D., Ghandi K.

Open Chemistry

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2008

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vol. 6

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issue 3

347-358

EN

Tetra-alkyl Phosphonium ionic liquids are phosphonium salts with melting points near room temperature. We report the NMR studies of water-trihexyl (tetradecyl) phosphonium chloride ionic liquid mixtures. The proton chemical shifts were used to investigate the intermolecular interactions in mixtures of ionic liquids and water. The OH chemical shifts were found to decrease as the water concentration in the ionic liquid increased, and their rate of change with temperature decreased with water concentration. The CH2 and CH3 chemical shifts were found to move downfield with the increase in temperature, and moved further downfield as water concentration was decreased. The interface of experimental data and the results of quantum calculations suggest a significant binding of phosphonium cations to chloride anion and water molecules. As well, the analysis of the data suggests a possible transformation from cationchloride-water configuration at low water concentrations to cation-water-water at higher water concentrations. [...]

6

Methods of peptide conformation studies.

88%

Biedrzyński A.

Acta Biochimica Polonica

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2001

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vol. 48

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issue 4

1091-1099

EN

In solution most of the peptides assume multiple flexible conformations. Determination of the dominant conformers and evaluation of their populations is the aim of peptide conformation studies, in which theoretical and experimental methods play complementary roles. Molecular dynamics or Monte Carlo methods are quite effective in searching the conformational space accessible to a peptide but they are not able to estimate, precisely enough, the populations of various conformations. Therefore, they must be supplemented by experimental data. In this paper, a short review of the experimental methods, most widely used in peptide conformational studies, is presented. Among them NMR plays the leading role. Valuable information is also obtained from hydrogen exchange, fluorescence resonance energy transfer, and circular dichroism measurements. The advantages and shortcomings of these methods are discussed.

7

The Henry reaction: spectroscopic studies of nitrile and hydroxylamine by-products formed during synthesis of psychoactive phenylalkylamines

88%

Guy M., Freeman S., Alder J., Brandt S.

Open Chemistry

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2008

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vol. 6

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issue 4

526-534

EN

A clandestine two-step route to psychoactive racemic phenylalkylamines utilises the Henry reaction. In the first step an aromatic aldehyde reacts with a nitroalkane to give the nitrostyrene intermediate. In the second step the nitrostyrene is reduced to the phenylalkylamine. An impurity profile of both steps was evaluated through the synthesis and analysis of common street derivatives. The formation of nitrile impurities in the nitroaldol reaction and hydroxylamine impurities in the reduction step were shown by NMR spectroscopy and GC-MS. A selection of reducing agents has been used to give the phenylalkylamines, together with variable quantities of the partially reduced hydroxylamine product. GC-MS analysis of the hydroxylamines showed heat-induced disproportionation which led to the detection of the corresponding oximes. [...]

8

Oxygen decorating at the one ring and at the N-mouth of (10, 0) aluminum nitride nanotube: A DFT investigation

88%

Seif A., Torkashavand L., Mohammadi F.

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issue 2

131-139

EN

We have investigated oxygen decorating in the (10, 0) aluminum nitride nanotube (AlNNT) by density functional theory. Band gaps, total (TDOS) and partial (PDOS) densities of state and chemical-shielding isotropic (CSI) and chemical-shielding anisotropic (CSA) have been calculated or determined in three models of the investigated (10, 0) AlNNT: pristine (model.0), O-decorating at the one ring in the middle of AlNNT (Model.1) and O-decorating at the nitrogen mouth of AlNNT (Model.2). The results indicated that the dipole moment does not detect the significant effects of dopant whereas TDOS, PDOS and band gap energies detect notable effects. The CSI and CSA values for the Al and N atoms-contributed to the Al-O bonds or those atoms close to the decorated region, in both models of O-decorated AlNNTs are changed.

9

1,3-bis(2,4,6-trinitrophenylaminooxy)propane and its 4-cyano-2,6-dinitrophenyl congener: Synthesis and properties

88%

Covaci I., Ionita P., Caproiu M., Socoteanu R., Constantinescu T., Balaban A.

Open Chemistry

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2003

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vol. 1

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issue 1

53-64

EN

Starting from N-hydroxyphthalimide (5) and 1,3-dibromopropane (6) we obtained 1,3-bis(phthalimidooxy)propane (7) which led to 1,3-bis(aminooxy)propane dihydrochloride (8). From its reaction with picryl chloride or 4-cyano-2,6-dinitrochlorobenzene, the two title compounds (4b, 4a) were obtained. 1H-NMR and 13C-NMR spectra are presented. For comparison with the analogous N-methoxy-2,6-dinitro-4-R-anilines 1a, 1b (R=CN or R=NO2), wer report the hydrophobic characteristics (by RPTLC), electronic spectra for the neutral compounds and their anions, pKa values, and the behavior towards oxidizers (DPPH, PbO2, Pb(CH3COO)4, KMnO4 and Ag2O); DPPH converts compounds 1a, 1b and 4a, 4b into betainic structures 2a, 2b respectively.

10

Synthesis and stereochemistry of some new 1,3,5-tris(1,3-dioxan-2-yl)-benzene derivatives

88%

Florian M., Cîrcu M., Toupet L., Terec A., Grosu I., Ramondenc Y., Dincă N., Plé G.

Open Chemistry

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2006

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vol. 4

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issue 4

808-821

EN

The synthesis and the stereochemistry of new 1,3,5-tris(1,3-dioxan-2-yl)-benzene derivatives are reported. The anancomeric structure and the axial orientation of the aryl group with respect to all 1,3-dioxane rings, and the cis-trans isomerism of some of the compounds are revealed. The data are supported by NMR investigations and by the molecular structure of one compound determined by single crystal X-ray diffractometry.

11

Synthesis and NMR spectroscopic characterization of Si-substituted 1-silacyclobutene derivatives

88%

Khan E., Wrackmeyer B.

Open Chemistry

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2011

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vol. 9

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issue 1

126-132

EN

Hydroboration of trialkyn-1-yl(organo)silanes with one equivalent and two equivalents of 9-borabicyclo[3.3.1]nonane, 9-BBN afford dialkyn-1-ylsilanes and alkyn-1-ylsilanes, respectively. The alkyn-1-ylsilane derivatives are stable at room temperature and can be store under dry argon for prolong period of time. These compounds are attractive materials for further rearrangements to afford novel 1-silacyclobutene derivatives bearing Si-alkenyl or Si-alkynyl functionalities. The hydroboration reaction is well controlled by the Si-R1 function, i.e., the starting silanes with R1 = Ph selectively afford hydroboration of one Si-C≡C bond with one equivalent of 9-BBN, leaving the other two functionalities untouched. Under mild reaction conditions (25°C), the starting silanes with R1 = Me lead to mixture containing dialkyn-1-ylsilane, alkyn-1-ylsilane and their respective 1-silacyclobutene derivatives. All new compounds are sensitive towards air and moisture and were studied by multinuclear magnetic resonance spectroscopy (1H, 13C, 11B, 29Si NMR) in solution.

12

Spectroscopic evaluation of chiral and achiral fluorescent ionic liquids

88%

Marwani H.

Open Chemistry

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2010

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vol. 8

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issue 4

946-952

EN

In this study, spectroscopic investigation of chiral and achiral room temperature ionic liquids is achieved. New ionic liquids were prepared via metathesis, accomplished by the reaction of either L-phenylalanine ethyl ester hydrochloride, chlorpromazine hydrochloride or 1,10-Phenanthroline monohydrate hydrochloride with lithium bis(trifluoromethane) sulfonamide in water. The resulting ionic liquids were produced in high yield and purity. The results obtained by use of 1H NMR and IR experiments were in very good agreement with the chemical structures of the synthesized ionic liquids. In addition, the results of thermal gravimetric analysis suggested that these ionic liquids have good thermal stability. UV-Vis and fluorescence spectroscopy measurements indicated that these ionic liquids are strongly optically absorbent and fluorescent. Lastly, time-based fluorescence steady-state measurements demonstrated the high photostability of these ionic liquids. [...]

13

Differences in metabolic profiles of planktonic and biofilm cells in Staphylococcus aureus - 1H Nuclear Magnetic Resonance search for candidate biomarkers

88%

Junka A., Deja S., Smutnicka D., Szymczyk P., Ziółkowski G., Bartoszewicz M., Młynarz P.

Acta Biochimica Polonica

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2013

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vol. 60

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issue 4

701-706

EN

Staphylococcus aureus is responsible for many types of infections related to biofilm presence. As the early diagnostics remains the best option for prevention of biofilm infections, the aim of the work presented was to search for differences in metabolite patterns of S. aureus ATCC6538 biofilm vs. free-swimming S. aureus planktonic forms. For this purpose, Nuclear Magnetic Resonance (NMR) spectroscopy was applied. Data obtained were supported by means of Scanning Electron Microscopy, quantitative cultures and X-ray computed microtomography. Metabolic trends accompanying S. aureus biofilm formation were found using Principal Component Analysis (PCA). Levels of isoleucine, alanine and 2,3-butanediol were significantly higher in biofilm than in planktonic forms, whereas level of osmoprotectant glycine-betaine was significantly higher in planktonic forms of S. aureus. Results obtained may find future application in clinical diagnostics of S. aureus biofilm-related infections.

14

Synthesis, NMR characterization and reactivity of 1-silacyclohex-2-ene derivatives

88%

Khan E., Wrackmeyer B.

Open Chemistry

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2012

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vol. 10

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issue 5

1633-1639

EN

The chloro functionality of allyldichlorosilane (HSiCl2(C3H5)) and allyldichloromethylsilane (MeSiCl2(C3H5)) were replaced by alkynyl groups and new compounds, allyldialkynylsilane 1 and allyldialkynylmethylsilane 2, were obtained. These silanes, which served as starting materials for the onward reactions, were purified by fractional distillation. They were further subjected to hydroboration with 9-BBN (9-borabicyclo[3.3.1]nonane) and were converted into 1-silacyclohex-2-ene derivatives 5 and 6. The competition between C≡C and C=C in the reaction was studied. The hydroborating reagent 9-BBN was expected to prefer terminal C=C bonds and to leave C≡C bond untouched. This hypothesis of preferable hydroboration was experimentally proved, and hence, 1-silacyclohex-2-ene derivatives were obtained in reasonably pure form. The reaction of allyldialkynylsilane 2 with one equivalent of 9-BBN affords 1-silacyclohex-2-ene bearing Si-C≡C-function, ready to be hydroborated further with one equivalent of 9-BBN. The obtained compound bears two C-B bonds, which are attractive synthones for further transformations. This study aims to highlight the chemistry of C-B and Si-H functional groups. All new compounds obtained were colorless air and moisture sensitive oils, and they were studied by multinuclear magnetic resonance spectroscopy (1H, 13C, 11B, 29Si NMR) in solution. [...]

15

NMR-based localization of ions involved in salting out of hen egg white lysozyme

88%

Poznański J.

Acta Biochimica Polonica

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2006

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vol. 53

|

issue 2

421-424

EN

NaCl-induced aggregation of hen egg white lysozyme (HEWL) was monitored by NMR spectroscopy. Small, but significant, changes induced by salt addition in TOCSY spectra were attributed to the effect of local reorganization of protein backbone upon ion binding. Salt-induced variations in HN and Hα chemical shifts were mapped on the HEWL 3D structure which allowed the construction of a scheme of the spatial localization of potential ion binding sites. It was found that in a 0.5 M NaCl solution six chloride anions and at least one sodium cation are bound to preferred sites on the HEWL surface.

16

Analyzing of coatings on steel – reinforced concrete elements by mobile NMR

87%

Orlowsky J., Orlowsky J.

Archives of Civil Engineering

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2016

|

issue 1

17

Overview of the RNA G-quadruplex structures

75%

Malgowska M., Czajczynska K., Gudanis D., Tworak A., Gdaniec Z.

Acta Biochimica Polonica

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2016

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vol. 63

|

issue 4

609-621

EN

G-quadruplexes are non-canonical secondary structures which may be formed by guanine rich sequences, both in vitro and in living cells. The number of biological functions assigned to these structural motifs has grown rapidly since the discovery of their involvement in the telomere maintenance. Knowledge of the G-quadruplexes' three-dimensional structures plays an important role in understanding of their conformational diversity, physiological functions, and in the design of novel drugs targeting the G-quadruplexes. In the last decades, structural studies have been mainly focused on the DNA G-quadruplexes. Their RNA counterparts gained an increased interest along with a still-emerging recognition of the central role of RNA in multiple cellular processes. In this review we focus on structural properties of the RNA G-quadruplexes, based on high-resolution structures available in the RCSB PDB data base and on structural models. In addition, we point out the current challenges in this field of research.

18

STUDY OF THE EFFECT OF THE PHYSICOCHEMICAL PROPERTIES OF CHITOSAN ON ITS HAEMOSTATIC ACTIVITY

75%

Kadyseva O. V., Bykov V. N., Strelova O. Y., Grebenyuk A. N.

Progress on Chemistry and Application of Chitin and its Derivatives

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2021

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vol. 26

112-120

EN

Chitosan are biopolymers that are actively used for the production of local haemostatic agents. The physicochemical characteristics that determine its biological properties include the molecular weight and the deacetylation degree. However, there is no linear relationship between these parameters and haemostatic activity. The most reliable method of confirming the effectiveness is still in vivo experiments. The ability to initiate haemostasis depends on the conformational transition of chitosan macromolecules. The highest efficiency in vitro was for samples in which the transition of a significant part of the molecules from the ‘rigid rod’ state to the ‘globule’ occurred at physiological pH. It is proposed to expand the list of indicators of chitosan that can be controlled to evaluate the quality of raw materials, related to haemostatic activity, to include the definition of the conformational transition at physiological pH.

19

Cyclic enkephalin-deltorphin hybrids containing a carbonyl bridge: structure and opioid activity

75%

Ciszewska M., Ruszczyńska K., Oleszczuk M., Chung N., Witkowska E., Schiller P., Wójcik J., Izdebski J.

Acta Biochimica Polonica

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2011

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vol. 58

|

issue 2

225-230

EN

Six hybrid N-ureidoethylamides of octapeptides in which an N-terminal cyclic structure related to enkephalin was elongated by a C-terminal fragment of deltorphin were synthesized on MBHA resin. The synthetic procedure involved deprotection of Boc groups with HCl/dioxane and cleavage of the peptide resin with 45 % TFA in DCM. d-Lys and d-Orn were incorporated in position 2, and Lys, Orn, Dab, or Dap in position 5. The side chains of the dibasic amino function were protected with the Fmoc group. This protection was removed by treatment with 55 % piperidine in DMF, and cyclization was achieved by treatment with bis-(4-nitrophenyl)carbonate. Using various combinations of dibasic amino acids, peptides containing a 17-, 18-, 19- or 20-membered ring structure were obtained. The peptides were tested in the guinea-pig ileum (GPI) and mouse vas deferens (MVD) assays. Diverse opioid activities were observed, depending on the size of the ring. Extension of the enkephalin sequence at the C-terminus by a deltorphin fragment resulted in a change of receptor selectivity in favor of the δ receptor. The conformational propensities of selected peptides were determined using the EDMC method in conjunction with data derived from NMR experiments carried out in water. This approach allowed proper examination of the dynamical behavior of these small peptides. The results were compared with those obtained earlier with corresponding N-(ureidoethyl)pentapeptide amides.

20

Comparison of structure, logP and P388 cytotoxicity of some phenyl and ferrocenyl cyclic chalcone analogues. Application of RP-TLC for logP determination of the ferrocenyl analogues

75%

Perjési P., Takács-Novák K., Rozmer Z., Sohár P., Bozak R., Allen T.

Open Chemistry

|

2012

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vol. 10

|

issue 5

1500-1505

EN

Cyclic chalcone analogues (2–5) and their ferrocenyl counterparts (6–10) were synthesized and their logP and P388 cyctotoxity were investigated. The structures of the newly synthesized compounds were confirmed by IR 1H and 13NMR spectroscopy. Comparison of conjugation and stereochemistry of the respective derivatives showed similar characteristics compared to ones with some higher degree of conjugation in the ferrocenyl series. Comparison of logP of the ferrocenyl derivatives determined by a validated RP-TLC method showed the ferrocenyl derivatives to have higher logP TLC. The results demonstrate that the differences in three dimensional shape, conjugation and lipophilicity do not have strong influence on the P388 cytotoxicity of the investigated phenyl (1−5) and ferrocenyl (6−10) enones. [...]

Refine search results

New serinolic amino-s-triazines by chemoselective amination of cyanuric chloride and their (pro)diastereomerism in restricted rotational phenomena

Identification of 2-[2-nitro-4-(trifluoromethyl)benzoyl]- cyclohexane-1,3-dione metabolites in urine of patients suffering from tyrosinemia type I with the use of 1H and 19F NMR spectroscopy

Complexation of [2.2]paracyclophane with β- and γ-cyclodextrins studied by HPLC and NMR

Direct determination of enantiomeric enrichment of chiral, underivatized aminophosphonic acids - useful for enantioselective bioconversion results evaluation

Nuclear magnetic resonance spectroscopic studies of the trihexyl (tetradecyl) phosphonium chloride ionic liquid mixtures with water

Methods of peptide conformation studies.

The Henry reaction: spectroscopic studies of nitrile and hydroxylamine by-products formed during synthesis of psychoactive phenylalkylamines

Oxygen decorating at the one ring and at the N-mouth of (10, 0) aluminum nitride nanotube: A DFT investigation

1,3-bis(2,4,6-trinitrophenylaminooxy)propane and its 4-cyano-2,6-dinitrophenyl congener: Synthesis and properties

Synthesis and stereochemistry of some new 1,3,5-tris(1,3-dioxan-2-yl)-benzene derivatives

Synthesis and NMR spectroscopic characterization of Si-substituted 1-silacyclobutene derivatives

Spectroscopic evaluation of chiral and achiral fluorescent ionic liquids

Differences in metabolic profiles of planktonic and biofilm cells in Staphylococcus aureus - 1H Nuclear Magnetic Resonance search for candidate biomarkers

Synthesis, NMR characterization and reactivity of 1-silacyclohex-2-ene derivatives

NMR-based localization of ions involved in salting out of hen egg white lysozyme

Analyzing of coatings on steel – reinforced concrete elements by mobile NMR

Overview of the RNA G-quadruplex structures

STUDY OF THE EFFECT OF THE PHYSICOCHEMICAL PROPERTIES OF CHITOSAN ON ITS HAEMOSTATIC ACTIVITY

Cyclic enkephalin-deltorphin hybrids containing a carbonyl bridge: structure and opioid activity

Comparison of structure, logP and P388 cytotoxicity of some phenyl and ferrocenyl cyclic chalcone analogues. Application of RP-TLC for logP determination of the ferrocenyl analogues