柔性间隔基对于香豆素取代二乙炔LB膜聚合及手性形成的影响

设计合成了2种香豆素取代二乙炔单体,7-(10,12-二十三双炔酰氧基)-香豆素(CODA)和7-(10,12-二十三双炔酰氧乙氧基)-香豆素(CO2DA),研究了柔性间隔基对香豆素取代二乙炔单体在气-液界面的组装、单体LB膜的聚合以及聚二乙炔主链螺旋结构形成的影响.利用Langmui-Blodgett(LB)技术,以纯水为亚相,膜压在35 mN/m时沉积制备了香豆素取代二乙炔单体LB膜.尽管CODA是非手性的,但其LB膜均表现出明显的宏观手性信号.这是由于在压缩过程中香豆素基团间强烈的π-π堆积,形成了螺旋排列,显示出超分子手性.而CO2DA LB膜无明显CD信号.经254 nm紫外光辐照,CODA LB膜聚合成蓝相,聚二乙炔主链表现出明显的宏观手性.而CO2DA LB膜聚合后无明显的CD信号.薄膜中香豆素功能基团的不规则排列不利于二乙炔单体的固态聚合以及聚二乙炔主链螺旋结构的形成.     

带树枝状侧链聚苯乙炔的合成与结构表征

合成了带树枝状聚苯甲醚修饰基团的苯乙炔单体,在Rh[(nbd)Cl2]2催化剂的作用下得到了侧链带聚苯甲醚树枝的新型聚苯乙炔衍生物,用红外吸收光谱、核磁共振谱、紫外可见吸收光谱和凝胶渗透色谱表征了聚合物的结构.发现聚合物的重均分子量达到了57300,在氯仿、N,N-二甲基甲酰胺、四氢呋喃等有机溶剂中有良好的溶解性能.由于侧链上聚苯甲醚树枝体积庞大,聚合物主链采取立构规整的顺-顺式构象,紫外可见吸收光谱在440nm附近出现了显著的共轭主链的吸收肩峰;立构规整的顺-顺式构象使树枝状侧链形成了对主链保护的"夹套效应",聚合物热分解温度从聚苯乙炔母体的225℃提高到295℃.     

奇偶效应诱导的苯丙氨酸类水凝胶手性反转

为了模拟生物大分子(如DNA和蛋白质等)螺旋手性反转的现象,设计合成了4种酰胺基或脲基共价连接L-苯丙氨酸和苯环,外围为二甘醇胺与3-氨基-1,2-丙二醇的C2对称小分子凝胶因子,利用酰胺基(CONH)与脲基(NHCONH)之间的奇偶效应实现了超分子螺旋手性的反转.通过核磁共振波谱仪(1H-NMR和13C-NMR),高分辨质谱仪(HRMS)对凝胶因子结构和分子量进行了分析表征.并运用圆二色光谱(CD)、扫描电子显微镜(SEM)、紫外可见吸收光谱(UV-Vis)和红外光谱(FTIR)对其组装纤维结构和组装方式进行研究.实验结果表明酰胺基(CONH)与脲基(NHCONH)之间的奇偶效应改变凝胶因子的组装方式,调控了超分子手性特征,实现了超分子水凝胶螺旋手性的反转.     

基于醋酸铑、磺酸和手性亚磺酰胺基脲共催化的α-重氮酯与酰胺不对称N—H插入反应研究

研究了醋酸铑[Rh2(OAc)4]、手性亚磺酰胺基脲和非手性磺酸共催化的α-重氮酯与酰胺化合物的不对称N—H插入反应.研究发现α-重氮酯在醋酸铑催化下形成金属卡宾,该金属卡宾与酰胺反应生成潜手性活泼叶立德中间体.在催化剂量的手性亚磺酰胺基脲和非手性磺酸存在下,潜手性叶立德中间体发生不对称质子化,合成了手性α-氨基酸衍生物.反应过程中,手性亚磺酰胺基脲和非手性磺酸作为"手性质子梭"催化不对称质子迁移从而实现了反应的对映选择性控制.该方法发展了非手性铑、手性亚磺酰胺基脲和非手性磺酸不对称共催化体系,为合成α-氨基酸衍生物提供了一种新途径,反应收率最高可达84%,对映选择性最高可达77%.     

新型氨基酸衍生物手性固定相的制备及应用

氨基酸是手性小分子,其选择和固定化的方法,有助于开发新的“刷型”手性固定相(CSP)。 分别以L-缬氨酸和L-丙氨酸为原料制备了10种新型氨基酸衍生物手性固定相(CSPs),包括8种氨基酸三嗪衍生物CSPs(CSP-1~CSP-8)和两种对甲基苯甲酰氨基酸CSPs(CSP-9~CSP-10),在正相色谱条件下,考察了所合成的CSPs对邻、间和对硝基苯酚位置异构体以及萘普生乙酯、丙环唑、苯醚甲环唑、戊唑醇、己唑醇和联萘酚6种外消旋样品的分离能力。 结果表明,硝基苯酚的3种位置异构体在CSP-1~CSP-3和CSP-6~CSP-8上获得较好分离。 相同条件下,由丙氨酸制得的CSPs对外消旋样品表现出更好的手性识别能力,萘普生乙酯在CSP-6上获得基线分离。 由化学软件Gaussian 09计算出的L-丙氨酸三取代三嗪衍生物CSP-Ⅵ与萘普生乙酯的两个光学异构体之间相互作用的结合能分别为52.51和133.9 kJ/mol,也说明了手性选择子与R、S形成的非对映配合物的稳定性不同,Gaussian 09所给出的结合构型图显示手性选择子与样品之间有明显的氢键作用。 Gaussian 09的计算结果有助于认识CSPs的手性识别机理。     

手性亚砜类药物的手性识别研究

以L-亮氨酸的衍生物二齿手性氨基醇为主体、氘代氯仿为溶剂、手性亚砜类药物奥美拉唑消旋体和兰索拉唑消旋体为客体,分别考察了主体对两种客体消旋体的手性识别能力,最大化学位移差值(ΔΔδ)分别达到28.5 Hz和14 Hz。     

芳香取代基结构对螺旋聚乙炔高效液相色谱手性固定相手性识别性能的影响

设计合成了3种源于脯氨酸的手性乙炔基单体——(S)-2-乙炔基-N-芳香胺基甲酰基吡咯烷. 在氯化降冰片二烯铑二聚体{[Rh(nbd)Cl]₂}-三乙胺催化下, 3种单体被转化为相应的光学活性螺旋聚合物. 用高效液相色谱评估了3种聚合物作为手性固定相(CSPs)对9种底物的手性识别性能. 以正己烷/异丙醇(体积比9∶1)为流动相时, 3种聚合物对3对种氢键给体分子苯偶姻(α=1.35~1.44)、 三氟-1-(9-蒽基)乙醇(α=1.11~1.53)、 2,2′-二羟基-1,1′-联萘(α=1.09~1.11)及乙酰丙酮钴(α=1.84~2.38)表现出很好的手性识别能力; 当以正己烷为流动相时, 3种聚合物都能立体选择性地识别氢键给体分子2,2-二甲基-1-苯基-1-丙醇(α=1.12~1.22), 聚[(S)-2-乙炔基-N-(2′-萘基胺基甲酰基)吡咯烷]能识别氢键受体分子2-苯基环己酮(α=1.11). 结合核磁共振波谱、 拉曼光谱、 旋光测试、 紫外吸收光谱和圆二色光谱及液相色谱等方法, 系统研究了芳香侧基结构与连接位置对聚合物螺旋构象和对映体选择性拆分能力的影响. 分子对接模拟结果表明, 1-萘基的空间位阻大于2-萘基且可促进形成更强的分子内氢键, 不利于大尺寸底物(如联萘酚)的手性拆分. 与苯基相比, 引入萘基有利于增强聚合物与底物间的π-π相互作用, 提高聚合物的立体选择性和手性识别能力.     

硅胶负载手性氨基醇聚合物的合成及其应用

以L-亮氨酸(L-Leu)为手性源,经酯化、格氏化、酰胺化等步骤制备手性单体(L-NALAA),以该单体为手性识别基团,在引发剂偶氮二异丁腈和交联剂乙二醇二甲基丙烯酸酯(EDMA)的作用下,与烯化功能硅胶发生自由基共聚反应,制备了新型键合硅胶手性固定相,其结构经FT-IR、TGA、EA表征。以4种对映异构体为模型药物对手性材料手性固定相的手性拆分性能进行研究,结果表明,手性材料手性固定相对奥美拉唑和兰索拉唑的拆分效果较好。     

氨基酸聚合物作为高效液相色谱手性固定相的研究

将L-丙氨酸、L-缬氨酸、L-色氨酸、L-苯甘氨酸和L-苯丙氨酸5种氨基酸的手性单体与甲基丙烯酸-3-(三甲氧基硅基)丙酯共聚到硅胶表面制备了5种氨基酸聚合物手性固定相,并用作高效液相色谱手性固定相。考察了它们的手性识别能力,L-丙氨酸、L-缬氨酸和L-色氨酸聚合物手性固定相具有较好的手性拆分效果,并且它们之间的手性识别能力还具有一定的互补性。     

光学活性螺旋聚(3,5-二取代苯乙炔)：构象调控、手性传递与自组装

聚苯乙炔衍生物是重要的动态螺旋聚合物,具有丰富可调的螺旋构象,在手性识别、对映体拆分、不对称催化、多通道传感、圆偏振发光等领域的潜在应用正受到越来越多的关注.本文总结了近年来笔者在聚(3,5-二取代苯乙炔)研究中取得的主要进展,包括:cis-cisoid螺旋构象的形成条件、影响因素与调控规律,手性双重传递模式与可调控的手性放大规律,有趣的自组装行为和超分子结构.最后,对螺旋聚苯乙炔衍生物手性功能材料今后的研究作了展望.     

Influence of stereoregularity and linkage groups on chiral recognition of poly(phenylacetylene) derivatives bearing L‐leucine ethyl ester pendants as chiral stationary phases for HPLC

Stereoregular poly(phenylacetylene) derivatives bearing L ‐leucine ethyl ester pendants, poly‐1 and poly‐2a , were, respectively, synthesized by the polymerization of N‐(4‐ethynylphenylcarbamoyl)‐L ‐leucine ethyl ester ( 1 ) and N‐(4‐ethynylphenyl‐carbonyl)‐L ‐leucine ethyl ester ( 2 ) using Rh(nbd)BPh₄ as a catalyst, while stereoirregular poly‐2b was synthesized by solid‐state thermal polymerization of 2 . Their chiral recognition abilities for nine racemates were evaluated as chiral stationary phases (CSPs) for high‐performance liquid chromatography (HPLC) after coating them on silica gel. Both poly‐1 and poly‐2a with a helical conformation showed their characteristic recognition depending on coating solvents and the linkage groups between poly(phenylacetylene) and L ‐leucine ethyl ester pendants. Poly‐2a with a shorter amide linkage showed higher chiral recognition than poly‐1 with a longer urea linkage. Coating solvents played an important role in the chiral recognition of both poly‐1 and poly‐2a due to the different conformation of the polymer main chains induced by the solvents. A few racemates were effectively resolved on the poly‐2a coated with a MeOH/CHCl₃ (3/7, v/v) mixture. The separation factors for these racemates were comparable to those obtained on the very popular CSPs derived from polysaccharide phenylcarbamates. Stereoirregular poly‐2b exhibited much lower chiral recognition than the corresponding stereoregular, helical poly‐2a , suggesting that the regular structure of poly(phenylacetylene) main chains is essential to attain high chiral recognition. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Remarkable Structure Effects on Chiroptical Properties of Polyisocyanides Carrying Proline Pendants

Chiral polymers with simple chemical structures and high helical conformation stabilities are important for their applications as chiral supports and asymmetrical catalysts. We report herein the synthesis of a series of aliphatic polyisocyanides carrying proline pendants of different chiralities, and an investigation of the effects of the chemical structures of these pendants on the chiroptical properties of the polymers. The configuration of the chiral center at the 4‐position of the proline pendants was changed from S to R to check its effect on the handedness of the helical conformation. To examine the effects of steric hindrance on the stabilities of the helical conformation for these aliphatic representatives, proline pendants with various substituents at both the carboxyl and amine terminals were designed. To further examine the steric effects of the proline pendants, aromatic counterparts were also prepared. In the latter case, the effects of hydrogen bonds between pendant units on the enhancement and stabilities of the helical conformation were investigated by switching from the ester to an amide linkage. The Cotton effects and signal intensities of both aliphatic and aromatic polyisocyanides from circular dichroism spectroscopy were compared based on the bulkiness of the pendant groups, solvent polarities, and solution temperatures. It was found that highly stable helical conformations of polyisocyanides could be imposed by small bulky monoproline pendants.     

Synthesis and chiral recognition of helical poly(phenylacetylene)s bearing l‐phenylglycinol and its phenylcarbamates as pendants

A series of novel stereoregular one‐handed helical poly(phenylacetylene) derivatives ( PPA‐1 and PPA‐1a～g ) bearing l ‐phenylglycinol and its phenylcarbamate residues as pendants was synthesized for use as chiral stationary phases (CSPs) for HPLC, and their chiral recognition abilities were evaluated using 13 racemates. The phenylcarbamate residues include an unsubstituted phenyl, three chloro‐substituted phenyls (3‐Cl, 4‐Cl, 3,5‐Cl₂), and three methyl‐substituted phenyls (3‐CH₃, 4‐CH₃, 3,5‐(CH₃)₂). The acidity of the phenylcarbamate N‐H proton and the hydrogen bonds formed between the N‐H groups of the phenylcarbamate residues were dependent on the type, position, and the number of substituents on the phenylcarbamate residues. The chiral recognition abilities of these polymers significantly depended on the dynamic helical conformation of the main chain with more or less regularly arranged pendants. The chiral recognition abilities seem to be improved by the introduction of substituents on the phenylcarbamate residues, and PPA‐1d bearing the more acidic N‐H groups due to the 3,5‐dichloro substituents, exhibited a higher chiral recognition than the others. PPA‐1d showed an efficient chiral recognition for some racemates, and baseline separation was possible for racemates 5 , 11 , 12 , and 15 . © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 809–821     

Helicity Induction and Memory of the Macromolecular Helicity in a Polyacetylene Bearing a Biphenyl Pendant

A novel, cis‐transoidal poly‐(phenylacetylene) bearing a carboxybiphenyl group as the pendant (poly‐ 1 ) was prepared by polymerization of (4′‐ethoxycarbonyl‐4‐biphenylyl)acetylene with a rhodium catalyst followed by hydrolysis of the ester groups. Upon complexation with various chiral amines and amino alcohols in dimethyl sulfoxide (DMSO), the polymer exhibited characteristic induced circular dichroism (ICD) in the UV/Vis region due to the predominantly one‐handed helix formation of the polymer backbone as well as an excess of a single‐handed, axially twisted conformation of the pendant biphenyl group. Poly‐ 1 complexed with (R)‐2‐amino‐1‐propanol showed unique time‐dependent inversion of the macromolecular helicity. Furthermore, the preferred‐handed helical conformation of poly‐ 1 induced by a chiral amine was further “memorized” after the chiral amine was replaced with achiral 2‐aminoethanol or n‐butylamine in DMSO. In sharp contrast to the previously reported memory in poly((4‐carboxyphenyl)acetylene), the present helicity memory of poly‐ 1 was accompanied by memory of the twisted biphenyl chirality in the pendants. Unprecedentedly, the helicity memory of poly‐ 1 with achiral 2‐aminoethanol was found to occur simultaneously with inversion of the axial chirality of the biphenyl groups followed by memory of the inverted biphenyl chirality, thus showing a significant change in the CD spectral pattern.     

Synthesis and property of helical poly(phenylacetylene)s bearing chiral ruthenium complexes and real space imaging of meso- and nanoscopic structures by atomic force microscopy

Novel sets of helical poly(phenylacetylene)s bearing a chiral ruthenium (Ru) complex with opposite chirality (Δ and Λ forms) as a bulky pendant (poly- 1 and poly- 2 ) were synthesized through the polymerization of the corresponding optically pure phenylacetylenes with a rhodium catalyst, and their structures in solution and morphology on solid substrates were investigated with NMR, ultraviolet–visible, and circular dichroism (CD) spectroscopies and with atomic force microscopy (AFM), respectively. The obtained cis–transoidal polymers (poly- 1 and poly- 2 ) showed characteristic Cotton effects in the region of metal-to-ligand charge transfer of the chiral Ru pendants. Poly- 1 and poly- 2 were thought to have a predominantly one-handed helical conformation induced by the chiral pendants. However, the apparent Cotton effects derived from the helically twisted π-conjugated polymer backbone could not be observed, probably because of the strong chiral chromophoric pendants. However, in the AFM images, the helical polymers adsorbed on mica could be easily discerned as isolated strands, and the visualization and discrimination of the right- and left-handed helical structures of the chiral polymers were achieved by high-resolution AFM imaging. On the basis of the AFM observations together with the CD measurements and computational calculation results, possible structures of poly- 1 and poly- 2 were examined. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4621–4640, 2004     

Chiral Recognition and Resolution Based on Helical Polymers

Helical polymers have attracted a great deal of attention and been extensively investigated due to their various applications.One of the most important applications of helical polymers is chiral recognition and resolution of enantiomers for the reason that a pair of enantiomers is commonly with different physiological and toxicological behaviors in biological systems.Helical polymers usually present unexpected high chiral recognition ability to a variety of racemic compounds.What's more,the chiral recognition and resolution abilities of the system are dependent on the highly ordered helical structures of the helical polymers.This mini review mainly focuses on the recent progress in chiral recognition and resolution based on helical polymers.The synthetic methodology for helical polymers is firstly discussed briefly.Then recent advances of chiral recognition and resolution systems based on helical polymers,especially polyacetylenes and polyisocyanides,are described.We hope this mini review will inspire more interest in developing helical polymers and encourage further advances in chiral-related disciplines.     

Chiral Overpass Induction in Dynamic Helical Polymers Bearing Pendant Groups with Two Chiral Centers

The dynamic behavior of helical polymers bearing pendant groups with two chiral centers was studied. Controlled conformational changes at the chiral units placed either closer to or further away from the main chain promote different helical structures. Although the first residue is usually responsible for determining a specific helicity (P or M), we now found that the second chiral center is also able to induce a preferred helical sense when it is located closer in space to the main chain, thereby cancelling the order from the first chiral moiety. This result was achieved through proper coordination with a metal cation. As proof of concept, poly(phenylacetylene)s (PPAs) that bear one and two chiral amino acid units of different sizes and configuration combinations (l /d ‐alanine and l /d ‐phenylalanine) as pendants were evaluated. In total, ten polymers were studied. This constitutes the first report of axial control from a remote stereocenter in polymers bearing complex chiral pendants.     

Preparation of a new crown ether-based chiral stationary phase containing thioester linkage for the liquid chromatographic separation of enantiomers

A new chiral stationary phase (CSP) containing thioester linkages was prepared by bonding (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid to mercaptopropylsilica gel. The chiral recognition ability of the new CSP was found to be greater than that of the previously reported CSP containing amide linkages in the resolution of the various α-amino acids that were tested, except for that of Met, Ser and Thr. In the resolution of racemic amines and amino alcohols, the new CSP was always better than the one containing amide linkages in terms of the separation factors (α) and the resolutions (R_S). Given the identical elution orders on the two CSPs, it was concluded that the chiral recognition mechanism is not affected by the change of the linkage type. In addition, the new CSP was found to be quite stable under the acidic mobile phase conditions that were utilized, indicating that the thioester linkage is useful as a tethering group.     

Main‐chain chiral poly(2‐oxazoline)s: Influence of alkyl side‐chain on secondary structure formation in solution

The synthesis and microwave‐assisted polymerization of a series of chiral 2‐oxazolines with varying alkyl pendant groups, namely R‐2‐ethyl‐4‐ethyl‐2‐oxazoline (R‐EtEtOx), R‐2‐butyl‐4‐ethyl‐2‐oxazoline (R‐BuEtOx), R‐2‐octyl‐4‐ethyl‐2‐oxazoline, 2‐nonyl‐4‐ethyl‐2‐oxazoline, and R‐2‐undecyl‐4‐ethyl‐2‐oxazoline (R‐UndeEtOx), are reported. A kinetic investigation of the polymerization of R‐EtEtOx revealed a living polymerization mechanism. The poly(2‐oxazoline)s containing an ethyl, butyl, and octyl pendant group form similar chiral structures according to circular dichroism measurements. When the pendant group is further elongated, the chiral structure becomes more flexible in trifluoroethanol and the thermal response in hexafluoroisopropanol (HFIP) significantly changes. The short‐range structure of poly‐R‐BuEtOx dissolved in HFIP is thermoresponsive in a complex way, due to HFIP hydrogen bonding to the polymeric amide groups, whereas the long‐range structure determined from small angle neutron scattering is insensitive to temperature demonstrating that only the local secondary structure changes with temperature. In addition, the chiral structure of poly‐R‐UndeEtOx depends on the polarity of the solvent. The short‐range structure becomes more flexible in polar solvents, most likely due to interactions with the amide groups disturbing the secondary structure. In contrast, the long‐range structural transition from an ellipsoid in the apolar n‐hexane to a rod structure in the polar n‐butanol is ascribed to better solvation of the long aliphatic side chains. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

L-lysine based gemini organogelators: their organogelation properties and thermally stable organogels

Novel gemini organogelators based on L-lysine, in which two L-lysine derivatives are linked by different alkylene chain lengths through the amide bond, have been simply and effectively synthesized, and their organogelation abilities and thermal stabilities have been investigated. In a series of L-lysine ethyl ester derivatives, the organogelation abilities decreased with increasing alkylene spacer length. In particular, bis(N(epsilon)-lauroyl-L-lysine ethyl ester) oxalyl amide is a good organogelator that gels most organic solvents such as alcohols, cyclic ethers, aromatic solvents and acetonitrile. Various oxalyl amide derivatives with different alkyl ester groups such as hexyl, decyl, dodecyl, 2-ethyl-1-hexyl and 3,5,5-trimethylhexyl also showed good organogelation abilities. Furthermore, it was found that the cyclohexane gels formed by some oxalyl amide derivatives have a high thermal stability.