Nouvelles réactions d'halogenopyridines avec le n-butyllithium. proposition d'un mécanisme par métallation et migration du brome

The reaction of n-butyllithium with 2-bromo-3-chloro pyridine as a function of temperature, the amount of n-butyllithium used and the order of introduction of the reagents, gives, besides bromine-lithium exchange, an unexpected métallation of the pyridine ring and bromine migration from the 3 to 4 position. A novel mechanism to explain this and the similar behavior of 3-bromo-2-fluoro pyridine with n-butyllithium is proposed.     

Control on Crystal Forms of Ultrafine Barium Carbonate Particles and Study on its Mechanism

1 INTRODUCTION Barium carbonate is one of the important che- mical materials as well as one of the most important barium salts. Its application covers multitudinous in- dustries and fields such as building material, meta- llurgy, electron, chemical industry and so on[1]. With the fast development of science and technology, it is becoming more and more demanding with barium carbonate’s quality, and more and more scientific workers do researches on the control of Barium car- bonate’s crys…     

Theoretical study of structure and vibrational properties of MgnOn (n = 3–10) clusters

The structure and harmonic vibrations of Mg_nO_n (n = 3–10) clusters have been investigated using density functional theory. All structures are found to be cumulenic D_nh rings (equal bonds, alternating angles), with one intense out‐of‐plane mode and three infrared (IR)‐active degenerate modes, of which the highest one is extremely intense and increases asymptotically to 1000 cm^?1 for n = 10 at the B3LYP/6‐311++G(2d,2p) level. Comparisons with C_2n clusters show that B_nN_n and Be_nO_n clusters, the structure and bonding type for the Mg_nO_n clusters are consistent with those of the C_2n (n = 3, 5, 7,…) clusters B_nN_n(n = 3–10) and Be_nO_n(n = 3–10) clusters. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Direct observation of a series of non-covalent complexes formed by phosphorylated flavonoid-protein interactions through electrospray ionization tandem mass spectroscopy

In the work described in this paper, 7-hydroxyflavone and chrysin were phosphoylated by a modified Atheron-Todd reaction. Three new phosphorylated flavonoids (PF) were obtained, and the structures of the target products were determined by X-ray and NMR data and electrospray ionization (ESI) tandem mass spectroscopy (MS). The mixed solutions of the phosphorylated flavonoids and different proteins such as insulin, lysozyme, and cytochrome c were injected in an ion trap mass spectrometer. The results show that all the phosphorylated flavonoids could form non-covalent complexes with the proteins mentioned above, while non-covalent complexes were not detected from the mixed solution of the chrysin or 7-hydroxyflavone with proteins. The research shows that the phosphorylated flavonoids could enhance the interaction with proteins. It may imply their important role in biological processes. The method described in this paper provides us additional information for studying such interactions for phosphorylated flavonoids in this important field.     

Metallation of pyridines and quinolines in the presence of a remote carboxylate group. New syntheses of heterocyclic quinones

2-(3- and 2-Pyridylcarbonyl)benzoic acids (2,3), 2-(2-pyridylcarbonyl)thiophene-3-carboxylic acid (6), 2-(3-quinolylcarbonyl)benzoic acid (10), and most of the corresponding esters (compounds 1,7 and 9 ) are readily synthesized and involved in a deprotonation-condensation sequence. Biologically active aza-anthraquinones such as benzo[g]isoquinoline-5,10-dione (2-azaanthraquinone, 4 ) and benzo[g]quinoline-5,10-dione (1-azaanthraquinone, 5) are prepared using the strategy. Extension to other heterocyclic quinones such as thieno[3,2-g]quinoline-4,9-dione (8) and benzo[j]phenanthridine-7,12-dione (11) is also investigated.     

双核钴卟啉/DMF体系的吸氧热力学研究

关于单核金属卟啉体系的吸氧热力学已有广泛的研究．七十年代末至八十年代初，报导了一类面对面双时批双核钴的双氧配合物，根据ESR谱，认为存在Co-O-Co的超氧桥式结构．关于Co：02＝1：1的双核钴双卟啉配合物的吸氧热力学，迄今未见报导．本工作用电子光谱法研究了一种由十个碳原子的脂肪二酰胺链连接两个四苯基卟啉的双核钴（Ⅱ）配合物在DMF溶液中与双氧的可逆结合作用，测定了吸氧热力学数据，用ESR谱法研究了钻离子与双氧的结合方式．1实验部分五·五样品和试剂双核钴（11）双环叶琳，CO。diTPP（diAMCs）的合成见文献间，其…     

复盐K2Mg(IO3)4 2H2O的热力学性质

由于碱金属碘酸盐晶体在电学性质的利用上有重要价值和发现碘酸盐晶体非线性性质［‘］，七十年代以来，Vinogradov等对碘酸盐-碘酸-水系统发生了极大的兴趣，做了大量研究工作［’－‘］，发现在碘酸盐．碘酸一水三元体系里有碘酸盐复盐K2M（IO3）4·2H2O（M＝Mn2＋、Co2＋、N     

Application of preparative high-speed counter-current chromatography for isolation and separation of schizandrin and gomisin A from Schisandra chinensis

Following an initial cleaning-up step on the D101 macroporous resin, a preparative high-speed counter-current chromatography (HSCCC) with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (1:0.9:0.9:1, v/v) was used to isolate and separate schizandrin and gomisin A from Schisandra chinensis. A total of 107 mg schizandrin and 36 mg gomisin A with purities of 99.5% and 99.1% were obtained from 400 mg crude extract in one-step elution and less than 3 h, and the structure identification was performed by UV, IR, MS, 1H NMR and 13C NMR.     

Inhibitory effects of schisantherin F from Schisandra propinqua subsp. sinensis on human melanoma A375 cells through ROS-induced mitochondrial dysfunction and mitochondria-mediated apoptosis

Abstract

Schisandra propinqua subsp. sinensis is a traditional medicinal plant used in Chinese folk medicine. Melanoma is the most dangerous form of skin cancer. To discover bioactive phytochemicals for preventing human melanoma, we have investigated the inhibitory effects of schisantherin F in Schisandra propinqua subsp. sinensis on human melanoma A375 cells and relevant mechanisms. The results showed that schisantherin F can inhibit A375 cells through inducing apoptosis. Further investigations have demonstrated schisantherin F attenuated the overproduction of ROS, depolarization of MMP, and mPTP opening. Meanwhile, schisantherin F inhibited the activity of Caspase-3 and up-stream Caspase-9, down-regulated Bcl-2 and up-regulated Bax. These findings propose the inhibitory mechanisms of schisantherin F in A375 cells include induction of mitochondrial dysfunction and mitochondria-mediated apoptosis.     

五配位阴离子型有机锡化合物的合成及[C5H5NH][Ph2Sn(μ2-SCH2COO)Cl]和[CH3PhNH2][Ph2Sn(μ2-SCH2COO)Cl]晶体结构

近年来，由于离子型有机锡化合物的分子结构的多样性、较好的生物活性以及在有机合成上的应用，而引起广泛注意，前文报道了Ph3SnCl与HSCH2COOH在有机胺存在下发生Sn-Ph键断裂，生成二苯基锡的离子型有机锡化合物，本文用Ph2SnCl2与HSCH2COOH在有机胺存在下，采用同样的反应条件Sn-Ph键不再断裂，得到与前文结构相类似的化合物，反应方程式如下：