Baeyer-Villiger单加氧酶在有机合成中的应用

综述了Baeyer-Villiger单加氧酶在有机合成中的应用.较之传统的化学反应, 氧化酶催化剂反应有较好的选择性、可控性和经济性. 环己酮加氧酶是一种还原型辅酶I (NADPH)依赖型氧化酶, 是最早被报道能够催化Baeyer-Villiger氧化的酶. 这些重要反应产生了合成化学家很感兴趣的扩环产物. 环己酮加氧酶也是有用的生物催化剂, 由于辅酶再生的问题已被工程菌克服了, 所以能像全细胞催化剂那样使用. 对酮包括杂环酮进行Baeyer-Villiger氧化和动态动力学拆分, 放大这种反应作为合成路线是很有前途的.     

Influence of amino acid side chain packing on Fe-methionine coordination in thermostable cytochrome C

Paramagnetic NMR and optical studies of the oxidized forms of mesophile Pseudomonas aeruginosa cytochrome c(551) and its quintuple mutant (F7A/V13M/F34Y/E43Y/V78I), and thermophile Hydrogenobacter thermophilus cytochrome c(552) demonstrated that the amino acid side chain packings in the protein interior influence the coordination bond between the heme iron and the axial methionine in the proteins. The strength of heme axial coordinations was found to correlate with the overall protein thermostability.     

Controlled ring‐opening polymerization of propylene oxide catalyzed by double metal‐cyanide complex

A double metal‐cyanide catalyst based on Zn₃[Co(CN)₆]₂ was prepared. This catalyst is very effective for the ring‐opening polymerization of propylene oxide. Polyether polyols of moderate molecular weight having low unsaturation (<0.015 meq/g) can be prepared under mild conditions. The molecular weight of polymer is entirely controlled by a reacted monomer‐to‐initiator ratio. The polymers prepared with stepwise addition of monomer exhibit a narrower molecular weight distribution as compared with those prepared with one‐step addition of monomer. Various compounds containing active hydrogen, except basic compounds and low‐carbon carboxylic acid, may be used as initiators. The reaction rate increases with increasing catalyst amount and decreases with rising initiator concentration. Polymerization involves a rapid exchange reaction between the active species and the dormant species. It was also proven that, to a certain extent, the chain termination of this catalytic system is reversible or temporary. ¹³C NMR analysis showed that the polymer has a random distribution of the configurational sequences and head‐to‐tail regiosequence. It is assumed that the polymerization proceeds via a cationic coordination mechanism. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1142–1150, 2002     

Electronic gel protein transfer and identification using matrix-assisted laser desorption/ionization-mass spectrometry

An electronic protein transfer technique is described for achieving the rapid and efficient recovery of sodium dodecyl sulfate (SDS)-protein complexes from polyacrylamide gels. This process involves the use of small-dimension capillaries in physical contact with a resolved protein band within the polyacrylamide gel, providing a large potential drop and high electric field strength at the capillary/gel interface. Several factors controlling the electronic protein transfer, including the applied electric field strength, the electrophoresis buffer concentration, and the capillary dimension, are studied to further enhance the use of field-amplification for sample stacking of extracted SDS-protein complexes. As a result of sample stacking, the extracted proteins from a 50 ng gel loading are present in a narrow ( approximately 80 nL) and highly concentrated (0.46 mg/mL or 3.3 x 10(-5) M for cytochrome c) solution plug. Three model proteins with molecular mass ranging from 14 kDa (cytochrome c) to 116 kDa (beta-galactosidase) are stained by Coomassie blue and electrophoretically extracted from gels with protein loadings as low as 50 ng. The capillary format of the electronic protein transfer technique allows direct deposition of extracted proteins onto a matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) target. Various matrices and solvent compositions are evaluated for the analysis of extracted and concentrated SDS-protein complexes using MALDI-MS. The electronic protein transfer technique, when operated under optimized conditions, is demonstrated for the effective (>70% recovery), speedy (less than 5 min), and sensitive MS identification of gel resolved proteins (as low as 50 ng).     

Synthesis of hollow spherical silica with MCM-41 mesoporous structure

Hollow spherical mesoporous silica was synthesized by using sodium silicate as a precursor and a low concentration of cetyltrimethylammonium bromide (CTAB) (0.154 mol dm^–3). The resulting hollow spherical particles were characterized with scanning electron microcopy (SEM), small-angle X-ray diffraction (SXRD), transmission electron microscopy (TEM), and N₂ gas adsorption and desorption techniques. The results showed that regular spherical mesoporous silica could be obtained only if the molar ratio of propanol to CTAB was in the range of approximately 8:1–9:1. The spherical particles were hollow (inside), and the shell consisted of smaller particles with a pore structure of hexagonal symmetry. With an increase of the molar ratio of propanol to CTAB, the distance (a value) between centers of two adjacent pores increased, and the pore structure of mesoporous silica became less ordered. N₂ adsorption–desorption curves revealed type IV isotherms and H1 hysteresis loops; with an increase of the molar ratio of propanol to CTAB, the pore size with Barrett–Joyner–Halenda (BJH) diameter of the most probable distribution decreased, but the half peak width of the pore size distribution peak increased     

Highly Regioselective Sequential 1,1‐Dihydrosilylation of Terminal Aliphatic Alkynes with Primary Silanes

A regioselective double 1,1‐hydrosilylation of terminal aliphatic alkynes with primary silanes catalyzed by one cobalt catalyst has been developed. gem‐Bis(dihydrosilyl)alkanes containing four silicon‐hydrogen bonds are efficiently constructed in an atom‐economical manner. Tolerated substrates include simplest alkyne‐ethyne, a complicated drug derivative and various functionalized terminal aliphatic alkynes. Asymmetric approach using two catalysts is achieved with excellent enantioselectivities to access corresponding chiral products. The transformations of Si—H bonds into Si—C, Si—O, and Si—F bonds and the synthesis of enantioriched α‐hydroxysilane show synthetic utility.     

A Facile Method of Synthesis of a Calix[4]arene Amide and the Crystal Structure of a Self-assembled Calix[4]arene Amide via van Der Waals Interaction

A new facile method of synthesis of calix[4]arene amide via the aminolysis of the calix[4]arene esters was reported. One ethyl ester of the compound (2) was aminolysized byn-butylamine. The crystal structure of compound (1)shows that one ethyl ester of compound (1) enters into thecavity of another compound (1) forming a long chainhost-guest supramolecule. From the 2D NMR data, the compound(1) does not assemble in THF or CHCl₃ solution. The CH- interaction and crystallization energy might be theimportant driving forces for forming the self-assembledcalix[4]arene.     

水热一步法合成Ti-SBA-15分子筛及其催化性能研究

采用钛酸丁酯和乙酰丙酮作用后的产物作为钛的前驱体，水热法一步合成出了 Ti-SBA-15分子筛。通过X射线衍射、N2气吸附脱附、紫外—可见漫反射等表征手段 ，证明在Si/Ti＝50，25，20时，钛原子成功地取代了SBA-15中的硅原子而没有改 变SBA-15高度有序的介孔二维六角结构，其中钛全部以四配位状态存在，而且高度 分散。当Si/Ti＝12．5时，钛的分散度降低，部分钛聚集生成二氧化钛。与用两步 法合成的Ti-SBA-15比较，一步法合成的Ti-SBA-15中钛分散度好，添加量高，对催 化氧化环己烯有较高的催化活性。对一步法和两步法合成Ti-SBA-15的机理以及相 应产物在结构以及催化活性上的差异进行了探讨。     

超分子砌块间苯二酚杯芳烃的研究进展

间苯二酚杯芳烃是一类以间苯二酚为单元的杯芳烃, 作为新一代超分子砌块, 在分子催化、分子识别、超分子自组装、晶体工程和纳米材料等方面都获得了广泛的应用, 已成为当今化学研究的新热点. 综述了间苯二酚杯芳烃的功能化修饰及其应用新进展.     

高中有机化学教材“烃类化合物”的国际比较研究

基于闫春更等建立的二维度四指标教材难度微观评价模型，重点对中国、美国、新加坡、澳大利亚、日本、英国的高中化学教材中"烃类化合物"内容的整合广度、表征深度进行测评和比较。研究发现6国教材内容的整合广度整体上差异不大，但其表征深度差异明显；美国教材注重学生认识物质的思路和方法的渗透，日本教材注重基本知识与技能的掌握，中国教材将概念诠释与样例分析相融合；英国、新加坡、美国教材注重情境推理或比较等信息处理策略的运用，对学习者学习的引导性较强。