Publications by authors named "Jan K Maurin"

24 Publications

  • Page 1 of 1

Comprehensive Characterisation of the Ketoprofen-β-Cyclodextrin Inclusion Complex Using X-ray Techniques and NMR Spectroscopy.

Molecules 2021 Jul 5;26(13). Epub 2021 Jul 5.

Falsified Medicines and Medical Devices Department, National Medicines Institute, Chełmska 30/34, 00-725 Warsaw, Poland.

Racemic ketoprofen (KP) and β-cyclodextrin (β-CD) powder samples from co-precipitation (), evaporation (), and heating-under-reflux () were analysed using X-ray techniques and nuclear magnetic resonance (NMR) spectroscopy. On the basis of NMR studies carried out in an aqueous solution, it was found that in the samples obtained by methods and there were large excesses of β-CD in relation to KP, 10 and 75 times, respectively, while the sample obtained by method contained equimolar amounts of β-CD and KP. NMR results indicated that KP/β-CD inclusion complexes were formed and the estimated binding constants were approximately 2400 M, showing that KP is quite strongly associated with β-CD. On the other hand, the X-ray single-crystal technique in the solid state revealed that the ()-KP/β-CD inclusion complex with a stoichiometry of 2:2 was obtained as a result of heating-under-reflux, for which the crystal and molecular structure were examined. Among the methods used for the preparation of the KP/β-CD complex, only method is suitable.
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http://dx.doi.org/10.3390/molecules26134089DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8271474PMC
July 2021

Structural, Thermal, and Vibrational Properties of N,N-Dimethylglycine-Chloranilic Acid-A New Co-Crystal Based on an Aliphatic Amino Acid.

Materials (Basel) 2021 Jun 14;14(12). Epub 2021 Jun 14.

Institute of Organic Chemistry Polish Academy of Sciences, Kasprzaka 44, 01-224 Warsaw, Poland.

The new complex of N,N-Dimethylglycine (DMG) with chloranilic acid (CLA) was synthesized and examined for thermal, structural, and dynamical properties. The structure of the reaction product between DMG and CLA was investigated in a deuterated dimethyl sulfoxide (DMSO-d6) solution and in the solid state by Nuclear Magnetic Resonance (NMR) (Cross Polarization Magic Angle Spinning-CPMAS NMR). The formation of the 1:1 complex of CLA and DMG in the DMSO solution was also confirmed by diffusion measurement. X-ray single crystal diffraction results revealed that the N,N-dimethylglycine-chloranilic acid (DMG-CLA) complex crystallizes in the centrosymmetric triclinic P-1 space group. The X-ray diffraction and NMR spectroscopy show the presence of the protonated form of N,N-dimethylglycine and the deprotonated form of chloranilic acid molecules. The vibrational properties of the co-crystal were investigated by the use of neutron (INS), infrared (IR), and Raman (RS) spectroscopies, as well as the density functional theory (DFT) with periodic boundary conditions. From the band shape analysis of the N-CH bending vibration, we can conclude that the CH groups perform fast (τ ≈ 10 to 10 s) reorientational motions down to a temperature of 140 K, with activation energy at ca. 6.7 kJ mol. X-ray diffraction and IR investigations confirm the presence of a strong N-H···O hydrogen bond in the studied co-crystal.
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http://dx.doi.org/10.3390/ma14123292DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8232199PMC
June 2021

"Clicking" fragment leads to novel dual-binding cholinesterase inhibitors.

Bioorg Med Chem 2021 Jul 7;42:116269. Epub 2021 Jun 7.

National Medicines Institute, Chełmska 30/34, 00-725 Warsaw, Poland; National Centre for Nuclear Research, 05-400 Otwock-Świerk, Poland.

Cholinesterase inhibitors are potent therapeutics in the treatment of Alzheimer's disease. Among them, dual binding ligands have recently gained a lot of attention. We discovered novel dual-binding cholinesterase inhibitors, using "clickable" fragments, which bind to either catalytic active site (CAS) or peripheral anionic site (PAS) of the enzyme. Copper(I)-catalyzed azide-alkyne cycloaddition allowed to effectively synthesize a series of final heterodimers, and modeling and kinetic studies confirmed their ability to bind to both CAS and PAS. A potent acetylcholinesterase inhibitor with IC = 18 nM (compound 23g) was discovered. A target-guided approach to link fragments by the enzyme itself was tested using butyrylcholinesterase.
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http://dx.doi.org/10.1016/j.bmc.2021.116269DOI Listing
July 2021

Some mechanistic aspects regarding the Suzuki-Miyaura reaction between selected -substituted phenylboronic acids and 3,4,5-tribromo-2,6-dimethylpyridine.

Beilstein J Org Chem 2018 11;14:2384-2393. Epub 2018 Sep 11.

Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland.

Atropisomers are very interesting stereoisomers having axial chirality resulting from restricted rotation around single bonds and are found in various classes of compounds. Substituted arylpyridines are an important group of them. A regio- and atropselective Suzuki-Miyaura cross-coupling reaction on 3,4,5-tribromo-2,6-dimethylpyridine was studied. Reactions with various amounts of -substituted phenylboronic acids with 3,4,5-tribromo-2,6-dimethylpyridine gave a series of mono- di- and triarylpyridine derivatives which allowed to draw conclusions about the order of substitution. Also, the observed selectivity in the case of -methoxyphenylboronic acid suggested an additional metal -chelation effect in the transition state, apparently not present in the -chloro analogues. The rotational barrier in selected atropisomers was determined on the basis of HT NMR and thermal epimerisation experiments. The structure of most presented atropisomeric derivatives of 2,6-dimethylpyridine was confirmed by single-crystal X-ray analysis. Racemic chiral, differently substituted atropisomers were also examined by H NMR spectroscopy in the presence of a chiral solvating agent. This regio- and atropselectivity may be generally applicable to other arylpyridine systems. A regio- and atropselective Suzuki-Miyaura cross-coupling process has been observed, giving an efficient access to a class of atropisomeric compounds. An opposite selectivity using a differently -substituted phenylbornic acid was observed.
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http://dx.doi.org/10.3762/bjoc.14.214DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6142784PMC
September 2018

Domino Reaction of Pyrrolidinium Ylides: Michael Addition/[1,2]-Stevens Rearrangement.

J Org Chem 2018 04 13;83(7):4105-4110. Epub 2018 Mar 13.

National Medicines Institute , Chełmska St. 30/34 , 00-725 Warsaw , Poland.

A novel domino reaction featuring a Michael addition/[1,2]-Stevens rearrangement reaction of pyrrolidinium ylides with electrophilic alkenes is described. Ylides generated under mild conditions from 2-aryl- N-cyanomethyl- N-methylpyrrolidinium salts entered the Michael addition, followed by a [1,3]-hydrogen shift and finally the [1,2]-Stevens rearrangement to give 3-aryl-2-cyano-2-(2-EWG-ethyl)-1-methylpiperidines.
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http://dx.doi.org/10.1021/acs.joc.7b03278DOI Listing
April 2018

Lipase-Catalyzed Kinetic Resolution of Novel Antifungal N-Substituted Benzimidazole Derivatives.

Chirality 2016 Apr 29;28(4):347-54. Epub 2016 Feb 29.

Faculty of Chemistry, Institute of Biotechnology, Warsaw University of Technology, Warsaw, Poland.

A series of new N-substituted benzimidazole derivatives was synthesized and their antifungal activity against Candida albicans was evaluated. The chemical step included synthesis of appropriate ketones containing benzimidazole ring, reduction of ketones to the racemic alcohols, and acetylation of alcohols to the esters. All benzimidazole derivatives were obtained with satisfactory yields and in relatively short times. All synthesized compounds exhibit significant antifungal activity against Candida albicans 900028 ATCC (% cell inhibition at 0.25 μg concentration > 98%). Additionally, racemic mixtures of alcohols were separated by lipase-catalyzed kinetic resolution. In the enzymatic step a transesterification reaction was applied and the influence of a lipase type and solvent on the enantioselectivity of the reaction was studied. The most selective enzymes were Novozyme SP 435 and lipase Amano AK from Pseudomonas fluorescens (E > 100).
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http://dx.doi.org/10.1002/chir.22591DOI Listing
April 2016

Formal synthesis of (-)-podophyllotoxin through the photocyclization of an axially chiral 3,4-bisbenzylidene succinate amide ester--a flow photochemistry approach.

Org Biomol Chem 2016 Jan;14(2):460-469

Faculty of Chemistry, University of Warsaw, Pasteura 1, Warsaw 02-093, Poland.

We have developed a strategy for the stereoselective synthesis of cyclolignans related to podophyllotoxin and its derivatives. The crucial step of the synthesis is the photocyclization of a chiral atropoisomeric 1,2-bisbenzylidenesuccinate amide ester, which can be prepared from suitable aromatic aldehydes, diethyl succinate and l-prolinol. The photocyclization was found to be more efficient when irradiation was performed in a home-built continuous flow photochemical reactor. The in-flow irradiation also allowed us to perform the reaction on a multigram scale. The chiral auxiliary was removed by reductive cleavage with the Schwartz's reagent to give the cytotoxic 1R,2R-cis-podophyllic aldehyde, which in turn could be easily reduced to the corresponding alcohol, completing the formal synthesis of (-)-podophyllotoxin.
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http://dx.doi.org/10.1039/c5ob01844gDOI Listing
January 2016

The enantioselective synthesis of (S)-(+)-mianserin and (S)-(+)-epinastine.

Beilstein J Org Chem 2015 28;11:1509-13. Epub 2015 Aug 28.

Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093, Warsaw, Poland.

A simple enantioselective synthetic procedure for the preparation of mianserin and epinastine in optically pure form is described. The key step in the synthetic pathway is the asymmetric reduction of the cyclic imine using asymmetric transfer hydrogenation conditions.
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http://dx.doi.org/10.3762/bjoc.11.164DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4578372PMC
October 2015

Chemical aspects of the primary ionization mechanisms in matrix-assisted laser desorption ionization.

Eur J Mass Spectrom (Chichester) 2014 ;20(6):437-44

National Medicines Institute, Chełmska 30/34, 00-725 Warsaw, Poland.

It has been proposed that the primary ionization mechanism occurring in matrix-assisted laser desorption ionization (MALDI) experiments originates from the presence, in the solid-state matrix-analytes sample, of matrix dimers. These species are formed by the interaction of carboxylic groups present in the matrix molecules with the formation of strong hydrogen bonds. Theoretical calculations proved that the laser irradiation of these structures leads to one or two H-bridge cleavages, giving rise to an "open" dimer structure or to disproportionation with the formation of MH(+) and [M-H](-) species. The ions so formed can be considered highly effective in their reaction with analyte ions, leading to their protonation (or deprotonation). To achieve further evidence for these proposals, in the present study the energetics of the reactions of ions from different aromatic carboxylic acids with two amino acids (glycine and lysine) and three multipeptides (gly-gly, gly-gly-gly and gly-gly-gly-gly) was investigated. The lowest ∆G values were obtained for 2,5- dihydroxybenzoic acid, widely employed as the MALDI matrix. Also, for p-nitrobenzoic acid the reaction is slightly exothermic, while for the other aromatic carboxylic acids derivatives positives values of ∆G are present.
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http://dx.doi.org/10.1255/ejms.1296DOI Listing
May 2015

Synthesis of imperatorin analogs and their evaluation as acetylcholinesterase and butyrylcholinesterase inhibitors.

Arch Pharm (Weinheim) 2013 Nov 14;346(11):775-82. Epub 2013 Oct 14.

Faculty of Chemistry, University of Warsaw, Warsaw, Poland; Faculty of Pharmacy, Department of Pharmacognosy and Molecular Basis of Phytotherapy, Medical University of Warsaw, Warsaw, Poland.

In this study, we synthesized several imperatorin analogs using imperatorin and xanthotoxin as substrates. The anti-cholinesterase activities of all compounds were evaluated in in vitro experiments according to the modified Ellman's method. For each synthesized compound, IC50 values for both enzymes were established. Galantamine hydrobromide was used as a positive control in the enzymatic experiments. All active compounds showed selectivity toward butyrylcholinesterase (BuChE) rather than acetylcholinesterase. The most active ones were 8-(3-methylbutoxy)-psoralen and 8-hexoxypsoralen with IC50 values for BuChE of around 16.5 and 16.4 µM, respectively. The results of our study may be considered as the beginning of a search for potential anti-Alzheimer's disease drugs based on the structure of natural furocoumarins.
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http://dx.doi.org/10.1002/ardp.201300259DOI Listing
November 2013

On the Primary Ionization Mechanism(s) in Matrix-Assisted Laser Desorption Ionization.

J Anal Methods Chem 2012 27;2012:161865. Epub 2012 Nov 27.

National Council of Researches, Institute of Molecular Sciences and Technologies, Corso Stati Uniti 4, I35100 Padova, Italy.

A mechanism is proposed for the first step of ionization occurring in matrix-assisted laser desorption ionization, leading to protonated and deprotonated matrix (Ma) molecules ([Ma + H](+) and [Ma - H](-) ions). It is based on observation that in solid state, for carboxyl-containing MALDI matrices, the molecules form strong hydrogen bonds and their carboxylic groups can act as both donors and acceptors. This behavior leads to stable dimeric structures. The laser irradiation leads to the cleavage of these hydrogen bonds, and theoretical calculations show that both [Ma + H](+) and [Ma - H](-) ions can be formed through a two-photon absorption process. Alternatively, by the absorption of one photon only, a heterodissociation of one of the O-H bonds can lead to a stable structure containing both cationic and anionic sites. This structure could be considered an intermediate that, through the absorption of a further photon, leads to the formation of matrix ions. Some experiments have been performed to evaluate the role of thermal ionization and indicate that its effect is negligible. Some differences have been observed for different matrices in the formation of analyte molecule (M) ion [M + H](+), [M - H](-), M(+•), and [M - 2H](-•), and they have been explained in terms of ionization energies, pKa values, and thermodynamic stability.
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http://dx.doi.org/10.1155/2012/161865DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3515899PMC
December 2012

3-(2-Acetamido-eth-yl)-1H-indol-5-yl 4-nitro-phenyl carbonate.

Acta Crystallogr Sect E Struct Rep Online 2012 Oct 12;68(Pt 10):o2915. Epub 2012 Sep 12.

National Medicines Institute, Chełmska 30/34, 00-725 Warsaw, Poland ; NationalCentre for Nuclear Research, 05-400 Otwock-Świerk, Poland.

In the title mol-ecule, C(19)H(17)N(3)O(6), the indole ring system is essentially planar (r.m.s. deviation = 0.009 Å) and forms a dihedral angle of 31.96 (9)° with the nitro-substituted benzene ring. In the crystal, mol-ecules are linked by pairs of N-H⋯O hydrogen bonds, forming inversion dimers which are connected by further N-H⋯O hydrogen bonds into a two-dimensional network parallel to (102).
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http://dx.doi.org/10.1107/S1600536812038238DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3470262PMC
October 2012

Recognition of active ingredients in tablets by chemometric processing of X-ray diffractometric data.

Talanta 2010 Jul 19;82(2):850-3. Epub 2010 May 19.

Department of Medicinal Chemistry, Medical University of Lublin, Lublin, Poland.

The paper presents an approach to use Partial Least Squares Discriminant Analysis (PLS-DA) on X-ray powder diffractometry (XRPD) dataset to build a model which recognizes a presence (or absence) of particular drug substance (acetaminophen) in unknown mixture (OTC tablet). The dataset consisted of 33 XRPD signals, measured for 12 pure substances and 21 tablets containing them in different quantitative and qualitative ratios, along with unknown excipients. The model was built with an external validation dataset chosen by Kennard-Stone algorithm. The RMSECV value was equal to 0.3461 (87.8% of explained variance) and external predictive error (RMSEP) was equal to 0.3123 (86.2% of explained variance). The result suggests that small but properly prepared training datasets give ability to construct well-working discriminant models on XRPD signals.
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http://dx.doi.org/10.1016/j.talanta.2010.05.012DOI Listing
July 2010

Trimethyl-3-meth-oxy-4-oxo-5-triphenyl-phospho-ranyl-idene-cyclo-pent-1-ene-1,2,3-tricarboxyl-ate.

Acta Crystallogr Sect E Struct Rep Online 2010 Oct 9;66(Pt 11):o2792. Epub 2010 Oct 9.

The title compound, C(30)H(27)O(8)P (2), was formed as one of two products {(1) [Krawczyk et al. (2010 ▶). Acta Cryst. E66 (cv2752)] and (2)} in the reaction of dimethyl acetyl-enedicarboxyl-ate with triphenyl-phosphine. The mol-ecule of (2) consists of a five-membered carbocyclic ring. The P atom is a part of a triphenylphosphoranylidene substituent. In contrast to (1), the five-membered ring of (2) is planar, the r.m.s. deviation being only 0.009 (2) Å.
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http://dx.doi.org/10.1107/S1600536810037815DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3009217PMC
October 2010

Tetra-methyl 1,1,2-triphenyl-2H-1λ-phosphole-2,3,4,5-tetra-carboxyl-ate.

Acta Crystallogr Sect E Struct Rep Online 2010 Oct 9;66(Pt 11):o2791. Epub 2010 Oct 9.

The title compound, C(30)H(27)O(8)P (1), was formed as one of two products {(1) and (2) [Krawczyk et al. (2010 ▶). Acta Cryst. E66 (cv2753)]} in the reaction of dimethyl acetyl-enedicarboxyl-ate with triphenyl-phosphine. The mol-ecule of (1) consists of a five-membered ring, in which the P atom is incorporated. One of the phenyl groups of the triphenyl-phosphine migrated to a vicinal C atom during the reaction. The five-membered ring of (1) is corrugated [r.m.s. deviation = 0.0719 (8) Å], whereas that in compound (2) is planar, the r.m.s. deviation being only 0.009 (2) Å.
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http://dx.doi.org/10.1107/S1600536810037827DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3008977PMC
October 2010

Synthesis and anti-HIV studies of 2- and 3-adamantyl-substituted thiazolidin-4-ones.

Eur J Med Chem 2009 Jan 10;44(1):303-11. Epub 2008 Mar 10.

Rega Institute for Medical Research, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium.

A series of novel thiazolidin-4-ones bearing a lipophilic adamantyl substituent at position 2 or 3 were synthesized. A majority of them showed a modest anti-HIV-1 activity, whereas 2-adamantan-1-yl-3-(4,6-dimethylpyrimidin-2-yl)-thiazolidin-4-one (8) was endowed with a remarkable antiviral potency (EC(50)=0.67 microM). The new series of compounds (22-29) with an adamantyl moiety at the 3-position of the thiazolidinone ring showed good to modest anti-HIV-1 activity (EC(50)=1.0-11 microM) but also pronounced cytostatic activity. For example 24, 26 and 29 showed an EC(50) of 1.0-2.0 microM, while the 50% effective concentrations for 23 and 28 were 7.8 and 11.0 microM, respectively. X-ray studies and quantum chemical calculations revealed that the anti-HIV activity of the compounds strongly depends on their dipole moments and conformation of the thiazolidinones.
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http://dx.doi.org/10.1016/j.ejmech.2008.02.039DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7127420PMC
January 2009

The oxidation products of melatonin derivatives exhibit acetylcholinesterase and butyrylcholinesterase inhibitory activity.

J Pineal Res 2008 Aug 12;45(1):40-9. Epub 2008 Feb 12.

Faculty of Chemistry, Warsaw University, Warsaw, Poland.

It is already well documented that melatonin exhibits strong antioxidant properties. It traps several reactive oxygen species including singlet oxygen, peroxyl and hydroxyl radicals. Also, peroxynitrite-induced reactions are inhibited by melatonin. The oxidation of melatonin by singlet molecular oxygen [O(2) ((1)Delta(g))] may produce cyclic 3-hydroxymelatonin whose structure we have already studied. In this investigation we report on the synthesis of several melatonin analogues having a carbamate substituent instead of the methoxy group at 5 position of the indole ring. These compounds behave analogously to melatonin with respect to singlet oxygen and produce the corresponding cyclic 3-hydroxymelatonin analogues. The structures of the products were investigated with spectral methods and X-ray crystallography. The compounds obtained possess the 2,3,8,8a-tetrahydropyrrolo[2,3-b]indole heterocyclic system which is a structural motif characteristic of alkaloids, physostigmine and phenserine, that are potent acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitors used in the Alzheimer's disease treatment. We measured the inhibitory activity of the obtained compounds against AChE and BChE from human erythrocytes and serum. In the case of the compounds having a phenylcarbamate and methoxyphenylcarbamate substituents, the inhibitory activity (IC(50)) ranged from 0.252 +/- 0.033 to 3.804 +/- 0.581 microM. Other compounds were less active and showed rather complex interactions with the structure-activity relationship in need of further investigation.
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http://dx.doi.org/10.1111/j.1600-079X.2008.00554.xDOI Listing
August 2008

The Suzuki-Miyaura reaction in the chemical transformations of vindoline.

Acta Biochim Pol 2007 8;54(4):857-61. Epub 2007 Dec 8.

Faculty of Chemistry, Warsaw University, Warszawa, Poland.

Vindoline and its analogues are important constituents of the Madagascan periwinkle Catharanthus roseus, and some of them are valuable chemotherapy drugs used in treatment for some types of cancer, including leukaemia, lymphoma, breast and lung cancer. The search for semi-synthetic congeners of natural substances is still an important task for organic chemistry. In this communication we report the synthesis of five new vindoline derivatives, 15-(2-methoxyphenyl)vindoline 11, 15-(3-methoxyphenyl)vindoline 12, 15-(2-nitrophenyl)vindoline 13, 15-(3-cyanophenyl)vindoline 15, and 15-(4-cyanophenyl)vindoline 16 using the Suzuki-Miyaura reaction as the key step. X-Ray analysis of compound 16 is also reported.
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August 2008

Synthesis and anti-HIV studies of 2-adamantyl-substituted thiazolidin-4-ones.

Eur J Med Chem 2007 Jul 20;42(7):993-1003. Epub 2007 Jan 20.

Rega Institute for Medical Research, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium.

A series of novel thiazolidin-4-ones bearing a lipophilic adamantyl substituent at position 2, and versatile substituents on the nitrogen atom of the thiazolidine ring, were synthesized whereas several compounds exhibited a modest anti-HIV-1 activity, (+/-)-2-adamantan-1-yl-3-(4,6-dimethyl-pyridin-2-yl)-thiazolidin-4-one 22 was endowed with a remarkable antiviral potency (EC(50)=0.35 microM). The adamantane moiety played an important role in the eventual antiviral activity of the compound. This compound behaved as a typical non-nucleoside reverse transcriptase (RT) inhibitor (NNRTI) with non-competitive inhibition against RT with respect to the substrate (K(i)=12 microM). Separation of the enantiomers via diastereoisomeric salts was performed for 22. X-ray studies enabled us to ascribe an S configuration to (-)-2-adamantan-1-yl-3-(4,6-dimethyl-pyridin-2-yl)-thiazolidin-4-one (-)-22. Furthermore, it was found that the (+)-22 isomer was predominantly responsible for the potent anti-HIV-1 activity (EC(50) value of 0.178 microM), while the levo isomer was more than 60-fold less active.
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http://dx.doi.org/10.1016/j.ejmech.2007.01.003DOI Listing
July 2007

The usefulness of simple X-ray powder diffraction analysis for counterfeit control--the Viagra example.

J Pharm Biomed Anal 2007 Mar 28;43(4):1514-8. Epub 2006 Nov 28.

The National Drug Institute, Chełmska 30/34, 00-725 Warsaw, Poland.

Counterfeit and illegally manufactured drugs become a very important problem all over the world, hence, a search for new fast, easy, reliable and not expensive methods of drugs screening is essential. We describe the use of X-ray powder diffraction method for the fast screening of tablets for counterfeit medicines identification. The original Viagra tablets and some counterfeit and/or imitations of Viagra were used as example. We demonstrate the application of diffraction method for discrimination of tablets coatings and for identification of differences in drug composition. The X-ray diffraction method turns out to be very fast and reliable for detecting counterfeits and imitation, and it correctly predicts the presence or absence of active substance and/or particular excipients.
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http://dx.doi.org/10.1016/j.jpba.2006.10.033DOI Listing
March 2007

Crystal structure of lead(II) acetylacetonate and the structure of the acetylacetone solvated lead(II) ion in solution studied by large-angle X-ray scattering.

Dalton Trans 2006 Sep 13(33):3972-6. Epub 2006 Jun 13.

Department of Radiochemistry, Institute of Nuclear Chemistry and Technology, Dorodna 16, PL-03-195, Warsaw, Poland.

The crystal structure of bis(acetylacetonato)lead(II) and the structure of the acetylacetone solvated lead(II) ion in solution have been determined by single-crystal X-ray diffraction and large-angle X-ray scattering (LAXS), respectively. The acetylacetone is deprotonated and acts as a bidentate anionic ligand (acac-) in the solid Pb(acac)2 compound. The lead(II) ion binds four oxygen atoms strongly in a nearly flat pyramidal configuration with Pb-O bond lengths in the range 2.32-2.37 A, and additionally three oxygens from neighboring complexes at 3.01-3.26 A. Acetylacetone acts as a solvent (Hacac) at dissolution of lead(II) trifluoromethanesulfonate forming a pentasolvate with a mean Pb-O bond distance of 2.724(5) A. The 6s2 lone electron pair on the lead(II) ion becomes stereochemically active in the crystalline acetylacetonate complex, while it is inactive in the solvate in solution. The solution was also analysed using IR and 1H NMR spectroscopy.
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http://dx.doi.org/10.1039/b606543kDOI Listing
September 2006

Towards enantioselective synthesis of tryptophan-derived alkaloids.

Adv Exp Med Biol 2003 ;527:637-41

Faculty of Chemistry, Warsaw University, Pasteur St. 1, 02-093, Warsaw, Poland.

Tryptamine was subjected to a series of reactions with derivatives of L-Ala, L-Val that ended with final diketopiperazines 9 and 10, having (R) configuration on the newly created, via 1,4-chirality transfer, stereogenic center. On the other hand, when L-Pro was used the opposite chirality sense was formed at this position.
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http://dx.doi.org/10.1007/978-1-4615-0135-0_73DOI Listing
September 2004

Vindoline and 16-demethoxyvindoline: two catharanthus-derived alkaloids.

Acta Crystallogr C 2004 May 30;60(Pt 5):o377-80. Epub 2004 Apr 30.

Chemistry Department, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland.

Vindoline, C(25)H(32)N(2)O(6), and 16-demethoxyvindoline, C(24)H(30)N(2)O(5), both of which are naturally occurring biologically active products derived from plants, are important as possible starting materials for the synthesis of valuable anticancer antibiotics, viz. vincristine and vinblastine, and other pharmaceuticals. The vindoline framework consists of two five- and three six-membered condensed rings. One of the six-membered rings adopts a boat conformation, one adopts a sofa conformation and the third is planar. Both five-membered rings have envelope structures. The intramolecular hydrogen bonds present in the structures are characteristic of vinca alkaloids.
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http://dx.doi.org/10.1107/S0108270104004342DOI Listing
May 2004

Pseudosymmetry in ammonium [(carboxymethyl)sulfanyl]acetate.

Acta Crystallogr C 2003 Nov 31;59(Pt 11):o656-8. Epub 2003 Oct 31.

National Institute of Public Health, Chełmska 30/34, 00-725 Warsaw, Poland.

The structure of the title compound, NH(4)(+).C(4)H(5)O(4)S(-), is composed of monocarboxylate anions of [(carboxymethyl)sulfanyl]acetic acid linked into infinite chains via strong O-H...O(-) hydrogen bonds. The three-dimensional structure is completed by the ammonium cations, which interlink neighbouring chains via N-H...O hydrogen bonds. Solution and refinement in the true space group Pn led to an unambiguous position for the single carboxyl H atom. In the higher symmetry space group P2/n, the carboxylate anion would be located on a twofold axis.
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http://dx.doi.org/10.1107/s010827010302287xDOI Listing
November 2003
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