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901.
Chonticha Masusai Darunee Soorukram Chutima Kuhakarn Patoomratana Tuchinda Chaveng Pakawatchai Vichai Reutrakul Manat Pohmakotr 《Helvetica chimica acta》2012,95(10):1912-1927
The Morita? Baylis? Hillman (MBH) reactions of (4S,5R,7R,8R)‐ and (4R,5R,7R,8R)‐4‐hydroxy‐7,8‐dimethoxy‐7,8‐dimethyl‐6,9‐dioxaspiro[4.5]dec‐2‐en‐1‐ones ( 2 and 3 , resp.) with aldehydes using various catalysts were studied. A combination of Bu3P/phenol in THF was found being optimum conditions giving the corresponding MBH adducts with high diastereoisomeric ratios. After separation, each stereomerically pure isomer of the MBH adducts was subjected to hydrolysis employing 1% aq. CF3COOH (TFA) in a water bath of an ultrasonic cleaner to afford the corresponding polyhydroxylated cyclopentenones in good yields. 相似文献
902.
《Analytical letters》2012,45(9):1543-1551
Abstract The synthesis of a new type of chiral stationary phase, prepared from triethoxysilyl derivatives of calixarenes, and by the chemical immobilisation of these chiral molecular baskets to 3μm silica particles, is reported. Specifically, a silica-bonded calix[4]arene, funcrionalised at the lower rim with L-(-)-ephedrine, is prepared and packed into a short LC column for rapid chiral separations. Using reversed phase conditions and high flow rate, such new phases based on funcrionalised calixarenes are applicable to chiral aromatic and non-aromatic solutes and are capable of resolving the enantiomers of R(-) and S(+)-1-phenyl-2,2,2-trifluoroethanol in less than 45 seconds. 相似文献
903.
《Analytical letters》2012,45(17):3177-3186
Abstract A capillary electrophoresis (CE) method for the simultaneous separation of geometry isomers and enantiomers of nateglinide was built. Several different dyclodextrin (CD) derivatives were tested for the chiral separation of nateglinide, and it was proved that ionic CDs [i.e., carboxymethy-β-CD (CM-β-CD) and sulphonic-β-CD (S-β-CD)] could show better chiral selectivity for both geometry isomers and enantiomers than the neutral CDs. The separation of geometry of both isomers and enantiomers of nateglinide was obtained by CE in a 75-µm i.d. × 60 cm (effective length 45 cm) fused-silica capillary at 11 kV voltage, while 30 mM phosphate (pH = 8.38) acted as running buffer and a mixture of 40 mM S-β-CD + 21 mM CM-β-CD served as chiral selector. The detective wavelength was set at 254 nm. 相似文献
904.
《Analytical letters》2012,45(3):631-638
Abstract This paper reported the enantioseparation of uniconazole and imazalil using four different self‐prepared cellulose derivative columns, namely, CTB, CTMB, CTPC, and CDMPC. The mobile phase composition including the type of the alcohol modifier and the ethanol concentration in hexane changed, and the influence on the retention factor (k′); for each enantiomer, the separation factor (α) and the resolution (RS) was studied. The influence of the structures of the analytes on the chiral separation was investigated. The results showed that uniconazole obtained the best resolution of 2.16 on CTPC, while imazalil obtained the best separation on CTMB, with the maximal resolution of 4.83. It was concluded that the structure of solutes and CSP play a key role in the chiral recognition. And the chiral attraction between them is the predominant factor. 相似文献
905.
手性流动相添加法拆分酮康唑外消旋体 总被引:1,自引:0,他引:1
采用C18反相色谱柱,利用在流动相中加入手性选择剂的方法实现酮康唑对映体的拆分。研究了手性选择剂的种类及浓度、流动相pH值、甲醇比例和柱温等因素对酮康唑手性分离的影响,结果表明磺丁基-β-环糊精可以使酮康唑对映体完全分离,最后选择的流动相组成为甲醇-0.02 mol/L磷酸二氢钠(体积比为60∶40,含0.02%三乙胺和1.0 mmol/L磺丁基-β-环糊精,用稀磷酸调节pH值到3.00)。酮康唑对映体在6 min内得到基线分离,分离度为2.05。方法简便,分离效果好,对酮康唑对映体的拆分具有应用价值。 相似文献
906.
Acoustic stop bands in almost-periodic and weakly randomized stratified media: perturbation analysis 总被引:1,自引:0,他引:1
In this paper, we analyze the effect of both deter- ministic and random perturbations of a regular multi-layered elastic structure on its stop band properties. The tool of choice is the transfer matrix method, which is both versatile and easy to implement. In both cases, we find that the stop-bands widen. We observe the appearance of very narrow pass-bands within the stop-bands, which can be observed in other instances in optics. 相似文献
907.
ZHANG Hong-Hao YAN Wen-Bin J.K. Parry LI Xue-Song 《理论物理通讯》2008,49(3):723-724
The compact form of the electroweak chiral Lagrangian is a reformulation of its original form and is expressed in terms of chiral rotated electroweak gauge fields, which is crucial for relating the information of underlying theories to the coefficients of the low-energy effective Lagrangian. However the compact form obtained in previous works is not complete. In this letter we add several new chiral invariant terms to it and discuss the contributions of these terms to the original electroweak chiral Lagrangian. 相似文献
908.
HOU Jing-Min 《理论物理通讯》2009,52(2):247-250
We investigate ultracold fermionic atoms in the trilayer honeycomb lattice. In the low energy approximation, we derive an effective Hamiltonian for pseudospins. The energy spectrum shows a cubic form of the wavevector and is gapless. The quasiparticles and quasiholes are chiral and show Berry's phase π when thewavevector adiabatically evolves along a closed circle. Furthermore, the experimental detection of the energy spectrum is proposed with Bragg scattering techniques. 相似文献
909.
高效液相色谱手性固定相法拆分阿折地平对映体 总被引:2,自引:0,他引:2
建立了阿折地平对映体的高效液相色谱拆分方法。采用Chiralpak AD-H (250 mm×4.6 mm, 5.0 μm, Daicel公司)手性色谱柱在正相条件下直接拆分阿折地平对映体,考察了固定相种类、流动相组成及柱温等对阿折地平对映体分离的影响。确定了最佳的拆分条件: 流动相为正己烷-异丙醇(90:10, v/v),流速为0.8 mL/min,检测波长为254 nm;柱温为20 ℃;在此条件下阿折地平对映体的分离度为3.3。该法简单快速,重现性好。 相似文献
910.
手性高效液相色谱法测定板蓝根中表告依春和告依春含量 总被引:2,自引:0,他引:2
采用Chiralpak IC手性柱(250 mm×4.6 mm, 5 μm),建立了正相高效液相色谱测定板蓝根中表告依春(R-告依春)和告依春(S-告依春)含量的方法。考察了流动相组成、流速和柱温对分离度的影响。经优化后的实验条件: 以正己烷-异丙醇(体积比为90:10)为流动相,流速为0.8 mL/min;检测波长为245 nm,柱温为20 ℃。在此优化条件下,表告依春和告依春分离度为3.4,检出限为2.0 mg/L,在0.02~2.0 g/L范围内有良好的线性关系,平均回收率为101%,相对标准偏差(RSD)小于3.0%(n=6)。本方法可将具有抗病毒活性的表告依春与其对映体告依春基线分离并测定,专属性强,能有效控制板蓝根的质量。 相似文献