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1.
Recent advances in organocatalytic asymmetric synthesis of polysubstituted pyrrolidines 总被引:1,自引:0,他引:1
Chiral substituted pyrrolidines are important N-heterocyclic structural motifs, existing in many natural products, drug candidates, ligands and organocatalysts. We summarise herein the recent (between January 2010 and July 2013) developments on synthesising the chiral polysubstituted pyrrolidines through asymmetric organocatalysis. The organocatalytic strategies for constructing the pyrrolidine scaffolds can be divided into one-step and sequential approaches, respectively. The straightforward one-step approach is mainly the [3+2] cycloaddition based on the iminium activation, chiral Brønsted acid catalysis, bifunctional organocatalysis and SOMO activation. In the sequential approach (multi-step or one-pot reactions), the primary construction of chiral linear precursors is followed by the sequential cyclisation. Other important strategies, such as the organocatalytic bromoaminocyclisation were also described. These organocatalytic strategies have enriched the synthetic chemistry of chiral pyrrolidines, especially towards the target-, diversity- and application-oriented synthesis. New organocatalytic approaches are thus expected for the facile construction of polysubstituted pyrrolidines with well-controlled stereochemistry and for the practical synthesis of pyrrolidine-related natural alkaloids, drug candidates and functional proline derivatives. 相似文献
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A number of 1,3-disubstituted derivatives are associated with various types of biological activity [1]. Some thioureas are useful as herbicides, insecticides and plant-growth regulators. Treatment of acylisothiocyanates, prepared from aroyl chlorides (0.0431mol) and potassium thiocyanate (33ml ofa 33% KSCN solution) using tetrabutylammonium bromides as a catalyst, were treated with aniline to yield the corresponding thioureas. However, probable hydrolysis of the aroyl chlorides led to decreased yields. The reaction of acid chlorides with different phenylthioureas or N1-acetyl-N3-arylthioureas requires high temperature and long reaction times. None of the other reported methods proved satisfactory. As a continuation of our earlier work on the biological activity of these compounds, [2-5] we now report acid chlorides are quantitatively converted to the acylisothiocyanates under solid-liquid phase-transfer conditions using PEG-400 as the catalyst. Treatment of these isothiocyanates with polymethylenediamines provides compounds 3 in high yields (scheme 1). The results were summarized in table 1. 相似文献
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The use of natural compounds in the preparation of new materials can improve the biocompatibility of the materials and avoid
any potential toxicity of the degradation products when used for biomedical applications. Bile acids are amphiphilic molecules
biosynthesized in the liver. They are used to prepare various polymers and oligomers. These polymers made of bile acids are
promising materials in both biomedical and pharmaceutical fields. 相似文献
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在北京谱仪(BES)原有模拟程序框架下,建立了适用于J/ψ,ψ‘衰变到VP和PP模式,以及ψ‘→π^ π^-/J/ψ‘衰变到J/ψ衰变到VP和PP模式的事例产生器,考虑了相应的角分布,为J/ψ,ψ‘物理的研究提供了方便,在ψ‘→γη,γη‘,ωπ^0,π^ π^-,K^ K^-等分支比的测量中,这一事例产生器可用于选择效率的确定和本底估计。 相似文献
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Steady structures originating from dynamic self-assembly have begun to show their advantages in new generation materials, and pose challenges to equilibrium self-assembly. In view of the important role of confinement in self-assembly, here, we propose a new type of confinement leading to dynamic steady structures, which opens a new window for the conventional confinement.In our model, we consider the self-assembly of ellipsoids in 2D circular confinement via the boundary performing periodically stretching and contracting oscillation. Langevin dynamics simulations reveal the achievement of non-equilibrium steady structures under appropriate boundary motions, which are novel smectic structures with stable topological defects. Different from the confinement with a static boundary, ellipsoids close to the boundary have variable orientations depending on the boundary motion.Order-order structural transitions, accompanied by the symmetry change and varied defect number, occur with the change of oscillating amplitude and/or frequency of the boundary. Slow and fast dynamics are distinguished according to whether structural rearrangements and energetic adjustment happen or not. The collective motion of confined ellipsoids, aroused by the work performed on the system, is the key factor determining both the structure and dynamics of the self-assembly. Our results not only achieve novel textures of circular confined liquid crystals, but also inspire us to reconsider the self-assembly within the living organisms. 相似文献
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基于胆酸的功能性分子的研究进展 总被引:1,自引:0,他引:1
胆酸是存在于人和动物体内的天然分子,由胆固醇在肝脏中合成.其结构上具有亲水的一面和憎水的一面,以其作为结构单元可以合成各种各样的功能性分子.这些分子因其独特的物理化学特性,被广泛应用到化学、生物医学等领域.本文回顾了近几年来国内外研究人员以胆酸为结构单元合成的高分子和低聚物及这些分子在生物医用材料方面的应用. 相似文献
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Cao XueLei Jiang WeiChun Meng Bin Zhang WanChang Luo Tao Yang Sheng Zhang ChunLei Gu YuDong Sun Liang Liu XiaoJing Yang JiaWei Li Xian Tan Ying Liu ShaoZhen Du YuanYuan Lu FangJun Xu YuPeng Guan Ju Zhang ShuangNan Wang HuanYu Li TiPei Zhang ChengMo Wen XiangYang Qu JinLu Song LiMing Li XiaoBo Ge MingYu Zhou YuPeng Xiong ShaoLin Zhang Shu Zhang YongJie Cheng ZeHao Zhang Fei Li MaoShun Liang XiaoHua Gao Min Yang EnBo Liu XiaoHang Liu HongWei Yang YiJung Zhang Fan 《中国科学:物理学 力学 天文学(英文版)》2020,63(4):1-19
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A series of 1,4-disubstitued thiosemicarbazides and their related heterocyclic compounds have been found to possess important biological activities[1]. Some thiosemicarbazides have been found to be useful as herbicides, insecticides and plant-growth regulators [1]. In view of these and in continuation of our earlier work on the synthesis and biological activity of thiosemicarbaides derivatives [2], we now report a convenient and efficient method for the preparation of thiosemicarbazides derivatives of 2-ethoxybenzoic acid under the condition of solid-liquid phase transfer catalysis using PEG-400 as the catalyst. 相似文献
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