Advances in Atroposelectively De Novo Synthesis of Axially Chiral Heterobiaryl Scaffolds

Axially chiral heterobiaryl frameworks are privileged structures in many natural products, pharmaceutically active molecules, and chiral ligands. Therefore, a variety of approaches for constructing these skeletons have been developed. Among them, de novo synthesis, due to its highly convergent and superior atom economy, serves as a promising strategy to access these challenging scaffolds including C-N, C-C, and N-N chiral axes. So far, several elegant reviews on the synthesis of axially chiral heterobiaryl skeletons have been disclosed, however, atroposelective construction of the heterobiaryl subunits by de novo synthesis was rarely covered. Herein, we summarized the recent advances in the catalytic asymmetric synthesis of the axially chiral heterobiaryl scaffold via de novo synthetic strategies. The related mechanism, scope, and applications were also included.     

金属有机骨架高温自还原制备高性能等级孔碳负载Co基催化剂

以钴基金属有机框架为前驱体,利用一步高温碳化自还原法,通过精确调控碳化过程,实现等级孔道结构及钴纳米颗粒分散性的可控调节,制备出高催化活性及产物选择性的等级孔碳负载Co基催化剂.研究发现,600℃碳化后的催化剂为具有高比表面积的等级孔道结构和高分散的钴纳米颗粒,在选择性催化1,3-丁二烯加氢反应中,丁二烯完全转化温度低至60℃,对应丁烯的选择性高达61%,实现了低温高选择性催化加氢.     

Neocornuside A–D,Four Novel Iridoid Glycosides from Fruits of Cornus officinalis and Their Antidiabetic Activity

Four previously undescribed iridoid glycosides neocornuside A–D (1–4), along with six known ones (5–10), were isolated from Cornus officinalis fruit. Their structures were elucidated by extensive spectroscopic (NMR, UV, IR, and MS) analysis and comparison with data reported in the literature. All isolates were assessed for their antidiabetic activity on the relative glucose consumption in insulin-induced insulin-resistant HepG2 cells. The results showed that compounds 1, 3, and 7 exhibited significant antidiabetic activities with EC₅₀ values of 0.582, 1.275, and 0.742 μM, respectively. Moreover, compounds 1, 3, and 7 could improve the ability of 2-NBDG uptake of insulin-induced HepG2 cells.     

A Dendron-Based Fluorescence Turn-On Probe for Tumor Detection

Specifically amplifying the emission signals of optical probes in tumors is an effective way to improve the tumor-imaging sensitivity and contrast. In this paper, the first case of dendron-based fluorescence turn-on probes mediated by a Förster resonance energy transfer (FRET) mechanism is reported. Dendrons up to the fourth generation with a hydrophilic oligo(ethylene glycol) scaffold are synthesized by a solid-phase synthesis strategy, and show precise and defect-free chemical structures. To construct the fluorescence turn-on probe, one Cy5.5 molecule is conjugated to the focal of a G3 dendron through a robust linkage and eight Black Hole Quencher 3 (BHQ-3) molecules are conjugated to its periphery through a PEG chain bearing a reductively cleavable disulfide linkage. By in vitro and in vivo experiments, it is demonstrated that the fluorescence of the dendron-based probe can be activated effectively and rapidly in the reductive environments of tumor cells and tissues, and the probe thus exhibits amplified tumor signals and weak normal tissue signals. Compared with the reported nanoscale turn-on probes, the dendron-based probe has several significant advantages, such as well-defined chemical structure, precisely controllable fluorophore/quencher conjugation sites and ratio, desirable chemical stability, and reproducible pharmacokinetic and pharmacological profiles, and is very promising in tumor detection.     

Preparation and Cellular Uptake of pH‐Dependent Fluorescent Single‐Wall Carbon Nanotubes

Fluorescent single‐wall carbon nanotubes (SWCNTs) were prepared by mixing cut SWCNTs with acridine orange (AO). The optical absorbance and fluorescence characteristics of AO–SWCNT conjugates display interesting pH‐dependent properties. Fluorescence microscopy in combination with transmission electron microscopy proves that AO–SWCNTs can enter HeLa cells and are located inside lysosomes. The endocytosis‐inhibiting tests show that the clathrin‐mediated endocytosis is a key step in the internalization process. The internalized AO–SWCNTs remain inside lysosomes for more than a week and have little effect on cell proliferation. These findings may be useful in understanding the SWCNT‐based intracellular drug delivery mechanism and help to develop new intracellular drug transporters.     

低密度奇偶校验码的性能分析与水下通信验证

在ADSP-BF561上实现了低密度奇偶校验码的编码算法。为解决编码复杂度高的问题,将校验矩阵变换后存入数据空间。为节省存储空间,采用压缩算法,并提出相应的编码算法,没有增加复杂度。对不同码率的低密度奇偶校验码在不同信道中的性能进行仿真分析。将不同码率的低密度奇偶校验码应用于水声通信系统进行浅海试验,结果表明低密度奇偶校验码能提高通信系统的鲁棒性,码率越低性能越好。当解码前符号信噪比在7～8dB时,可达到近似无误码的通信性能。     

Condition number for the w-weighted drazin inverse and its applications in the solution of rectangular linear system

In this paper, we generalized the results of [23, 26], and get the results of the condition number of the W-weighted Drazin-inverse solution of linear systemWAWx =b, whereA is anm x n rank-deficient matrix and the index ofAW isk ₁, the index ofWA isk ₂,b is a real vector of sizen in the range of (WA) ^k2 ,x is a real vector of sizem in the range of (AW) ^k1 . Let α and β be two positive real numbers, when we consider the weighted Frobenius norm $\left\| {\left[ {\alpha W AW,\beta b} \right]} \right\|_{Q,\tilde P}^{(F)} $ on the data we get the formula of condition number of the W-weighted Drazin-inverse solution of linear system. For the normwise condition number, the sensitivity of the relative condition number itself is studied, and the componentwise perturbation is also investigated.     

Clifford分析中Isotonic柯西型积分的边界性质

本文主要刻画了定义于偶数维欧氏空间中光滑曲面而取值于复Clifford代数的isotonic柯西型积分的边界性质.对具有H(o|¨)lder密度函数的isotonic柯西型积分,得到了Privalov定理和Sokhotskii-Plemelj公式,并证明了多复变函数论中经典Bochner-Martinelli型积分的Privalov定理和Sokhotskii-Plemelj公式为其特殊情形.