Sulfur-containing ferrocenyl alcohols and oximes: new promising antistaphylococcal agents.

A small library containing four different series of new ferrocene derivatives, 2-(alkylsulfanyl)-1-ferrocenylethan-1-ols, 3-(alkylsulfanyl)-1-ferrocenylpropan-1-ols, (E)- and (Z)-2-(alkylsulfanyl)-1-ferrocenylethan-1-one oximes, and (E)- and (Z)-3-(alkylsulfanyl)-1-ferrocenylpropan-1-one oximes (36 different compounds in total) was synthesized starting from ferrocene and the corresponding sulfanyl acids. All compounds were spectrally (IR and NMR) and electrochemically characterized. In general, the obtained compounds were found to exhibit very strong antimicrobial activities (broth microdilution assay) against the tested microorganisms (six common human pathogens). For the majority of the tested compounds, the determined MIC values were either under the 10 µg/ml MIC limit recognized to delimit efficient antimicrobials or were comparable to/lower than those of the used positive controls (tetracycline/nystatin). The most susceptible organism was found to be Staphylococcus aureus with MIC values even reaching 0.001 µg/ml. The presence of -CH(OH)(CH(2))(n)S- and -CH(=NOH)(CH(2))(n)S- (n=1 or 2) structural fragments seems to be essential for the observed strong activity (introduction of hydroxyimino and alcohol functionalities, instead of the keto function, resulted in a more than 10(5)-fold increase in antistaphylococcal activity in some instances). Nevertheless, a possible influence of the ferrocenyl-core redox chemistry (Fe(2+)/Fe(3+)) should not be disregarded. The studied alcohols exhibited a reversible one-electron redox couple at almost the same position as ferrocene, while the hydroxyimino group conjugated with cyclopentadienyl ring considerably shifted the redox potential of the ferrocene unit in oximes.

Synthesis and antimicrobial activity of some new pyrazole derivatives containing a ferrocene unit.

A series of new imines and amines have been synthesized by condensation of 1H-3-ferrocenyl-1-phenylpyrazole-4-carboxaldehyde with the corresponding amines, followed by reduction with sodium borohydride. The synthesized compounds have been screened for their in vitro antimicrobial activity against 11 bacteria and three fungal/yeast strains, using disc diffusion and broth microdilution susceptibility assays. They have shown a wide range of activities, from completely inactive to the highly active compounds.

The Alternatives to Traditional Materials for Subsoil Stabilization and Embankments.

Major infrastructure projects require significant amount of natural materials, often followed by the soft soil stabilization using hydraulic binders. This paper presents the results of a laboratory study of alternative waste materials (fly ash and slag) that can be used for earthworks. Results of high plasticity clay stabilization using fly ash from Serbian power plants are presented in the first part. In the second part of the paper, engineering properties of ash and ash-slag mixtures are discussed with the emphasis on the application in road subgrade and embankment construction. Physical and mechanical properties were determined via following laboratory tests: Specific gravity, grain size distribution, the moisture-density relationship (Proctor compaction test), unconfined compressive strength (UCS), oedometer and swell tests, direct shear and the California bearing ratio (CBR). The results indicate the positive effects of the clay stabilization using fly ash, in terms of increasing strength and stiffness and reducing expansivity. Fly ashes and ash-slag mixtures have also comparable mechanical properties with sands, which in combination with multiple other benefits (lower energy consumption and CO2 emission, saving of natural materials and smaller waste landfill areas), make them suitable fill materials for embankments, especially considering the necessity for sustainable development.

Electrochemical bromination of cholest-5-enes.

Four 5,6-unsaturated steroids--3beta-chlorocholest-5-ene (1a), cholesterol (1b) and its acetate (1c) and benzoate (1d)-were subjected to constant current electrolysis (50 mA, 2 F mol(-1)) in an electrolytic cell divided by a ceramic membrane, using a platinum foil as the anode and a graphite stick as the cathode. When electrolysis was carried out in a solution of tetraethylammonium bromide in aprotic solvents (dichloromethane, acetonitrile or acetic anhydride), the addition of electrochemically-generated elemental bromine onto the double bond of the cholesterol derivatives gave their corresponding 5alpha,6beta-dibromosteroids--3beta-chloro-5alpha,6beta-dibromocholestane (2a), 5alpha,6beta-dibromocholestan-3beta-ol (2b), 5alpha,6beta-dibromocholestan-3beta-yl acetate (2c) and 5alpha,6beta-dibromocholestan-3beta-yl benzoate (2d)--as the sole products, and in good yields (58-91%). However, the electrolysis of steroids 1a-c in a solution of tetraethylammonium bromide with methanol as the solvent proceeded to give, in addition to dibromides 2a-c, the corresponding diastereomeric pairs of 5-bromo-6-methoxysteroids: 5alpha-bromo-3beta-chloro-6beta-methoxycholestane (3a) and 5beta-bromo-3beta-chloro-6alpha-methoxycholestane (4a), 5alpha-bromo-6beta-methoxycholestan-3beta-ol (3b) and 5beta-bromo-6alpha-methoxycholestan-3beta-ol (4b) and 5alpha-bromo-6beta-methoxycholestan-3beta-yl acetate (3c) and 5alpha-bromo-6beta-methoxycholestan-3beta-yl acetate (4c). The benzoate 1d was not soluble enough in methanol, even with heating. The products were characterized by physical and spectral data (IR, 1H NMR and 13C NMR). Single crystal X-ray structure determinations of compounds 2a and 3a are also reported.

Ferrier rearrangement promoted by an electrochemically generated zirconium catalyst.

In situ generated zirconium catalyst from a sacrificial zirconium anode was successfully applied to promote Ferrier rearrangement of 3,4,5-tri-O-acetyl-D-glucal and 6-deoxy-3,4-di-O-acetyl-L-glucal (3,4-di-O-acetyl-L-rhamnal) in the presence of three thiols and eleven thiophenols as nucleophiles. A simple constant current electrolysis (20 mA, 0.4 F mol(-1)) of an acetonitrile solution of lithium perchlorate (0.1 M) containing the corresponding glycal and S-nucleophiles, using a zirconium anode and a platinum cathode resulted in the successful synthesis of the corresponding 2,3-unsaturated peracetylated thioglycosides (with an average anomer ratio α/ß=4.129 in the case of peracetylated D-glucal and 8.740 in the case of L-rhamnal). The same procedure proved to be appropriate in synthesizing dihydropyran derivatives ('C-glycosides') using allyltrimethylsilane as the nucleophile (only 'α-anomers' were obtained). All new compounds were fully characterized by spectral data, whereas single-crystal X-ray analysis was performed for two thioglycosides.

Electrochemical synthesis and X-ray crystal structures of beta-D-2-phenylselenyl-1,3,4,6-tetra-O-acetylglucopyranose and alpha-D-2-phenylselenyl-1,3,4,6-tetra-O-acetylmannopyranose.

Electrochemical acetoxyphenylselenation of 3,4-dihydro-2H-pyran and D-3,4,6-tri-O-acetylglucal was studied. The constant current electrolysis (50mA) of dihydropyran and diphenyl diselenide in an acetic acid solution of tetramethylammonium chloride was performed at room temperature in an undivided cell using a graphite anode and an aluminum cathode and yielded trans-DL-2-acetoxy-3-phenylselenyltetrahydropyran (27%), in agreement with Markovnikov's rule. The analysis of the 1H NMR spectral data showed that the acetoxy and phenylselenyl groups adopt axial positions in the most stable conformation of this compound due to the anomeric effect. Under the same conditions D-3,4,6-tri-O-acetylglucal afforded D-2-phenylselenyl-1,3,4,6-tetra-O-acetylglucopyranose and D-2-phenylselenyl-1,3,4,6-tetra-O-acetylmannopyranose, which were separated by column chromatography and isolated in 87% overall yield (isomer ratio 60:40). The structures of these compounds were established by spectral data. Single crystal X-ray structure determinations of the diastereomers are reported.

Discovery of anxiolytic 2-ferrocenyl-1,3-thiazolidin-4-ones exerting GABAA receptor interaction via the benzodiazepine-binding site.

Herein, we report on the synthesis, spectral, crystallographic and electrochemical properties of a small library of N-substituted 2-ferrocenyl-1,3-thiazolidin-4-ones, designed as novel GABAA benzodiazepine-binding site ligands. The anxiolytic properties of the title compounds were evaluated in several different in vivo models, whereas the involvement of the GABAA receptor complex in the activity of the most potent compound, 2-ferrocenyl-3-(4-methoxyphenylethyl)-1,3-thiazolidin-4-one, was inferred from experiments with known GABAA-targeting agents. Ligand docking experiments revealed that the high, dose-dependent, anxiolytic activity of the new compounds might be due to their favorable interactions with the benzodiazepine-binding site of the GABAA receptor complex. The incorporation of the ferrocene core and fine tuning of the distance between the thiazolidinone core and an additional aromatic ring were judged to be crucial structural requirements for the observed anxiolytic effect.

Electrochemical bromochlorination of peracetylated glycals.

Peracetylated glycals-3,4,5-tri-O-acetyl-D-glucal (1a), 3,4,5-tri-O-acetyl-D-galactal (1b) and 3,4-di-O-acetyl-6-deoxy-L-glucal (1c)-have been bromochlorinated by a suitable halogenating agent, generated electrochemically from a mixture of bromides and chlorides in dichloromethane. The reaction was performed in two ways: (i) by a constant current electrolysis (2Fmol(-1)) of bromides and substrates in a milieu containing an excess of chlorides (Br(θ)/1/Cl(θ)=1:1:6.8) and (ii) by anodic generation of free chlorine from chlorides (2Fmol(-1)) and subsequent addition of bromides and substrates in a ratio Br(θ)/1=1:1. The corresponding 2-bromo-2-deoxy-glycopyranosyl chlorides were obtained in high yields.