拟除虫菊酯农药和氰戊菊酸手性分离的研究

采用液相色谱,对甲氰菊酯、高效氯氰菊酯和氰戊菊酯等3种拟除虫菊酯的手性分离进行了研究,其中甲氰菊酯和高效氯氰菊酯可直接在Chiralcel OD柱上实现对映体分离.对氰戊菊酯,采用非手性和手性HPLC相结合,也成功实现了4个异构体的有效分离.采用气相色谱-质谱联用,通过衍生化法,在β-DEX120手性柱上成功分离了氰戊菊酸的两个对映体,并在此基础上对加标土壤样品中的氰戊菊酸进行了对映体测定,验证了手性分离的准确性.     

Electrolytic synthesis of nipecotic acid ethyl ester

An electrolytic method was suggested for the synthesis of nipecotic acid ethyl ester in a diaphragm electrolytic cell on a copper cathode in aqueous alcoholic alkali solution.     

Chiral separation of amino acid esters by micellar electrokinetic chromatography

Micellar electrokinetic chromatography (MEKC) was used for the chiral separation of uncharged analytes (C- and N-protected amino acids). Sodium dodecyl sulfate (SDS) was the micelle forming agent, and different cyclodextrin (CD) derivatives were added as chiral selectors. Suitable conditions for the enantioseparation were found by variation of the separation conditions. The influence of addition of organic solvents like acetonitrile or methanol, and other chiral additives (camphor-10-sulfonic acid, malic acid) was examined. The addition of an organic modifier resulted in different effects on micelle formation, and thereby on the separation. The used chiral additives did not improve the selectivity. Furthermore, dependence of the electroosmotic flow (EOF), and the capacity factors on the concentration of CDs was investigated. Increasing the CD concentration, both the EOF to a smaller extent as well as the capacity factors decrease. Nevertheless, the enantioseparation is improved with a CD-concentration up to 30 mM. Higher CD-concentrations reduce the separation of the analytes.     

Chiral CE separation of dopamine-derived neurotoxins.

An enantiomeric separation of dopamine-derived neurotoxins by capillary electrophoresis has been developed. Tetrahydroisoquinoline (TIQ), dopamine (DA), (R/S)-1-benzyl-TIQ (BTIQ), (R/S)-6,7-dihydroxy-1-methyl-TIQ (salsolinol, Sal), and (R/S)-6,7-dihydroxy-1, 2-dimethyl-TIQ (N-methyl-salsolinol, NMSal) were studied as model compounds. The CE running buffer (50 mM phosphate buffer at pH 3.0) contained 1.5 M urea and 12 mM beta-CD as a chiral selector. During separation, the (R)-enantiomers formed more stable inclusion complexes with beta-CD, and thus had a longer migration time than their optical antipodes. It was noticed that the recovery rates of these TIQ derivatives were very poor (< 15%) during protein precipitation, a procedure widely used for cleaning up biological samples. The recovery was significantly improved by pre-mixing the sample with a surfactant (e.g., sodium hexanesulfonate or Triton X-100) to reduce the co-precipitation. The present method in combination with electrospray ionization tandem mass spectrometry (ESI-MS/MS) was applied to study samples obtained from in vitro incubation of two catecholamines, dopamine and epinine, with aldehydes forming neurotoxins including (S)- and (R)-NMSal enantiomers. The later is known to induce Parkinsonism in rats.     

Chiral separation of amide conjugates of jasmonic acid by liquid chromatography

Summary Synthetic amide conjugates of (−)-jasmonic acid and its (+)-enantiomer were resolved by means of chiral liquid chromatography. The diastereomeric pairs prepared by chemical reaction of (±)-jasmonic acid with a series of (S)- or (R)-amino acids and with some (S)-amino acid alcohols were completely separated on Chiralpak AS using a mixture of n-hexane/2-propanal as mobile phase. The retention data indicate that the (−)-jasmonic acid conjugates eluted faster than those of the (+)-enantiomer, independent on the configuration of the bound amino acid. Likewise, enantiomeric derivatives of (±)-jasmonic acid and non-chiral amino acids were completely separated on the chiral stationary phase and showed the same elution sequence. The resolution factors,Rs, were found to range between 1.13 and 6.64. The separated compounds were chiropatically analyzed by measurement of the circular dichroism. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996     

Chiral separation by capillary electrophoresis with oligosaccharides.

Maltodextrins, i.e., mixtures of linear alpha-(1-4)-linked D-glucose polymers, were found to be effective as chiral electrolyte modifiers to perform direct, rapid separations by capillary electrophoresis of racemic mixtures of 2-arylpropionic acid non-steroidal anti-inflammatory compounds and coumarinic anticoagulant drugs, and also diastereomeric cephalosporin antibiotics. Enantioselectivity seemed to be dependent on an as yet unidentified combination of variables.     

First asymmetric syntheses of 6-substituted nipecotic acid derivatives

Various nipecotic acid derivatives are known to be potent GABA uptake inhibitors thus being useful in the treatment of a number of neurological and psychological disorders. In this paper, the first asymmetric syntheses of 6-substituted nipecotic acid derivatives are presented. The synthetic strategy was designed to provide access to a large variety of enantiomerically pure 6-substituted nipecotic acid derivatives. The synthesis starts from the chiral N-acyldihydropyridines 15 and 16 obtained via asymmetric electrophilic α-amidoalkylation reaction of a chiral N-acylpyridinium ion. These were utilized for the preparation of enantiomerically pure 6-(4,4-diphenylbutyl)nipecotic acids and 6-(4,4-diphenylbutenyl)nipecotic acids in a multistep synthesis, including the removal of the dimethylphenylsilyl blocking group from the dihydropyridine ring, the reduction of the dihydropyridine heterocycle, a Horner-Wittig reaction and the removal of the chiral auxiliary. The obtained target molecules, however, showed only negligible affinity to the GAT-1- and GAT-3 transport proteins.     

Chiral separation of agricultural fungicides

Fungicides are very important and diverse environmental and agricultural concern species. Their determination in commercial formulations or environmental matrices, requires highly efficient, selective and sensitive methods. A significant number of these chemicals are chiral with the activity residing usually in one of the enantiomers. The different toxicological and degradation behavior observed in many cases for fungicide enantiomers, results in the need to investigate them separately. For this purpose, separation techniques such as GC, HPLC, supercritical fluid chromatography (SFC) and CE have widely been employed although, at present, HPLC still dominates chromatographic chiral analysis of fungicides. This review covers the literature concerning the enantiomeric separation of fungicides usually employed in agriculture grouping the chiral separation methodologies developed for their analysis in environmental, biological, and food samples.     

Chiral separation by electrokinetic capillary chromatography using newly synthesized linear polymers containing L-amino acid moieties.

Chiral linear polymers were prepared by the thermal polymerization of N-acryloyl-L-valine and N-acryloyl-L-alanine derivatives using 3-mercaptopropionic acid (3-MPA) as a radical transfer agent. C-Terminal groups of the derivatives were methyl and tert-butyl esters later removed, and N-methylamide moieties. The N'-methylamide derivative of N-acryloyl-L-valine was copolymerized with methyl ester at a molar mixing ratio of 1:1. The ester groups were removed to provide anionic linear polymers terminated with carboxylic acid of the amino acid residue. The polymers are thus shown to function as pesudostationary phases that separate enantiomeric solutes in electrokinetic capillary chromatography (EKC). Racemic 3,5-dinitrobenzoylamino isopropyl esters were separated with the polymer derived from N-acryloyl-L-valine esters and with the copolymer from N-acryloyl-L-valine methyl ester and N-acryloyl-L-valine N'-methylamide at pH 7.0. These separations could not be observed at pH 9.0 in migrating solutions containing anionic linear polymers. This pH dependence can be discussed from the standpoint of the microscopic hydrophobicity of the polymers, as assessed from the fluorescence of pyrene adsorbed onto the polymers in water.     

Enantiomeric separation by capillary electrochromatography. II. Chiral separation of dansyl amino acids and phenoxy acid herbicides on sulfonated silica having surface-bound hydroxypropyl-beta-cyclodextrin

A chiral silica-based stationary phase having surface-bound hydroxypropyl-beta-cyclodextrin (HP-beta-CD) with a relatively strong electroosmotic flow (EOF) was introduced for enantioseparation by capillary electrochromatography (CEC). The stationary phase contained a hydrophilic sulfonated sublayer to which a chiral top layer of HP-beta-CD was immobilized. While the sulfonated sublayer was to provide a relatively strong EOF, the top HP-beta-CD was to confer the desired chiral recognition towards enantiomeric solutes. This HP-beta-CD sulfonated silica (CDSS) stationary phase proved useful for the rapid separation of anionic enantiomers such as dansyl amino acids and phenoxy acid herbicides. The effects of the organic modifier content, pH, and ionic strength of the mobile phase on enantioseparation were investigated. Under the optimized separation conditions, ten dansyl amino acids and six phenoxy acid herbicides were enantioseparated with a resolution greater than unity.     

Chiral separation of disease biomarkers with 2‐hydroxycarboxylic acid structure

Chiral 2‐hydroxycarboxylic acids are compounds that have been linked to particular diseases and are putative biomarkers with some diagnostic potential. The importance of identifying whether a particular enantiomer is related to certain diseases has been encouraged recently. However, in many cases it has not yet been elucidated whether there are stereochemical implications with respect to these biomarkers and whether their enantioselective analysis provides new insights and diagnostic potential. In this study 13 disease‐related chiral 2‐hydrocarboxylic acids were studied for their chiral separation by high‐performance liquid chromatography on three cinchona alkaloid‐derived chiral stationary phases. From a subgroup of eight 2‐hydroxymonocarboxylic acids, baseline resolution could be achieved and inversion of elution order by exchanging tert‐butylcarbamoyl quinidine chiral stationary phase (Chiralpak QD‐AX) for the corresponding quinine analogue (Chiralpak QN‐AX) is shown for seven of them. Furthermore, conditions for chiral separation of the 2‐hydroxydicarboxylic acids, citramalic acid, 2‐isopropylmalic acid, and 2‐hydroxyadipic acid are reported and compared to the previous reported conditions for 2‐hydroxyglutaric acid and malic acid.     

Acetals of lactams and acid amides. 41. Enamino amides in the synthesis of pyrimidine derivatives

The reaction of -cyano--dimethylaminomethyleneacrylamide with arylamines was used to synthesize -cyano--arylaminoacrylamides, which react readily with dimethylformamide diethylacetal to give the corresponding N-dimethylaminomethylene derivatives. The latter undergo cyclization to 1-aryl-5-cyano-4-pyrimidinones when they are heated in dimethylformamide or acetic anhydride and to pyrimido-[5,4-c]quinolone derivatives when they are heated in glacial acetic acid.See [1] for communication 40.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 538–542, April, 1984.     

Chiral separation of sympathomimetics by ligand exchange capillary electrophoresis.

A rapid and simple approach to the chiral separation of sympathomimetic drugs with amino alcohol structure by ligand exchange capillary electrophoresis is described. An N-(2-hydroxyoctyl)-L-4-hydroxyproline/copper(II) complex is used as chiral selector. Thirteen sympathomimetics were resolved, nine with baseline resolution. The influence of pH and composition of the electrolyte on resolution was investigated. The optimal pH for complexation of these amino alcohols was found to be 12.     

Chiral separation of NBD-amino acids by ligand-exchange micro-channel electrophoresis.

The chiral separation of amino acid derivatives by ligand-exchange electrophoresis in a microchannel chip was performed for the first time. A Cu(II) complex with L-prolinamide was used as a chiral selector. The migration behaviors of eleven NBD-DL-amino acids were investigated by ligand-exchange capillary electrophoresis (LE-CE). The enantiomer of five NBD-amino acids (Ser, Thr, Val, Phe and His) could be separated by LE-CE using a 20 mM ammonium acetate buffer (pH 9.0) containing 10 mM copper acetate, 20 mM L-prolinamide and 1 mM SDS. NBD-His was eluted in the order D-form and L-form, while the elution order of another enantiomers was L-form and D-form. Under this condition, the enantioseparation of these five NBD-amino acids by ligand-exchange microchip electrophoresis (LE-ME) was investigated using a glass microchip. The enantioseparation of NBD-Ser, -Thr and -His could be successfully accomplished by LE-ME. LE-ME was superior to LE-CE in terms of the short migration time and a good enantiomeric separation.     

Silicon-containing dimethylphosphoric acid amides

α-Silylmethylamines MeNHCH₂SiMen(OMe)_3?n (n=0, 2) were involved into Todd-Atherton reaction with (MeO)₂P(O)H giving N-methyl-N-trimethoxysilylmethyl-and N-methyl-N-dimethyl-(methoxy)silylmethylamides of dimethylphosphoric acid. A reaction of these compounds with BF₃·Et₂O led to the formation of the corresponding N-methyl-N-trifluoro-and N-methyl-N-(dimethyl)fluorosilylmethylamides of dimethylphosphoric acid. (MeO)₂P(O)N(Me)CH₂SiF₃ existed as an (O-Si)-chelate with a pentacoordinate silicon due to the occurrence of a rare and unstudied intramolecular coordinating interaction P=O → Si.     

Chiral ligand-controlled asymmetric conjugate addition of lithium amides to enoates

The external chiral ligand-controlled asymmetric conjugate addition reaction of lithium amides with alpha,beta-unsaturated esters provided beta-amino esters in high yields and high enantioselectivities.     

Synthesis of thiophosphoric acid amides

Conclusions The cyclohexylamido- and piperididothiophosphoric acids were obtained for the first time, and also piperazido-N,N-bisthiophosphoric acid as the Na and NH₄ salts.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2402–2403, October, 1982.