Resolution of ketoconazole enantiomers by high-performance liquid chromatography and inclusion complex formation between selector and enantiomerss

The analytical resolution of ketoconazole (KTZ) enantiomers was performed by high-performance liquid chromatography with sulphobutylether-β-cyclodextrin (SBE-β-CD) as a chiral mobile phase additive (chiral selector). Some important factors affecting the resolution of KTZ enantiomers were investigated. In addition, the molecular interaction between KTZ and SBE-β-CD was studied using the UV absorption spectrum and HPLC for an understanding of the resolution process. The results show that the type and concentration of the chiral mobile phase additive, the pH of the mobile phase and the volume fraction of methanol (?_MeOH) in the mobile phase all have a clear influence on the resolution of KTZ enantiomers. Under optimal conditions, namely the use of 0.5 mmol L^?1 SBE-β-CD as the chiral mobile phase additive, pH of 4.0 and ?_MeOH in the mobile phase of 0.6, KTZ enantiomers are resolved with a resolution of 3.74. SBE-β-CD can bind to KTZ with a stability constant of 1157. The chromatographic method can provide the complexation stability constants of (+)-KTZ with SBE-β-CD (K₍₊₎) and (?)-KTZ with SBE-β-CD (K_(?)). The intrinsic enantioselectivity was calculated from the K₍₊₎ to (K_(?)) ratio as 1.34.     

Enantioseparation of Hydrobenzoin and Structurally Related Compounds on <Emphasis Type="Italic">β</Emphasis>-Cyclodextrin and Hydroxypropyl-<Emphasis Type="Italic">β</Emphasis>-cyclodextrin Bonded Chiral Stationary Phases

A β-cyclodextrin (β-CD) and a hydroxypropyl-β-cyclodextrin (HP-β-CD) bonded chiral stationary phase (CSP) were prepared. Comparative evaluations of these two CSPs for the enantioseparation of hydrobenzoin, benzoin and α-phenethyl alcohol by reversed-phase liquid chromatography were presented. The effects of buffer composition in the mobile phase on the retention and enantioseparation were investigated. The borate buffer had a significant influence on the retention and enantioseparation of hydrobenzoin. Linear solvent strength retention model was used to fit the chromatographic data. Good linearity existed between the logarithm of retention factor (k) and the volume fraction of organic modifier (φ). Another retention model, stoichiometric displacement theory for retention, was also tried to fit the chromatographic data. The results showed that not only acetonitrile, but also water molecules participated in the displacing process of the solute.     

Use of 6-<Emphasis Type="Italic">O</Emphasis>-mono-substituted derivatives of β-cyclodextrin-bearing substituent with two permanent positive charges in capillary electrophoresis

This study details the use of two permanently positively charged mono-substituted β-cyclodextrin derivatives, 6^I -deoxy-6^I-(N,N N′,N′,N^t’-pentamethyl-ethylene-1,2-diammonio)-cyclomaltoheptose dichloride (PEMEDA-β-CD) and the newly synthesised 6^I-deoxy-6^I-(N,N,N′,N′,N′-pentamethyl-propylene-1,3-diammonio)-cyclomaltoheptose (PEMPDA-β-CD) as chiral selectors in capillary electrophoresis. Cyclodextrin (CD) derivatives were tested as additives in various buffers at various pH values with the optional addition of an organic modifier. Fourteen anionogenic analytes were tested, including native amino acids, N-blocked amino acids and profens, which were detected using a UV-VIS detector at optimal wavelengths of 214 nm, 254 nm or 280 nm. A borate buffer (15 mmol L^?1) at pH 9.5 without the addition of an organic modifier was chosen as a suitable background electrolyte. In addition, the effect of the concentration of the chiral selector on the separation and enantioseparation of selected analytes was monitored. The additions of cyclodextrin derivatives varied within the concentration range of 0.0–5.0 mmol L^?1. Both chiral selectors were suitable for the enantioseparation of N-Boc-d,l-tryptophan, which was already separated on the baseline at 0.5 mmol L^?1 concentration of the chiral selector.     

Use of gold nanoparticles for immobilization of <Emphasis Type="Italic">L</Emphasis>-cysteine on TLC plates

A new method of immobilization of the chiral selector on the surface of TLC plates by means of stepwise impregnation by gold nanoparticles and L-cysteine is described. The novel silica- and alumina-based stationary phases for TLC demonstrate enantioselectivity toward tetrahydrozoline, hydroxyzine, ketoprofen, fenoprofen, pindolol, and fluoxetine. The influence of the composition of the mobile phase on the R _f values and enantioselectivity is also discussed.     

Synthesis and characterization of <Emphasis Type="Italic">D</Emphasis>-/<Emphasis Type="Italic">L</Emphasis>-methionine grafted PEDOTs for selective recognition of 3,4-dihydroxyphenylalanine enantiomers

Two pairs of amino-acid functionalized poly(3,4-ethylenedioxythiophene) (PEDOT) derivatives, namely, poly(N-(tert-butoxycarbonyl)-L-methionyl (3,4-ethylenedioxythiophene-2’-yl)methylamide) (L-PEDOT-Boc-Met) and poly(N-(tert-butoxycarbonyl)-D-methionyl (3,4-ethylenedioxythiophene-2’-yl)methylamide) (D-PEDOT-Boc-Met); poly(L-methionyl (3,4-ethylenedioxythiophene-2’-yl)methylamide) (L-PEDOT-Met) and poly(D-methionyl (3,4-ethylenedioxythiophene-2’-yl)methylamide) (D-PEDOT-Met) were synthesized via chemical oxidative polymerization of corresponding monomers. The structural characterization, spectroscopic properties and thermal stability of these monomers and polymers were systematically explored by FTIR spectra, Raman spectra, XRD spectra, UV-Vis spectra and thermogravimetric analysis. As chiral electrode materials, these polymers were employed to successfully recognize 3,4-dihydroxyphenylalanine (DOPA) enantiomers by cyclic voltammetry (CV) in sulphuric acid solution. The measurement results reveal that the tendency was hetero-chiral interaction between L-PEDOT-Met/PVA/GCE and D-DOPA, D-PEDOT-Met/PVA/GCE and L-DOPA, respectively. Also, the mechanism of chiral discrimination was discussed. All the results implied that the combination of electrochemical molecular recognition technology and chiral PEDOT materials can be a promising approach for chiral recognition and may open new opportunities for facile, biocompatible, sensitive and robust chiral assays in biochemical applications.     

Power consumption for an agitated vessel equipped with pitched blade turbine and short baffles

Power characteristics for an agitated vessel equipped with planar short baffles of length L and pitched blade turbine of pitch β are presented in the paper. The studies were carried out in the vessel of inner diameter D = 0.6 m, where the baffles were located in the distance p from the vessel bottom (p + L = H). Torque was measured using strain gauge method within the turbulent regime of the flow of Newtonian liquid in the agitated vessel. The effects of the pitch β and geometrical parameter p/H on the power number Ne were determined mathematically. The results showed that, for the assumed value of the angle β, the function Ne = f (L/H) decreases with the decrease in the baffle length L (i.e. with the increase in the parameter p). Moreover, for the assumed value of the baffle length L, the function Ne = f (β) increases with the increase in the angle β of the inclination of the impeller blade.     

Method for calculating the sizes of nucleation centers upon homogeneous crystallization from a supercooled liquid

An alternative approach to calculating critical sizes l_k of nucleation centers and work A_k of their formation upon crystallization from a supercooled melt by analyzing the variation in the Gibbs energy during the phase transformation is considered. Unlike the classical variant, it is proposed that the transformation entropy be associated not with melting temperature T_L but with temperature T < T_L at which the nucleation of crystals occurs. New equations for l_k and A_k are derived. Based on the results from calculating these quantities for a series of compounds, it is shown that this approach is unbiased and it is possible to eliminate known conflicts in analyzing these parameters in the classical interpretation.     

X-Ray diffraction study of the new ecdysteroid derivatives containing isoxazoline ring in the side chain

Crystal and molecular structure of (2β,3β,14α,20R,5′R)-14,20-dihydroxy-20-(3′-isopropylisoxazolin-5′-yl)-2,3-isopropylidenedioxy-5β-pregn-7-en-6-one and (2β,3β,14α,20R,5′R)-20-hydroxy-20-(3′-methylisoxazolin-5′-yl)-14-trimethylsilyloxy-2,3-isopropylidenedioxy-5β-pregn-7-en-6-one was investigated by XRD analysis. Compounds crystallize in the orthorhombic [space group P2₁2₁2₁; a 1.751(2), b 12.146(2), c 19.660(4) Å] and hexagonal [space group P6₁; a 14.138(3), b 14.138(3), c 27.597(7) Å] crystal systems, respectively. These compounds, which resulted from the 1,3-dipolar cycloaddition of isobutyronitrile oxide or acetonitrile oxide to the corresponding steroid olefin, have 5′R-stereochemistry of the formed chiral center. The conformation of the side chain of molecules is stable due to the intramolecular hydrogen bonds.     

Structural features of monomeric octahedral <Emphasis Type="Italic">d</Emphasis><Superscript>2</Superscript>-rhenium(V) monooxo complexes with oxygen atoms of bidentate-chelating neutral and acidic ligands (O,P)

The structural features of 38 mononuclear d ²-Re(V) octahedral monooxo complexes (I–XXXVIII) with oxygen atoms of bidentate-chelating (O, P) ligands (L ⁿ ) are considered. The atoms O(L ⁿ ) are mostly in trans positions to O(oxo) ligands. In three compounds of general formula [ReO(L_mono)(L ⁿ )₂] (XXXVI–XXXVIII), the O atoms of two L ⁿ ligands occupy both trans and cis positions to oxo ligands. In one complex, namely, in [ReO(L ⁿ )(L _tri ¹¹ )], n = 3 (XXXV), the atom O(L³) is in the cis position to the oxo ligand; the trans position to O(oxo) is occupied by the atom O(L _tri ¹¹ ).     

LC Enantioseparation of Aryl-Substituted β-Lactams Using Variable-Temperature Conditions

Direct reversed-phase high-performance liquid chromatographic methods were developed for the separation of enantiomers of β-lactams. The enantiomers of 7 aryl-substituted β-lactams were separated on chiral stationary phases containing the macrocyclic glycopeptide antibiotic teicoplanin (Chirobiotic T) and teicoplanin aglycone (Chirobiotic TAG) at 10-°C increments in the range 5–45 °C, using different compositions of 0.1% aqueous triethylammonium acetate (pH 4.1)/methanol (v/v) as mobile phase. The mobile phase composition and temperature were varied to achieve baseline resolutions in a single chromatographic run. The dependence of the natural logarithms of the selectivity factors ln α on the inverse of temperature, 1/T, was used to determine the thermodynamic data on the enantiomers. The thermodynamic data revealed that all the compounds in this study undergo separation via the same enthalpy-driven chiral recognition mechanism. The different methods were compared in systematic chromatographic examinations. The effects of the organic modifier, the mobile phase composition and the temperature on the separation were investigated.     

Molecular dynamics simulations of the characteristics of sodium carboxymethyl cellulose with different degrees of substitution in a salt solution

Sodium carboxymethyl cellulose (SCMC) with different degrees of substitution (DS) possesses structural characteristics and physicochemical properties that are important in broad areas of industrial applications. This reported work investigated the structural characteristics, including the effective length (L _ef), the radius of gyration (R _g), and the hydrodynamic radius (R _H), and the physicochemical properties, including intrinsic viscosity ([η]) and salt tolerance, of SCMC with a DS more than 1.0 in NaCl solution using molecular dynamics (MD) simulations. In the MD simulations, the DS of SCMC varied from 1.2 to 2.8, and the NaCl concentration varied from 0 to 1.4 mol/L. MD simulation results showed that with the increment of NaCl concentration, the L _ef (or R _g or R _H) of SCMC decreased; with the increment of the DS, the L _ef of SCMC increased. Also, the variation tendency of [η] in the NaCl solution was consistent with its L _ef (or R _g or R _H). It was noted that the salt tolerance (represented by D) of SCMC increased as the DS increased. In addition, the sharp variation of the D value of SCMC occurred in the range of DS of 1.6 to 2.0, which agreed with the reported experimental results. Radial distribution function analyses showed that the Na⁺ cations had a stronger interaction with the carboxyl groups in SCMC with lower DS when it was present in a salt solution of higher concentration, which also reasonably explained the variation of L _ef, R _g, R _H, [η], and D of SCMC in NaCl solution.     

Synthesis,crystal structure,and hydrogen-bonded displacive-type structural phase transition of guanidine dichloroacetate

Guanidine dichloroacetate was synthesized and separated as crystals. Differential scanning calorimetry (DSC) measurement shows that this compound undergoes a reversible phase transition at about 275 K with a heat hysteresis of 28 K. Step-like dielectric anomaly observed at 274 K further confirms the phase transition. The single-crystal X-ray diffraction data suggested that these was a transition from a room-temperature phase with the space group of P2₁/n (a = 8.030(5), b = 12.014(9), c = 8.124(6) Å, β = 96.089(1)°, V = 779.3(1) Å³, and Z = 4) to a low-temperature one with the space group of P2₁/c (a = 7.941(2), b = 11.828(3), c = 10.614(2) Å, β = 130.985(1)°, V = 752.6(3) Å³, and Z = 4). The displacements of hydrogen bonds induce the structure phase transition.     

Synthesis,structural phase transition,and characterization of potassium hydrogen bis-dichloroacetate

Potassium hydrogen bis-dichloroacetate (1) was synthesized and separated as crystals. Differential scanning calorimetry (DSC) measurement reveals that this compound undergoes a reversible phase transition at about 259 K with a heat hysteresis of 23.5 K. Dielectric anomaly observed at 260 K in the heating process further confirms the phase transition. The room temperature X-ray single-crystal structure determination indicates that 1 crystallizes in the monoclinic crystal system with a centrosymmetric space group P2₁/c, and cell parameters are a =?6.240(1), b =?23.177(4), c =?7.335(1) Å, β =?106.938(1)°, V =?1014.8(3) ų, and Z =?4. In the low temperature phase, 1 also crystallizes in monolinic with space group P2₁/c, and cell parameters are a =?6.180(1), b =?22.988(2), c =?7.200(1) Å, β =?108.098(1)°, V =?972.4(1) ų, and Z =?4. The structural phase transition is dominating caused by the torsion of bond angles.     

CE Enantioseparation of Betti Bases with Cyclodextrins and Crown Ether as Chiral Selectors

Direct capillary zone electrophoretic methods were developed for the separation of the enantiomers of 1-(α-aminoarylmethyl)-2-naphthol and 2-(α-aminoarylmethyl)-1-naphthol analogues. The effects of selector and buffer concentrations, electrolyte pH and applied voltage on the separation efficiency were studied. Variation of the electrophoretic conditions with the application of negative polarity, hydrodynamic injection, an unmodified silica capillary, different buffers and sulfated cyclodextrins and (S,S)-dimethylpyridino-18-crown-6 ether as chiral selectors led to the baseline resolution of all the compounds investigated.     

Syntheses,Structures, and Properties of Two Coordination Polymers Based on 2-Pyrimidineamidoxime

Two coordination polymers, {[Cd(L¹)₂(L₂)] · 0.25H₂O} _n (I) and {[Cd(L¹)(L₃)H₂O] · 2H₂O} _n (II) (L¹ = 2-pyrimidineamidoxime, L² = 4-sulfobenzoate dianion and L³ = 5-sulfosalicylate dianion), has been synthesized and structurally characterized by single-crystal X-ray diffraction (CIF files CCDC nos. 1565646 (I) and 1565728 (II)). Complex I crystallizes in monoclinic space group P2₁/n with a = 10.1462(3), b = 16.0152(5), c = 14.0349(5) Å, β = 93.267(3)°, V = 2276.87(13) ų, C₆₈H₆₆N₃₂O₂₉S₄Cd₄, M = 2373.36, ρ_calcd = 1.731 g/cm³, μ(MoK_α) = 1.109 mm^?1, F(000) = 1186, GOOF = 0.806, Z = 1, the final R¹ = 0.0287 and wR² = 0.0733 for I > 2σ(I). Complex II crystallizes in monoclinic space group P2₁ with a = 6.882(2), b = 17.138(2), c = 7.883(2) Å, β = 103.83(3)°, V = 902.8(4) ų, C₁₂H₁₆N₄O₁₀SCd, M = 520.75, ρ_calcd = 1.916 g/cm³, μ(MoK_α) = 1.388 mm^?1, F(000) = 520, GOOF = 1.047, Z = 2, the final R¹ = 0.0739 and wR² = 0.2041 for I > 2σ(I). Crystal structural analysis reveals that complex I possesses the corrugated 1D chain structure extending along the \([\bar 101]\) direction. However, complex II displays a 2D coordination network lying on the ab crystal plane, which can be simplified as a binodal 3-connected 6³ topological network by considering Cd²⁺ ions and L³ ligands as 3-connected nodes. Their photoluminescent and thermal properties were also investigated.     

Laterally non-symmetric aza cryptand molecules stitched by water

Crystal structure of the compound L·4H₂O (L = aza cryptand) and its supramolecular assembly via H-bonding through water molecules are described here. The compound crystallizes in the cubic space group Pa3 (no. 205) with the following lattice parameters: a=b=c=19.023(2) Å, V=6883.9(4) Å³, Z=8, R ₁=0.0592, wR ₂ = 0.1572, S=0.964.     

Chiral guest in a chiral framework: X-ray diffraction study

The inclusion compound of zinc lactate terephthalate with R-butan-2-ol, [Zn₂(R-Bu^sOH) (bdc)(S-lac)]?(R-Bu^sOH) (Bu^sOH is butan-2-ol, H₂bdc is terephthalic acid, S-H₂lac is lactic acid), was prepared by soaking crystals of [Zn₂(dmf)(bdc)(S-lac)]?DMF in pure R-butan-2-ol. The positions of chiral alcohol molecules in voids of the chiral framework and the host–guest contacts were determined by X-ray diffraction. These data provide an explanation for the origin of chiral discrimination of zinc lactate terephthalate toward the R-isomer of butan-2-ol.     

Chiral separation of α-cyclohexylmandelic acid enantiomers using ionic liquid/salt aqueous two-phase system

In this paper, an ionic liquid-based aqueous two-phase system (ILATPS) was applied to the chiral separation of α-cyclohexylmandelic acid (α-CHMA) enantiomers with hydroxypropyl-β-cyclodextrin (HP-β-CD) as the chiral selector. Several influencing parameters were investigated including the types and concentration of ionic liquids, the amount of phase-forming salt, temperature, mixing time, pH, and the content of HP-β-CD. The results showed that not all ILATPS had the ability to chirally recognise the selected enantiomers and that [C₄mim]BF₄/(NH₄)₂SO₄-based ATPS possessed the best enantioseparation ability of the investigated ILATPSs. Under optimal conditions, the separation factor (α) attained 1.59 in a single-step extraction. ILATPS is much “greener” than other liquid-liquid extraction systems, showing its potential for application to the chiral separation.     

Tetrakis [<Emphasis Type="Italic">N</Emphasis>-(2-pyridyl) sulfonamide] di palladium: synthesize,X-ray diffraction,antibacterial properties and as a novel binuclear Pd-complex for coupling reactions

The N-(2-pyridyl) 4-toluene sulfonamide as a free ligand (PTS) was prepared from the reaction of 2-amino pyridine and 4-toluenesulfonyl chloride in the presence of potassium hydroxide solution 1 M as a base and THF was used as a solvent. The complex tetrakis [N-(2-pyridyl) sulfonamide] di palladium (1) (Pd₂L₄) was also prepared from the reaction of PdCl₂(CH₃CN)₂ using (PTS) in the presence of NaOH 0.5 M and its application in Heck and Suzuki reactions. This complex consists of a binuclear unit consisting of four ligands linked to two palladium atoms via the nitrogen of pyridines ring and the nitrogen of sulfonamides. These compounds were confirmed by FT-IR and ¹H NMR spectroscopy. Moreover, the structure of the complex was studied by single-crystal X-ray diffraction method. The green crystal of Pd₂L₄ [L = N-(2-pyridyl) sulfonamide](1) was found to crystallize in the monoclinic space group C2/c with a = 18.2013(19), b = 19.7544(16), c = 17.2898(19) Å, β = 120.179(8) °; V = 5374.0(9) ų; Z = 4; the final R ₁ = 0.0894, wR ₂ = 0.1754 (or 5867 observed reflections and 318 variables). The Pd–Pd distance is 2.567(2) Å. In addition, PTS and Pd₂L₄ presented different antibacterial behaviors. The free ligand was active against Staphylococcus aureus and Escherichia coli, but the complex was inactive against them.     

Determination of the oxidation state of iron by X-ray fluorescence spectroscopy using chemometric approaches

A possibility of identification of the oxidation state of iron by wavelength dispersive X-ray fluorescence spectroscopy using both the position and intensity of L _α and L _β spectral lines of iron and by principal component analysis score data obtained by the decomposition of the spectral region corresponding to spectral L-series lines of iron is demonstrated. The application of scores ensures a more reliable identification in comparison with line parameters (position and intensity). Two approaches based on projection on latent structures (PLS) regression for the determination of the concentration of iron in different oxidation states are proposed. The first approach consists in using reference models with compositions similar to those of analyzed samples. In the second approach, PLS regression was build using model spectra obtained from spectra of readily available iron compounds.