Jindrich Karban

The Czech Academy of Sciences | AVCR · Institute of Chemical Process Fundamentals

Control of anomeric stereoselectivity in glycosylation with deoxofluorinated glycosyl donors is critical for assembly of fluorinated oligosaccharides. Here, we report the synthesis of benzylated 3-fluoro and 4-fluoro analogues of phenyl 1-thioglucosazide and galactosazide donors and evaluation of their stereoselectivity in glycosylation of a series...

Glucose‐substituted ruthenium complexes [(η6‐benzyl‐glucose)RuCp*]+Cl−, where Cp* = η5‐C5Me5; benzyl‐glucose = peracetylated benzyl β‐d‐glucopyranoside (1), benzyl β‐d‐glucopyranoside (2), have been prepared and used as efficient antimigration and anti‐invasive agents against metastatic breast cancer cells (MDA‐MB‐231) and cisplatin‐resistant ovari...

A complete series of eight 1,6:2,3- and 1,6:3,4-dianhydro-β-D-hexopyranoses were subjected to fluorination with DAST. The 1,6:3,4-dianhydropyranoses yielded solely products of skeletal rearrangement resulting from migration of the tetrahydropyran oxygen (educts of D-altro and D-talo configuration) or of the 1,6-anhydro bridge oxygen (D-allo, D-gala...

NiMo sulfide catalysts were prepared by the impregnation of high surface area supports with an aqueous solution made of NiCO3·2Ni(OH)2, MoO3 and citric acid, followed by freeze drying and sulfidation in H2S/H2 mixture. N2 physisorption and X-ray diffraction were selected to investigate the amphoteric oxides Al2O3 and TiO2, acidic SiO2-Al2O3 and act...

The effect of substitution on intermolecular interactions was investigated in a series of 1,6-anhydro-2,3-epimino-hexopyranoses. The study focused on the qualitative evaluation of intermolecular interactions using DFT calculations and the comparison of molecular arrangements in the crystal lattice. Altogether, ten crystal structures were compared,...

Three series of poly(ionic) carbosilane dendrimers peripherally functionalized with imidazolium groups substituted on N-3 with methyl, isopropyl and 2,6-diisopropylphenyl (Dipp) were prepared up to the 3rd generation together with model monovalent imidazolium iodides and used as N-heterocyclic carbene (NHC) precursors. Catalytic activity of model a...

Galectins are widely expressed galactose-binding lectins implied, for example, in immune regulation, metastatic spreading, and pathogen recognition. N-Acetyllactosamine (Galβ1-4GlcNAc, LacNAc) and its oligomeric or glycosylated forms are natural ligands of galectins. To probe substrate specificity and binding mode of galectins, we synthesized a com...

Multiple fluorination of glycostructures has emerged as an attractive way of modulating their protein affinity, metabolic stability, and lipophilicity. Here we described the synthesis of a series of mono-, di- and trifluorinated N -acetyl-ᴅ-glucosamine and ᴅ-galactosamine analogs. The key intermediates are the corresponding multiply fluorinated glu...

Fully acetylated deoxyfluorinated hexosamine analogues and non-fluorinated 3,4,6-tri-O-acylated N-acetyl-hexosamine hemiacetals have previously been shown to display moderate anti-proliferative activity. We prepared a set of deoxyfluorinated GlcNAc and GalNAc hemiacetals that comprised both features: O-acylation at the non-anomeric positions with a...

The Tn antigen (GalNAcα1-Thr/Ser) is abundantly expressed in many tumors but rarely found in healthy tissues, which makes it an attractive epitope for antitumor immunotherapy. The use of the Tn antigen in the development of therapeutic antitumor vaccines is hampered by its low immunogenicity, which may be enhanced by deoxyfluorination of the GalNAc...

Multiple fluorination of glycostructures has emerged as an attractive way of modulating their protein affinity, metabolic stability, and lipophilicity. Here we described the synthesis of a series of mono-, di- and trifluorinated N -acetyl-D-glucosamine and D-galactosamine analogs. The key intermediates were the corresponding multiply fluorinated gl...

Ruthenium tetrazene complexes with general formula [Cp*RuCl(1,4‐R2N4)] (Cp* = η5‐C5Me5), where R = benzyl (1), 2‐fluorobenzyl (2), β‐d‐glucopyranosyl‐unprotected (3a) and acyl‐protected (3b–d), 2‐acetamido‐β‐d‐glucopyranosyl‐unprotected (4a) and acyl‐protected (4b–d), propyl‐β‐d‐glucopyranoside‐unprotected (5a), and O‐acetylated (5b), were synthesi...

Fluorinated glycans are valuable probes for studying carbohydrate-protein interactions at the atomic level. Glucosamine is a ubiquitous component of glycans, and the stereoselective synthesis of α-linked fluorinated glucosamine is a challenge associated with the chemical synthesis of fluorinated glycans. We found that introducing a 6-O-acyl protect...

Cervical cancer is one of the most common types of cancer in women, with approximately 500,000 new cases and 250,000 deaths every year. Radiotherapy combined with chemotherapy represents the treatment of choice for advanced cervical carcinomas. The role of the chemotherapy is to increase the sensitivity of the cancer cells to irradiation. Cisplatin...

A series of new highly fluorophilic ionic liquids ( f > 110) was synthetized from 3‑iodopropyltris(3,3,4,4,5,5,6,6,7,7,8,8,8‐tridecafluorooctyl)silane and N‐alkyl imidazoles, followed by anion exchange. N‐heterocyclic carbenes generated in situ from obtained imidazolium salts were employed to catalyze redox esterification ( umpolung ) of cinnamalde...

In this study, 9-(diphenylphosphanyl)[7]helicene was prepared as a suitable ligand for the subsequent synthesis of palladium complexes. The corresponding PdL2Cl2 complex was then successfully obtained in both racemic and enantiopure forms. The PdL2Cl2 complex emerges exclusively in the trans arrangement showing dynamic interconversion between its h...

Chemotherapy plays an essential role in the management of cancer worldwide. However, it is a non-specific treatment limited by major drawbacks, thus identification and testing of new promising molecular structures representing potential drug candidates are urgently needed. In this work, ferrocene complexes as potential antitumor drugs that display...

Mo, CoMo and NiMo sulfide catalysts were prepared using MgO, Al2O3, ZrO2, TiO2, MCM-41 and activated carbon supports. The catalysts were tested in parallel hydrodeoxygenation (HDO) of octanoic acid and hydrodesulfurization (HDS) of 1-benzothiophene. For all supports, NiMo catalysts were more active in both HDO and HDS than Mo and CoMo catalysts. HD...

Turmeric (Curcuma longa L.) was extracted with supercritical carbon dioxide (sc-CO 2 ) and turmerones, compounds with strong biological activity, were concentrated using semi-preparative supercritical chromatography (p-SFC) with sc-CO 2 . The extraction was performed at temperature of 40 °C and pressures of 9–66 MPa. Influence of pressure, type of...

A family of ferrocene derivatives of the general formula [Fe(η⁵-C5H4CH2(p-C6H4)CH2(N-het))2] bearing saturated six- and five-membered N-heterocycles (N-het) was prepared. Reactions of the selected complexes with acids (HCl, acetic acid) afforded either the corresponding hydrochlorides or led to deprotection of the functionalized pendant N-heterocyc...

Cyclopentenediones (CPDs) are compounds with a variety of applications ranging from the preparation of functional polymers to the development of antimicrobial agents, suggesting the potential use of CPDs as novel bioactive compounds or drugs. For this reason, a detailed characterization of CPDs and the development of robust analytical methods for t...

Background: Derivatives of D-glucosamine and D-galactosamine represent an important family of the cell surface glycan components and their fluorinated analogs found use as metabolic inhibitors of complex glycan biosynthesis, or as probes for the study of protein-carbohydrate interactions. This work is focused on the synthesis of acetylated 3-deoxy...

PM2.5 mass concentrations and chemical compositions sampled over a 13-month period at a Central European rural background site Košetice) are presented in this work. A comprehensive chemical analysis of PM2.5 was performed, which provided elemental composition (Al, Si, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Y, Zr, Pb) and t...

Background: Ovarian cancer is the seventh-most common cancer amongst women and the most deadly gynecologic cancer. Cisplatin based drugs are used in first line therapy, but resistance represents a major obstacle for successful treatment. In this study, we investigated the anticancer effects and mechanism of action of three titanocene difluorides,...

Ferrocenes represent an interesting group of drugs with potential antitumor properties. Moreover, their electronic properties make them suitable for electrochemical studies. We determined an uptake of novel ferrocene derivative in low µM concentrations by selected cancer cell lines and showed its localization predominantly in cytoplasm, using glass...

The series of novel substituted titanocene complexes have been prepared by hydrosilylation of organic substrates containing a terminal double bond by cyclopentadienyl complexes of titanium bearing a Si–H functional group. This new synthetic protocol is demonstrated by synthesis of mono-, bi- and tri-homonuclear complexes.

In the study of the simultaneous hydrodesulfurization of 1-benzothiophene and the olefin hydrogenation of 1-methylcyclohex-1-ene (1-MCH), we encountered a rearrangement of 1-MCH during the first step of catalytic hydrogenation, which yielded various branched cyclic olefins; mainly ethylcyclopentene and dimethylcyclopentene isomers. The volatile iso...

Peracetylated 3-deoxy-3-fluoro analogues of D-glucosamine and D-galactosamine 3 and 4, respectively, were prepared from 1,6:2,3-dianhydro-4-O-benzyl-β-D-mannopyranose (6). Azidolysis of 6 followed by reaction with diethylaminosulfur trifluoride gave 1,6-anhydro-2-azido-4-O-benzyl-2,3-dideoxy-3-fluoro-β-D-glucopyranose (9). Cleavage of the internal...

Titanocene dichlorides of general formula [(?5-C5H5)(?5-C5H4R)TiCl2] (where R = 5-deoxy-1,2-di-O-isopropylidene-3-O-benzyl-α-d-xylofuranos-5-yl (Xylf) (8a); R = 5-deoxy-1,2-di-O-isopropylidene-3-O-benzyl-α-d-ribofuranos-5-yl (Ribf) (8b)) and [(?5-C5H4R)2TiCl2] (R = Xylf (9a); R = Ribf (9b)) were prepared by reaction of the corresponding lithium cyc...

Carbosilane metallodendrimers of the first generation Si{CH2CH2CH2SiMe2CH2CH2SiMe2(CH2)nC5H4TiCl2C5H5}4 and Si{CH2CH2CH2SiMe[CH2CH2SiMe2(CH2)nC5H4TiCl2C5H5]2}4 (n = 1, 5) and of the second generation Si{CH2CH2CH2SiMe[CH2CH2CH2SiMe2CH2CH2SiMe2(CH2)nC5H4TiCl2C5H5]2}4 (n = 1, 5) and Si{CH2CH2CH2SiMe[CH2CH2CH2SiMe(CH2CH2SiMe2(CH2)nC5H4TiCl2C5H5)2]2}4 (...

Supercritical fluid extraction was used to isolate volatile compounds from savory (Satureja hortensis L.), thyme (Thymus vulgaris L.), lavender (Lavandula angustifolia L.) and peppermint (Mentha piperita L.). Three types of extracts were prepared using the benefit of variable solvent power of supercritical carbon dioxide under different extraction...

A new PtCl2/PtCl4-catalyzed hydroarylation/cycloisomerization cascade reaction leading to the formation of two aromatic or heteroaromatic rings in one step is reported. The strategy developed is exemplified by the synthesis of the 5,6-dihydrobenzo[c]phenanthrene and 6H-naphtho[2,1-c]chromene skeletons. Attempts to prepare [8]helicene-like molecules...

The ability of LC-NMR to detect simultaneously free and conjugated phytosterols in natural extracts was tested. The advantages and disadvantages of a gradient HPLC-NMR method were compared to the fast composition screening using SEC-NMR method. Fractions of free and conjugated phytosterols were isolated and analyzed by isocratic HPLC-NMR methods. T...

The products of phenylsilane dehydrocoupling were analyzed by means of advanced NMR techniques including LC-NMR. Attention was paid to the -SiPh- units not containing Si-H bonds. These units were observed in the Si-29 NMR spectra reported previously. The (1)J and (2)J 29Si INADEQUATE experiments were used to reveal the connectivities within oligosi...

Colloidal silica sol was used as a binder for the preparation of Al–SBA-15 pellets. Only 18wt.% of silica was sufficient to form pellets that possessed mechanical strength comparable with industrial catalysts. Moreover, these pellets exhibited only minor changes in texture parameters in comparison with parent powder (the decrease of mesopore surfac...

We have prepared a full series of 1,6-anhydro-2,3,4-trideoxy-4-fluoro-2,3-epimino-beta-d-hexopyranoses. The key step was the reaction of azido sulfonates possessing a free C-4 hydroxyl with DAST and subsequent LiAlH(4) reduction. Nucleophilic displacement of the hydroxyl activated by DAST proceeded without rearrangement and with moderate to good yi...

CO2 extracts and essential oil obtained by hydrodistillation from feverfew aerial parts were applied to Spodoptera littoralis (Boisduval) larvae to examine their effects on mortality, antifeedancy and growth inhibition, and their composition of volatile substances was determined using GC. The mortality strongly correlates with the content of terpen...

A modular synthetic approach leading to 2-aza[6]helicene is reported. It involves assembly of key hetero biphenylylnaphthalenes from functionalized building blocks and study of their metal catalyzed cycloisomerization.

The chemical constitution of antioxidants contained in honey is derived from its origin. Forty honey samples (harvest 2006), which came from various locations of the Czech Republic and varied in their origins, were evaluated spectrophotometrically for their total polyphenol content, total flavonoids and 3',4'-dihydroxyflavones and flavonols, and ma...

Z-1,4-disilyl-2-butenes ,R3SiCH2CH=CHCH2SiR3 (R3 = Me3,Me2H,Me2(CH2CL), Me2Ph(CH2)3, Me(2Bu)2 and Et3) were prepared by the reaction of 1,4-dilithio-2-butene with the corresponding terialkylchlorosilanes.

1,6-Anhydro-2,3,4-trideoxy-2,3-(tosylepimino)-beta-D-hexopyranoses 1 and 2 underwent aziridine ring-opening reactions with halides and other heteroatom-centered nucleophiles. Ribo-epimine 1 provided trans-diaxial and cis products. The lyxo-epimine 2 gave trans-diaxial and trans-diequatorial products, depending upon the reaction conditions (acid cle...

Extracts from savory (Satureja hortensis L.) and thymus (Thymus vulgaris L.) were obtained by supercritical fluid extraction, hydrodistillation, and Soxhlet extraction with benzene and ethanol. The composition of volatile compounds in the extracts was determined by gas chromatography, and the toxicity and antifeedant effects of the extracts on larv...

The new approach provides nonphotochemical syntheses of helicenes based on the easy, convergent, and modular assembly of key biphenylyl-naphthalenes and their platinum-catalyzed double cycloisomerization. This sequence of reactions provides a synthetic route to helicenes in two steps from simply accessible building blocks. Furthermore, the method e...

The crystal structures of a complete series of configurational isomers of 2,3-epimino and 3,4-epimino derivatives of 1,6-anhydro-β-D-hexopyranoses were determined by single-crystal X-ray analysis. The structures exhibited conformational rigidity within the series regardless of the position and orientation of the aziridine ring. Possible formation o...

A highly contaminated groundwater (235 mg l(-1) MTBE and 112.6 mg l(-1) BTEX) was subjected to UV/H2O2 photolysis at ambient temperature in a batch UV reactor. GC/MS analysis showed that BTEX are completely destroyed while the degradation of MTBE proceeds via tert-butyl formate as the main reaction byproduct. High MTBE conversions (> 99.9 %) were o...

A Suzuki cross-coupling reaction of hindered 2-bromo-1-trimethylsilylethynylbenzenes with 1-naphthaleneboronic acid yielding (2-ethynylphenyl)naphthalenes has been achieved. Their subsequent cyclization was carried out, giving benzo[c]phenanthrenes, without the use of photochemical procedures.

The formation of polychlorinated dibenzo-p-dioxins, dibenzofurans, biphenyls and benzenes in de novo synthesis experiments have been studied on model fly ashes with a wide range of matrices. The model fly ash consisted of 18 selected matrices with the addition of CuCl(2) x 2H(2)O, activated charcoal and NaCl. The studied matrices were not restricte...

This article deals with those derivatives in which an aziridine ring is fused to a pyranose or furanose ring or to an exocyclic part of a carbohydrate molecule. These compounds are termed carbohydrate aziridines or epimines. Carbohydrate aziridines do not occur naturally, although a few noncarbohydrate aziridines have been found among antibiotics.1...

Influence of UV and combined MW-UV irradiation on 4-tert-butylphenol (4TBP) transformation was investigated in the presence and in the absence of sensitizers with different value of singlet and triplet energy and in the presence of solvents with different polarity. Irradiation by UV and also by MW-UV gave C O and C C products: 4 � ,5-di-tert-butyl-...

Starting from 1,6-anhydro-beta-d-glucopyranose 1 (levoglucosan), N-o-nitrobenzenesulfonyl (nosyl) 3,4-epimino derivatives with d-allo, d-galacto, and d-talo configurations have been prepared via NaBH(4) reduction of suitably substituted azido tosylates. The benefits and limitations of this method over the classical LiAlH(4) reduction method are dis...

Influence of UV and combined MW–UV irradiation on 2-tert-butylphenol (2TBP) transformation was investigated in the presence and in the absence of sensitizers with different value of singlet and triplet energy and in the presence of solvents with different polar-ity. Irradiation by UV and also by combination MW–UV gave three C–C dimers: 3,3 -di-tert...

A complete series of 2,3,4-trideoxy-2,3-epimino and 2,3,4-trideoxy-3,4-epimino derivatives of 1,6-anhydro-beta-D-hexopyranoses were prepared by lithium aluminium hydride reduction of vicinal trans azido tosylates. Unusual formation of the aziridine ring from precursors with the trans-diequatorial arrangement of the reacting groups was observed. NMR...

Pathways of pentachlorophenol dechlorination have been investigated on municipal waste incineration fly ash at 200 degrees C under nitrogen atmosphere. Thermodynamic calculations have been carried out for these dechlorination conditions using the method of total Gibbs energy minimization for the whole system consisting of gaseous components, i.e.,...

Silylation of N,O-diacylhydroxylamines with N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide produces only O-silylated products and no N-silylated derivative. Steric interactions of the substituents on the nitrogen atom with the O−N oxygen atom control the configuration on the CN bond in the product:  a Z isomer is formed almost exclusively f...

The aziridine ring cleavage of N-nosylepimines 3 and 7 having D-allo and D-manno configurations with halides led regioselectively to N-o-nitrobenzenesulfonylated 2-halo-3-amino- and 3-halo-2-amino-2,3-dideoxy derivatives of 1,6-anhydro-beta-D-glucopyranose 8-14 in 59-81% yields. Removal of o-nitrobenzenesulfonyl protecting group with benzenethiol a...

15N isotopic enrichment was necessary for the unequivocal assignment of the 1H NMR lines to the protons in the NH–OH fragment of benzohydroxamic acid, BHXA, C6H5CONHOH, in dry dimethyl sulfoxide solutions. The assignment [δ(NH) = 11.21, δ(OH) = 9.01, 1J(15N,1H) = 102.2 Hz, 2J(15N,1H) <1.5 Hz], which is opposite to that used by other authors, confir...

Background, Aims and Scope In the first part of this paper the main principles which control the dehalogenation of polychlorinated aromatic compounds on municipal waste incineration fly ash (MWI-FA) have been discussed and the model fly ash of similar dehalogenation activity has been proposed. Even if both systems show comparable dehalogenation pro...

It is well known that the fly ash from filters of municipal waste incinerators (MWI-FA) shows dehalogenation properties after heating it to 240-450 degrees C. However, this property is not general, and fly ash samples do not possess dehalogenation ability at all in many cases. Fly ash has a very variable composition, and the state of the fly ash ma...

In the first part of this paper the main principles which control the dehalogenation of polychlorinated aromatic compounds on municipal waste incineration fly ash (MWI-FA) have been discussed and the model fly ash of similar dehalogenation activity has been proposed. Even if both systems show comparable dehalogenation properties, the main question...

The effect of reaction time on formation of polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) was studied under laboratory conditions in the system containing municipal waste incineration fly ash, activated carbon and copper chloride dihydrate at 300 degrees C in 99.999% N2 and N2 + 10% O2 atmosphere. The concentrations of tetra- to...

The aziridine ring opening of N -tosylepimino carbohydrates 1 - 6 having D- allo , D- manno , D- galacto and D- talo configurations with benzyl alcohol, benzylamine and phenylmethanethiol afforded 2-, 3- and 4- O -benzyl-, benzylsulfanyl and benzylamino derivatives of 1,6-anhydro-β-D-hexopyranoses of D- gluco , D- galacto and D- manno configuration...

Well defined E/Z isomers of N-methoxy-p-nitrobenzimidoyl chloride, N-methoxybenzimidoyl chloride, methyl N-methylbenzohydroximate and ethyl N-hydroxybenzimidate were prepared in order to provide model data for studies of benzhydroximic acid derivatives and related compounds. NMR parameters [1H, 13C and 15N chemical shifts and 1J(13C, 13C) coupling...

O-tert-butyldimethylsilyl (1) and O-tert-butyldiphenylsilyl (2) benzhydroxamates were prepared and their structure in the solid state was determined by X-ray diffraction and NMR spectroscopy (15N, 13C and 29Si). The solution NMR spectra indicate some processes. In chloroform, both compounds isomerize to an equilibrium mixture of hydroxamic (A) and...

A complete series of 2,3-dideoxy-2,3-epimino- and 3,4-dideoxy-3,4-epimino-1,6-anhydro-beta -D-hexopyranoses were prepared by lithium aluminum hydride reduction of the corresponding trans-azido tosylates or trans-azido epoxides of 1,6-anhydro-beta -D-hyxopyranoses. The structure of the epimino derivatives was confirmed by (1)H and (13)C NMR spectra.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and...