Complexation of 6-Deoxy-6-(aminoethyl)amino-β-cyclodextrin with Sodium Cholate and Sodium Deoxycholate

In order to study its guest binding and the inclusion phenomena, 6-deoxy-6-(aminoethyl)amino--cyclodextrin (CDN) was synthesised and its binding properties examined. The complexation phenomena of sodium cholate (NaC) and sodium deoxycholate (NaDC) with CDN has been monitored by the NMR method using ¹³C chemical shift data. The method of continuous variation Job's method has been used to determine the stoichiometry of these supramolecular complexes. The Job's plot confirms the 1 : 1 supramolecular complex for NaC: CDN and the 1 : 2 supramolecular complex for NaDC: CDN. The interaction of NaC and NaDC with CDN has been obtained through two-dimensional Rotational Nuclear Overhauser Effect Spectroscopy (ROESY) NMR. Equilibrium constants were also obtained from ¹³C chemical shift data (C-1, C-3 & C-4) at different pH values (7, 9, & 11).     

Dual Solvatochromism of Neutral Red

Abstract— The effect of solvent polarity on the electronic absorption and fluorescence properties of neutral red (NR), a phenazine-based dye of biological importance has been investigated in several neat and mixed solvents. An unusual dual solvatochromic behavior has been observed that reveals the existence of two closely spaced electronic excited states in NR. In low-polarity solvents the fluorescence of the NR is mainly emitted from the localized excited state, whereas in high-polarity solvents the emission from the charge transfer state dominates. The dipole moments of the localized and charge transfer states of NR have been estimated from the solvatochromic shifts. The dipole moment of the localized excited state (4.8 D) is only slightly higher than that of the ground state (2.0 D), while that of the charge transfer state is drastically higher (17.5 D). Fluorescence quantum yields and the life-times of NR have been determined in different solvents and correlated with the solvatochromic shifts.     

EPR on Medically Relevant NO Adsorbed to Zn-LTA

For medical purposes, materials are required that store and target specifically deliver exogenous nitric oxide (NO). Partially zinc-exchanged Na-LTA (Linde type A) zeolite (Zn-LTA) has high potential in this respect due to its non-toxicity and adsorption capacity for NO. In contrast to NO adsorbed to LTA zeolites prepared for catalytic purposes, lower dehydration temperature prior to NO adsorption is used to achieve a balance between production cost and high activity. In order to study the interaction of NO with the metal sites in the samples prepared under these medical conditions, continuous-wave X-band electron paramagnetic resonance has been applied. In contrast to Na-LTA with only one weakly interacting NO monomer, three different monomers, having stronger interaction to the metal sites than in Na-LTA, were observed in Zn-LTA. To improve the storage capacity of Zn-LTA, higher dehydration temperatures would be necessary.     

Synthesis, structure, and transformations of N-(bicyclo[2.2.1]hept-5-en-endo-2-ylmethyl)-N-[(oxiran-2-yl) methyl]-arenesulfonamides

Reaction of N-(bicyclo[2.2.1]hept-5-en-endo-2-ylmethyl)arenesulfonamides with epichlorohydrin in the presence of tetramethylammonium iodide afforded a group of framework N-[(oxiran-2-yl)methyl]sulfonamides and also a series of new dioxiranes, N-(oxiran-2-yl)methyl-N-(exo-5,6-epoxybicyclo[2.2.1]heptan-endo-2-ylmethyl)arenesulfonamides. The aminolysis of N-(oxiran-2-yl)methyl]arenesulfonamides with benzylamine and benzylpiperazine led to the chemo- and regioselective opening of the epoxy ring according to Krasusky rule. The structure of compounds was established by spectral methods and the XRD analysis.     

Natural and synthetic manganese minerals

The mineral and microelement composition and structures have been studied and a comparative analysis has been carried out for manganese minerals with the general formula [Mn(O,OH)₂]⁺[R_0.5–1(OH)_21.5] · nH₂O (R = Mn, Na, K, Ni, Co, Ca, and others) that built iron-manganese concretions raised from different areas of the Sea of Okhotsk and the Bering Sea, and their synthetic analogues. The structures of synthetic manganese species were found to better withstand temperature impacts than those of the native minerals studied under the same conditions.     

Regioselective Synthesis of Thiopyrano[3,2‐c][1]benzothiopyran‐5(2H)‐one and Thieno[3,2‐c][1]benzothiopyran‐4(2H)‐one

4‐Mercaptothiocoumarin was alkylated with different propargylic and allylic halides under phase‐transfer‐catalyzed conditions in the presence of tetrabutylammonium bromide (TBAB) or benzyl triethylammonium chloride (BTEAC) catalyst in dichloromethane–aqueous NaOH solution (1%) at room temperature. These 4‐thiopropynyl and thioallyl thiocoumarins were then refluxed in chlorobenzene and quinoline to give thiopyrano[3,2‐c][1]benzothiopyran‐5(2H)‐one and thiopyrano[3,2‐c][1]benzothiopyran‐4‐one respectively.     

Effect of grain size on the sorption and desorption of SeO4 2− and SeO3 2− in columns of crushed granite and fracture infill from granitic water under dynamic conditions

The sorption of 2 × 10^?5 mol/dm³ Na₂SeO₄ and Na₂SeO₃ dissolved in synthetic granitic water (SGW) were investigated in columns of crushed granite and fracture infill (clay minerals) of various grain sizes. Desorption was studied using pure SGW. The goal of study was the quantification of the effect of grain size on the retardation and distribution coefficients of SeO₄ ^2? and SeO₃ ^2?, as well as on the other transport parameters (Peclet number and hydrodynamic dispersion coefficient). A model based on the erfc-function, assuming a non-linear reversible equilibrium sorption/desorption isotherm, was used for evaluation of sorption/desorption and transport parameters. The determination of selenium was performed using an ICP-MS technique. The experimental breakthrough curves were fitted using non-linear regression procedure, in the course of which the parameters mentioned were sought. Summing up, no sorption was recorded in the case of SeO₄ ^2? under these conditions. The values of retardation coefficients were practically one for all studied grain sizes. On the other hand, significant sorption was found for SeO₃ ^2?: depending on the grain size, the retardation coefficients varied between 1.6–8.7 in pure granite and 1.8–37.2 in infill materials. These values correspond to distribution coefficients of 0.2–2.5 and 0.2–12.7 cm³/g, respectively. The both parameters have similar values in a case of desorption which reflects the reversible character of sorption process. It was found that retardation and distribution coefficients and sorption capacity for SeO₃ ^2? also increase with decreasing grain size.     

Sorption of 125I−, 137Cs+, 85Sr2+ and 152,154Eu3+ during their transport in undisturbed vertical and horizontal soil cores under dynamic flow conditions

Transport and sorption of ¹²⁵I^?, ¹³⁷Cs⁺, ⁸⁵Sr²⁺ and ^152,154Eu³⁺ in undisturbed soil cores have been studied under dynamic conditions. Radionuclides were dissolved in synthetic groundwater (SGW) of 0.015 mol/dm³ ionic strength, pH 8.4 and redox potential E_h = 145 mV. The soil samples were taken vertically and horizontally from the river bed at 5–100 cm depths, about 120 m southward of the Dukovany Low and Medium Level Radioactive Waste Repository. The respective water-soluble carriers in the 10^?6 mol/dm³ concentration were added into the SGW prior to the experiments. The soil cores of 9 cm height and 3.8 cm in diameter were placed into columns made of 150 cm³ PE injection syringes of suitable dimensions. The SGW was introduced into columns from the Mariotte’s bottle through a glass manifolds to supply the soil columns by gravity flow at a constant flow-rate about 1.2 cm³/h. Into the water stream, radioactive nuclides were added individually in a form of a short pulse in 0.1 cm³ of demineralized water. In the case of ¹²⁵I^? transport, retardation and hydrodynamic dispersion coefficients were determined, using an integral form of a simple advection-dispersion equation. For each radionuclides, sorption and desorption data have been obtained, evaluated and the results were compared mutually. Residual distributions of the sorbed cationic radionuclides along the soil columns were also presented.     

Synthesis of Derivatives of 2,6-Dideoxy-2,2-Difluoro-3-O-Methyl-l-Arabinopyranose (2,2-Difluorooleandrose)

Abstract

L-Oleandrose is the carbohydrate constituent of the potent anthelmintic agents the avermectins. Diethylaminosulfur tri-fluoride treatment of appropriate uloses did not give gem-difluoro sugars. Trifluorofluoroxymethane or xenon difluoride addition to the double bond of 4-O-benzoyl-6-deoxy-2-fluoro-3-O-methyl-L-glucal produced protected 2,2-difluorooleandrose derivatives activated at their anomeric center and ready for glycosidation.     

Intramolecular aglycon delivery for (1 → 2)-β-mannosylation: towards the synthesis of phospholipomannan of Candida albicans

A high yielding method for 1,2-cis-β-D-mannosylation by intra-molecular aglycon delivery (IAD) through p-methoxy benzyl ether/acetal exchange and phenylsulfoxide donor is reported, along with its application in iterative assembly of antigenic (1 → 2)-β-pentamannoside domain of phospholipomannan (PLM) of fungal pathogen Candida albicans.