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Strategies for constructing seven-membered rings:Applications in natural product synthesis

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Chinese Chemical Letters 2024年第6期35卷 53-70页

作者： Peng Chen Lijuan Liang Yufei Zhu Zhimin Xing Zhenhua jia Teck-Peng loh College of Advanced Interdisciplinary Science and Technology Henan University of TechnologyZhengzhou 450001China Division of Chemistry and Biological Chemistry School of Chemistry Chemical Engineeringand BiotechnologyNanyang Technological UniversitySingapore 637371Singapore Institute of Advanced Synthesis School of Chemistry and Molecular Engineering Nanjing Tech UniversityNanjing 211816China State Key Laboratory of Applied Organic Chemistry Department of ChemistryLanzhou UniversityLanzhou 730000China

The seven-membered ring motifs are found in bioactive pharmaceuticals and a wide range of natural products,including alkaloids and terpenoids,which hold significant importance in synthetic chemistry and has garnered considerable attention from both academia and *** the challenges faced in the past decade,the total synthesis of natural products incorporating the non-aromatic cycloheptane skeletons remains a compelling ***,numerous elegant strategies for constructing the sevenmembered ring system have been successfully *** review focuses on the recent advancements in this field from 2017 to April 2023,highlighting key transformations utilized to construct the non-aromatic cycloheptane core structures and serves as a valuable guide for synthetic chemists engaged in the total synthesis of natural products containing seven-membered ring motifs.

关键词： Seven-membered rings Total synthesis Natural products Synthetic strategy Cycloheptane

Hetero-trans-β-Glucanase Produces Cellulose-Xyloglucan Covalent Bonds in the Cell Walls of Structural Plant Tissues and Is Stimulated by Expansin

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Molecular Plant 2020年第7期13卷 1047-1062页

作者： Klaus Herburger Lenka Frankova Martina Picmanova jia wooi loh Marcos Valenzuela-Ortega Frank Meulewaeter Andrew D.Hudson Christopher E.French Stephen C.Fry The Edinburgh Cell Wall Group Institute of Molecular Plant SciencesSchool of Biological SciencesThe University of EdinburghEdinburgh EH93BFUnited Kingdom Institute of Quantitative Biology Biochemistry and BiotechnologySchool of Biological SciencesThe University of EdinburghEdinburgh EH93BFUnited Kingdom BASF BBCC Innovation Center Gent-Trait Research9052 Gent(Zwijnaarde)Belgium Zhejiang University-University of Edinburgh Joint Research Centre for Engineering Biology Zhejiang UniversityHainingZhejiang 314400China Present address:Section for Plant Glycobiology Department of Plant and Environmental SciencesUniversity of CopenhagenFrederiksberg 1871Denmark

Current cell-wall models assume no covalent bonding between cellulose and hemicelluloses such as xyloglu-can or mixed-linkageβ-D-glucan(MLG).However,Equisetum hetero-trans-β-glucanase(HTG)grafts cellu-lose onto xyloglucan oligosaccharides(XGOs)-and,we now show,xyloglucan polysaccharide-in vitro,thus exhibiting CXE(cellulose:xyloglucan endotransglucosylase)*** addition,HTG also catalyzes MLG-to-XGO bonding(MXE activity).In this study,we explored the CXE action of HTG in native plant cell walls and tested whether expansin exposes cellulose to HTG by disrupting hydrogen *** quantify and visu-alize CXE and MXE action,we assayed the sequential release of HTG products from cell walls pre-labeled with substrate *** demonstrated covalent cellulose--xyloglucan bonding in plant cell walls and showed that CXE and MXE action was up to 15%and 60%of total transglucanase action,respectively,and peaked in aging,strengthening tissues:CXE in xylem and cells bordering intercellular canals and MXE in *** bacterial expansin(EXLX1)strongly augmented CXE activity in *** and MXE ac-tion in living Equisetum structural tissues potentially strengthens stems,while expansin might augment the HTG-catalyzed CXE reaction,thereby allowing efficient CXE action in *** methods will enable surveys for comparable reactions throughout the plant ***,engineering similar hetero-polymer formation into angiosperm crop plants may improve certain agronomic traits such as lodging tolerance.

关键词： cell wall cellulose hemicelluloses hetero-trans-p-glucanase hetero-transglycosylation xyloglucan

Antibacterial and angiogenic dual-functional fibrous membrane dressing for infected wound healing

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Biomedical Engineering Communications 2024年第1期3卷 4-14页

作者： Chao Zhou Che Zhao Hao-Yu Dai Tian-Jun Zhu jia-Pei Yao Li Chen Jing-Jing Wen jia Ling Celestine loh Xin-Die Zhou Yong Huang School of Medical and Health Engineering Changzhou UniversityChangzhouJiangsu 213164China School of Aerospace and Mechanical Engineering Changzhou Institute of TechnologyChangzhouJiangsu 213032China Department of Orthopedics The Affiliated Changzhou Second People's Hospital of Nanjing Medical UniversityChangzhou Medical CenterNanjing Medical UniversityChangzhou 213000China Duke-NUS Graduate Medical School National University of SingaporeKent Ridge 169547Singapore

Background:Skin,being a vital organ that regulates physiological responses in the human body,is prone to injury from external environmental *** full-thickness skin defects becomes especially challenging when infections and vascular injuries are *** wound dressings with single functions,such as antibacterial or angiogenic properties,fall short in achieving rapid wound *** address this,there is a need to develop wound dressing materials that possess both effective antibacterial and angiogenic ***:In this study,we utilized electrospinning technology to fabricate hyaluronic acid-cellulose acetate fibrous membrane dressings,incorporating poly(ionic liquid)as an antibacterial polymer and deferoxamine as an angiogenic ***:The resulting fibrous membrane dressing contained poly(ionic liquid)and deferoxamin showcased a microporous structure,drug-releasing capabilities,and excellent air *** not only demonstrated highly effective antibacterial properties but also exhibited remarkable angiogenesis,thereby promoting the healing of full-thickness skin defect wounds in both in vitro and in vivo ***:These findings highlight the immense potential of this wound dressing material for future clinical applications.

关键词： electro spinning antibacterial polymer angiogenesis wound healing membrane dressing

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三芳基碳正离子在有机合成中的应用

有机化学 2024年第2期44卷 421-437页

作者：李路瑶贺忠文张振国贾振华罗德平河南工业大学前沿交叉科学与技术学院郑州450001 南洋理工大学物理与数学科学学院化学与生物化学系新加坡637371

三芳基碳正离子作为一种优异的路易斯酸,其最低空分子轨道(LUMO)轨道能级较低,易接受一对电子,被广泛应用于合成转化中,是重要的试剂和催化剂.近年来,三芳基碳正离子在有机合成中主要被用作催化剂、预催化剂、共催化剂和添加剂.此外,三... 详细信息

三芳基碳正离子作为一种优异的路易斯酸,其最低空分子轨道(LUMO)轨道能级较低,易接受一对电子,被广泛应用于合成转化中,是重要的试剂和催化剂.近年来,三芳基碳正离子在有机合成中主要被用作催化剂、预催化剂、共催化剂和添加剂.此外,三芳基碳正离子作为关键中间体,可以成功应用于四芳基甲烷的合成.综述了近年来三芳基碳正离子在有机合成中的应用进展,并总结了三芳基碳正离子在有机合成中的多种功能作用,希望引起广泛的关注.

关键词：三芳基碳正离子催化剂有机合成无金属

Ultrahigh Loading Copper Single Atom Catalyst for Palladium-free Wacker Oxidation

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Chemical Research in Chinese Universities 2022年第5期38卷 1239-1242页

作者： SONG Jingting LIU jia loh Kian Ping CHEN Zhongxin Department of Chemistry National University of SingaporeSingapore 117543Singapore Joint School of National University of Singapore and Tianjin University International Campus of Tianjin UniversityFuzhou 350207P.R.China

Wacker oxidation is an industry-adopted process to transform olefins into value-added epoxides and ***,traditional Wacker oxidation involves the use of homogeneous palladium and copper catalysts for the olefin addition and reductive ***,we demonstrated an ultrahigh loading Cu single atom catalyst(14%Cu,mass fraction)for the palladium-free Wacker oxidation of 4-vinylanisole into the corresponding ketone with N-methylhydroxylamine hydrochloride as an additive under mild *** studies by ^(18)O and deuterium isotope labelling revealed a hydrogen shift mechanism in this palladium-free process using N-methylhydroxylamine hydrochloride as the oxygen *** reaction scope can be further extended to Kucherov *** study paves the way to replace noble metal catalysts in the traditional homogeneous processes with single atom catalysts.

关键词： Single atom catalyst Wacker oxidation Ultrahigh loading High valued chemical Organic catalysis

Engineering Single Atom Catalysts for Flow Production:From Catalyst Design to Reactor Understandings

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Accounts of Materials Research 2023年第1期4卷 27-41页

作者： Zhongxin Chen jia Liu Kian Ping loh Department of Chemistry National University of SingaporeSingapore 117543Singapore

CONSPECTUS:In heterogeneous catalysis,the long-standing challenge isto achieve extremely high activity and chemoselectivity in liquid-phaseorganic transformations comparable to that of homogeneous or ***-atom catalysts(SACs)with atomically precise coordinationare developed with the objectives to mimic the homogeneous pathwaysbut face stability issues due to metal leaching or ***,thepractical application of SACs in chemical production is hampered by thelack of standard preparation protocols and low conversion using laboratorybatch *** Account focuses on our recent studies in both catalyst design andreactor-level engineering for the flow synthesis of fine chemicals via *** the catalyst and reaction level,we will discuss the intrinsic mechanismthat controls reactivity and chemoselectivity in the SAC-catalyzed processand highlight examples where SACs outperform other catalytic ***,we reported the SAC-mediated preparationand late-stage functionalization of pharmaceutical drugs,including lonidamine,Tamiflu,cavosonstat,indomethacin,and many othersby chemoselective transformations in a sequential or multicomponent *** ability of ultrahigh loading SACs in providing amultisite pathway for organic transformations involving two or more reactants is highlighted and contrasted with the single-sitepathway in conventional ***-level understanding on the dynamic catalytic cycle obtained using operando X-rayabsorption spectroscopies provides guidance for the design of more effective and leach resistant *** also calls for thetransformation of laboratory powder-based catalysts into industrially viable monolithic catalysts via formulation to further enhancethe leach *** the reactor level,we will highlight the importance of continuous-flow techniques in maximizing productivityand simplifying process transfer from laboratory to commercial ***,we discuss the use

关键词： catalyst overcome kinetics

Development of catalyst-free carbon-sulfur bond formation reactions under aqueous media and their applications

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Green Synthesis and Catalysis 2022年第4期3卷 309-316页

作者： Min Sun Kang Joycelyn Yi Xin Khoo Zhenhua jia Teck-Peng loh Division of Chemistry and Biological Chemistry School of ChemistryChemical Engineering and Biotechnology(CCEB)Nanyang Technological UniversitySingapore 637371Singapore Henan University of Technology 100 Lianhua StZhongyuan DistrictZhengzhou 450001China

Methods for the carbon-sulfur bond formation under catalyst-free,aqueous conditions are extremely useful in organic synthesis and chemical *** laboratory has developed methodologies to construct carbon-thiol bonds,carbon-sulfinic acid bonds,and carbon-disulfide bonds and such methodologies have been widely adopted by other research groups over multidisciplinary *** this article,our work on C-S bond formation in an aqueous solvent and its corresponding applications is summarized.

关键词： Green synthesis Biocompatible Water-based reaction Biologics C-S bond

Npac Is A Co-factor of Histone H3K36me3 and Regulates Transcriptional Elongation in Mouse Embryonic Stem Cells

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Genomics, Proteomics & Bioinformatics 2022年第1期20卷 110-128页

作者： Sue Yu jia Li Guanxu Ji Zhen Long Ng jiamin Siew Wan Ning Lo Ying Ye Yuan Yuan Chew Yun Chau Long Wensheng Zhang Ernesto Guccione Yuin Han loh Zhi-Hong jiang Henry Yang Qiang Wu Department of Biochemistry Yong Loo Lin School of MedicineNational University of SingaporeSingapore 117597Singapore Cancer Science Institute of Singapore Centre for Translational MedicineSingapore 117599Singapore The State Key Laboratory of Quality Research in Chinese Medicine Macao University of Science and TechnologyMacao Special Administrative Region 999078China Cam-Su Genomic Resource Center Soochow UniversitySuzhou 215123China Institute of Molecular and Cell Biology Singapore 138673Singapore

Chromatin modification contributes to pluripotency maintenance in embryonic stem cells(ESCs).However,the related mechanisms remain ***,we show that Npac,a"reader"of histone H3 lysine 36 trimethylation(H3K36me3),is required to maintain mouse ESC(mESC)pluripotency since knockdown of Npac causes mESC *** of Npac in mouse embryonic fibroblasts(MEFs)inhibits reprogramming ***,our chromatin immunoprecipitation followed by sequencing(ChIP-seq)results of Npac reveal that Npac co-localizes with histone H3K36me3 in gene bodies of actively transcribed genes in ***,we find that Npac interacts with positive transcription elongation factor b(p-TEFb),Ser2-phosphorylated RNA PolⅡ(RNA PolⅡSer2P),and Ser5-phosphorylated RNA PolⅡ(RNA PolⅡSer5 P).Furthermore,depletion of Npac disrupts transcriptional elongation of the pluripotency genes Nanog and *** together,we propose that Npac is essential for the transcriptional elongation of pluripotency genes by recruiting p-TEFb and interacting with RNA PolⅡSer2P and Ser5P.

关键词： Npac Pluripotency Reprogramming Histone H3K36me3 Transcriptional elongation

Stereoselective Synthesis of cis-2,5-Disubstituted Pyrrolidines via Copper-Catalyzed Cyclization of Alkenes

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Chinese Journal of Chemistry 2016年第11期34卷 1076-1080页

作者： Sai-Hu Cai Bing-Chao Da jia-Hui Zhou Yun-He Xu Teck-Peng loh Department of Chemistry University of Science and Technology of China Hefei Anhui 230026 China DiVision of Chemistry and Biological Chemistry School of Physical and Mathematical Sciences Nanyang Technological University 637371 Singapore

An efficient methodology for the stereoselective synthesis of cis-2,5-disubstituted pyrrolidines using copper catalyst was developed. The corresponding cis-2,5-disubstituted pyrrolidines could be obtained in reasonable yields and with good stereoselectivities in the presence of 4,4＇-di-tert-butyl-2,2＇-bipyridine as ligand and l-methyl-2-pyrrolidinone as solvent.

关键词： stereoselectivity pyrrolidines copper-catalyzed cyclization