Enantioface differentiation by using soluble chiral polymers having 2,3-exo-bornanediol groups

Soluble linear polymers containing 2,3-exo-dihydroxy-3-endo-p-tolyl-3-bornyl groups prepared by reaction of lithiated linear polystyrenes with (-)-2-exo-hydroxy-3-bornanone, are treated with lithium aluminium hydride to form complexes which can be used as reducing reagents. The highest enantioselectivity compared with those cases using crosslinked polystyrene as carrier and chiral low molecular weight compounds is achieved by linear polystyrene having chiral groups. The advantages of soluble polymer-bound chiral reagents are discussed. The effect of alcohols, the reaction temperature, the sort of solvents, and the molar ratio of the reagent to ketone on the asymmetric reduction is also discussed.     

Synthesis and characteristics of chiral polymers with camphanediol moieties

Optically active exo,exo-2,3-camphanediol (CPO) was synthesized from (+)-camphor. The chiral polymers poly(CPO-co-TDI) and poly(CPO-co-IPDI) were synthesized by step polymerization of chiral compound CPO with toluene-2,4-diisocyanate (TDI) and isophorone diisocyanate (IPDI). Effects of solvents, reaction time and temperature on the polymerization were investigated. To investigate the stereo structure of the chiral polymers, two kinds of model compounds, exo-exo-2,3-bornylene N,N′-diphenyldicarbamate and exo,exo-2,3-bornylene N,N′-dipropyldicarbamate, related to the prepared polymers were synthesized. Chiroptical characteristics and stereo structures of the chiral polymers were investigated by using a circular dichroic spectrometer. Effects of temperature and solvents on the specific rotation of the chiral polymers were evaluated. The results obtained in this investigation suggest that the synthesized chiral polymers have no one-handed helix conformation.     

Functional monomers and polymers, 98. Asymmetric induction by chiral polymers containing bornyl groups

In order to determine the catalytic ability of the polymers containing chiral bornyl groups to the asymmetric induction, the asymmetric addition reaction of dodecanethiol to isopropenyl methyl ketone was studied using synthetic chiral polymers having pendant bornyl groups, in comparison with the case of using a monomeric model compound, i.e. d-bornyl acetate, and also poly(methyl methacrylate). It was found that the polymers having chiral borynl groups were effective for the asymmetric induction, and the optical yield depended on the bornyl group content in the polymers.     

Synthesis and characterization of novel monomers and polymers containing chiral (−)-menthyl groups

To investigate the steric effects of chiral menthyl groups on the induction of cholesteric liquid crystals and the sensitivity of the photoisomerizable azobenzene derivatives, a series of chiral monomers and a photoisomerizable chiral azobenzene derivative with various spacers end-capped with (−)-menthyl group were synthesized. The structures of the novel chiral compounds synthesized in this investigation were identified using ¹³C NMR, FTIR, and elemental analysis. The phase transition temperatures of the chiral compounds were investigated using X-ray diffraction, differential scanning calorimetry, and polarizing optical microscopy. The thermogravimetric characteristics, the glass-transition temperatures (T_g) and the weight-average molecular weights (M_w) of the homopolymers were also evaluated. Polymers containing chiral menthyl groups with a biphenyl segment were found to reveal high thermal resistance. However, the existence of the steric hindered menthyl group disturbed the arrangement of chiral monomers leading to the disappearance of liquid crystal phases. The specific optical rotation of the synthesized monomers and polymers were also evaluated. The effect of the synthesized chiral compounds, monomers and photoisomerizable azobenzene derivative on the induction of the cholesteric liquid crystal films was investigated. The morphological network structure of the polymer matrix inside a liquid crystal cell was studied using a scanning electron microscope (SEM). The phototuning ability of the AzoM on the cholesteric liquid crystals was also established.     

高分子聚合物担载手性金属卟啉作为不对称催化剂的研究进展

手性金属卟啉经常用作催化合成对映体纯的化合物,但在实际应用中却有很多不利因素,如稳定性差、催化剂回收困难等。使用聚合物作为载体可以很好地解决这些问题。现常用的载体聚合物有电引发聚合物膜、大分子树脂和大孔分子筛,这些极大地提高了手性金属卟啉的催化性能。     

Transparent chiral polymers for optical applications

Optically active chiral polymers and copolymers of cholesteryl methacrylate have been studied for use in optical applications including plastic optical fibers. Homopolymers of chiral cholesteryl methacrylate with differing molecular weights and copolymers with methyl methacrylate were synthesized by free‐radical copolymerization in tetrahydrofuran using azobisisobutyronitrile at 67°C for 26 h. All polymers were characterized for molecular weight, glass‐transition temperature, optical rotation, transparency, and refractive index and solution blended to test for compatibility with poly(methyl methacrylate). Such chiral materials are of particular interest because they offer useful polarization properties without requiring bulk orientation of the molecules. This makes it possible to produce low cost optical elements such as circularly birefringent or circularly polarizing optical elements with potential applications in polarization manipulations and sensing. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 58–65, 2005     

Molecular Recognition of the HPLC Whelk-O1 Selector towards the Conformational Enantiomers of Nevirapine and Oxcarbazepine

The presence of stereogenic elements is a common feature in pharmaceutical compounds, and affording optically pure stereoisomers is a frequent issue in drug design. In this context, the study of the chiral molecular recognition mechanism fundamentally supports the understanding and optimization of chromatographic separations with chiral stationary phases. We investigated, with molecular docking, the interactions between the chiral HPLC selector Whelk-O1 and the stereoisomers of two bioactive compounds, the antiviral Nevirapine and the anticonvulsant Oxcarbazepine, both characterized by two stereolabile conformational enantiomers. The presence of fast-exchange enantiomers and the rate of the interconversion process were studied using low temperature enantioselective HPLC and VT-NMR with Whelk-O1 applied as chiral solvating agent. The values of the energetic barriers of interconversion indicate, for the single enantiomers of both compounds, half-lives sufficiently long enough to allow their separation only at critically sub-ambient temperatures. The chiral selector Whelk-O1 performed as a strongly selective discriminating agent both when applied as a chiral stationary phase (CSP) in HPLC and as CSA in NMR spectroscopy.     

Thermotropic chiral nematic side-chain polymers and cyclic oligomers

For all the theoretical, experimental and computational research on chiral nematic systems over the last four decades, understanding of cholesteric mesomorphism from the molecular perspective is still rather limited at the present time. Nevertheless, the unique property of selective wavelength reflection accompanied by circular polarization has presented tremendous potential for various optical applications. Theories governing optical birefringence and selective reflection bandwidth are outlined to serve as a foundation for molecular design. Both polymeric and low molar mass glass-forming chiral nematics are surveyed in terms of chemical structure, thermotropic and optical properties. Characterized by relative ease of processing, the low molar mass approach is illustrated with our recent results in terms of design concept, materials synthesis and characterization. We also highlight outstanding issues that need to be addressed to help advance chiral nematics as a class of advanced optical materials.     

Synthesis of chiral polymers having camphanediol moieties and their applications on the optical resolution of some racemates

Optically active exo-exo-2,3-camphanediol (CPO) (3) was synthesized from (+)-camphor. Chiral polymers poly(CPO-co-TDI) ( 6 ) and poly(CPO-co-IPDI) ( 7 ) were synthesized by the step polymerization of chiral compound CPO ( 3 ) with toluene-2,4-diisocyanate (TDI) and isophorone diisocyanate (IPDI). To investigate the stereo structure of the chiral polymers, two kinds of model compounds, exo-exo-2,3-di[(phenylamido)oxy]camphane ( 4 ) and exo-exo-2,3-di[(propylamido)oxy]camphane ( 5 ), related to polymers ( 6 ) and ( 7 ) were synthesized. Chiroptical characteristics and stereo structures of the chiral polymers were investigated using a circular dichroic spectrometer. The results obtained in this investigation suggest that the chiral polymers ( 6 ) and ( 7 ) have no one-handed helix conformation. The optical resolution ability as chiral adsorbent for HPLC of the chiral polymers was investigated. It was found that chiral polymers ( 6 ) and ( 7 ) are effective for the optical resolution of some racemates. © 1995 John Wiley & Sons, Inc.     

基于壳聚糖的分子印迹聚合物的制备和应用

壳聚糖具有良好的生物相容性和独特的分子结构,基于其制备的分子印迹聚合物因亲和性和选择性高、应用范围广等特点引起了广泛的关注。本文首先总结了壳聚糖和改性壳聚糖在分子印迹聚合物制备中的作用,然后介绍了壳聚糖分子印迹聚合物在环境污染治理、医药、蛋白质分离与识别、手性物质分离以及吸附功能成分等方面的应用,分析了壳聚糖分子印迹聚合物在各个应用领域的优缺点及发展方向。最后,从发展绿色分子印迹技术以及分子印迹技术与电化学传感器结合等层面对壳聚糖分子印迹聚合物的应用前景进行了展望。     

Synthesis and characterization of ferroelectric side chain liquid crystal polymers bearing banana-shaped chiral mesogens

A series of ferroelectric liquid crystal polymers having banana-shaped side chain mesogens were synthesized through photo-polymerization of epoxide moiety. 2,5-disubstituted-thiophene sub-unit was used in synthesizing the banana-shaped monomers. These liquid crystal compounds were characterized by NMR, differential scanning calorimetry (DSC) and optical polarized microscopy (POM). Mesomorphism was investigated as a function of spacer units. All the synthesized low molar mass banana-shaped compounds exhibit smectic blue phase, but chiral smectic C phase could be observed only on compounds having longer spacer. The clearing temperature of low molar mass compounds fluctuated a little when spacer length varies. All polymers exhibit cholesteric mesophase and an observable glass transition. These liquid crystalline compounds reveal strong photoluminescence at visible region (λ_max = 475 nm for M9EPX) and have potential use in polarized organic light emitting diode materials.     

Effect of catalyst on the reactive processing of polyesters with epoxy-functional polymers

The objective this work was to determine the effects of selected polyester catalysts on the reaction of a polyester with epoxy functional polymers. Polyesters containing various catalyst metals were melt blended with either an ethylene-co-glycidyl methacrylate or a styrene-co-glycidyl methacrylate copolymer. The viscosities of the blends were monitored as a function of mixing time using torque rheometry. In addition, the molecular weight distributions of selected samples were analyzed using gel permeation chromatography. Both the torque rheometry and the gel permeation chromatography results indicate that the polyester reacts with epoxy functional polymers. This reaction occurs under conditions and at processing times which are readily obtainable in conventional melt processing equipment. Furthermore, the reaction kinetics of polyesters with glycidyl methacrylate copolymers are dramatically affected by the nature of the catalyst system used to prepare the polyester. Under the conditions used, antimony catalysts are particularly effective at promoting the reaction between polyesters and the epoxy functionality and the activity of the catalysts studied appears to decrease in the following order: antimony > gallium > tin ? titanium > germanium. Manipulation of the polyester catalyst system may offer a method to control the extent of reaction obtained in reactive processing of polyesters with epoxy functional compounds.     

In situ polymerization preparation of chiral molecular imprinting polymers monolithic column for amlodipine and its recognition properties study

Amlodipine is a first-line therapeutic drug for hypertension and angina pectoris and its vasodilating effect only resides in the S-(-)-enantiomer. But mostly commercial chiral separating matrixes are not capable of enantio-separating of racemic amlodipine. The amlodipine’s the chiral molecular imprinting polymers monolithic column (CMIPMC) was firstly and successfully synthesized by in situ molecular imprinting technique, utilizing S-(-)-amlodipine as the template molecule, methacrylic acid (MAA) as a monomer, and the resulting monolithic colunm could be directly integrated into the high performance liquid chromatography (HPLC) systems. The scanning electron microscope (SEM) was employed to identify the micro-morphologic features of the obtained polymers. Further, the molecule-special recognition mechanism and special selective absorbent properties for the corresponding template were studied by chromatographic system and Scatchard analysis model, respectively. Meanwhile, the optimized chromatographic conditions for chiral separation of amlodipine enantimoers were established. The results showed the obtained CMIPMC had a high specific affinity and selectivity for the template molecule S-(-)-amlodipine, in which chiral separation of racemic amlodipine was achieved under optimized conditions. The mechanism investigation results showed that two kinds of binding sites prevail in the CMIPMC, besides the molecular shape complementation of template molecular and CMIPMC, hydrogen bond or ionic interaction seem to play an important role in the enantio-selective recognition of the CMIPMC. The research laid fundament for the study of expanding the amlodipine chiral separating medium.     

Allylic polymers from resin acids. Monomer synthesis at high temperature

New chemical compounds, i. e. ketones of the abietic acid-diallyl maleate Diels-Alder adduct, have been synthesized when the reaction of abietic acid and diallyl maleate was carried out at high temperatures (up to 250°C). Having unsaturated groups in their structure, they are polymerizable substances. The monomers and the polymers have been investigated by commonly used chemical and physical methods. The polymers are soluble in polar organic solvents only at low molecular weights. The behavior of these compounds as crosslinking monomers in copolymer systems has been examined.     

Enantioface differentiation by chiral polymers containing dimethylaminobornyl moieties

Chiral monomers cis,endo-3-dimethylamino-2-bornyl methacrylate (DABM) and N,N-dimethyl[cis,endo-2-(2-vinyloxy-ethoxy)-3-bornyl]amine (DVEBA) were synthesized from (+)-camphor. The homopolymerization of both DABM and DVEBA, and the copolymerization of both chiral monomers with achiral methylmethacrylate (MMA) and styrene (St) were carried out with 2,2-azobisisobutyronitrile (AIBN) in various organic solvents. Effects of temperature, solvents, reagent molar ratio and reaction time on the polymerizations were studied. Dependences of the feeding concentration and reaction conditions on the specific rotation of the chiral copolymers were investigated. Enantioface differentiation by using the chiral polymers having dimethylaminobornyl moieties synthesized in this investigation were investigated. Effects of temperature and solvent on the asymmetric induction were also studied. © 1994 John Wiley & Sons, Inc.     

Synthesis of functional π-conjugated polymers from aromatic acetylenes

Because of their unique structures and properties, π-conjugated polymers have attracted the attention of scientists and engineers. The authors have studied the synthesis of two kinds of π-conjugated poly(aromatic acetylene)s, i.e. poly(arylacetylene)s and poly(aryleneethynylene)s with the aim of obtaining new polymers having novel functions or higher performances. This review mainly concerns the authors' results, as follows: first, we describe the synthesis and properties of achiral poly(arylacetylene)s, containing trimethylsilyl groups, oligodimethylsiloxanyl groups, dendritic groups, and glavinoxyl groups, for application as oxygen permselective membrane materials. Their self-membrane-forming abilities and high oxygen permeabilities are presented. Second, the synthesis by asymmetric-induced polymerization of chiral poly(arylacetylene)s having both a main-chain chirality and chiral pendant groups and their application as optical resolution membranes are described. Third, two new synthetic methods for preparing chiral helical poly(phenylacetylene)s without the coexistence of any other chiral moieties are presented. One is helix-sense-selective addition polymerization and the other is in situ removal of chiral pendant groups from membranes of poly(arylacetylene)s that also contain a main-chain chirality. The chiral helical poly(arylacetylene)s were tested as optical resolution membranes. The chiral and achiral poly(arylacetylene)s were synthesized by addition polymerization using metathesis catalysts or rhodium complexes. Finally, the synthesis of regiospecific poly(aryleneethynylene)s bearing stable radicals by the polycondensation of bromoethynylanthracene derivatives using a Pd(0) complex is described. The magnetization and the static magnetic susceptibility of the polyradicals are explained.     

Optical resolution ability of chiral polymers having camphanediol moieties

Optically active exo-exo-2,3-camphanediol (CPO) ( 3 ) was synthesized from (+)-camphor. Chiral polymers poly(CPO-co-TDI) ( 6 ) and poly(CPO-co-IPDI) ( 7 ) were synthesized by the step polymerization of chiral compound CPO ( 3 ) with toluene-2,4-diisocyanate (TDI) and isophorone diisocyanate (IPDI). To investigate the stereo structure of the chiral polymers, two kinds of model compound exo-exo-2,3-di[(phenylamido)oxy]camphane ( 4 ) and exo-exo-2,3-di[(propylamido)oxy]camphane ( 5 ) related to polymers ( 6 ) and ( 7 ) were synthesized. Chiroptical characteristics and stereo structures of the chiral polymers were investigated by using circular dichroic spectrometry. The results obtained in this investigation suggest that the chiral polymers ( 6 ) and ( 7 ) do not have onehanded helix conformation. Optical resolution ability as chiral adsorbent for high-performance liquid chromatography of the chiral polymers was investigated. It was found that chiral polymers ( 6 ) and ( 7 ) are effective for the optical resolution of some racemates.     

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.     

利用分子印迹聚合物对外消旋药物萘普生的手性拆分

采用丙烯酰胺为功能单体,以二甲基丙烯酸乙二醇酯为交联剂,在模板分子(S)-萘普生的存在下,制备(S)-萘普生的分子印迹聚合物,并对其进行了高效液相色谱评价.结果表明,萘普生的外消旋混合物得到了较好的拆分,而且分离了与萘普生结构相似的布洛芬、酮洛芬,探讨了萘普生手性拆分的机理,考察了流速、流动相中乙酸含量对分离效果的影响.     

Degraded products in weathered polymers

Styrene–methyl vinyl ketone copolymers, methyl methacrylate–methyl vinyl ketone copolymers, and styrene–methyl vinyl ketone–2,6-di-t-butyl-4-acroylaminomethylphenol terpolymers as well as polystyrene and polypropylene have been weathered either by artificial irradiation or by outdoor exposure. The weathered products were analyzed using GC mass spectrometry, liquid chromatography, IR, UV, NMR, and wet analytical methods. Most of the weathered products proved to be low molecular weight polymers with various functional groups, and many low molecular weight compounds were identified. From the degradates of styrene copolymers, acetone, acetic acid, acetophenone, benzoic acid, formic acid, phenol, benzaldehyde, etc., were identified; from the degradates of methyl methacrylate copolymers, acetone, acetic acid, methanol, methyl methacrylate, methyl vinyl ketone, etc., were identified; and from the degradates of polypropylene, aliphatic acids up to propionic were analyzed. In many cases, the most abundant species was acetic acid. From polypropylene weathered outdoors for two years, 1.2 μl/g acetic acid was obtained. The degradates of styrene copolymers were found to contain fluorescent substances.