MOFs材料在不对称催化中的应用

目前金属-有机框架（MOFs）材料已经在多个领域得到了发展,其中包括气体吸附、催化等方向.近年来,由于不对称催化的快速发展,手性MOFs材料在立体选择性催化中也得到了研究者们的广泛关注.手性MOFs材料具有很强的手性识别能力,并且由于有机配体的可修饰性,使MOFs材料具有更多的活性催化位点.文章详细介绍了手性MOFs材料的分类、合成思路,及其在不对称催化应用中的最新进展.     

Application of modified amino acid as a chiral building block in asymmetric synthesis

Phenylglycine 1 as a representative of natural resourceful α-amino acid was modified by reduction and protection of functional group to afford the amino alcohol as a chiral building block 3. A new chiral compound, the chiral building block/spiro-cyclopropane derivative containing four stereogenic centers, compound 7, has been obtained in 52% yield with de⩾98% via the tandem double Michael addition/internal nucleophilic substitution under mild condition of 5-l-menthyloxy-3-bromo-2-(5H)-furanone 4 with the nucleophilic reagent, the amino alcohol 3. The new chiral compound 7 is identified on the basis of its analytical data and spectroscopic data, such as UV, IR,¹H NMR,¹³C NMR, MS and elementary analysis. The absolute configuration of the interesting spiro-cyclopropanes 7 was established by X-ray crystallography. This result can provide new route and method for the introduction of chiral building block and the important synthetic strategy in synthesis of some complex molecules containing spiro-cyclopropane skeleton with multiple chiral centers and the study of their biological activity.     

手性稀土配合物在不对称催化应用中的研究进展

近年来随着光学纯化合物需求的不断增大,不对称催化逐渐成为科学研究的前沿领域之一.稀土元素则是由周期表中ⅢB族Sc、Y和镧系元素(La~Lu)的17种元素组成.相比其他过渡金属与各类配体轨道间的作用,稀土金属有其独特之处,因此,近年来手性稀土配合物在不对称催化领域的应用,也逐渐引起人们的重视.根据各类手性配体中所含配位原子的不同,对手性稀土配合物的类型及相关的不对称催化反应作简要综述.     

Natural products as inspiration for the development of asymmetric catalysis

Biologically active natural products often contain particularly challenging structural features and functionalities in terms of synthesis. Perhaps the greatest difficulties are those caused by issues of stereochemistry. A useful strategy for synthesizing such molecules is to devise methods of bond formation that provide opportunities for using enantioselective catalysis. In using this tactic, the desire for a particular target structure ultimately drives the development of catalytic methods. New enantioselective catalytic methods contribute to a greater fundamental understanding of how bonds can be constructed and lead to valuable synthetic technologies that are useful for a variety of applications.     

Green chemistry: C-C coupling and asymmetric reduction by innovative catalysis

A catalytic method has been developed, which allows aryl halides to couple with various electron-rich olefins to give 1,1＇-substituted olefins. The palladium-catalysed coupling in ionic liquid solvent proceeds with high efficiency and remarkable regioselectivity without the need for any costly or toxic halide scavengers. Parallel to this, an environmentally-appealing method for the asymmetric reduction of ketones has been established, with which a variety of chiral alcohols can be accessed with high enantioselectivity in water with no need for any organic solvents. The same chemistry has been explored for the reduction of aldehydes, which is shown to be fast and highly chemoselective. These methods add new tools to the armoury of synthetic chemists.     

Green chemistry: C-C coupling and asymmetric reduction by innovative catalysis

A catalytic method has been developed, which allows aryl halides to couple with various electron-rich olefins to give 1,1’-substituted olefins. The palladium-catalysed coupling in ionic liquid solvent proceeds with high efficiency and remarkable regioselectivity without the need for any costly or toxic halide scavengers. Parallel to this, an environmentally-appealing method for the asymmetric reduction of ketones has been established, with which a variety of chiral alcohols can be accessed with high enantioselectivity in water with no need for any organic solvents. The same chemistry has been explored for the reduction of aldehydes, which is shown to be fast and highly chemoselective. These methods add new tools to the armoury of synthetic chemists.     

Nucleic acid sequence-based amplification.

Nucleic acid sequence-based amplification (NASBA) is a primer-dependent technology that can be used for the continuous amplification of nucleic acids in a single mixture at one temperature.     

高效液相色谱测量啤酒中氨基酸

本文建立了测量啤酒氨基酸的有效方法,该方法使用高效液相色谱采用梯度洗脱测定啤酒中的氨基酸,结果回收率为99.2%,RSD为2.01%,表明本方法精密度高,稳定性好,可作为检测啤酒氨基酸有效方法。     

Thermodynamic control by frequent quantum measurements

Heat flow between a large thermal 'bath' and a smaller system brings them progressively closer to thermal equilibrium while increasing their entropy. Fluctuations involving a small fraction of a statistical ensemble of systems interacting with the bath result in deviations from this trend. In this respect, quantum and classical thermodynamics are in agreement. Here we predict a different trend in a purely quantum mechanical setting: disturbances of thermal equilibrium between two-level systems (TLSs) and a bath, caused by frequent, brief quantum non-demolition measurements of the TLS energy states. By making the measurements increasingly frequent, we encounter first the anti-Zeno regime and then the Zeno regime (namely where the TLSs' relaxation respectively speeds up and slows down). The corresponding entropy and temperature of both the system and the bath are then found to either decrease or increase depending only on the rate of observation, contrary to the standard thermodynamical rules that hold for memory-less (Markov) baths. From a practical viewpoint, these anomalies may offer the possibility of very fast control of heat and entropy in quantum systems, allowing cooling and state purification over an interval much shorter than the time needed for thermal equilibration or for a feedback control loop.     

Structural insights into amino acid binding and gene control by a lysine riboswitch

In bacteria, the intracellular concentration of several amino acids is controlled by riboswitches. One of the important regulatory circuits involves lysine-specific riboswitches, which direct the biosynthesis and transport of lysine and precursors common for lysine and other amino acids. To understand the molecular basis of amino acid recognition by riboswitches, here we present the crystal structure of the 174-nucleotide sensing domain of the Thermotoga maritima lysine riboswitch in the lysine-bound (1.9 ?ngstr?m (A)) and free (3.1 A) states. The riboswitch features an unusual and intricate architecture, involving three-helical and two-helical bundles connected by a compact five-helical junction and stabilized by various long-range tertiary interactions. Lysine interacts with the junctional core of the riboswitch and is specifically recognized through shape-complementarity within the elongated binding pocket and through several direct and K(+)-mediated hydrogen bonds to its charged ends. Our structural and biochemical studies indicate preformation of the riboswitch scaffold and identify conformational changes associated with the formation of a stable lysine-bound state, which prevents alternative folding of the riboswitch and facilitates formation of downstream regulatory elements. We have also determined several structures of the riboswitch bound to different lysine analogues, including antibiotics, in an effort to understand the ligand-binding capabilities of the lysine riboswitch and understand the nature of antibiotic resistance. Our results provide insights into a mechanism of lysine-riboswitch-dependent gene control at the molecular level, thereby contributing to continuing efforts at exploration of the pharmaceutical and biotechnological potential of riboswitches.     

杂多酸催化合成乙酸乙酯

研究了杂多酸催化乙酸和乙醇合成乙酸乙酯的反应,探讨了原料配比,反应时间,催化剂用量等参数对酯化率的影响,在适宜工艺条件下,酯化率高达９４．８％,催化剂的重复使用表明,杂多酸是合成乙酸乙酯的适宜催化剂。     

PITC derivatives in amino acid analysis

Refined methods for separating PTC-amino acids on reverse phase columns may pose a challenge to traditional ion exchange techniques.     

不对称连续梁桥施工控制中的自适应控制方法

本文针对常用连续梁桥施工控制方法在不对称连续梁桥施工控制中的局限，引入自适应控制理论．通过对结构参数进行有效识别，降低计算模型与实际结构之间的误差，使不对称连续梁桥的合龙精度与主梁线形均较佳．     

相转移催化氧化合成对硝基苯甲酸

考察了以KMnO4为氧化剂,相转移催化氧化合成对硝基苯甲酸的有关影响因素．结果表明十六烷基三丁基溴化磷的催化效果最好,收率达76.6％;以价廉易得的季铵盐A-1为氧化剂,能进行缓和反应,且收率提高,达74.3％．此外,KMnO4的自身分解严重影响它对底物的氧化作用,由此确定反应以在中性介质中发生为宜．     

Thermodynamic analysis of the compositional control of inclusions in cutting-wire steel

Data from a thermodynamic database and the calculation software FactSage were used to investigate the phase diagrams of the MnO-CaO-SiO₂-Al₂O₃ system in cutting-wire steel and the effects of oxide components on the low-melting-point (LMP) zone in the corresponding phase diagrams. Furthermore, the activities of oxide components in the quaternary system at an Al₂O₃ content of 25wt% were calculated. The contents of dissolved [Al] and [O] in liquid steel in equilibrium with LMP inclusions in the MnO-CaO-SiO₂-Al₂O₃ system were optimized. The results show that the MnO-CaO-SiO₂-Al₂O₃ system possesses the largest LMP zone (below 1400°C) at an Al₂O₃ content of 25wt% and that the CaO content should be simultaneously controlled in the range of 40wt% to 45wt%. The activities of the oxide components CaO, MnO, and SiO₂ should be restricted in the ranges of 0 to 0.05, 0.01 to 0.6, and 0.001 to 0.8, respectively. To obtain LMP inclusions, the [Al] and [O] contents in cutting-wire steel must be controlled within the ranges of 0.5×10-6 to 1.0×10-5 and 3.0×10-6 to 5.0×10-5, respectively.     

金属离子与氨基苯甲酸及吡啶单羧酸配合物的研究

合成了２１种金属离子Ｌａ（Ⅲ）Ｃｕ（Ⅱ）Ｎｉ（Ⅱ）和Ｃｏ（Ⅱ）与氨基苯甲酸及吡啶意境羧酸的化合物，其中１４种是尚未报道过的新化合物，通过元素分析，红外光谱、Ｘ－射线粉末衍射，ＴＧ－ＤＴＧ等表征了产物的结构特征和热分解过程，表明，配体酸中氨基和羧基的相对位置影响着配体酸与金属离子的反应能力和反应产物的稳定性。     

鲈鱼肌肉氨基酸含量及组成的分析

用柱后衍生高效液相色谱技术测定鲈鱼肌肉氨基酸的含量,分析了其氨基酸的种类及比例,并对它的营养成分进行了评价.结果表明鲈鱼肌肉中氨基酸总量比例为1.308%,其中呈味氨基酸含量高达氨基酸总量的42.5%.