高分辨气相色谱法手性固定相拆分α—羟基酮光学异构体

使用高分辨气相色谱法环糊精接枝聚硅氧烷（二环[2,6-二－戊基－3－O－乙基（－5）五环[2,6-二－O－基3－O-甲基]－β环糊精－聚氧烷）作手性固定相,实现了α－羟基酮的有效拆分,并测定了一系列光学活性3－羟基－2－丁酮的对映体过剩值（e.e值）。结果表明,所选取的手性固定相对测定此类不对称催化反应产物的光学产率,评价催化体系的手性选择性均具有较好的效果。     

手性Salen配合物水解拆分环氧氯丙烷的动力学

在立体控制合成有机化合物方面,环氧化合物是一类极有价值的中间体,其中以外消旋混合物形式存在的端基环氧化合物因其价廉易得更是备受关注. 在试图获得高光学纯形式环氧化物的研究中,Jacobsen等[1]对消旋的端基环氧化物的水解动力学拆分(HKR)反应,取得了令人鼓舞的结果,获得了高立体选择性和高产率的手性环氧化物(Y=44%,e.e.＞98%)和1,2-二醇化合物(Y=50%,e.e.=98%). 在该项研究中,水是唯一的试剂,手性Salen-CoⅢ显示出良好的催化性能,并得到反应速率与催化剂浓度的平方成正比的反应动力学结果. Jacobsen等[2]又将手性Salen-CoⅢ催化剂固载于聚苯乙烯树脂和硅胶上,用于催化HKR反应,产物的对映选择性又获得进一步提高(Y=41%,e.e.=99%);他们提出了与Salen-CrⅢ配合物催化TMSN3(三甲基叠氮基硅烷)开环环氧化物相似的双金属协同作用机理[3]. 近年来,Salen金属催化的HKR反应广泛地用于高光学纯药物中间体和天然产物的制备. 首先,Jacobsen等[4,5]成功地利用HKR反应高选择性地制备合成出多种β-肾上腺素的关键中间体,并完成了天然产物Muconin的首次全合成. 随后,Gurjar等[6]和Gandour等[7]也通过HKR反应合成了一些在天然产物及药物分子不对称合成中有广泛应用的中间体. 在国内,上海有机化学所的戴立信等[8]利用HKR反应成功地合成了三种β-肾上腺素的构建模块. 吴毓林等[9,10]则通过HKR反应完成了天然番茄枝内酯类化合物4-Deoxyannomontacin的全合成. 所有这些工作,或是重在提高产物的对映体过量及催化剂的活性,或是重在HKR反应在天然产物及药物化学合成中的应用. 由于对外消旋环氧化物的水解拆分反应机理缺乏详细的研究,从而限制了对新型催化剂的开发及对现有催化剂的改进. 本文以各类手性Salen金属配合物为催化剂,通过对水解拆分环氧氯丙烷反应动力学的研究,考察了浓度、温度、催化剂种类对HKR反应的影响,得到一些反应动力学规律;根据动力学实验数据,进一步证实了环氧氯丙烷的水解拆分反应属于双金属催化的过程.     

气相色谱法手性拆分氯代和溴代环氧苯乙烷

用手性毛细管气相色谱法(使用2，6-戊基-3-丙基-γ-环糊精柱，Chiraldex G-PN)对3种溴代环氧苯乙烷和3种氯代环氧苯乙烷对映体进行了拆分,初步讨论了对映体在该手性毛细管柱上的保留行为,已用于此类化合物对映体过量值(ee值)的测定．     

气相色谱法手性拆分氯代和溴代环氧苯乙烷

用手性毛细管气相色谱法 (使用 2 ,6 戊基 3 丙基 γ 环糊精柱 ,ChiraldexG PN)对 3种溴代环氧苯乙烷和 3种氯代环氧苯乙烷对映体进行了拆分 .初步讨论了对映体在该手性毛细管柱上的保留行为 .已用于此类化合物对映体过量值 (ee值 )的测定     

气相色谱手性固定相进展

1966年Gil-Av等人首次用手性固定相在毛细管柱上分离了氨基酸对映体。至今这种方法已发展为研究和分离对映体的一种重要技术,并愈来愈多地用于天然产物绝对构象(外激素、香料成分等)的测定,不对称选择合成中对映体纯度及过剩量测定,手性药物中对映体纯度的测定,手性化合物在化学转移机理等方面的研究。目前气相色谱中用于分离对映体的     

气相色谱环糊精手性毛细管柱的研制

〕本文报道了全戊基取代的β-环糊精衍生物手性固定相合成和超动态法快速制备手性毛细管柱的方法,并对几种卤代烃、酯对映体进行了分离。     

手性环氧氯丙烷的制备及其药物应用

手性环氧氯丙烷作为医药和化工等领域的重要中间体, 可以从廉价的外消旋体中分离得到, 具有广阔的市场前景. 综述了它的生物和化学法制备进展, 及其在药物合成方面的应用, 并展望了其制备工艺的发展趋势.     

气相色谱手性固定相研究进展

本文评述了气相色谱手性分离的发展过程,介绍了氨基酸、二肽、金属配合物、环糊精、多糖、手性离子液体、环肽、键合以及交联类气相色谱手性固定相以及各类型的拆分机理,展望了气相色谱手性固定相的研究前景。     

气相色谱手性固定相研究进展

本文评述了气相色谱手性分离的发展过程,介绍了氨基酸、二肽、金属配合物、环糊精、多糖、手性离子液体、环肽、键合以及交联类气相色谱手性固定相以及各类型的拆分机理,展望了气相色谱手性固定相的研究前景.     

Static headspace and purge-and-trap gas chromatography for epichlorohydrin determination in drinking water

Epichlorohydrin (ECH) can enter drinking-water supplies due to leaching from epoxy resins in contact with water and/or through the use of flocculating water treatment agents. Potential human exposure from drinking waters poses a particular concern on account of toxicological studies showing severe acute and long-term toxic effects of ECH. Recently a parametric value of 0.1 μg/L for ECH in drinking water has been established by European Union.A few methods for ECH determination in water are available. However, they usually adopt cumbersome procedures for sample preparation and provide sensitivity not matching the EU criteria for water monitoring purposes.In this study we investigated the analytical performance of gas extraction techniques, such as static headspace (HS) and purge and trap (P&T), coupled to gas chromatography (GC) with an electron capture detector (GC-ECD) for the determination of ECH in drinking water. The influence of different parameters affecting the analytical response was studied in details in order to enhance the method sensitivity, thus fulfilling the regulatory requirements.The P&T GC-ECD method was proved capable of determining ECH in water for human consumption at a detection limit of 0.01 μg/L fully complying the regulatory levels. On the contrary, the HS GC-ECD method is far less sensitive (LOD≅40 μg/L) than the previous cited method. The P&T GC-ECD method is simple, rapid, automated, safe for operators and does not require large sample volumes. Therefore, it is useful for routine laboratory activities both for control and research actions.     

Monitoring of optical isomers of chiral alcohols and derivatives by chiral gas chromatography. Effect of derivatization on the enantio-differentiation

Summary Gas chromatographic chiral separation of several chiral 2-and 3-alkanols and diols was studied both in their free hydroxyl and in their trimethylsilyl ether forms. First, the derivatization procedure was verified through the identification of the trimethylsilyl ethers formed on the basis of their mass spectra and optimized to obtain quantitative reaction. The optimized procedure was applied to the trimethylsilylation of racemic mixtures of various hydroxyl compounds. The silylation was found to be highly effective in the improvement of the separation of the individual enantiomers. The major advantages of the derivatization process can be summarized as: (i) excellent baseline separation of the enantiomers of the silyl ethers was achieved in contrast to the parent OH-containing compounds, (ii) the sensitivity of detection highly increased, (iii) the separations do not show any significant concentration dependence and finally (iv) the analysis time needed decreased significantly. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997     

Gas chromatographic determination of epichlorohydrin in workplace atmospheres

Summary A new method has been developed for the determination of trace amounts of epichlorohydrin in workplace atmospheres. Collection is peroormed in two bubblers in series both containing dichloromethane. Optimum conditions for sampling and analysis have been established. The lower limit of determination is 0.05 g/mL with an RSD of ±5%.     

A chiral porous organic cage for molecular recognition using gas chromatography

Molecular organic cages as shape-persistent organic molecules with permanent and accessible cavities have attracted a lot of interest because of their importance as host-guest systems. Herein, we report a chiral porous organic cage (POC) CC9 diluted with a polysiloxane OV-1701 to fabricate a CC9-coated capillary column, which was used for the high-resolution gas chromatographic separation of organic compounds, including positional isomers and racemates. On the CC9-coated capillary column, a large number of racemic compounds such as chiral alcohols, esters, ethers and epoxides can be resolved without derivatization. By comparing the chiral recognition ability of the CC9-coated column with the commercially available β-DEX 120 column and the POC CC3-R coated column recently reported by our group, the CC9-coated column offered good resolution during the separation of some racemates, that were not separated using the β-DEX 120 column or POC CC3-R coated column. Therefore, the CC9-coated column can be complementary to the β-DEX 120 column and CC3-R coated column. The results indicated that the CC9-coated column exhibited great potential for application in the separation of positional isomers and enantiomers with great selectivity, high resolution and good reproducibility.     

The determination of phenol in urine by enzymatic hydrolysis/headspace gas chromatography

Summary A new method has been developed for the determination of phenol in urine in which the phenol conjugates are hydrolysed enzymatically and the liberated phenol is analysed by headspace chromatography. The results compare favourably with those obtained by the method of van Haaften and Sie in which acid hydrolysis is carried out in a heated GC precolumn. The enzymatic hydrolysis headspace technique appears to be very reliable and does not suffer from the disadvantages of precolumn acid hydrolysis.Since this paper was submitted, we have found a report on the enzymatic hydrolysis of phenyl glucuronide in urine followed by gas chromatographic analysis which seems to have been overlooked by later workers. The paper is by H. Desoille, T. F. Gandenzi-Britto and M. Philbert in Archives des Maladies Professionelles, de Medecine du Travail et de Securite Sociale (Paris),30 (3), 129 (1969).     

Properties of L-phenylalanine tetraamides as chiral selectors for D,L-amino acids by capillary gas chromatography

Summary A wide series of L-phenylalanine tetraamide selectors (Phe-n-O-TA) have been synthesized and used as stationary phases for chiral resolution of D,L-amino acids by capillary gas chromatography. The influence of length and polarity of the oxaalkanoyl bridge spacing the diamide chains of the selectors and the effects of steric hindrance on separating power were investigated. The characteristics of the chiral columns and the separation factors of D,L-n-butyl-N-trifluoroacetyl amino esters are reported.     

Determination of amino acid enantiomers in orange juices by chiral phase capillary gas chromatography

Summary The configurations of free amino acids (AAs) in orange juice beverages (commercial products of satisfactory and unsatisfactory quality), an orange juice concentrate (bulk product suspected of being adulterated), and in an orange juice that has been contaminated by addition ofLactobacillus plantarum as a model for microbial spoilage, were determined, after derivatization, by means of gas-liquid chromatography (GC) using fused-silica capillary columns coated with Chirasil-L-Val or Chirasil-D-Val as stationary phases. AAs were isolated from juices by treatment with Dowex WX8 ion-exchanger and were investigated, by GC, as theirN(O)-pentafluoropropionylorN(O)-trifluoroacetyl 1-propyl esters. It was found that the high quality orange juice beverage contained L-AAs exclusively whereas this juice, after fermentation withLactobacillus, contained free D-Ala (32.7%), D-Val (62.3%), D-Phe (20.0%), D-Glu (24.3%), D-Ser (2.6%), D-Asp (0.8%), and significant amounts of D-Pro [% D=100 D/(D+L)]. D-Ala (8.8%) and D-Ser (4.2%) were found in a sensory and analytically unsatisfactory orange juice beverage, whilst D-Ala (27.5%) and D-Ser (14.3%) were detected in the orange juice concentrate suspected of being adulterated.Although capillary GC on chiral stationary phases is regarded as being highly suitable for the determination of AA enantiomers in fruit juice beverages, detection of D-AAs is currently not considered as conclusive proof of fruit juice adulteration caused by addition of AA racemates since a non-microbial origin of D-AAs in the respective juice, or an original occurrence of D-AAs, in either the free, substituted, or peptide-bonded form in the fruits, cannot be excluded with certainty.Presented in part at the Deutscher Lebensmittelchemikertag, Sept. 18–21, 1990, Frankfurt and at the 14. Jahrestagung Deutscher Lebensmitteltechnologen, Nov. 15–17, 1990, Düsseldorf.     

Enantiomer separation of 2-halocarboxylic acid esters by chiral complexation gas chromatography

The enantiomer separation of 2-halocarboxylic acid esters on two chiral nickel(II) bis-((perfluoroacyl)terpeneketonates) by complexation gas chromatography is described. The quantitative entiomer separation of branched 2-halocarboxylic acid esters is achieved with nickel (II) bis (3-(heptafluorobutanoyl)(1R, 2S)-pinan-4-onate) 1 while unbranched 2-halocarboxylic acid esters are preferably separated on nickel(II) bis(3-(heptafluorobutanoyl)-(1S)-10-methylenecamphorate) 2. The metal chelates 1 and 2 are accessible in both enantiomeric forms allowing the determination of the enantiomeric excess (ee) effective and reliable.     

Enantioseparation of chiral sulfonates by liquid chromatography and subcritical fluid chromatography

Tert‐butylcarbamoyl‐quinine and ‐quinidine weak anion‐exchange chiral stationary phases (Chiralpak® QN‐AX and QD‐AX) have been applied for the separation of sodium β‐ketosulfonates, such as sodium chalconesulfonates and derivatives thereof. The influence of type and amount of co‐ and counterions on retention and enantioresolution was investigated using polar organic mobile phases. Both columns exhibited remarkable enantiodiscrimination properties for the investigated test solutes, in which the quinidine‐based column showed better enantioselectivity and slightly stronger retention for all analytes compared to the quinine‐derived chiral stationary phase. With an optimized mobile phase (MeOH, 50 mM HOAc, 25 mM NH₃), 12 of 13 chiral sulfonates could be baseline separated within 8 min using the quinidine‐derivatized column. Furthermore, subcritical fluid chromatography (SubFC) mode with a CO₂‐based mobile phase using a buffered methanolic modifier was compared to HPLC. Generally, SubFC exhibited slightly inferior enantioselectivities and lower elution power but also provided unique baseline resolution for one compound.     

Separation of the enantiomers of 2-phenylcyclopropanecarboxylate esters by capillary gas chromatography on derivatized cyclodextrin stationary phases

Summary Separation of the enantiomers of 2-phenylcyclopropanecarboxylate esters has been investigated on derivatized cyclodextrin chiral stationary phases (CD CSPs) to enable direct determination of the enantiomeric purity of the products of enantioselective cyclopropanation. Four stereoisomers of these chiral compounds could be resolved to baseline on permethylated β-cyclodextrin CSP. Some unusual phenomena, iso-enthalpy retention behavior and entropically driven chiral separation, were observed for the enantioseparation of 2-phenylcyclo-propanecarboxylates on the CD CSPs. Thermodynamic parameters were evaluated and an enthalpy-entropy compensation effect was observed forn-alkyl esters of 2-phenylcyclopropanecarboxylate separated on CD CSPs.