Ewa Janus

Spectroscopic studies of amino acid ionic liquid-supported Schiff bases.

Amino acid ionic liquid-supported Schiff bases, derivatives of salicylaldehyde and various amino acids (l-threonine, l-valine, l-leucine, l-isoleucine and l-histidine) have been investigated by means of various spectroscopic techniques (NMR, UV-Vis, IR, MS) and deuterium isotope effects on 13C-NMR chemical shifts. The results have shown that in all studied amino acid ionic liquid-supported Schiff bases (except the l-histidine derivative) a proton transfer equilibrium exists and the presence of the COO− group stabilizes the proton transferred NH-form.

Modification of Rapana thomasiana hemocyanin with choline amino acid salts significantly enhances its antiproliferative activity against MCF-7 human breast cancer cells

This is the first study on the interactions of ionic liquids with large metalloproteins, in particular hemocyanins (Hcs). At first, complexes of a Hc from Rapana thomasiana (RtH) with a series of biocompatible choline amino acid salts [Chol][AA] were obtained. Applying UV-vis spectroscopy, Fourier-transformed infrared spectroscopy and differential scanning calorimetry the effect of these organic salts on the structure and thermal stability of RtH was assessed. Then, the cytotoxic effect of RtH–[Chol][AA] on breast cancer cells (MCF-7) and 3T3 fibroblast cells (non cancerous) was evaluated. We found that all [Chol][AA] induced clear time- and concentration-dependent alterations in the RtH conformation. The conformation and the thermal stability of IL-modified RtH depend strongly on the type of the anion of the tested compounds. All [Chol][AA]-modified RtHs exhibited lower thermal stability than the native RtH. At the same time, we established a good correlation between the structure of RtH and its antitumor activity. Namely, RtH–[Chol][AA] complexes exhibited enhanced antiproliferative activity toward the MCF-7 cell line. The observed antiproliferative effect was cell specific and the compounds have no effect or in some cases have stimulatory effect on fibroblasts.

Rapana thomasiana hemocyanin modified with ionic liquids with enhanced anti breast cancer activity.

This is the first study on the surface modification of a hemocyanin from marine snail Rapana thomasiana (RtH) with series of imidazolium-based amino acid ionic liquids [emim][AA]. We monitored the induced by [emim][AA] conformational changes in RtH molecule and evaluated the effect of these ionic liquids (ILs) on the protein thermal stability. The cytotoxicity of all obtained RtH-[emim][AA] complexes was assessed toward breast cancer cells (MCF-7) and murine fibroblasts (3T3). As a whole, even small amounts of the tested ILs altered the secondary structure of RtH. The thermal denaturation of RtH in presence of [emim][AA] displayed multi-component transitions, which were shifted toward lower temperatures in comparison to those estimated for the native RtH. The profiles of the RtH-IL calorimetric curves show a clear dependence on the structure of the added salts. In addition, all RtH-[emim][AA] complexes exhibited an enhanced antiprofilerative activity of toward MCF-7 cells in comparison to that of the native RtH. The best results are observed for RtH-[emim][Leu], RtH-[emim][Trp] or RtH-[emim][Ile], which applied in concentration of 700 μg/mL inhibited the MCF-7 cell viability (for 24h) by 66, 63 and 53%, respectively. In addition, these IL-RtH complexes were less cytotoxic to 3T3 cells, i.e. they exhibited some cell specificity.

Efficient method for Knoevenagel condensation in aqueous solution of amino acid ionic liquids (AAILs)

Abstract This work reports on the use of the amino acid ionic liquids (AAILs) which have been used as catalysts in Knoevenagel condensation of various aldehydes with malononitrile. For research we use tetrabutylammonium ionic liquids based on eight natural amino acids. The reaction was carried out in an aqueous medium. Using water as solvent provided efficient and simple method of isolation of pure product with high yield. Moreover, amino acid ionic liquid dissolved in water could be reused many times without any loss of its catalytic activity. The influence of the anion was studied. Moreover the effect of technological parameters such as: the temperature, the catalyst content, and the reaction time on yield of reaction were investigated.

N-hexylpyridinium bis(trifluoromethylsulfonyl)imide and Lewis acids — catalytic systems for Diels-Alder reaction

AbstractA comparative study of the Diels-Alder reactions between cyclopentadiene (1) and dienophiles (2 a–c) in N-hexylpyridinium bis(trifluoromethylsulfonyl)imide in a temperature range of 20–45°C is reported. The reaction rate constants and activation energies were calculated. Moreover, the catalytic systems based on N-hexylpyridinium bis(trifluoromethylsulfonyl)imide and Lewis acids were tested as a reaction media to perform the Diels-Alder reaction. Yb, Y, Mg, Zn triflates and chlorides (0.005 to 0.1 mmol) were used as catalysts. The recycling of catalytic system consisted of YCl3 and ionic liquid was performed.

Mg(OTf)2 + ionic liquid - recyclable catalytic system in diels-alder reaction

Mg(OTf)2 + ionic liquid - recyclable catalytic system in diels-alder reaction A comparative study of Diels-Alder reaction between cyclopentadiene and dimethyl maleate in catalytic system is reported. The catalytic system was formed from ionic liquid which was made of N-hexylpyridinium bis(trifluoromethylsulfonyl)imide and magnesium trifluoromethanesulfonate. The yields, TONs, TOFs and endo:exo ratios were calculated. The optimal catalyst concentration was found in order to obtain the mixture of endo, exo isomers with the highest yields. Moreover recycling of the catalytic system consisting of Mg(OTf)2 (2 mol%) and ionic liquid was performed. The distillation was noticed to be a better product removal method than extraction by organic solvent, taking into consideration both the TON and TOF values.

Ionic liquids - deanol derivatives as the Diels-Alder reaction solvents

AbstractThe Diels-Alder reaction between cyclopentadiene and dienophiles in deanol derivatives containing bis(trifluoromethylsulfonyl)imide anion as media have been studied. The effect of the substituents attached to the cation on the endo:exo selectivity as well as the reaction yield have been evaluated in the absence and presence of Lewis acid catalyst - Y(OTf)3. Catalytic activity of metal triflates and the recycling of chosen catalytic systems have also been investigated

Chiral pyrrolidinium salts derived from menthol as precursor – synthesis and properties

Abstract Six new chiral pyrolidinium salts with chiral substituent at quaternary nitrogen atom were synthesized with high overall yields from (-)-menthol as cheap chiral precursor and were identified by NMR and HRMS spectroscopy. It was shown that anion type had the effect on chemical shift of protons adjacent to quaternary nitrogen atom and physical properties of these salts. Salts with NTf2 or NPf2 were in a liquid state at room temperature and characterized with the highest thermal stability among others. Furthermore, chiral ionic liquid with NTf2 anion was used as solvent in Diels-Alder reaction and gave higher yield and stereoselectivity than in ionic liquids with achiral cations. Synthesized chiral salts have the potential as chiral solvents in synthesis and auxiliaries in analytical methods to improve chiral recognition.

Lewis acids immobilized in ionic liquid – application for the acetal synthesis

Abstract Catalytic systems composed of metal chloride (InCl3, ScCl3, YCl3, YbCl3, LaCl3, BiCl3, ZnCl3 and CuCl3) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)-imide, [C1C4Pyrr][NTf2] as ionic liquid were prepared. Catalytic activity of all the systems were compared in acetalization reaction between cyclohexanone and triethyl orthoformate. 1,1-Diethoxycyclohexane were formed with high yield and the selectivity at 0°C within 5 minutes. Selected metal chlorides immobilized in ionic liquid were recycled 5 times without a decrease in their activities

Kinetic study of the phase-transfer catalytic epoxidation of 1,4-bis(allyloxy)butane

The epoxidation of 1,4-bis(allyloxy)butane (DiBan) with hydrogen peroxide as an oxidant in the presence of o-phosphoric acid and sodium tungstate as an epoxidation catalyst was carried out in an organic solvent/aqueous solution two-phase medium. A few different phase-transfer catalysts were used in the process. The effect of the stirring speed, nature of solvent, the type of PT catalyst and molar ratio of H(2)O(2):DiBan, DiBan:Na(2)WO(4):H(3)PO(4) on the DiBan conversion as the function of time was studied. Based on the experimental results, a pseudo-first-order expression for the reaction rate was applied and most efficient conditions epoxidation were developed.