Direct TLC Resolution of the Enantiomers of Three β-Blockers by Ligand Exchange with Cu(II)–l-Amino Acid Complex, Using Four Different Approaches

TLC experiments have been performed to resolve the enantiomers of three β-blockers by complexation chiral TLC with Cu(II) cation and five l amino acids. Loading was carried out by using the Cu(II)–l amino acid complex as chiral mobile phase additive with untreated silica gel plates; by mixing the Cu complex with silica gel before preparing the TLC plates; by ascending development of untreated plates with solutions of the Cu complex; and by using a solution of Cu(II) acetate as mobile phase additive for plates prepared by mixing the l amino acid with silica gel. Spots were located by use of iodine vapour.     

Enantioseparation of Aminoglutethimide by High-speed Countercurrent Chromatography Using Carboxymethly-β-cyclodextrin as Chiral Selector

The high-speed countercurrent chromatography (HSCCC) is a liquid-liquid partitioning chromatography, in which the stationary phase is immobilized by centrifugal force and the chiral selector can be conveniently added to stationary phase or mobile phase. I…     

Investigation of Enantiomeric Separation of Chiral Drugs by CE Using Cu(II)–Clindamycin Complex as a Novel Chiral Selector

The enantiomeric separation of several basic drugs was investigated using copper(II)–clindamycin as a new chiral selector. The results show that the chiral selector allows high-resolution separation of some racemic basic drugs, including tropicamide, propranolol, sotalol, bisoprolol, epinephrine, esmolol, atenolol, and metoprolol. The enantioselectivity was influenced by parameters such as the type of metal ion, ratio of clindamycin and Cu(II), pH of the background electrolyte, clindamycin concentration, applied voltage, and capillary temperature. The optimal separation conditions were determined to be 20 mM clindamycin/10 mM Cu²⁺, pH 9.06, at 20 kV and 22 °C within 25 min.

     

Investigation of Enantiomeric Separation of Chiral Drugs by CE Using Cu(II)�CClindamycin Complex as a Novel Chiral Selector

The enantiomeric separation of several basic drugs was investigated using copper(II)?Cclindamycin as a new chiral selector. The results show that the chiral selector allows high-resolution separation of some racemic basic drugs, including tropicamide, propranolol, sotalol, bisoprolol, epinephrine, esmolol, atenolol, and metoprolol. The enantioselectivity was influenced by parameters such as the type of metal ion, ratio of clindamycin and Cu(II), pH of the background electrolyte, clindamycin concentration, applied voltage, and capillary temperature. The optimal separation conditions were determined to be 20 mM clindamycin/10 mM Cu²⁺, pH 9.06, at 20 kV and 22 °C within 25 min.     

Enantioseparation of Three β-Agonists Using Di-n-butyl d-Tartrate-Boric Acid Complex as Chiral Selector by Means of MEEKC

In this study, a self-prepared complex chiral selector, di-n-butyl d-tartrate-boric acid complex, by the reaction of di-n-butyl d-tartrate with boric acid in a running buffer was used as a chiral selector for the enantioseparation of three β-agonists including clenbuterol, cycloclenbuterol and tulobuterol by means of microemulsion electrokinetic chromatography (MEEKC). Three β-agonists were successfully enantioseparated using the chiral system, indicating that the di-n-butyl d-tartrate-boric acid complex was a useful chiral selector. The effects of di-n-butyl d-tartrate and sodium tetraborate concentration, surfactant concentration, cosurfactant, phosphate, buffer pH and composition, as well as applied voltage were extensively investigated to achieve a good enantioseparation. The di-n-butyl d-tartrate and sodium tetraborate concentration in the running buffer had great influence on the chiral resolution (R _s). Three β-agonists which could not be separated with only di-n-butyl d-tartrate, obtained good chiral separation using the complex chiral selector; among them, two pairs including clenbuterol and cycloclenbuterol could be baseline resolved in 7 min under optimized experimental conditions of 0.8% (w/v) di-n-butyl d-tartrate, 40 mM sodium tetraborate, 3.0% (w/v) Tween-20 and 60 mM sodium dihydrogen phosphate with 25 kV as running voltage. The results indicated that the method could be used for the enantioseparation of three β-agonists.

     

Investigation of Mixed Chiral Selectors of Different Metal Ion-L-Alanine Complex and β-Cyclodextrin on the Chiral Separation of Dansyl Amino Acids with Capillary Electrophoresis

Chiral separation of dausyl amino acids by capillary electrophoresis using mixed selectors of Mn(ll)-L-alanine complex and β-cyclodextrin (β-CD) was studied. Resolution was considerably superior to that obtained by using either Mn (Ⅱ)-L-alanine complex or β-CD alone. The effects of separation parameters, such as pH value of buffer solution, capillary temperature, the concentration of Mn (Ⅱ)-L-alanine complex, the types of CD and ligand on the migration times and resolutions were investigated. Six different transition metal complexes,Cu(Ⅱ), Zn(Ⅱ), Co(Ⅱ), Ni(Ⅱ), Hg(Ⅱ) and Cd(Ⅱ)-L-alanine complexes have been employed and compared with Mn(Ⅱ)complex. Differences in retention and selectivity were found.The substitution of Cu(Ⅱ), Zn(Ⅱ), Co(Ⅱ) and Ni(Ⅱ) for Mn(Ⅱ) resulted in a better chiral resolution while Hg(Ⅱ) and Cd(Ⅱ) showed poorer resolution abilities. The chiral separation mechanism was also discussed briefly.     

Asymmetric Synthesis of Perfluoroalkylated α-Amino Acids through Generated Radicals Using a Chiral Ni(II) Complex

Perfluoroalkylated α-amino acids (PFAAs) are a unique class of compounds for biochemistry and pharmaceutical science. In this context, we report the successful intermolecular coupling of the Belokon’s chiral dehydroalanine Ni(II) complex with a variety of perfluoroalkyl iodides. A 4-cyanopyridine/B₂Pin₂ catalytic system generates perfluoroalkyl radicals, which after trapping by the ligand sphere of a chiral Ni(II) complex provide the diastereomeric complexes with up to >20 : 1 dr (seven examples). The obtained major (S,S)-diastereomers were easily isolated by simple silica column chromatography in 33–54 % yields. The perfluoroalkylated α-AA was subsequently released from the obtained Ni(II) complex through aqueous HCl treatment. The chiral auxiliary ligand ((S)-BPB=(S)-2-(N-benzylprolyl)aminobenzophenone) can be easily recycled after the acidic complex decomposition and reused for the synthesis of the starting dehydroalanine Ni(II) complex.     

Enantioseparation of Novel Chiral Tetrahedral Clusters on a Chiral Stationary Phase (CSP) by High Performance Liquid Chromatography

In recent years, the synthesis of chiral tetrahedral clusters has been studied extensively and various types are accessible , which are a kind of organometallic compounds with greatly growing interest due to their potential application to asymmetric reaction catalysts. As an efficient     

Comparison of the Microbiological Activities of Different Varieties of Hop (Humulus lupulus) Extracts by Thin-Layer Chromatography—Direct Bioautography

JPC – Journal of Planar Chromatography – Modern TLC - Commercially available hop pellets of different origins were extracted by use of ethanol and water, chromatographed on silica...     

Oligosaccharide-Crowned Hyperbranched Poly(ethyleneimine) as an Additive to Thin-Layer Chromatography Systems for the Separation of Vitamins,Amino Acids and β-Blocker Enantiomers

JPC – Journal of Planar Chromatography – Modern TLC - Impregnation of a stationary phase by organic and inorganic agents in high-performance thin-layer chromatography (HPTLC) may result...     

Enantioseparation of Tropic Acid and Its Esters by CEKC Using Sulfated β-Cyclodextrin as a Chiral Selector

Capillary electrokinetic chromatography was successfully applied to the enantioseparation of tropic acid and its four alkyl esters (methyl, ethyl, propyl and butyl), with the same chiral center, Separation was with sulfated β-cyclodextrin (4%, m/v) containing 20 mM phosphate buffer at pH 3.0 as background electrolyte at 20 °C. The results showed that, besides hydrogen-bonding interactions between these compounds with sulfated β-CD, for tropic acid and its methyl ester the steric hindrance effect was also an important factor. However, for the other esters (ethyl, propyl and butyl), the hydrophobicity effect was higher.     

Enantiomeric Resolution of (±)-Etodolac by Direct Approach Using Both Achiral Phases in Thin-Layer Chromatography: A Conceptual Approach

JPC – Journal of Planar Chromatography – Modern TLC - Direct enantioresolution of (±)-etodolac has been achieved by adopting a new conceptual approach involving both achiral phases...     

Asymmetric Cyclopropanation Catalyzed by Four Stereoisomers of a Copper-(Schiff-base) Complex with Double Chiral Centers

Catalytic asymmetric cyclopropanation of diazoacetates with olefins has attracted much attention. Those catalysts containing various metals and optically active ligands have been employed for this reaction1,2. The first catalytic asymmetric cyclopropanation reaction was reported in 1966 by Nozaki et al.3. The author used the copper(II) complex 1 bearing a salicyladimine ligand as catalyst though with a low e.e. value of 6%. Aratani and his coworkers designed the copper-(Schiff-base) comp…     

Asymmetric Borohydride Reduction of Acetophenone Catalyzed by Chiral Salen-Co(Ⅱ) Complex Using Sodium Borohydride

Development of efficient catalytic asymmetric reactions is the most challenging task in current synthetic chemistry; much effort has been devoted to create the chiral metal complexes of asymmetric catalysis. In the last two decades' many brand-new ligands had been synthesized and their combination with various metal ions has been applied in asymmetric catalysis. However, most ligands have only narrow applications and their use is limited to some reactions. Exceptionally, a few ligands and their metal complexes such as binaphthol, semicollin,and binap show wide applicability. Chiral salen ligand is one of such ligands and their metal complexes are now used as the catalysts for a variety of asymmetric reactions such as epoxidation^[1], aziridination^[2], cyclopropanation^[3], Diels-Alder reaction^[4], asymmetric transfer hydrogenation of aromatic ketones^[5] and kinetic resolution of racemic epoxides^[6] and so on.     

Cellular Uptake of the ATSM−Cu(II) Complex under Hypoxic Conditions

The Cu(II)-diacetyl-bis (N4-methylthiosemicarbazone) complex (ATSM−Cu(II)) has been suggested as a promising positron emission tomography (PET) agent for hypoxia imaging. Several in-vivo studies have shown its potential to detect hypoxic tumors. However, its uptake mechanism and its specificity to various cancer cell lines have been less studied. Herein, we tested ATSM−Cu(II) toxicity, uptake, and reduction, using four different cell types: (1) mouse breast cancer cells (DA-3), (2) human embryonic kidney cells (HEK-293), (3) breast cancer cells (MCF-7), and (4) cervical cancer cells (Hela) under normoxic and hypoxic conditions. We showed that ATSM−Cu(II) is toxic to breast cancer cells under normoxic and hypoxic conditions; however, it is not toxic to normal HEK-293 non-cancer cells. We showed that the Cu(I) content in breast cancer cell after treatment with ATSM−Cu(II) under hypoxic conditions is higher than in normal cells, despite that the uptake of ATSM−Cu(II) is a bit higher in normal cells than in breast cancer cells. This study suggests that the redox potential of ATSM−Cu(II) is higher in breast cancer cells than in normal cells; thus, its toxicity to cancer cells is increased.     

Catalytic Cyclotrimerization of Arylnitriles Using the Novel Samarium(II) Complexes as Catalysts

ＩｎｔｒｏｄｕｃｔｉｏｎＴｒｉａｚｉｎｅｓａｒｅｕｓｅｆｕｌｐｒｅｃｕｒｓｏｒｓｏｆｍａｎｙｂｉｏｌｏｇｉｃａｌｌｙａｃｔｉｖｅｃｏｍｐｏｕｎｄｓ ,1 3 ａｎｄｓｅｖｅｒａｌｓ ｔｒｉａｚｉｎｅｓ4 ,5ａｒｅａｌｓｏｒｅｃｏｇｎｉｚｅｄｔｏｂｅｔｈｅｐｏｗｅｒｆｕｌｃｈｅｌａｔｉｎｇａｇｅｎｔｓ .Ｔｈｅｃｏｍ ｍｏｎｍｅｔｈｏｄｓｌｅａｄｉｎｇｔｏｓ ｔｒｉａｚｉｎｅｓｉｎｃｌｕｄｅｏｘｉｄａｔｉｏｎｏｆａｒｏｍａｔｉｃａｌｄｅｈｙｄｅｓａｎｄｃｙｃｌｏｔｒｉｍｅｒｉｚａｔｉｏｎｏｆｎｉｔｒｉｌｅｓ .…     

Capillary Electrophoresis for the Simultaneous Determination of Metals by Using Ethylenediamine Tetraacetic Acid as Complexing Agent and Vancomycin as Complex Selector

A new separation system of capillary electrophoresis for the simultaneous determination of metals by using ethylenediamine tetraacetic acid （EDTA） as complexing agent and employing vancomycin as complex selector was described. The Z-shape cell capillary electrophoresis was used to enhance the sensitivity for the determination of the complexes of Cu（Ⅱ）, Ni（Ⅱ）, Co（Ⅱ） and Fe（Ⅲ） with EDTA. The partial filling method （co-current mode） was used in order to increase the selectivity of the electrophoretic method, meanwhile vancomycin was not present at the detector path during the detection of metal-EDTA complexes. The vancomycin concentration, phosphate concentration and pH of the buffer strongly influenced mobility, resolution and selectivity of the studied analytes. Under the optimal condition, the relative standard deviations （n=5） of the migration time and the peak area were less than 3.14% and 7.35%, respectively. Application of the Z-shape cell capillary electrophoresis method with UV detection and vancomycin loading led to the reliable determination of these metal ions in tap water and the recoveries were 97%-101%. The detection limits based on a signal to noise ratio of 3 ： 1 were found in the range of 2-10 μg·L^-1.     

Enantioseparation of Novel Chiral Tetrahedral Clusters on an Amylose Tris-(3,5-dimethylphenylcarbamate) Chiral Stationary Phase by Normal Phase HPLC

Introduction In recent years, chiral transition metal cluster has at-tracted a great deal of interests due to its potential ap-plication in asymmetric catalytic reaction.1-3 Producing catalysis for asymmetric induction using a rigid chiral framework would not only bring a basically conceptual breakthrough in the asymmetric catalysis, but also en-rich the methodology in the design of new chiral cata-lysts.4 So far, a lot of chiral clusters have been re-ported,5-9 but only a few of them have bee…     

Approaches to the Synthesis of Candelabrone Synthesis of (±)-Margocilin O-Methyl Ether

Model studies to elaborate a synthetic approach to candelabrone have provided an intermediate from which (±)-margocilin O-methyl ether has been synthesised.