Recent Advances in Divergent Synthetic Strategies for Indole-Based Natural Product Libraries

Considering the potential bioactivities of natural product and natural product-like compounds with highly complex and diverse structures, the screening of collections and small-molecule libraries for high-throughput screening (HTS) and high-content screening (HCS) has emerged as a powerful tool in the development of novel therapeutic agents. Herein, we review the recent advances in divergent synthetic approaches such as complexity-to-diversity (Ctd) and biomimetic strategies for the generation of structurally complex and diverse indole-based natural product and natural product-like small-molecule libraries.     

钌联吡啶络合物与脱氧核糖核酸分子相互作用的荧光光谱研究与分析应用

合成了2苯基(4溴)咪唑[f]邻菲咯啉(简称PIP(Ⅲ)新的配体及〔Ru(bpy)_2PIP(Ⅲ)]~(2+)新的络合物,用荧光光谱研究了络合物与小牛胸腺DNA分子的结合情况,在 pH7.4,络合物与DNA作用后,在587nm(λ_(ex)=471nm)产生很强的荧光峰,其发光强度与DNA浓度呈线性关系;线性范围0～1.2mg/L;检测限(3a(?))为2.8mg/L.该方法具有较高灵敏度和准确度,对合成样品测定,结果令人满意.     

镍基甲烷化催化剂中的助剂作用 Ⅱ重稀土氧化物添加剂的结构效应和电子效应

应用ＢＥＴ、气相色谱、红外光谱、竞争加氢反应和ＸＰＳ等方法,在以前工作的基础上继续考察了Ｙ２Ｏ３、Ｓｍ２Ｏ３、Ｅｕ２Ｏ３、Ｇｄ２Ｏ３、Ｔｂ４Ｏ７、Ｄｙ２Ｏ３、Ｅｒ２Ｏ３、Ｔｍ２Ｏ３、Ｙｂ２Ｏ３作为添加剂,对镍在γ－Ａｌ２Ｏ３表面的分散度、甲烷化活性、ＣＯ在镍上的吸附态及表面镍原子的电子状态的影响．结果表明,稀土氧化物添加剂不仅明显地提高了金属镍的分散度和甲烷化活性,还直接地影响表面镍原子的电子状态．对不同稀土氧化物,这些效应各异．作者认为,利用稀土氧化物添加剂调节表面镍原子的电子状态,可能成为改进甲烷化催化剂活性的一个有效途径．     

Layered metal phosphonates containing pyridyl groups: Syntheses and characterization of Mn2(2-C5H4NPO3)2(H2O) and Zn(6-Me-2-C5H4NPO3)

This paper reports the syntheses and characterization of two phosphonate compounds with layered structures, namely, Mn₂(2-C₅H₄NPO₃)₂(H₂O) (1) and Zn(6-Me-2-C₅H₄NPO₃) (2). In compound 1, double chains are found in which the {Mn₂O₂} dimers are linked by both aqua and O-P-O bridges. These double chains are connected through corner-sharing of {MnO₅N} octahedra and {CPO₃} tetrahedra, forming an inorganic layer. The pyridyl groups fill the inter-layer spaces. In compound 2, each {ZnO₃N} tetrahedron is vertex-shared with three {CPO₃} tetrahedra and vice versa, hence forming an inorganic honeycomb layer. The pyridyl groups reside between the layers. Magnetic studies show that weak antiferromagnetic interactions are mediated between the manganese ions in compound 1. Crystal data for 1: monoclinic, space group C2/c, , , , β=107.3(1)°. For 2: orthorhombic, space group Pbca, , , .     

Theoretical study of properties of H bonds and intermolecular interactions in linear cis-,trans-cyclotriazane clusters (n = 2-8)

Our calculations based upon Becke's three-parameter functional of density-functional theory (DFT) with the correlation of Lee, Yang, and Parr (B3LYP), natural bond orbital, and atoms in molecule indicate that in drastic contrast to most H-bonded systems, the anticooperative and cooperative effects coexist in the linear H-bonded cis-,trans (c,t)-cyclotriazane clusters (n = 2-8). As cluster size increases, the properties along the H-bonded chains at trans-positions take on the unexpectedly anticooperative changes which are reflected in elongation of the N...H hydrogen bonds, frequency blueshift in the N-H stretching vibrations, decay in the n(N)-->sigma*(N-H) charge transfers, and weakening of strengths of the N...H bonds. And the cooperative changes in the corresponding properties for the cis- H-bonded chains are observed to be concurrent with the anticooperativities. The rise and fall in the n(N)-->sigma*(N-H) interactions cause increment and decrement in capacities of the clusters to concentrate electrons at the bond critical points of the N...H bonds, and thereby leading to the cooperative and the anticooperative changes especially in the N...H lengths and the N-H stretching frequencies. In terms of three-body symmetry-adapted perturbation theory (three-body SAPT), the first exchange nonadditivity plays a more important role in stabilizing trimer than the nonadditive induction. However, the dominance of the first exchange nonadditivity in three-body interaction unexpectedly triggers the anticooperative effect that counteracts the concurrent cooperative effect. According to the SAPT(DFT), which is a combination of SAPT with asymptotically corrected DFT, DFT/B3LYP is able to succeed in describing the electrostatic, exchange, and induction components, but fails to yield satisfactory interaction energies due to the fact that about 40% of short-range dispersion energy is neglected by the DFT, which is different from many H-bonded described well by the DFT. A quantum cluster equilibrium model illustrates that the c,t-cyclotriazane liquid phase exhibits a weak cooperative effect.     

Structure determination of protein-ligand complexes by transferred paramagnetic shifts

Rational drug design depends on the knowledge of the three-dimensional (3D) structure of complexes between proteins and lead compounds of low molecular weight. A novel nuclear magnetic resonance (NMR) spectroscopy strategy based on the paramagnetic effects from lanthanide ions allows the rapid determination of the 3D structure of a small ligand molecule bound to its protein target in solution and, simultaneously, its location and orientation with respect to the protein. The method relies on the presence of a lanthanide ion in the protein target and on fast exchange between bound and free ligand. The binding affinity of the ligand and the paramagnetic effects experienced in the bound state are derived from concentration-dependent (1)H and (13)C spectra of the ligand at natural isotopic abundance. Combined with prior knowledge of the crystal or solution structure of the protein and of the magnetic susceptibility tensor of the lanthanide ion, the paramagnetic data define the location and orientation of the bound ligand molecule with respect to the protein from simple 1D NMR spectra. The method was verified with the ternary 30 kDa complex between the lanthanide-labeled N-terminal domain of the epsilon exonuclease subunit from the Escherichia coli DNA polymerase III, the subunit theta, and thymidine. The binding mode of thymidine was found to be very similar to that of thymidine monophosphate present in the crystal structure.     

由5-磺基水杨酸组装的镧系金属有机骨架配合物的合成及结构

在水热条件下,合成了6个新的镧系金属配位聚合物,Ln₂(SSA)₂(phen)₄(H₂O)₂(Ln=Er(Ⅲ) (1),Yb(Ⅲ) (2)),[La₂(SSA)₂(phen)₂(H₂O)₄·(phen)·(H₂O)_{1.33相似文献}   

Oxidation of guanine in G, GG, and GGG sequence contexts by aromatic pyrenyl radical cations and carbonate radical anions: relationship between kinetics and distribution of alkali-labile lesions

Oxidatively generated DNA damage induced by the aromatic radical cation of the pyrene derivative 7,8,9,10-tetrahydroxytetrahydrobenzo[a]pyrene (BPT), and by carbonate radicals anions, was monitored from the initial one-electron transfer, or hole injection step, to the formation of hot alkali-labile chemical end-products monitored by gel electrophoresis. The fractions of BPT molecules bound to double-stranded 20-35-mer oligonucleotides with noncontiguous guanines G and grouped as contiguous GG and GGG sequences were determined by a fluorescence quenching method. Utilizing intense nanosecond 355 nm Nd:YAG laser pulses, the DNA-bound BPT molecules were photoionized to BPT*+ radicals by a consecutive two-photon ionization mechanism. The BPT*+ radicals thus generated within the duplexes selectively oxidize guanine by intraduplex electron-transfer reactions, and the rate constants of these reactions follow the trend 5'-..GGG.. > 5'-..GG.. > 5'-..G... In the case of CO3*- radicals, the oxidation of guanine occurs by intermolecular collision pathways, and the bimolecular rate constants are independent of base sequence context. However, the distributions of the end-products generated by CO3*- radicals, as well as by BPT*+, are base sequence context-dependent and are greater than those in isolated guanines at the 5'-G in 5'-...GG... sequences, and the first two 5'- guanines in the 5'-..GGG sequences. These results help to clarify the conditions that lead to a similar or different base sequence dependence of the initial hole injection step and the final distribution of oxidized, alkali-labile guanine products. In the case of the intermolecular one-electron oxidant CO3*-, the rate constant of hole injection is similar for contiguous and isolated guanines, but the subsequent equilibration of holes by hopping favors trapping and product formation at contiguous guanines, and the sequence dependence of these two phenomena are not correlated. In contrast, in the case of the DNA-bound oxidant BPT*+, the hole injection rate constants, as well as hole equilibration, exhibit a similar dependence on base sequence context, and are thus correlated to one another.     

Mass spectrometry analysis of terpene lactones in Ginkgo biloba

Terpene lactones are a family of compounds with unique chemical structures, first recognised in an extract of Ginkgo biloba. The discovery of terpene lactone derivatives has recently been reported in more and more plant extracts and even food products. In this study, mass spectrometric characteristics of the standard terpene lactones in Ginkgo biloba were comprehensively studied using both an ion trap and a quadrupole time-of-flight (QTOF) mass spectrometer. The mass spectral fragmentation data from both techniques was compared to obtain the mass spectrometric fragmentation pathways of the terpene lactones with high confidence. The data obtained will facilitate the analysis and identification of terpene lactones in future plant research via the fragmentation knowledge reported here.     

Solid-state electrochemiluminescence of a novel iridium(Ⅲ) complex

The sofid-state ECL behavior of a water-insoluble bis-cyclometalated (pq)2Ir(N-phMA) complex is presented, in which pq is a 2-phenylquinoline anion and N-phMA is N-phenyl methacrylamide, a monoanionic bidentate ligand. The MWNTs/(pq)2Ir(N-phMA) film, MWNTs/Ru(bpy)32+ film and (pq)2Ir(N-phMA) directly modified glassy carbon electrode were fabricated; only the MWNTs/(pq)2Ir(N-phMA) film can produce steady ECL in the presence of tri-n-propylamine as a coreactant.