Chiral pool based synthesis of pyrrolidinium ionic liquids

Chiral ionic liquids show promising applications in various different fields. A series of pyrrolidinium-based chiral ionic liquids bearing a chiral cation, a chiral anion or both was prepared in good yields using an efficient, economic and simple pathway. The chirality was introduced using (l)-lactate and (l)-menthol derivatives. The resultant chiral compounds were characterized by both spectroscopy and polarimetry. We envision that these new chiral compounds can serve as effective reaction media and chiral catalysts for asymmetric reactions, which are presently being investigated in our lab.     

Heterocyclic effect for optical properties of naphthoquinone-based pigment: 2-methyl-3-heteroarylthio-1,4-naphthalenedione

Three novel naphthoquinone-based heterocyclic pigments, 2-methyl-3-[(1-methyl-1H-imidazol-2-yl)thio-1,4-naphthalenedione, (4-methyl-4H-1,2,4-triazol-3-yl)thio-1,4-naphthalenedione, and (1-methyl-1H-tetrazol-5-yl)thio]-1,4-naphthalenedione, are synthesized, and their optical properties in both solution and solid states are investigated. Depending on the heteroarylthio ring in the pigment, variation in optical properties is observed, e.g. characteristic colours for each pigment in the solution and solid states. The achiral pigment containing the 1-methyl-1H-tetrazol-5-yl ring exhibits a chiral space group and a CD signal in the solid state.     

Total synthesis of chrysamide B

We report an efficient synthesis of the dimeric trans-epoxyamide chrysamide B, recently isolated from the deep-sea-derived fungus Penicillium chrysogenum SCSIO41001. Our synthetic strategy exploits a convergent approach using solid-phase peptide synthesis for the piperazine core and a Sharpless-Katsuki epoxidation to prepare the chiral epoxyacid. The double amidation final step provides chrysamide B that was thoroughly characterized with all spectra identical to those of the natural sample. The approach was devised to facilitate the preparation of a library of analogs of chrysamide B.     

Diastereoselective hydrogenation of α,β-unsaturated but-2-enamides to access the chiral 3-(p-tolyl) butanoic acids

An alternative methodology for the synthesis of chiral 3-(p-tolyl) butanoic acids is presented. This was accomplished through the diastereoselective hydrogenation reaction of different chiral N-3-(p-tolyl) but-2-enamides, using Pd/C in EtOH, to produce the corresponding chiral N-3-(p-tolyl) butanamides with high chemical yields and moderate diastereomeric ratios. Removal of the chiral auxiliary from N-3-(p-tolyl) butanamides gave the respective enantiomerically pure acids.     

Enantioselective rhodium-catalyzed hydroacylation to access the four stereoisomers of anti-rodent difenacoum

An efficient asymmetric synthesis of the four stereoisomers of difenacoum, an anticoagulant currently used as a rodenticide in racemic form, is performed using a key step of rhodium catalyzed enantioselective intramolecular hydroacylation. Optimization of the last step, condensation of 4-hydroxycoumarin with chiral 3-([1,1′-biphenyl]-4-yl)-1,2,3,4-tetrahydronaphthalen-1-ol, is also discussed. After chromatographic separation of the cis and trans diastereoisomers, the four stereoisomers were all obtained with excellent enantioselective and diastereoselective excess (ee ≈ 96% and de >96%).     

超分子作用构筑具有高光学不对称性的表面等离子纳米粒子手性组装体

《Science》杂志最近刊发了吉林大学刘堃团队关于手性纳米材料研究的重要进展: 通过超分子作用诱导金纳米棒与人胰岛淀粉样多肽之间共组装, 构筑具有类似于手性液晶结构的纳米螺旋超结构. 与单独的金纳米棒相比, 长程有序的纳米螺旋结构的手性各向异性因子(g-factor)提高了4600倍, 高达0.12. 该工作在液晶与手性无机纳米结构间建立了联系, 为构筑有机-无机光学活性结构提供了统一的设计原则, 并为淀粉样类疾病药物在复杂生物介质中的筛选开发了新方法.     

Electrochemical Recognition of Chiral Molecules with Poly(4‐bromoaniline) Modified Gold Electrode

A poly(4‐bromoaniline) (PBA) film is electrochemically synthesized on a gold electrode for the recognition of amino acids enantiomers. Scanning electron microscopy measurements show that the porous PBA films are made up of nano‐ribbons. At the PBA modified Au electrode differential pulse voltammograms of L ‐ and D ‐glutamic acids not only have very different current densities, but also produce different waveforms, providing an intuitive way to differentiate the two chiral molecules. Similar results are obtained in analyzing L ‐ and D ‐aspartic acids. Control experiments suggest that the observed sensing behavior arises from synergistic interactions between Au and the PBA film, where polymerization at the meta‐position creates a steric structure needed for differentiating chiral molecules.     

Synthesis and Reaction of Some Indenopyridine and Thieno[2,3-b]Indeno[2,1-e]Pyridine Derivatives

Synthesis of indenopyridine-2-thione derivatives 6a-e via reaction of compound 1 with thioamides 2a-e in good yields. Several thieno[2,3-b]indeno[2,1-e]pyridine 9a-e have been synthesized. Some of them was used as a key intermediate in synthesis of 10-12. On the other hand, compound 1 reacted with various reagents to yield 16, 19, 21-24.     

Ionic Copolymerizations

It is shown that for the reported instances of “random” copolymerization in cationic systems, N values related to relative reactivity may be derived for monomers. The N values approximate reasonably well the values of the function, exp (-e) - 1.23, where e is the polarity e of the Q-e scheme for free-radical copolymerizations.

In a recent paper [1] it was shown that for the reported instances [2-4] of “random” copolymerization (r₁,r₂ = 1) in cationic systems, N values, related to relative reactivity, might be derived for monomers, employing styrene as a base monomer (N = 1). Thus d[M₁]/d[M₂] =N₁[M₁]/N₂[M₂] (1)

where d[M₁]/d[M₂] is the instantaneous copolymer composition, [M₁]/[M₂] is the ratio of unreacted monomers, and N₁ and N₂ are parameters related to general monomer reactivity of monomers 1 and 2, respectively, in cationic copolymerization.     

Elucidation of chiral recognition processes of macrocyclic antibiotic vancomycin

A theoretical investigation was carried out on the retention and separation of enantiomeric molecules including nonsteroidal anti-inflammatory drugs, anti-neoplastic compounds and N-derivatized amino acids by capillary electrophoresis using macrocyclic antibiotics, a new class of chiral selectors, as stationary phase. Firstly docking methods were used to study the enantiorecognition in chiral electrophoresis. The molecular dynamics simulations of the two diastereoisomer complexes were then performed in order to understand how these antibiotics recognize the enantiomers. Another approach was applied in this study to establish a quantitative structure-enantioselectivity relationship (QSER) model, able to describe the resolution of a series of chiral compounds in capillary electrophoresis using vancomycin as the resolving agent.