Chiral separation with novel (S)-biotin-bonded silica gel for liquid chromatography

Liquid chromatographic separation of enantiomers was accomplished using a chiral stationary phase (CSP) derived from (S)-biotin on silica gel. In both nonaqueous and aqueous media, this CSP (1) permitted separation of racemic amino acid derivatives based on hydrogen bonding with a urea moiety of the biotin moiety.     

HPLC separation of nitrogen-containing compounds on silica gel modified with gold nanoparticles stabilized by chitosan

The potentialities of using silica gel modified with gold nanoparticles stabilized by chitosan are evaluated in the normal phase of HPLC as an example of the separation of aniline and pyridine derivatives, as well as triazole fungicides by elution with mixtures of hexane with isopropyl alcohol, isobutanol, or chloroform. The influence of the nature and content of the polar additive on the efficiency and separation selectivity of the column have been studied. The possibility of separating mixtures containing penconazole, propiconazole, diniconazole, difenoconazole, and aminopyridines is shown.     

Sulfur nanoparticles stabilized in the presence of water-soluble polymers

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Solvent-free silica gel mediated decarboxylation of C–O coupling products of β-diketones and β-oxo esters with malonyl peroxides

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Acrylamide polymers with covalently linked zinc(ii)tetraphenylporphyrin groups: synthesis and complexation with amino acids

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New heterogeneous catalytic systems based on highly porous ceramic materials modified with immobilized d-metal cage complexes for H2 production from CH4

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Effect of the nature of functional groups grafted on the surface of silica nanoparticles on properties of the hybrid proton-conductive membranes based on N-phosphorylated polybenzimidazole

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Macroporous monolithic columns modified with cholesterol-containing glycopolymer for cholesterol solid-phase extraction

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Microwave-assisted synthesis of ultra-small iron oxide nanoparticles for biomedicine

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Novel reactions of ninhydrin oxime with mercaptoalkanoic acids

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Preparation and properties of chitosan microspheres based on polyglycerol polyricinoleate stabilized emulsions

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Reactions of carbamoylated amino enones with 3-substituted chromones for the preparation of 2-pyridones and chromeno[4,3-b]pyridine-2,5-diones

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New approach to chemical modification of PIM-1 for gas separation membranes

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Chiral separation of amino acids using a chiral crown ether by impregnation on a polymeric support and monoamine modified silica gel

A chiral monoaza-15-crown-5 ether derivative was prepared from l-Leucinol and used as a chiral stationary phase. The new chiral stationary phases CSP-1 and CSP-2 were employed in separating the enantiomers of the sodium and potassium salts of amino acids. The sodium and potassium salt of the d-enantiomers of all amino acids (PhyAlaNa, PhyAlaK and PhyGlyNa, PhyGlyK, and TrpNa, TrpK) show higher selectivity than the l-enantiomers for both CSP-1 and CSP-2.     

Ion-exclusion chromatography of carboxylic acids on silica gel modified with aluminium

The modification of silica gel with aluminium by a coating method was effective for the preparation of a silica-based stationary phase, which acted as a cation exchanger under strongly acidic conditions. In order to expand the utility of the laboratory-made aluminium-adsorbing silica gel it was applied as a stationary phase to the ion-exclusion chromatography of various carboxylic acids. Good separations for both aliphatic carboxylic acids and benzenecarboxylic acids with a hydrophobic nature under acidic eluent conditions were achieved in 25 min.     

Dendro-shaped blocks with arylsulfanyl fragments based on p-toluic acid

Chloromethylation of p-toluic acid affords 3,5-bis(chloro- methyl)-4-methylbenzoic acid whose subsequent treatment with arenethiols brings about spacer dendrimeric blocks containing polyfluoroarylsulfanyl fragments in a total yield of 60-75%.     

Efficient synthetic approach to copolymers of glycolic and lactic acids for biomedical applications

An efficient approach to copolymers of glycolic and lactic acids applied in biomedical materials was developed using ring-opening polymerization catalysts based on alkoxy complexes of ‘biometals’ (Mg, Al, and Zn) and 3-methyl- 1,4-dioxane-2,5-dione and glycolide as comonomers.     

1,1′-Carbonyldiimidazole as a cyclodehydrating agent for the Castagnoli–Cushman reaction of dicarboxylic acids and imines

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A fast,new method to enhance the enantiomeric purity of non-racemic mixtures: self-disproportionation of enantiomers in the gas antisolvent fractionation of chlorine-substituted mandelic acid derivatives

Gas antisolvent precipitation is a particle formation technique, when typically pressurized carbon dioxide is added to an organic solution resulting in immediate and high oversaturation and precipitation of fine particles. Provided that a reasonable share of the originally dissolved material remains dissolved in the carbon dioxide – organic mixed solvent, these components can be extracted during the washing phase. This method is called gas antisolvent fractionation. Gas antisolvent fractionation has been applied for the first time to enantiomeric enrichment of non-racemic mixtures, and demonstrated on the example of chlorinated mandelic acid derivatives. Due to self-disproportionation of enantiomers, the precipitated solid and the extracted fractions have different enantiomeric excesses if gas antisolvent fractionation is carried out on a non-racemic mixture. However, there is a limit in the enantiomeric excess (ee) that can be achieved correlating strongly with the atmospheric melting eutectic behavior of the compounds. Thus, if initial enantiomeric mixtures have a higher than eutectic ee, a >99% ee can be reached in the crystalline product. The strong correlation between the high-pressure experiments and the atmospheric melting eutectic behavior suggest that despite the very large oversaturation during the antisolvent precipitation, the composition of the products (i.e., the crystalline and the extracted phases) is thermodynamically determined. Technological advantages such as short operational time, or the possibility of controlling the crystal morphology suggest that the development of an efficient technique of enantiomeric purification is possible based on gas antisolvent fractionation.