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I Wawer

Publications and source records attributed to I Wawer.

14 recordsLinked to original sources
PubMed2001

Crystal structure and solid state 13C NMR analysis of N-(methyl 3,4,6-tri-O-acetyl-alpha, and beta-D-glucopyranosid-2-yl)-oxamide derivative of p-chloroaniline, N,N-diethylamine, N-methylaniline and N-ethylaniline.

The X-ray diffraction analysis of N-(methyl 3,4,6-tri-O-acetyl-alpha-D-glucopyranosid-2-yl)-N'-p-chlorophenyloxamide (1), N-(methyl 3,4,6-tri-O-acetyl-alpha-D-glucopyranosid-2-yl)-N',N'-diethyloxamide (2), N-acetyl, N-(methyl 3,4,6-tri-O-acetyl-beta-D-glucopyranosid-2-yl), N'-methyl, N'-phenyloxamide (3), N-acetyl, N-(methyl 3,4,6-tri-O-acetyl-beta-D-glucopyranosid-2-yl), N'-ethyl, N'-phenyloxamide (4) was performed. It was found that the oxamide group in compounds 1-4 can be characterized as two structurally independent amides because there is no pi conjugation across the oxalyl OC-CO bond. Only the oxamide group of 1 is planar and adopts trans conformation stabilized as two intramolecular N-H...O hydrogen bonds.

Aniline Compounds↗
PubMed1999

13C cross-polarization magic angle spinning NMR and gauge-independent atomic orbital, coupled Hartree-Fock calculations of buspirone analogues. Part 2. Hydrochlorides and perchlorates of 1-arylpiperazine-4-alkylimides.

13C cross-polarization (CP) magic angle spinning (MAS) solid state NMR spectra of hydrochlorides and perchlorates of buspirone analogues (2-5) were recorded. In the spectra for each compound, one set of signals appeared, in agreement with single crystal X-ray diffraction data indicating the presence of one molecule per crystal unit. The resonances of 2-5 hydrochlorides were assigned by comparison with the solution chemical shifts. For perchlorate 2b and diperchlorate 2c, the reasonable assignment of signals was made with the aid of the theoretical studies. Ab initio calculations of the carbon shieldings were performed by means of the GIAO-CHF method for two model systems: perchlorate and diperchlorate of quinoline-(N-methyl)piperazine. As no remarkable differences between carbon chemical shifts of hydrochlorides 3-5 in solid state and in solution were observed, it was concluded that in solution these compounds adopted the same conformation as in the solid state.

Buspirone↗
PubMed1998

NMR spectroscopy in pharmacy.

Since drugs in clinical use are mostly synthetic or natural products, NMR spectroscopy has been mainly used for the elucidation and confirmation of structures. For the last decade, NMR methods have been introduced to quantitative analysis in order to determine the impurity profile of a drug, to characteristic the composition of drug products, and to investigate metabolites of drugs in body fluids. For pharmaceutical technologists, solid state measurements can provide information about polymorphism of drug powders, conformation of drugs in tablets etc. Micro-imaging can be used to study the dissolution of tablets, and whole-body imaging is a powerful tool in clinical diagnostics. Taken together, this review covers applications of NMR spectroscopy in drugs analysis, in particular, methods of international pharmacopoeiae, pharmaceutics and pharmacokinetics. The authors have repeated many of the methods describe in their own laboratories.

Chemistry, Pharmaceutical↗
PubMed1998

13C CP MAS NMR study of ureido sugars, derivatives of 2-amino-2-deoxy-beta-D-glucopyranose and dipeptides.

3C CP MAS NMR spectra of solid methyl 3,4,6-tri-O-acetyl-2-deoxy-2-ureido-beta-D-glucopyranosides with dipeptide residues (protected by OMe, OEt or OBz group) were recorded. Broader resonances enabled assignment of carbons linked to nitrogen. Chemical shifts of sugar carbons varied within 2-6 ppm although the acetylated glucose moiety is the same in all compounds. From the six carbonyl groups in the molecule only the resonances of N6-C5=O are shifted by 2.9-8.3 ppm downfield in the spectra of solid compounds, comparing to the solution, indicating that the molecules are linked by NH...O=C5 hydrogen bonds. The C2=O group of ureido bridge is not involved in H-bonding, ester group probably forms intramolecular H-bonds.

Carbohydrates↗
PubMed1998

13C CP (cross-polarization) MAS (magic angle spinning) NMR and GIAO-CHF calculations of buspirone analogues. Part 1. 3a,4,7,7a-Tetrahydro-2-[4-[4-(2-quinolinyl)-1-piperazinyl]butyl ]-4,7-ethane-1H-isoindole-1,3(2H)-dione hydrochloride and hydrobromide.

13C CP (cross-polarization) MAS (magic angle spinning) solid state NMR spectra of buspirone analogue 3a,4,7,7a-tetrahydro-2-[4-[4-(2-quinolinyl)-1-piperazinyl]butyl]-4,7-eth ane-1H-isoindole-1,3(2H)-dione were recorded. In the spectra of hydrochloride and hydrobromide, two sets of signals appeared, in agreement with single crystal X-ray diffraction data indicating that in each of the salts two independent cations were present in the crystal unit. The largest shielding differences of 3.2-4.6 ppm between two sets of signals were found for quinoline aromatic carbons C3 and C2. Ab initio calculations of the carbon and nitrogen shielding constants were performed with the use of the GIAO-CHF method for structural fragments: N-butylsuccinimide, quinoline-(N-methyl) piperazine hydrochloride and hydrobromide. Linear correlations between theoretical and solid state results were obtained, thus enabling a reasonable assignment of carbon resonances of the conformations present in the solid state. Due to the fast dynamics in solution, the carbon chemical shifts corresponded to the averaged values of the forms present in the solid state.

Anti-Anxiety Agents↗
PubMed1997

13C-CP-MAS-NMR studies of flavonoids. I. Solid-state conformation of quercetin, quercetin 5'-sulphonic acid and some simple polyphenols.

13C-CP-MAS-NMR spectra were measured in order to characterise the orientation of hydroxyl groups of quercetin, quercetin-5'-sulphonic acid and polyphenol-type compounds such as catechol, pyrogallol and gallic acid. The locked conformation of the OH group in the solid results in an increased shielding of carbon proxime to C-OH hydrogen. Carbon shieldings suggest that there is orientational disorder of three OH groups of pyrogallol and gallic acid and that two OH groups of catechol are not equivalent. In solid quercetin and quercetin-5'-sulphonic acid the C7-OH points towards C6-H and the C3'-OH hydrogen is near C2'-H.

Carbon Isotopes↗
PubMed1996

Crystal structure and solid-state NMR analysis of methyl 2,3,6-tri-O-acetyl-2-deoxy-2-[3-(2-phenylethyl)-ureido]-beta-D- glucopyranoside.

The X-ray diffraction analysis of methyl 2,3,6-tri-O-acetyl-2-deoxy-2-[3-(2-phenylethyl)-ureido]-beta-D- glucopyranoside has been performed, establishing that molecules are associated by two types of NH...O hydrogen bonds, N-1-H with carbonyl-oxygen and N-3-H with anomeric oxygen, with N...O distances 2.902 and 2.904 A, respectively. The urea moiety of the molecule is in anti Z,Z conformation. The signals in the 13C CP MAS NMR spectrum are neither multiplied nor split, indicating that there is one molecule in the crystal asymmetric unit. The difference in chemical shifts between solid- and liquid-state spectra are significant for C-2 and C-3 of D-glucose moiety (2.3-2.5 ppm) and for NCH2, CH2Ph carbon atoms.

Antineoplastic Agents↗
PubMed1996

A solution and solid state 15N NMR study of hydrogen bonding in a Schiffs base.

The 15N results reveal a difference in the extent of intramolecular hydrogen bond formation exhibited by the Schiffs base, compound 2, in solution and the solid state. Comparison of the 15N shielding changes observed, with those arising from protonation, provides the basis for a quantitative estimate of the strength of the hydrogen bonds formed.

Hydrogen Bonding↗
PubMed1996

An 15N NMR study of the protonation of two di-(alpha-pyridyl) compounds in solutions and the solid state.

15N NMR data are reported for two Di-(alpha-pyridyl) derivatives in various stages of protonation. A combination of 15N NMR measurements taken, on a number of solutions, and on the solid state provide a quantitative overall view of the progress of protonation of these compounds. 15N shieldings, J(15N-1H) and 2J (15N-1H) interactions all provide information indicative of unsymmetrical monoprotonation in the solid state and producing both the monoprotonated [N-H-N]+ structure and the diprotonated structure in the presence of an excess of TFA.

Magnetic Resonance Spectroscopy↗
PubMed1995

15N and 13C solid-state nuclear magnetic resonance study of 5-thiomethyltetrazole.

15N and 13C cross-polarization magic-angle spinning nuclear magnetic resonance (CP-MAS NMR) spectra of 5-thiomethyltetrazole have been measured. Two kinds of tetrazole molecules are found in the hydrogen bond chain system depending on the configuration of the S-CH3 group in relation to the ring hydrogen atom. The two-dimensional 15N CP-MAS experiment excludes the possibility of proton tautomeric dynamics in this system.

Carbon Isotopes↗
PubMedDate not supplied

13C cross-polarization MAS NMR study of some steroidal sapogenins.

Cross-polarization (CP) magic angle spinning (MAS) solid-state 13C NMR spectra of five steroidal sapogenins: tigogenin ((25R)-5alpha-spirostan-3beta-ol), hecogenin (3beta-hydroxy-(25R)-5alpha-spirostan-12-one), diosgenin ((delta5-(25R)-5alpha-spirosten-3beta-ol), sarsasapogenin ((25S)-55beta-spirostan-3beta-ol), and smilagenin ((25R)-5beta-spirostan-3beta-ol) were recorded. The solid-state chemical shifts are almost the same as for solution, which indicate that confirmations of sapogenins are similar in both phases. The doubling of some resonances in the spectra of solid diosgenin shows that there are two molecules in the crystallographic asymmetric unit. The cross-polarization time constants T(CP) and relaxation times in the rotating frame T(1rho)H were obtained from the variable-contact cross-polarization experiments for tigogenin and diosgenin. The values of T(CH) for methyl carbons indicate fast rotation of methyl groups and are close (0.30-0.35 ms), suggesting that the interaction with their intramolecular neighbors is similar. The values of T(1rho)H for carbons of tigogenin are longer than of diosgenin. Very efficient cross-polarization dynamics results in short time required for obtaining a spectrum of sapogenin of remarkably good quality.

Carbon Isotopes↗
PubMedDate not supplied

Electron spin resonance assessment of the antioxidant potential of medicinal plants. Part I. Contribution of anthocyanosides and flavonoids to the radical scavenging ability of fruit and herbal teas.

Radical scavenging properties of the extracts of some fruits and flowers, as well as of their complex formulations used as fruit teas, were tested on DPPH radical using electron spin resonance spectroscopy. The contents of anthocyanosides and flavonoids in plant materials were determined with spectrophotometric method. The most effective DPPH radical scavengers were extracts from Fructus Aroniae, Fructus Myrtilli and Fructus Rosae and the fruit teas, including them as main ingredients. No simple correlation was found between the scavenging activity and the content of anthocyanosides and flavonoids. The results can be rationalised by taking into account the presence of catechins and ascorbic acid.

Anthocyanins↗
PubMedDate not supplied

Triterpenoid sapogenin from Anthyllis vulneraria L.

Triterpene pentacyclic sapogenin, 3beta,22beta,24-trihydroxy-olean-12-ene, soyasapogenol B, was isolated for the first time from the Anthyllis vulneraria L.. Identification and structure assignment was performed by 1H and 13C NMR spectroscopy.

Europe↗