Enantiomeric Separation of Meptazinol Hydrochloride by Capillary Electrophoresis

Aim To establish a capillary electrophoresis method for enantiomericseparation of meptazinol hydrochlo-ride. Methods The separation conditions such ascyclodextrin(CD)type, buffer pH, concentration of 2,3,6-O-trimethyl-β-cyclodextrin and organicadditives were optimized. An optimum concentration was 30 mmol· L^(-1) phosphate (pH 7.02) with 10%(W/V) TM-β-CD and 2% acetonitrile. Results Baseline resolution of the enantiomer was readilyachieved using 2, 3, 6-O-trimethyl-β-cyclodextrin. Conclusion This is a convenient method for fastenantiomeric resolution of meptazinol hydrochloride.

Syntheses, Crystal Structures, and Biological Activities of Two Enantiomeric 2-Trifluoromethylthieno[2,3-d]pyrimidin-4-amine Derivatives

Two enantiomeric 2-trifluoromethyl-6,7-dihydro-5H-cyclopenta[4,5]thieno[2,3-d] pyrimidin-4-amine derivatives were synthesized by nucleophilic substitution of two chiral amines with 4-chloro-2-trifiuoromethyl-6,7-dihydro-5H-cyclopenta[4~5]thieno[2-3-d]pyrimidine, which started from 2-amino-5,6-dihydro-4H-cyclopenta[b]thiophene-3-carbonitrile, trifluoroacetic acid （TFA） and phosphoryl trichloride via one-pot procedure. Their structures were determined by single-crystal X-ray diffraction. Enantiomer （R）-3,（R）-N-（1-phenylethyl）-2-trifluoromethyl-6,7- dihydro-5H-cyclopenta[4,5]thieno[2,3-d]pyrimidin-4-amine crystallizes in the tetragonal system, space group P43 with a = 8.6847（6）, b = 8.6847（6）, c = 22.419（2） A, V= 1690.9（3） A3, Z = 4, Dc = 1.428 g/cm^3, p = 0.228 mm-1, F（000） = 752, the final R = 0.0463 and wR = 0.1257 for 3442 observed reflections with 1〉 20（/）. Enantiomer （S）-3,（S）-N-（1-phenylethyl）-2-trifluoromethyl-6,7-dihydro- 5H-cycloperita[4,5]thieno[2,3-d]pyrimidin-4-amine crystallizes in the tetragonal system, space group P41 with a = 8.688, b = 8.688, c = 22.421 A, V = 1692.4 A3, Z = 4, Dc = 1.426 g/cm^3, μ= 0.227 mm^-1, F（000） = 752, the final R = 0.0682 and wR = 0.1806 for 3182 observed reflections with ≥20（I）. The preliminary bioassay indicated that the R-enantiomer exhibits higher antitumor activity against MCF-7 than gefitinib.

A Chiral Phosphorous Derivatizing Agent for the Determination of the Enantiomeric Excess of Chiral Alcohols, Amines by ^(31)P NMR

A chiral phosphorous derivatizing agent prepared from PCl3 and (S)-BINOL was described. It is used to determine the enantiomeric excess of chiral alcohols and amines by 31P NMR.

Using the Chiral Organophosphorus Derivatizing Agents for Determination of the Enantiomeric Composition of Chiral Carboxylic Acids by ^(31)PNMR Spectroscopy

The use of chiral organophosphoras derivatizing agents prepared in situ from chiral tartrate or chiral diamine for the 31PNMR determination of the enantiomeric composition of chiral carboxylic acids is described. The method is accurate, reliable and convenient.

Determination of Enantiomeric Purity of ν-Pyrrolidinyl Phenylpropanol by Capillary Electrophoresis Using β-Cyclodextrin Polymer as Chiral Selector

Enantiomer of n-pyrrolidinyl phenylpropanol was studied by capillary electrophoresis using b-cyclodextrin polymer as chiral selector. We determined the enantiomeric excess value of n-pyrrolidinyl phenylpropanol with RSD 0.48%.

A useful quantitative model for determination of enantiomeric composition of racemate praziquantel by ultraviolet spectroscopy combined with partial least squares and its application to praziquantel tablets

A simple and novel method has been proposed to determine the enantiomeric composition ofracemate praziquantel(PzQ)by using the analysis of ultraviolet(UV)spectroscopy combinedwith partial least squares(PLS),This method does not rely on the use of expensive carbohydratessuch as cyclodextrins,but on the use of inexpensive sucrose,which is equally effective as car-bohydrate.PZQ has two enantiomers.Through measuring the slight diference in the UV spectralabsorption of PzQ due to different interactions between its two enantiomers and sucrose,theenantiomeric composition was determined by a quantitative model based on PLS analysis.Themodel showed that the correlation coeficients of calibration set and validation set were 0.9971and 0.9972,respectively.The root mean square error of calibration(RMSEC)and the root meansquare error of prediction(RMSEP)were 0.0167 and 0.0129,respectively,Then,the independentdata of PZQ tablets were also used to test how well the quantitative model of PLS predicted theenantiomeric composition,The ratio of S-PZQ in tablet was 0.492,determined by high-perfor-mance liquid chromatography as the reference value,Six solutions of the tablet samples were prepared,and the ratios of S-PZQ in tablet samples in the validation set were predicted by the PLS model.,Theirrelative erors with the reference value were not more than 4%.Therefore,the established model couldbe accurate and employed to predict the enantiomeric compositions of PzQ tablets.

Enantiomeric Separation of Four Chiral Compounds Using Immobilized Cellulose 3, 5-Dimethylphenylcarbamate as Chiral Stationary Phase

A new chiral stationary phase of 3, 5-dimethylphenylcarbamates of cellulose, chemically bonded to 3-aminopropylsilica gel at the 6-positions of the glucose units, was prepared. The solvent versatility of the CSP was investigated for the enantioselective separation of four pairs of enantiomers using THF and chloroform as non-standard mobile phase eluent in HPLC. The influence of temperature on the resolution was investigated.

Determination of Enantiomeric Excess of Glutamic Acids by Lab-made Capillary Array Electrophoresis

Simulated enantiomeric excess of glutamic acid was determined by a lab-made sixteen-channel capillary array electrophoresis with confocal fluorescent rotary scanner. The experimental results indicated that the capillary array electrophoresis method can accurately determine the enanfiomefic excess of glutamic acid and can be used for high-throughput screening system for combinatorial asymmetric catalysis.

Determination of enantiomeric impurity of etomidate by high performance liquid chromatography

Objective To determine enantiomeric impurity of etomidate using high performance liquid chromatography. Methods (R)-etomidate and (S)-etomidate were separated on a CHIRALPAK AD-H column. The mobile phase consisted of 20∶80(v/v) isopropanol-n-hexane. The flow rate of the mobile phase was 0.5mL/min. The detected wavelength was 242nm. Results (R)-etomidate and (S)-etomidate could be separated completely under these conditions. The precision of (R)-etomidate was 1.57% (n=3). The limit of detection of (R)-etomidate was 4.25ng/mL. The average percentage content of (S)-etomidate was 0.09% in the samples. Conclusion The method was repeatable and sufficiently sensitive to determine the enantiomeric impurity of etomidate. It allows the quantitation of the impurities at the 0.085% (w/w) level relative to etomidate at a concentration of the test solution of 5mg/mL.

PREPARATION OF ENANTIOMERICALLY PURE SYN-4,5-DIHYDROXY CARBOXYLIC ACID LACTONES BY MICROBIAL REDUCTION

Enantiomerically pure syn-4,5-dihydroxy carboxylic acid lactones were prepared by microbial reduction of acyl lactones with resting cell of Aspergillus niger.

HPCE Enantiomeric Separation of Nafronyl Oxalate

The addition of methanol to the buffer enhanced 2.6-di-O-carboxymethyl-beta-CD's enantioselectivity to nafronyl oxalate, of which four enantiomers were separated in CZE successfully.

Determination of Enantiomeric Composition of Substituted Tetrahydroisoquinolines Based on Derivatization with Menthyl Chloroformate

A method for the analysis of the optical purity of a series of chiral substituted tetrahydroisoquinolines (THIQs) was developed. The method is based on pre-column derivatization of the analytes with the derivatization reagent (–)-(1R)-menthyl chloroformate. The derivatization reaction selectively gives diastereomeric carbamates that are resolvable on an achiral non-polar GC column. The developed technique covers variously substituted THIQs, which differ significantly in volatility, steric and electronic properties. In all cases, the resolution factors (R) exceeded the value of 1.5. The method represents a robust way of analysis of mixtures of THIQs, which are often present in various matrixes such as body fluids, tissues and reaction mixtures.

Enantiomeric Separation of Epinephrine and Salbutamol by Micellar Electrokinetic Chromatography Using β-Cyclodextrin as Chiral Additive

Enantiomeric separation of epinephrine and salbutamol was investigated by micellar electrokinetic chromatography employing β-cyclodextrin as chiral additive in ammonium chloride-ammonia solution. The analytes were detected by electrochemistry using gold microelectrode at +0.65 V versus SCE reference electrode. The effects of detection potential, concentration of β-cyclodextrin, concentration of sodium dodecyl sulfate, pH value of electrolyte and applied voltage were discussed.

Enantiomeric separation of phenylsuccinic acid by cyclodextrin-modified reversed phase high-performance liquid chromatography

The chiral separation of phenylsuccinic acid(PSA)was studied by reversed phase high-performance liquid chromatography(RP-HPLC)with cyclodextrins(CDs)as chiral mobile phase additives.The effects of types of CDs,concentration of hydroxypropyl-β-cyclodextrin(HP-β-CD),percentage of organic modifier,pH value and column temperature on enantioselective separation were investigated.The quantification property of the developed RP-HPLC method was examined.The chiral recognition mechanism of PSA was also discussed.The results show that a baseline separation of PSA enantiomers is achieved on a Lichrospher C18 column(4.6 mm(inner diameter)×250 mm,5μm)with HP-β-CD as chiral mobile phase additive.The capacity factors of R-PSA and S-PSA are 3.94 and 4.80,respectively.The separation factor and resolution are respectively 1.22 and 8.03.The mobile phase is a mixture of acetonitrile and deionized water(20-80,volume ratio)containing 10 mmol/L HP-β-CD and 0.05% trifluoroacetic acid(pH 2.5,adjusted with triethylamine)with a flow rate of 1.0 mL/min.The ultraviolet(UV)detector is set at 254 nm.The likely roles are inclusion interaction,induction and hydrogen bonding between HP-β-CD and PSA enantiomers.

Preparation of Enantiomerically Pure 1,1'-Bi-2-naphthols from 85% Cinchonine and 1,1'-Bi-2-naphtholboric Anhydride

A possibility of preparation of enantiomerically pure 1,1' bi 2 naphthols using an impure cinchonine has been examined. The solid and the mother liquor formed from the reaction of 1,1' bi 2 naphtholboric anhydride and 85 % cinchonine in toluene could give optically pure (S) ( ) and (R) (+) 1,1' bi 2 naphthol after acidification and kinetic crystallization, the overall yields were 40 % and 28 %, respectively.

Enantiomeric Cephalotaxus alkaloids from seeds of Cephalotaxus oliveri

Five undescribed alkaloids were isolated from the seeds of Cephalotaxus oliveri along with 27 known ones.The new structures were elucidated based on spectroscopic data including 1D and 2D NMR,MS and calculated ECD spectra.Among them,(+)-acetylcephalofortine C was an enantiomeric Cephalotaxine alkaloids.The performed bioassay revealed that those alkaloids were not cytotoxic against cancer cells and had no neuroprotective properties in the HEI-OC-1 cells model.

Diporphyrin tweezer for multichannel spectroscopic analysis of enantiomeric excess

Chiral 1,1’-binaphthyl-linked diporphyrin‘tweezers’(R)-1/(S)-1 and the corresponding zinc(II)complexes(R)-2/(S)-2 were prepared as chiral host molecules,and their utility for chiral analyses(especially enantiomeric excess(ee)determinations)were evaluated.Tris(1-n-dodecyl)porphyrins were used for the first time as the interacting units.Host capabilities of the diporphyrin tweezers were investigated by titrations with(R,R)-and(S,S)-cyclohexane-1,2-diamine(CHDA).The host molecules could be used as multichannel probes of ee by using UVvis,circular dichroism(CD),fluorescence emission and 1H nuclear magnetic resonance(1 H-NMR)methods.Chiral configurations could also be differentiated using CD or 1HNMR spectroscopy.All three optical techniques give good resolution of ee with reasonable sensitivity considering the low concentrations used(ca.10^-6 mol·L^-1).The ee determination of CHDA enantiomers using NMR spectroscopy is also possible because of the reasonably well separated resonances in the case of(R,R)-and(S,S)-CHDA.Non-metallated(R)-1/(S)-1 hosts could not be used to detect chiral information in a strongly acidic chiral guest.This work demonstrates the utility of 1,1’-binapthyllinked chiral hosts for chiral analysis of ditopically interacting enantiomers.