Chiral acid selectivity displayed by PEDOT electropolymerised in the presence of chiral molecules

Chiral conducting polymers prepared by electropolymerising PEDOT in the presence of chiral anions such as hyaluronic acid and anionic collagen or in a chiral nematic phase (hydroxypropyl cellulose, HPC) show excellent chiral acid recognition. This paper demonstrates the enantioselective recognition and transfer of protonated mandelic acid and protons using chiral PEDOTs. Discrimination between (R)-(-)- and (S)-(+)-mandelic acid was observed using cyclic voltammetry and square-wave voltammetry.     

Construction of Chiral Cyclic Compounds Enabled by Enantioselective Photocatalysis

Chiral cyclic molecules are some of the most important compounds in nature, and are widely used in the fields of drugs, materials, synthesis, etc. Enantioselective photocatalysis has become a powerful tool for organic synthesis of chiral cyclic molecules. Herein, this review summarized the research progress in the synthesis of chiral cyclic compounds by photocatalytic cycloaddition reaction in the past 5 years, and expounded the reaction conditions, characters, and corresponding proposed mechanism, hoping to guide and promote the development of this field.     

Chiral four-membered cyclic nitrones; asymmetric induction in the (4+2)-cycloaddition reaction of chiral ynamines and nitroalkenes

Chiral four-membered cyclic nitrones were synthesized by the asymmetric (4+2)-cycloaddition of nitroalkenes 1 and chiral ynamines 2. The subsequent stereoselective addition of nucleophiles to these nitrones enabled the synthesis of chiral N-hydroxyazetidines.     

Enantioselective Michael reaction catalyzed by well-defined chiral ru amido complexes: isolation and characterization of the catalyst intermediate,ru malonato complex having a metal-carbon bond

Chiral Ru amido complexes promote asymmetric Michael addition of malonates to cyclic enones, leading to Michael adducts with excellent ee's, in which the chiral Ru amido complexes react with malonates to give isolable catalyst intermediates, chiral Ru malonato complexes bearing a metal bound C-nucleophile.     

手性联萘酚类配体修饰的氢化物还原剂的应用

综述了手性联酚化合物作了手性配体在一系列不对称选择性还原反应（包括对不饱和羰基化合物，酰基锡烷，亚胺，酸酐，内消旋环１，２－二羰基亚胺等的不对称还原反应）中的应用，参考文献２７篇。     

One-step selective dehydrogenation of cyclic hemiacetal sugars toward to their chiral lactones

Chiral glycosyl lactone is an important class of bioactive compound and pharmaceutical intermediate in nature, especially for chiral lactones with 4 carbon atoms, which are very useful building blocks for synthesis of biologically interesting compounds. Herein, a selective dehydrogenation and solvent matched catalytic system under oxygen-free conditions was developed to try to achieve the one-step direct conversion of cyclic hemiacetal sugars toward their chiral glycosyl lactones. During the process, the inherent structural characteristics of sugar was efficiently utilized, and the transfer of its chiral centers was realized. Under the optimum condition, the corresponding lactones were successfully prepared from C4-C6 sugars with cyclic hemiacetal structure in acetonitrile. The reaction mechanism in acetonitrile was explored by the first principle density functional theory calculations and tracking reaction process. It was found that the high lactone yield in acetonitrile was due to the high proportion of α-conformation form among multiple tautomers in it. This selective dehydrogenation process may further extend the possibility of the preparation of chiral synthons from carbohydrates directly.     

Influence of hydroperoxides on the enantioselectivity of metal-catalyzed asymmetric Baeyer–Villiger oxidation and epoxidation with chiral ligands

Chiral hydroperoxides have a significant influence on the enantioselectivity of the metal-catalyzed asymmetric Baeyer–Villiger oxidation of cyclic ketones and the epoxidation of allylic alcohols, when chiral ligands are employed. If both the ligand and the hydroperoxide are enantiopure, the ligand determines the formation of the preferred product enantiomer in both reactions.     

Enantioselective synthesis of chiral sulfones by ir-catalyzed asymmetric hydrogenation: a facile approach to the preparation of chiral allylic and homoallylic compounds

A highly efficient and enantioselective Ir-catalyzed hydrogenation of unsaturated sulfones was developed. Chiral cyclic and acyclic sulfones were produced in excellent enantioselectivities (up to 98% ee). Coupled with the Ramberg-B?cklund rearrangement, this reaction offers a novel route to chiral allylic and homoallylic compounds in excellent enantioselectivities (up to 97% ee) and high yields (up to 94%).     

Chiral HPLC Separation on Derivatized Cyclofructan Versus Cyclodextrin Stationary Phases

Cyclodextrins (CDs) and cyclofructans (CFs) are chiral cyclic oligosaccharides. While β-CD is composed of seven glucopyranose units forming rigid cavity, hydrophobic inside, CF6 and CF7, contain six and seven fructofuranose units, respectively, creating a polar crown ether core. These basic structures can be easily derivatized to form even more potential chiral selectors that enable enantioselective separation of various chiral compounds. Chiral stationary phases (CSPs) based on CFs and CDs that were derivatized with the same derivatization group, either dimethylphenyl or R-naphthylethyl, were compared. A set of analytes with different interaction possibilities was used for characterization of retention and enantioseparation abilities of these CSPs in normal separation mode of HPLC. The results showed that both cyclic oligosaccharide structure and derivatization group influenced the retention/separation behavior of analytes. Complementary enantioseparations were obtained for some analytes.     

Chiral enrichment of serine via formation,dissociation, and soft-landing of octameric cluster ions

Chiral enrichment of serine is achieved in experiments that involve formation of serine octamers starting from non-racemic serine solutions. Serine octamers were generated by means of electrospray and sonic spray ionization of aqueous solutions of d(3)-L-serine (108 Da) and D-serine (105 Da) having different molar ratios of enantiomers. A cyclic process involving the formation of chirally-enriched octameric cluster ions and their dissociation, viz. Ser(1) --> Ser(8) --> Ser(1), allows serine monomers to be regenerated with increased enantiomeric excess as shown in two types of experiments: (1) Chiral enrichment in serine was observed in MS/MS/MS experiments in a quadrupole ion trap in which the entire distribution of serine octamers formed from non-racemic solutions was isolated, collisionally activated, and fragmented. Monomeric serine was regenerated with increased enantiomeric excess upon dissociation of octamers when compared with the enantiomeric composition of the original solution. (2) Chiral enrichment was observed in the products of soft-landing of mass-selected protonated serine octamers. These ions were generated by means of electrospray or sonic spray ionization, mass selected, and collected on a gold surface using ion soft-landing. Chiral enrichment of the soft-landed serine was established by redissolving the recovered material and comparing the intensities of protonated molecular ions of d(3)-L-serine and D-serine after APCI-MS analysis. Both of these experiments showed comparable results, suggesting that formation of serine octamers depends only on the enantiomeric composition of the serine solution and that the magnitude of the chiral preference is intrinsic to octamers formed from solutions of given chiral composition.     

Palladium-catalyzed asymmetric hydrosilylation of 1,3-dienes

Advances in the palladium-catalyzed asymmetric hydrosilylation of 1,3-dienes are presented according to substrate types and chiral monophosphine ligands. Chiral monodentate phosphine ligands with a binaphthyl moiety have been proven to be the most efficient ligands for cyclic 1,3-dienes, and planar chiral ferrocenylmonophosphine ligands with two ferrocenyl moieties for linear 1,3-dienes. The ferrocenylmonophosphine ligands have expanded the substrate scope to 1,3-enynes in the asymmetric hydrosilylation. Palladium-catalyzed asymmetric hydrosilylation of 1,3-dienes and 1,3-enynes leads to the stereoselective synthesis of allylsilanes and allenylsilanes, respectively.     

Enantioselective Protonation of Cyclic Carbonyl Ylides by Chiral Lewis Acid Assisted Alcohols

Chiral Lewis acid-catalyzed asymmetric alcohol addition reactions to cyclic carbonyl ylides generated from N-(α-diazocarbonyl)-2-oxazolidinones featuring a dual catalytic system are reported. Construction of a chiral quaternary heteroatom-substituted carbon center was accomplished in which the unique heterobicycles were obtained in good yields with high stereoselection. The alcohol adducts were successfully converted to optically active oxazolidine-2,4-diones by hydrolysis. Mechanistic studies by DFT calculations revealed that alcohols could be activated by Lewis acids, enabling enantioselective protonation of the carbonyl ylides.     

Pharmaceutical Industry Oriented Homogeneous Catalysis

Chiral therapeutics already makes up over one-third of pharmaceutical drugs currently sold worldwide. This is a growing industry with global chiral drug sales for 2002 increasing by 12% to $160 billion (Technology Catalysts International) of a total drug market of $410bn. The increasing demand to produce enantiomerically pure pharmaceuticals, agrochemicals, flavors, and other fine chemicals has advanced the field of asymmetric catalytic technologies. We aim to become a high value technology p…     

手性亚砜合成

手性亚砜及其衍生物广泛作为重要手性中间体和辅剂、手性配体和催化剂、手性药物。手性亚砜可以采用生物方法和化学方法来合成,化学方法包括手性辅剂诱导、手性氧化剂氧化、手性拆分和不对称催化等。本文简要综述了手性亚砜的各种用途和各种合成方法的研究进展,主要介绍了钛和钒催化的不对称硫醚氧化反应,也介绍了作者最近在钒催化的不对称硫醚氧化反应方面所做的研究工作。     

High-performance liquid chromatographic enantioseparation of methanobenzazocines

Chiral recognition and resolution of methanobenzazocines was investigated by HPLC using polysaccharide, Pirkle-type, native and derivatized β-cyclodextrin chiral stationary phases. Enantioseparation of phenyl substituted 2,6-methanobenzazocines was achieved with multiple chiral stationary phases throughout the classes described. Chiral resolution of the enantiomers of 1,5-methano-3-methyl-6-oxo-1,2,3,4,5,6-hexahydro-3-benzazocine was produced on both polysaccharide and Pirkle-type phases. In the case of 1,5-methano-3-methyl-6-phenyl-1,2,3,4,5,6-hexahydro-3-benzazocine only a dinitrophenyl substituted β-cyclodextrin produced a separation of enantiomers.     

Chiral Separations of Five Organic Catalysts by Cyclodextrin-modified Capillary Zone Electrophoresis

Chiral separation is very important and become a significant task of analytical chemistry in many fields. Capillary electrophoresis (CE) is a technique undergoing rapid development for chiral separation at the present time. With its high efficiency, simple operation, and extremely small sample volume,CE has become a powerful tool for chiral separation. There are many chiral selectors, such as cyclodextrins (CDs), proteins, chiral surfactants, antibiotics, bile salts, using in CE chiral separation. CDs has been most wildly used in them. Cyclodextrin (CD) is a cyclic sugar made of certain glucose units in which each has 5 chiral centers and it shows the shape of cavity with a big end and a small end. The inside of CD is hydrophobic and the outside is hydrophilic. The chiral selectivity of CD comes from the formation of host-guest compound between CD and analytes. The differences of the hydrogen-bond and the other interactions between CD and two enantiomers cause enantio-selectivity.     

手性噁唑硼烷的研究进展及其应用

手性噁唑硼烷是不对称合成的重要催化剂, 它可以高产率、高立体选择性地催化酮、内消旋酰亚胺以及亚胺的不对称还原, 催化立体选择性Diels-Alder反应、不对称Mukaiyama缩合反应等重要有机化学反应. 概述了近十年来手性噁唑硼烷在不对称合成中的研究进展以及在合成VB₁₂等多种天然及非天然活性化合物中的应用.     

手性有序无机介孔硅用作气相色谱固定相

手性介孔材料在手性分离、不对称催化、手性传感等领域具有广泛的应用价值。手性有序无机介孔硅是一类介孔结构高度有序、不含有机成分的手性材料。该文采用D-苯丙氨酸为手性源合成手性有序无机介孔硅(COIMS),将其用聚硅氧烷(OV-1701)稀释后用作固定相制备毛细管气相色谱手性柱,并对该手性柱的分离性能进行了考察,8种手性化合物在该手性柱上得到了拆分。COIMS柱对直链烷烃、醇的分离也表现出良好的选择性。该柱还具有分析时间短、在较高温度下测定稳定等优点,其具有开发成高温手性固定相的潜力。     

Naphtho[2,3-a]pyrene forms chiral domains on Au111

Chiral domains have been prepared by evaporation of a two-dimensionally chiral molecule, naphtho[2,3-a]pyrene (NP), onto the hexagonal Au(111) surface in an ultrahigh vacuum environment. High-resolution UHV scanning tunneling microscopy (STM) showed that NP formed chiral domains consisting of only one 2D enantiomer rather than racemic two-dimensional unit cells. A structural model is proposed that agrees with the STM observations. Chiral pockets between adsorbed molecules may be useful for binding a specific enantiomer of a 3D chiral molecule.     

苯丙氨酸衍生物手性凝胶的制备及其应用

手性超分子凝胶材料在传感器、人工触角、药物缓释、细胞培养等领域表现出潜在的应用前景。本文合成了一种新型的含偶氮苯官能团的D/L苯丙氨酸手性凝胶因子ALP和ADP,具有对称且完全相反的手性信号。该凝胶因子在多种有机溶剂和水混合溶剂中均可形成稳定的淡黄色凝胶,其中在DMSO和水混合溶剂中表现出最优的成凝胶性能,临界成胶浓度可达2.0mg/mL,表明该手性凝胶因子具有良好的成凝胶性能。手性凝胶可对热、光、pH等外界环境刺激产生响应,并伴有宏观上的凝胶-溶胶相互转变。手性凝胶因子自组装形成了不同螺旋纳米纤维结构,并发现L型手性纳米纤维相对于D型手性纳米纤维对细胞具有更好的粘附与增殖效果。