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Ivana Císarová

Publications and source records attributed to Ivana Císarová.

At least 19 recordsLinked to original sources
PubMed2006

Synthesis of unique cagelike thiacalix[4]arene derivatives in a 1,3-alternate conformation.

A novel type of doubly bridged thiacalix[4]arenes in the 1,3-alternate conformation has been prepared by direct aminolysis reaction of easily accessible thiacalix[4]arene tetraacetates with alpha,omega-diamines. Despite the high excess of diamine, both sites of a 1,3-alternate conformer can be intramolecularly bridged to form the cagelike structures in high yields. Optimum results were obtained using 1,2-ethanediamine as bridging units. X-ray analysis of the novel cagelike molecules revealed a highly preorganized array of -C(O)-NH- bonds pointing to the interior of the cavity.

Journal Article↗
PubMed2006

Dirubidium fluorotrioxophosphate, Rb2PO3F, at 290 and 130 K, and dicaesium fluorotrioxophosphate, Cs2PO3F, at 240 and 100 K.

The structure of Rb2PO3F was determined at 290 and 130 K, while that of Cs2PO3F was determined at 240 and 100 K. Both compounds belong to the beta-K2SO4 family. The structure analysis did not reveal signs of a phase transition in either compound. Crystal chemical considerations do not favour the presence of a phase transition in either Rb2PO3F or Cs2PO3F. However, glass-like phase transitions were observed by differential scanning calorimetry in slightly humid samples at 175 and 177 K for Rb2PO3F and Cs2PO3F, respectively, but were not observed in well dried samples. The bond distances are normal and Cs2PO3F is twinned.

Journal Article↗
PubMed2006

Investigation of vanadocene(IV) alpha-amino acid complexes: synthesis, structure, and behavior in physiological solutions, human plasma, and blood.

This work is focused on investigating the interaction of antitumor active metallocene vanadocene dichloride (Cp2VCl2) and amino acids in aqueous solution at physiological pH. Sixteen vanadocene amino acid complexes [Cp2V(aa)][X] (aa = gly, ala, val, leu, ile, phe, his, and trp; X = Cl, PF6) were prepared and characterized on the basis of spectral measurements (EPR, MS, IR, Raman). Amino acids are coordinated to the vanadocene fragment through the oxygen atom of the carboxylic group and the nitrogen of the amino group, resulting in a five-membered chelate ring. Complexes [Cp2V(val)][PF6] and [Cp2V(ile)][PF6] have been characterized by X-ray structure analyses. It was evidenced that all prepared complexes are stable in both aqueous solutions with physiological pH and in therapeutic NaCl solutions. EPR spectra of vanadocene amino acid complexes in Krebs-Ringer solution in human blood plasma and in whole blood showed that these complexes react with the hydrogen carbonate anion present forming complex Cp2V(O2CO).

Amino Acids↗
PubMed2006

Magneto-structural correlations in Cu(tn)Cl2 (tn = 1,3-diaminopropane): two-dimensional spatially anisotropic triangular magnet formed by hydrogen bonds.

A novel polymeric one-dimensional compound Cu(tn)Cl2 (tn = 1,3-diaminopropane) was prepared and structurally characterized, and its spectral, magnetic, thermodynamic, and thermal properties were studied. The unique structure shows ladderlike chains composed of Cu(II) atoms and chloro bridging ligands [Cu(-mu(3)-Cl-)Cu2] running along the crystallographic c axis. The coordination geometry about copper (4 + 2) approximates that of a strongly elongated octahedron. The equatorial plane of the coordination octahedron is formed by a chelate N-bonded tn ligand and two chloro ligands. One of the chloro ligands is terminal, and the other one, mu3-Cl-, forms two additional longer bonds to the neighboring copper atoms and thus occupies the axial octahedral positions. The electronic ground state of the Cu(II) ion is of d(z)2 symmetry and suggests the activation of intraladder and interladder Cl...H-N hydrogen bonds as exchange paths that form a two-dimensional pattern of a triangular symmetry. The interaction due to the hydrogen bonds seems to play an important role in molecular packing and magnetic coupling. The studies of magneto-structural correlations including electron paramagnetic resonance measurements and thermodynamic and magnetic properties revealed a two-dimensional character of magnetic correlations with the effective intralayer exchange coupling J/k(B) approximately -3 K. No phase transition to the ordered state has been observed down to 60 mK. Cu(tn)Cl2 with the interlayer coupling J' approximately 10(-3)J and moderate intralayer interaction represents an excellent example of a two-dimensional magnetic system.

Journal Article↗
PubMed2005

New route to 1-thia-closo-dodecaborane(11), closo-1-SB11H11, and its halogenation reactions. The effect of the halogen on the dipole moments and the NMR spectra and the importance of spin-orbit coupling for the 11B chemical shifts.

Reaction between nido-B10H14 (1) and elemental sulfur in CHCl3 in the presence of Et3N at room temperature, followed by treatment with Et3N.BH3 at 170-190 degrees C, resulted in the isolation of closo-1-SB11H11 (2) in 50% yield. Selected electrophilic halogenation reactions of compound led to the isolation of a series of monohalogenated derivatives of general constitution 12-X-closo-1-SB11H10 (12-X-, where X = Cl, Br, and I). The structures of 12-Cl- and 12-I- were determined by an X-ray diffraction analysis and the structures of all compounds were geometry optimised at the RMP2(fc)/6-31G* level. The constitution of all compounds is consistent with the results of mass spectrometry and multinuclear (1H and 11B) spectroscopy complemented by two-dimensional [11B-11B]-COSY and 1H{11B(selective)} NMR measurements. Experimental 11B chemical shifts generally show acceptable agreement with theoretical values calculated by GIAO methods, but spin-orbit coupling must be included for nuclei bearing heavy-atom substituents such as Br or I. The dipole moments determined for the B12-X bonds show similarities to those of aliphatic C-X bonds and confirm unambiguously the B12 --> S dipole moment orientation in the SB11 cage.

Journal Article↗
PubMed2005

Chromophoric binaphthyl derivatives.

A short synthetic route is outlined, starting from bromo-BN derivatives, via halogen lithium exchange, subsequent Michael reaction with dimethylaminoacrolein, hydrolysis to the corresponding aldehyde, and final condensation with a benzothiazolium unit to produce a BN-pentamethinium system, which absorbs in the visible range around 450 nm. Enantiopure ligands show a decent Cotton effect in the CD spectrum. Preliminary data show potential of these compounds in the area of supramolecular chemistry (enantioselective recognition) and also for medicinal application (induction of apoptosis). [reaction: see text]

Apoptosis↗
PubMed2005

Cyclam (1,4,8,11-tetraazacyclotetradecane) with one methylphosphonate pendant arm: a new ligand for selective copper(ii) binding.

The new ligand, [(1,4,8,11-tetraazacyclotetradecan-1-yl)methyl]phosphonic acid (H(2)te1P, H(2)L), was synthesized and its complexing properties towards selected metal ions were studied potentiometrically. The ligand forms a very stable complex with copper(ii)(logbeta(CuL)= 27.34), with a high selectivity over binding of other metal ions (i.e. logbeta(ZnL)= 21.03). The crystal structures of the free ligand (in its protonated form with bromide as counter-ion) and two copper(ii) complexes (obtained by crystallization at various pH) were determined. The free ligand adopts the common conformation for such macrocycles with the protonated nitrogen atoms in the corners of a virtual rectangle. In the trans-Br,O-[Cu(Br)(Hte1P)].H(2)O species, the central metal ion is surrounded by four in plane nitrogen atoms, one oxygen atom of the pendant moiety in the apical position and a bromide anion positioned trans to the oxygen atom, forming a distorted octahedral coordination sphere. In the compound [Cu(H(2)te1P)][Cu(Hte1P)]Br(3).6H(2)O, obtained from a highly acidic solution, the bromide anions are placed further away from the copper(ii) ion and the coordination environment (N(4)O) is thus square-pyramidal. In both structures, the protons are associated with non-coordinated phosphonate oxygen atoms.

Journal Article↗
PubMed2005

Two structural types of 1,3-alternate tetrapropoxycalix[4]arene derivatives in the solid state.

The solid state structures of seven tetrapropoxycalix[4]arene derivatives immobilised in a 1,3-alternate conformation were determined using single-crystal X-ray crystallography. The cavity shapes of investigated derivatives (upper rim unsubstituted, distally di-substituted and tetra-substituted) and the nature of intermolecular interactions in molecular packing were compared. The results indicate that there are only two structural types adopted by basic tetrapropoxycalix[4]arene derivatives in the 1,3-alternate conformation.

Journal Article↗
PubMed2005

On interpretation of a missing spectral band; IR spectra of acidic salts of benzohydroxamic acid.

Using solid benzohydroxamic acid (BHA) as a model compound for its salts, a broad absorption at 2730 cm(-1) was generally agreed to represent the nu(OH) band of the OH... ON bonds. The absence of nu(OH) band in the IR region 3600-1700 cm(-1) was taken to indicate the absence of OH groups in the solid salts. The same argument and conclusion was erroneously accepted for lithium (LiBHA) and potassium (KBHA) salts of BHA which are not "normal" but acid salts and do contain OH groups. X-ray diffraction results allow explanation of this discrepancy. The lithium and potassium acid salts have much shorter OH... ON bridges (O...O distances of 247 and 245 pm, respectively) than the model compound (258 pm). Accordingly, the nu(OH...O) bands in the acidic salts are shifted into the crowded 1600-700 cm(-1) interval. Obviously, interpretation of a missing spectral band in terms of molecular structure can be misleading when the models do not include all possible structural variations.

Crystallography, X-Ray↗
PubMed2004

Cocyclotrimerization of 6-alkynylpurines with alpha,omega-diynes as a novel approach to biologically active 6-arylpurines.

Transition metal complex catalyzed cocyclotrimerization of 6-alkynylpurines 1 with various diynes enables the preparation of a plethora of substituted 6-arylpurines 3 in good yields. The most general catalyst for the reaction is a user-friendly system based on a nickel-phosphine complex and reductant (NiBr(2)(dppe)/Zn) in MeCN. The reaction conditions are compatible with various protective groups on the purine moiety (Bn, THP). As far as other potential catalysts were concerned, only CoBr(PPh(3))(3) showed reasonable activity in cocyclotrimerization of alkynylpurines with dipropargyl ether. A comparison of catalytic with stoichiometric approaches and the ligand effect in the catalyst is also given. Cytostatic activity screening of title 6-arylpurines was performed and several moderately active compounds were found.

Magnetic Resonance Spectroscopy↗
PubMed2004

Neighboring group effect in Pd-catalyzed carbonylation terminated by lactonization: a need for a protective group and/or DMF.

Synthesis of analogues of antifungal podolactones via Pd-catalyzed processes revealed that tandem 6-exo-alkyne carbopalladation/carbonylative lactonization sequence is strongly solvent-dependent. Contrary to earlier reports, premature esterification was the predominant pathway when the starting enynes derived from (Z)-2-iodohex-2-en-1,4-diol were subjected to Pd-catalyzed carbonylation in MeOH. Apparently, irreversible complexation of Pd by the OH group prevented decarbonylation and hence 6-exo-alkyne carbopalladation. Similarly, the influence of the chelation was also evident when the reaction was applied to the analogous preparation of 3-hydroxymethylbutenolides. The neighboring group effect can be efficiently overcome through using DMF as the solvent in combination with protection of the OH function.

Antifungal Agents↗
PubMed2004

N,O-diacylhydroxylamines-structures in crystals and solutions.

The structures of four N,O-diacylhydroxylamines (RCOHNOCOR', R, R'= Me, Ph) were determined in the solid state by X-ray diffraction and studied by NMR and IR spectroscopies in solution. The interpretation of the results was supported by ab-initio calculations of various tautomers and conformers, rotational barriers and chemical shifts. The results indicate the absence of OH tautomers (R-C(OH)=N-O-C(O)-R', N-acyloxyimidic acid); the NH tautomers (R-C(O)-NH-O-C(O)-R', O-acylhydroxamic acid) are present in DMSO solutions as equilibrium mixtures of a few conformers, their exchange being the likely source of 15N and 13C NMR line broadening.

Journal Article↗
PubMed2004

Ferrocene-modified purines as potential electrochemical markers: synthesis, crystal structures, electrochemistry and cytostatic activity of (ferrocenylethynyl)- and (ferrocenylethyl)purines.

Palladium-catalyzed Sonogashira cross-coupling reactions of halopurines 9-benzyl-6-chloropurine (2 a), 9-benzyl-8-bromoadenine (2 b), and 9-benzyl-2-chloroadenine (2 c) with ethynylferrocene (1) gave the corresponding (ferrocenylethynyl)purines 3 a-c in moderate to good yields. Catalytic hydrogenation of these alkynes over Pd/C afforded the respective saturated [2-(ferrocenyl)ethyl]purines 4 a-c. The crystal structures 3 a, 3 b, 4 a and 4 b as determined by X-ray diffraction show interesting solid-state interactions, markedly different for purines 3 a and 4 a on one hand and adenines 3 b and 4 b that possess a free amino group on the other. Electrochemistry of electrochemically labelled purines 3 and 4 has been studied by voltammetry and cyclic voltammetry on platinum disc electrode and the experimental oxidation potentials were confirmed and explained by ionization potentials from theoretical DFT calculations. Several compounds of this series exhibited a considerable cytostatic effect.

Animals↗
PubMed2004

Li+ -induced sigma-bond metathesis: aryl for methyl exchange on boron in a methylated monocarbadodecaborate anion.

At 190 degrees C, formal sigma-bond metathesis between the B-CH3 bond in position 12 of the lithium monocarbadodecaborate derivative 1a and the C-Si(CH3)3 bond in p-bromophenyltrimethylsilane occurs and produces Si(CH3)4 and a salt of the arylated carborate anion 2, whose X-ray structure has been determined. The reaction requires the presence of active Li+ cations and does not occur with the cesium salt 1b or when 12-crown-4 is added to 1a. Possible mechanisms are briefly discussed.

Journal Article↗
PubMed2004

Chiral derivatives of 2-(1-naphthyl)-2-phenylacetic acid.

The spectral properties of diastereomeric esters and amides (1b-20b), derived from optically pure 2-(1-naphthyl)-2-phenylacetic acids (1-NPA), were systematically investigated. It was found that all compounds prepared exhibit the NMR spectral nonequivalence (Deltadelta) with regular sign distribution of particular groups according to the predicted model. Further, the analysis of data revealed that the phenyl ring is responsible for a shielding effect (upfield shift) instead of a naphthyl one. This conclusion is supported by the crystallographic analysis showing the almost ap-arrangement of the acid methine hydrogen atom and carbonyl group. In this arrangement, the phenyl ring faces toward the ester part of the molecule while the naphthyl one is orthogonal to the phenyl plane. Therefore, the mutual position of phenyl and alkyl groups with respect to the central molecule co-planarity thus determines the chemical shifts of the alcohol/amine substituents. The relative magnitude of the Deltadelta corresponds to those of Mosher's derivatives.

Journal Article↗
PubMed2003

Synthesis of alpha-amino acids via asymmetric phase transfer-catalyzed alkylation of achiral nickel(II) complexes of glycine-derived Schiff bases.

Achiral, diamagnetic Ni(II) complexes 1 and 3 have been synthesized from Ni(II) salts and the Schiff bases, generated from glycine and PBP (7) and PBA (11), respectively, in MeONa/MeOH solutions. The requisite carbonyl-derivatizing agents pyridine-2-carboxylic acid(2-benzoyl-phenyl)-amide 7 (PBP) and pyridine-2-carboxylic acid(2-formyl-phenyl)-amide 11 (PBA) were readily prepared from picolinic acid and o-aminobenzophenone or picolinic acid and methyl o-anthranilate, respectively. The structure of 1 was established by X-ray crystallography. Complexes 1 and 3 were found to undergo C-alkylation with alkyl halides under PTC conditions in the presence of beta-naphthol or benzyltriethylammonium bromide as catalysts to give mono- and bis-alkylated products, respectively. Decomposition of the complexes with aqueous HCl under mild conditions gave the required amino acids, and PBP and PBA were recovered. Alkylation of 1 with highly reactive alkyl halides, carried out under the PTC conditions in the presence of 10% mol of (S)- or (R)-2-hydroxy-2'-amino-1,1'-binaphthyl 31a (NOBIN) and/or its N-acyl derivatives and by (S)- or (R)-2-hydroxy-8'-amino-1,1'-binaphthyl 32a (iso-NOBIN) and its N-acyl derivatives, respectively, gave rise to alpha-amino acids with high enantioselectivities (90-98.5% ee) in good-to-excellent chemical yields at room temperature within several minutes. An unusually large positive nonlinear effect was observed in these reactions. The Michael addition of acrylic derivatives 37 to 1 was conducted under similar conditions with up to 96% ee. The (1)H NMR and IR spectra of a mixture of the sodium salt of NOBIN and 1 indicated formation of a complex between the two components. Implications of the association and self-association of NOBIN for the observed sense of asymmetric induction and nonlinear effects are discussed.

Alkylation↗
PubMed2003

Pergolide mesylate form II.

A new polymorph of pergolide mesylate or 8beta-[(methylsulfanyl)methyl]-6-propylergoline methanesulfonate, C(19)H(27)N(2)S(+).CH(3)SO(3)(-), is reported. Pergolide mesylate form II crystallizes in the trigonal system, which is unique for ergot derivatives. Although the hydrogen-bond system in form II differs completely from that in form I, the conformation of the pergolide moiety in various related structures is very similar.

Antiparkinson Agents↗