Bioinspired Total Synthesis of Complex Nucleoside Antibiotics A201A,A201D and A201E

Herein, bioinspired total syntheses of A201A, A201D, and A201E based on a previously reported biosynthetic pathway are presented. The challenging 1,2-cis-furanoside, a core structure of the A201 family, was obtained by remote 2-quinolinecarbonyl-assisted glycosylation. We accomplished the total synthesis of A201A and A201E based on the critical 1,2-cis-furanoside moiety through late-stage glycosylation without any interference from basic dimethyl adenosine. We also confirmed the absolute configuration of A201E by total synthesis. This modular synthesis strategy enables efficient preparation of A201 family antibiotics, allowing the study of their structure–activity relationships and mode of action. This study satisfies the increasing demand for developing novel antibiotics inspired by the A201 family.     

Organocatalytic Enantioselective Pictet–Spengler Reaction of α-Ketoesters: Development and Application to the Total Synthesis of (+)-Alstratine A

We report herein an asymmetric Pictet–Spengler reaction of α-ketoesters. In the presence of a catalytic amount of simple alanine-derived squaramide and p-nitrobenzoic acid, reaction of tryptamines with methyl 2-oxoalkanoates afforded the corresponding 1-alkyl-1-methoxycarbonyl tetrahydro-β-carbolines (THBCs) in high yields and ee values. A primary kinetic isotope effect (KIE=4.5) using C2-deteurium-labelled tryptamine indicates that rearomatization through deprotonation of the pentahydro-β-carbolinium ion could be the rate- and enantioselectivity-determining step. A concise enantioselective total synthesis of (+)-alstratine A, a hexacyclic cagelike monoterpene indole alkaloid, featuring this reaction as a key step, was subsequently accomplished. Remeasurement of the [a]_D value of the natural product indicates that natural alstratine A is dextrorotatory rather than levorotatory as it was initially reported in the isolation paper.     

中空MOFs材料制备及电催化应用的研究进展

水分裂、金属-空气电池和燃料电池等能源转换技术对解决未来的能源危机和环境问题至关重要.氧还原反应(ORR)、氧析出反应(OER)和氢析出反应(HER)作为其核心反应,存在反应动力学速率较慢的问题,因此,开发研制高效的非贵金属电催化剂具有重要意义.金属有机骨架(MOFs)材料因具有高度可调的组成和多孔晶体结构,在不同的应用领域引起了越来越多的关注.中空MOFs纳米材料具有MOFs材料高度可调的组成和结构优势,又具有中空结构纳米材料的优点(如更快的物质传输、更丰富的孔隙率、灵活多变的活性组分、更多的暴露活性位点及对苛刻条件的更好相容性等),在电催化领域显现出巨大的应用潜力.本文对近几年来基于中空结构MOFs材料的制备及在电催化方面应用的研究进展进行了综合评述,并对该领域面临的挑战和发展前景进行了总结和展望.     

Synthetic Advantages of Defluorinative C−F Bond Functionalization

Much progress has been made in the development of methods to both create compounds that contain C−F bonds and to functionalize C−F bonds. As such, C−F bonds are becoming common and versatile synthetic functional handles. This review summarizes the advantages of defluorinative functionalization reactions for small molecule synthesis. The coverage is organized by the type of carbon framework the fluorine is attached to for mono- and polyfluorinated motifs. The main challenges, opportunities and advances of defluorinative functionalization are discussed for each class of organofluorine. Most of the text focuses on case studies that illustrate how defluorofunctionalization can improve routes to synthetic targets or how the properties of C−F bonds enable unique mechanisms and reactions. The broader goal is to showcase the opportunities for incorporating and exploiting C−F bonds in the design of synthetic routes, improvement of specific reactions and advent of new methods.     

优化金属磷化物电催化析氢性能的策略

日益严重的能源危机和环境污染问题使得探索清洁的可再生能源载体及减少对传统化石燃料的过度依赖成为人们面临的一项重要任务.因此,各种可持续能源如太阳能、风能、海洋能和生物质能等得到了广泛研究并取得了一定的进展.然而,这些能源因存在间歇性和不稳定性等缺点阻碍了其实际应用.近年,氢气作为一种能源载体,以其高能量密度和无碳排放的优点引起了人们的广泛关注,被认为是缓解日益严重的污染问题的最有前途的环保能源.对比目前采用的天然气热解和煤炭气化等传统制氢策略,电催化水裂解由于催化效率高,制氢纯度高和不产生温室气体,被认为是高效、环保、可持续的制氢策略.电催化水裂解由两个独立的半反应组成,分别是析氢反应和析氧反应.析氢反应作为水裂解的一个半反应,在降低制氢成本及提高产氢催化效率方面起着关键作用.然而,目前的核心问题之一是要开发高效的析氢电催化剂,以加快反应速度.目前,铂和铂基纳米材料被认为是高效的析氢电催化剂,但是其稀缺性和高成本阻碍了大规模实际应用.金属磷化物由于具有较高的本征活性并且在不同的电解质中都具有良好的电催化析氢性能,被证明是一种优良的析氢电催化剂.此外,与普通催化剂相比,金属磷化电催化剂还具有合成简便、效率高、成本低、省时等优点.本文详细介绍了近年人们在金属磷化物用于电催化析氢研究中取得的进展.首先,介绍了电催化析氢反应机理,金属磷化物的结构及作用,并对其优缺点进行了总结;随后,综述了金属磷化物的合成方法,包括后处理、原位生成和电沉积策略,并对不同方法进行了比较和讨论.此外,从元素掺杂、界面工程、空穴工程、修饰特定载体、构建特定纳米结构、设计双或多金属磷化物和其他发展的新方法等七个方面详细总结了促进金属磷化物电催化活性的多种策略,并进行了对比和讨论.最后,归纳了金属磷化物在电催化析氢应用中存在的问题和面临的挑战,并对未来的研究发展提出了展望.     

壳层厚度对骨架Fe@HZSM-5核壳催化剂费托合成催化性能的影响

在不同的水热合成时间下, 以铁铝合金为铁源和铝源, 四丙基氢氧化铵为分子筛的模板剂和抽提合金中的铝的碱, 一步制得了以骨架铁为核、不同厚度的HZSM-5分子筛为壳的Raney Fe@HZSM-5催化剂. 采用元素分析、氮物理吸附、X射线粉末衍射、氨脱附、扫描电子显微镜等手段, 考察了水热时间对催化剂基本物化性质的影响. 随着水热时间的延长, HZSM-5分子筛壳层不断增厚, 结晶度不断增大, 但分子筛组成基本不变, 酸量与分子筛壳层厚度正相关. 在费托合成反应中, Raney Fe@HZSM-5核壳催化剂上的CO转化率和汽油段产物选择性随分子筛壳层厚度呈火山型变化趋势, 说明反应需要适宜的酸量, 酸量过低或过高均不利于得到高的催化活性及汽油段产物选择性. 在水热合成时间为4 d制得的Raney Fe@HZSM-5核壳催化剂上, 当CO转化率为92%时, C₅~C₁₁汽油段产物选择性可达71%, 异正比为1.9. 当合成气中的n(H₂)/n(CO)比从2降为1时, 汽油段产物选择性和异正比进一步提高至73%和2.1, 显示了将该催化剂用于煤基或生物质基合成气转化为高辛烷值汽油的良好潜力.     

含4(3H)-喹唑啉酮结构的取代1,3,4-噁二唑(噻二唑)化合物的合成及抗菌活性研究

以2-胺基苯甲酸为原料,通过环化、缩合、肼解、环化、硫醚化和氧化等步骤,合成了10个含喹唑啉酮取代1,3,4-噁二唑(噻二唑)化合物。通过1H NMR、13C NMR、MS 和元素分析进行确证其结构。初步抑菌活性测试表明,化合物浓度在50 μg/mL时,对葡萄座腔菌(Botryosphaeria dothidea)、拟茎点霉菌(Phomopsis sp.)和灰霉菌(B. cinerea)具有中等抑制活性。另外,目标化合物对猕猴桃溃疡病(Pseudomonas syringae pv. actinidia)均具有一定的抑制活性,其中化合物6a和6b对猕猴桃溃疡病的EC50值为11.7 μg/mL和20.5 μg/mL,优于对照药剂叶枯唑(24.5 μg/mL)。这类化合物具有较好抗菌的生物活性,在此基础上进行结构优化,有望发现较高活性化合物。     

Synthesis,Electrochemical and Luminescence Studies of Nickel and Vanadium Complexes Containing Tetradentate Schiff Base Ligand with N2O2 Donor Atoms

A symmetrical tetradentate Schiff base ligand was derived by the condensation of ortho‐vanillin and thiourea in 2:1 molar ratio and adjusted pH. Nickel and vanadyl complexes were obtained using the template method by the reaction of ortho‐vanillin and thiourea with Ni(OAc)₂. 4H₂O and VO(acac)₂ (2:1:1 molar ratio) in absolute ethanol and adjusted pH. The Schiff base ligand and its complexes have been characterized by FT‐IR, ¹H NMR, UV/Vis, elemental analysis and conductometry measurements. In nickel and also vanadyl complexes the ligands were coordinated to the metals via the imine N and enolic O atoms. The complexes have been found to possess 1:1 metal to ligand stoichiometry and the molar conductance data revealed that the metal complexes were non‐electrolytes. The nickel and vanadyl complexes exhibited tetrahedral and square pyramidal coordination geometry, respectively. The emission spectra of the ligand and its complexes were studied in DMSO. Electrochemical properties of the ligand and its complexes were also investigated in the DMF solvent at the 150 mVs^‐1 scan rate. The ligand and its complexes showed irreversible processes at this scan rate.     

A New and Facile Synthesis of Novel Pyrazolothienopyrimidines and Imidazopyrazolothienopyrimidines

4‐Amino‐3‐methyl‐1‐phenyl‐1H‐thieno[2,3‐c]pyrazole‐5‐carboxamide ( 5 ), which was synthesized by an innovative method, was used as a versatile precursor for synthesizing pyrazolothienopyrimidines and imidazopyrazolothienopyrimidines compounds. Reaction of amino thienopyrazole carboxamide 5 with triethyl orthoformate afforded thienopyrazolopyrimidine 6 . Chlorination of the latter compound, using phosphorus oxychloride afforded the chloro pyrazolothienopyrimidine 7 , which underwent nucleophilic substitution reactions with various primary and secondary amines to give the alkyl (aryl) amino pyrimidine compounds 8a–d . On the other hand, the reaction of chloropyrimidine 7 with thiourea afforded the pyrimidine thione compound 9 , which was alkylated with α‐halogentaed compounds to afford the S‐alkylated derivatives 10a–c . Also, chloroacetylation of the amino carboxamide 5 using chloroacetyl chloride yielded the chloromethyl pyrazolothienopyrimidine 12 , which underwent nucleophilic substitu‐ tion reactions with various primary and secondary amines to afford the alkyl (aryl) aminomethyl compounds 13a–f . The latter Compounds underwent Mannich reaction to give imidazopyrimidothieno‐ pyrazoles 14a–c . The newly synthesized compounds and their derivatives were fully characterized by elemental and spectral analysis.     

The Synthesis of New Organoselenium Heterocyclic Compounds: 2‐aryl‐4‐phenyl‐5,6,7,8‐tetrahydro‐4H‐selenochromenes

We have explored the reactions of 2‐(3‐oxo‐1‐aryl‐3‐phenylpropyl)cyclohexanone ( 1–3 ) with hydrogen selenide in situ in conditions of acid catalysis, and synthesized new 2‐aryl‐4‐phenyl‐5,6,7,8‐tetrahydro‐4H‐selenochromenes ( 4–6 ).