(4R)-5,5-二甲基-4-苄硫甲基-2-噁唑烷酮的合成

以价廉易得的天然L-半胱氨酸为原料,经巯基保护、酯化、氨基保护、格氏反应及环化等5步反应,合成了一个新的手性助剂(4R)-5,5-二甲基-4-苄硫甲基-2-噁唑烷酮,总收率31%.产物结构经IR,~1H NMR,~(13)C NMR及MS表征.     

Acceleration of Long‐Range Photoinduced Electron Transfer through DNA by Hydroxyquinolines as Artificial Base Pairs

The C‐nucleoside based on the hydroxyquinoline ligand (Hq) is complementary to itself and forms stable Hq–Hq pairs in double‐stranded DNA. These artificial Hq–Hq pairs may serve as artificial electron carriers for long‐range photoinduced electron transfer in DNA, as elucidated by a combination of gel electrophoretic analysis of irradiated samples and time‐resolved transient absorption spectroscopy. For this study, the Hq–Hq pair was combined with a DNA‐based donor–acceptor system consisting of 6‐N,N‐dimethylaminopyrene conjugated to 2′‐deoxyuridine as photoinducible electron donor, and methyl viologen attached to the 2′‐position of uridine as electron acceptor. The Hq radical anion was identified in the time‐resolved measurements and strand cleavage products support its role as an intermediate charge carrier. Hence, the Hq–Hq pair significantly enhances the electron hopping capability of DNA compared to natural DNA bases over long distances while keeping the self‐assembly properties as the most attractive feature of DNA as a supramolecular architecture.     

A selective colorimetric chemosensor based on calixarene framework for lanthanide ions-Dy and Er

A novel photochromic Schiff base derivative, 5,17-N,N′-(5,5′-di-methoxyl-benzlaldehyde)diimine-25,27-dipropoxy-calix[4]arene has been synthesized through incorporation of two imine groups into the upper rims of calix[4]arene. The experiments showed that the addition of Dy³⁺ or Er³⁺ ions to compound 4 results in the solution color change, but other metal ions caused less change. It indicated that the synthetic receptor can selectively recognize Dy³⁺ and Er³⁺ ion by naked eye over other lanthanide cations. Thus, these systems can be applied as chemosensor for Dy³⁺ and Er³⁺ ion in analytical chemistry.     

Determination of the helical screw sense and side-group chirality of a synthetic chiral polymer from Raman optical activity

Splitting it up: Excellent agreement between the experimental and the quantum-chemically simulated Raman optical activity (ROA) spectrum of (+)-poly(trityl methacrylate) shows that the polymer backbone adopts a left-handed helical conformation while the trityl side groups display a left-handed propeller conformation. Thus ROA can be used to determine the complete structure of synthetic chiral polymers in solution.     

一种含噻吩环酰腙及其Cu(Ⅱ)配合物的合成、晶体结构和抗氧化活性及量化计算

合成了一种酰腙类含硫Schiff碱4-(二乙胺基)水杨醛缩2-噻吩甲酰腙一水合物(H₂L·H₂O,1),采用扩散法制备了它的铜配合物[Cu(phen)L](2,phen=菲咯啉),通过元素分析、红外光谱、紫外光谱和X射线单晶衍射对它们进行了表征。1的晶体属正交晶系,P2₁2₁2空间群;2的晶体属单斜晶系,P2₁/c空间群。在2中H₂L以烯醇式脱除羟基质子与铜配位,中心离子的配位环境为畸变的四方锥构型。应用Gaussian 09程序,采用密度泛函方法(DFT),分别在B3LYP/6-31G(d)和UB3LYP/6-31G(d)水平对1和2进行了量化计算,对分子的前线分子轨道的能量和组成以及电子光谱进行了分析讨论。测试、分析了化合物的抗氧化活性。     

Synthesis and structure determination of pyrazine-containing macrocyclic polyazomethines

<正>Two pyrazine-contairting macrocyclic polyazomethines 2 and 3 were synthesized by direct[2 + 2]and[3 + 3]condensation reactions between 2,2'-[pyrazine-2,3-diylbis(oxy)]dibenzaldehyde(1) and hydrazine.Both 2 and 3 were characterized by NMR, HRMS,and their structures were determined via X-ray crystal diffraction studies.     

Enantioseparation of dansyl amino acids and dipeptides by chiral ligand exchange capillary electrophoresis based on Zn(II)-l-hydroxyproline complexes coordinating with γ-cyclodextrins

A chiral ligand exchange capillary electrophoresis (CLE-CE) method using Zn(II) as the central ion and l-4-hydroxyproline as the chiral ligand coordinating with γ-cyclodextrin (γ-CD) was developed for the enantioseparation of amino acids (AAs) and dipeptides. The effects of various separation parameters, including the pH of the running buffer, the ratio of Zn(II) to l-4-hydroxyproline, the concentration of complexes and cyclodextrins (CDs) were systematically investigated. After optimization, it has been found that eight pairs of labeled AAs and six pairs of labeled dipeptides could be baseline-separated with a running electrolyte of 100.0 mM boric acid, 5.0 mM ammonium acetate, 3.0 mM Zn(II), 6.0 mM l-hydroxyproline and 4.0 mM γ-CD at pH 8.2. The quantitation of AAs and dipeptides was conducted and good linearity (r² ≥ 0.997) and favorable repeatability (RSD ≤ 3.6%) were obtained. Furthermore, the proposed method was applied in determining the enantiomeric purity of AAs and dipeptides. Meanwhile, the possible enantiorecognition mechanism based on the synergistic effect of chiral metal complexes and γ-CD was explored and discussed briefly.     

Scorpio-Ligand: Synthesis of Biphenyl-Dihydroazepine Phosphoramidite Ligands for Asymmetric Hydrogenation

A novel dihydroazepine-bridged BIPHEP phosphoramidite ligand with an amino acid moiety in the backbone was synthesized and evaluated in the Rh-catalyzed asymmetric hydrogenation. The scorpion tail-like amino acid backbone is capable of hydrogen bond formation and able to shift the rotamer composition of the biphenyl axis with the two scissor-like arms. Pivaloyl-l -valine was studied as chiral selector unit and compared with pivaloylglycine as the achiral reference substance. The enantiomerization barrier of the pivaloylglycine-modified biphenylamide was determined to be ΔG^≠=110 kJ/mol. In the case of pivaloyl-l -valine, the (S_ax) isomer is thermodynamically favored. Due to the relatively high barrier, the ligand is atropisomeric at room temperature and allows the preparative separation of the stereoisomers. The obtained phosphoramidite ligands were separated by chiral HPLC. For the first eluting rotamer, Rh complex ([Rh(cod)(L)₂]BF₄) was generated in situ and examined in the enantioselective hydrogenation of 2-acetamidoacrylate and methyl 2-acetamido-3-phenylacrylate, achieving enantiomeric excesses of up to 94 %.     

Synthesis and In Vitro Anti-HIV Activity of Some New Schiff Base Ligands Derived from 5-Amino-4-phenyl-4H-1,2,4-triazole-3-thiol and Their Metal Complexes

New Schiff base ligands (6–9) derived from 5-amino-4-phenyl-4H-1,2,4-triazole-3-thiol 1 and substituted benzaldehydes (2–5) as well as their metal complexes with Cu(II), Fe(II), Au(III), and Mn(II) (12–17) have been synthesized. A new benzothiazole derivative (11) was prepared from coupling of 7 with N-(benzothiazol-2-yl)-2-chloroacetamide 10. Their spectral properties were investigated. The newly designed and synthesized Schiff base ligands and the metal complexes were assayed for anti-HIV-1 and HIV-2 activity by examination of their inhibition of HIV-induced cytopathogenicity in MT-4 cells. Compounds 11 and 16 were found to be the most active inhibitors in cell culture (EC₅₀ = 12.2 μg/mL (SI = 4) and > 2.11 μg/mL (SI = > 1), respectively) against HIV-1, whereas 11 showed inhibition against HIV-2 of EC₅₀ > 10.2 μg/mL with SI = 9, which provided a good lead for further optimization.