包结拆分在手性药物分离中的机理与应用

对外消旋体药物进行分离拆分是获取手性药物的重要方法。探讨了环糊精体系包结拆分法的机理，并对运用其机理于手性药物分离中的应用作了探讨。     

手性化合物拆分方法的研究进展

光学活性物质的合成对生命科学具有重大意义。已在医药和农药工业中占有越来越重要的地位。本文介绍了几种主要的外消旋化合物的拆分方法。     

高效毛细管电泳在手性药物分析中的应用

近年来,手性药物的毛细管电泳拆分技术发展迅速,文章综述了毛细管电泳法拆分手性药物的机理、方法及应用,并重点介绍近年来各类手性选择剂的发展现状。     

手性药物与手性技术

综述了工业上的手性技术和各种方法及其在制药行业的应用及手性技术的最新发展。     

农药手性中间体产业前景广阔

当前手性农药受到人们广泛的关注,其主要原因是在消旋体的农药中,当前手性农药受到人们广泛的关注,其主要原因是在消旋体的农药中,其中一半可能是没有活性的,将影响环境的保护,如西欧有一些国家已经立法,对具有手性的农药     

手性物质及其拆分方法

简要介绍了手性化合物的概念和发展情况以及获得手性化合物单一对映体的几种拆分方法。包括:结晶拆分法,化学拆分法,微生物酶拆分法,色谱拆分法,膜拆分法及电泳技术拆分法。并简要介绍了每种方法的应用情况及优缺点。     

分子烙印技术及其在手性药物拆分中的应用

分子烙印技术是一种能制备预定选择性分离介质的技术.简要介绍了该技术的合成过程、手性拆分机理及其在手性药物拆分中的应用及优点.     

生物技术在手性药物合成中的应用进展

药物分子的立体化学决定了其生物活性,手性已成为药物研究的一个关键因素,生物技术在手性药物合成中具有重要意义,利用酶催化的相关性质,通过酶拆分外消旋体、酶法不对称合成等方法合成手性药物,采用定向进化技术、酶分子修饰、辅酶再生等方法对手性药物合成方法进行改进,该文对近些年来生物技术在手性药物合成中的应用情况进行了综述。     

生物催化在手性药物合成中的应用

鉴于生物合成比化学合成常具有更高的化学、区域及立体选择性,生物催化反应已被广泛地用于合成手性药物中间体.综述了利用微生物或酶催化在合成抗高血压、抗胆固醇等手性药物中间体中的应用.     

手性冠醚在手性识别中的应用研究进展

近年来,手性冠醚作为手性分离选择剂,已成功的用于识别和拆分各种外消旋氨基化合物。本文对几种分别含有机酸单元、联萘酚单元、糖单元、醇单元的手性冠醚在手性识别伯胺、氨基酸、氨基酸酯等立体异构体方面的应用进行了总结。     

A new method for characterizing the release of drugs from single agglomerates

The purpose of this article is twofold; firstly, to introduce a new method for characterizing the release of drugs from single agglomerates and, secondly, to use the proposed method to investigate drug release from pellets made of microcrystalline cellulose, containing either sodium chloride or salicylic acid as model drug. The proposed experimental setup utilizes a recirculating flow-through system for the dissolution medium, and uses conductivity measurements to monitor its drug concentration. Pellets of two different porosities are investigated, and two different dissolution-medium flow rates are used. The mean dissolution time was used as a model-independent measure of the overall release rate. Analysis of variance was performed with two levels for each of the three factors drug solubility, pellet porosity, and dissolution-medium flow rate. Drug solubility and pellet porosity had highly significant effects on the drug release (p<0.001), whereas flow rate had no significant effect. It was also possible to extract physicochemical parameters characterizing the release process (effective diffusion coefficients, drug solubilities and dissolution rates), which in general showed good agreement with expected results. The proposed method yielded single-pellet release data of sufficient quality for meaningful conclusions to be drawn, even though the drug content of each pellet was as low as g.     

From stochastic single atomic switch to nanoscale resistive memory device

We study the switching characteristics of nanoscale junctions created between a tungsten tip and a silver film covered by a thin ionic conductor layer. Atomic-sized junctions show spectacular current induced switching characteristics, but both the magnitude of the switching voltage and the direction of the switching vary randomly for different junctions. In contrast, somewhat larger junctions with diameters of a few nanometres display a well defined, reproducible switching behavior attributed to the formation and destruction of nanoscale channels in the ionic conductor surface layer. Our results define a lower size limit of 3 nm for reliable ionic nano-switches, which is well below the resolution of recent lithographic techniques.     

Functional characterization of a supramolecular affinity switch at the single molecule level

Surface-immobilized and switchable resorcin[4]arene receptor molecules were quantitatively investigated with atomic force microscopy (AFM) and AFM-single molecule force spectroscopy (AFM-SMFS). The upper rim of the supramolecular receptor cavities was modified with two photodimerizable anthracene moieties. The molecular constitution can be externally switched and controlled by exposure to ultraviolet (UV) light and heat. The topography as well as the complexation affinity against small ammonium guest ions of the two isomers were investigated at the single molecule level. Our results demonstrate the feasibility to externally control the supramolecular receptor's affinity and simultaneously quantify and associate these binding properties with the structural change of the resorcin[4]arenes structure on the basis of the measured molecule corrugation height.     

Asymmetric Autocatalysis Triggered by Chiral Crystals Formed from Achiral Compounds and Chiral Isotopomers

Asymmetric autocatalysis with amplification of enantiomeric excess is found in the enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde using pyrimidyl alkanol as an asymmetric autocatalyst. Asymmetric autocatalysis has been employed as a method for clarifying the origin of homochirality. Circularly polarized light, inorganic chiral crystals and statistical fluctuation of enantiomeric imbalance act as chiral initiators in asymmetric autocatalysis to afford highly enantioenriched products. We have investigated asymmetric autocatalysis using chiral crystals formed from achiral and racemic compounds as an origin of chirality. Absolute control of the crystal chirality of cytosine was achieved by the removal of crystal water. Enantioselective carbon-carbon bond formation at the enantiotopic crystal face of aldehydes was established using diisopropylzinc vapor. In addition, asymmetric autocatalysis triggered by chiral compounds arising from H, C and O isotope substitution has been achieved.     

Two-Dimensional Chiral Molecular Networks from Achiral Building Blocks: A Computational Study

This article describes the application of computer simulations to explore the self-assembly of model achiral molecules on a solid surface leading to the creation of chiral overlayers. To that purpose the lattice gas Monte Carlo method is used to trace the spontaneous self-organization of cross- and tripod-shaped molecules which are represented by rigid planar structures comprising interconnected segments. The study focuses mainly on the influence of size and composition of the molecules on the morphology of the resulting superstructures. It is clearly demonstrated that the molecules, although intrinsically achiral, can assembly into globally chiral two-dimensional networks with regular cavities. Our simulations show also how the chiral networks can be obtained via co-assembly with much smaller molecules and how the additive fills the cavities. In this case, the mixed superstructure is further used as a model enantioselective adsorbent whose adsorptive properties are examined by simulating adsorption isotherms of a racemic mixture of a prototype chiral molecule. The results of this part indicate that the achiral molecular building blocks can be used to construct enantioselective surfaces with tunable adsorption properties.     

Optimal operation of batch enantiomer crystallization: From ternary diagrams to predictive control

In this work, the modeling and control of batch crystallization for racemic compound forming systems is addressed in a systematic fashion. Specifically, a batch crystallization process is considered for which the initial solution has been pre‐enriched in the desired enantiomer to enable crystallization of only the preferred enantiomer. A method for determining desired operating conditions (composition of the initial pre‐enriched solution and temperature to which the mixture must be cooled for maximum yield) for the batch crystallizer based on a ternary diagram for the enantiomer mixture in a solvent is described. Subsequently, it is shown that the information obtained from the ternary diagram, such as the maximum yield attainable from the process due to thermodynamics, can be used to formulate constraints for an optimization‐based control method to achieve desired product characteristics such as a desired yield. The proposed method is demonstrated for the batch crystallization of mandelic acid in a crystallizer with a fines trap that is seeded with crystals of the desired enantiomer. The process is controlled with an optimization‐based controller to minimize the ratio of the mass of crystals obtained from nuclei to the mass obtained from seeds while maintaining the desired enantioseparation. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1618–1637, 2018     

Planar Chiral Phosphines Derived from [2.2]Paracyclophane

[2.2]Paracyclophane offers an exciting framework for the synthesis of planar chiral phosphines. Its rigid structure and unusual electronic properties have led to the development of a range of mono- and di-phosphines including the commercially available ligand, PhanePhos. This review discusses the synthesis and use of [2.2]paracyclophane-based phosphines and aims to give an insight into their success and failures. It is hoped that this review will encourage the design of new planar chiral phosphines for use in transition metal-mediated catalysis and organocatalysis.     

Lower critical solution temperatures of thermo‐responsive poly(N‐isopropylacrylamide) copolymers with racemate or single enantiomer groups

BACKGROUND: Thermo‐responsive copolymers with racemate or single enantiomer groups are attracting increasing attention due to their fascinating functional properties and potential applications. However, there is a lack of systematic information about the lower critical solution temperature (LCST) of poly(N‐isopropylacrylamide)‐based thermo‐responsive chiral recognition systems. In this study, a series of thermo‐responsive chiral recognition copolymers, poly[(N‐isopropylacrylamide)‐co‐(N‐(S)‐sec‐butylacrylamide)] (PN‐S‐B) and poly[(N‐isopropylacrylamide)‐co‐(N‐(R,S)‐sec‐butylacrylamide)] (PN‐R,S‐B), with different molar compositions, were prepared. The effects of heating and cooling processes, optical activity and amount of chiral recognition groups in the copolymers on the LCSTs of the prepared copolymers were systematically studied. RESULTS: LCST hysteresis phenomena are found in the phase transition processes of PN‐S‐B and PN‐R,S‐B copolymers in a heating and cooling cycle. The LCSTs of PN‐S‐B and PN‐R,S‐B during the heating process are higher than those during the cooling process. With similar molar ratios of N‐isopropylacrylamide groups in the copolymers, the LCST of the copolymer containing a single enantiomer (PN‐S‐B) is lower than that of the copolymer containing racemate (PN‐R,S‐B) due to the steric structural difference. The LCSTs of PN‐R,S‐B copolymers are in inverse proportion to the molar contents of the hydrophobic R,S‐B moieties in these copolymers. CONCLUSION: The results provide valuable guidance for designing and fabricating thermo‐responsive chiral recognition systems with desired LCSTs. Copyright © 2008 Society of Chemical Industry