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  • Biotechnological and Therapeutic Applications of Natural Nucleic Acid Structural Motifs
    Top. Curr. Chem. (IF 6.721) Pub Date : 2020-02-18
    Jinwei Duan, Xing Wang, Megan E. Kizer

    Abstract Genetic information and the blueprint of life are stored in the form of nucleic acids. The primary sequence of DNA, read from the canonical double helix, provides the code for RNA and protein synthesis. Yet these already-information-rich molecules have higher-order structures which play critical roles in transcription and translation. Uncovering the sequences, parameters, and conditions which govern the formation of these structural motifs has allowed researchers to study them and to utilize them in biotechnological and therapeutic applications in vitro and in vivo. This review covers both DNA and RNA structural motifs found naturally in biological systems including catalytic nucleic acids, non-coding RNA, aptamers, G-quadruplexes, i-motifs, and Holliday junctions. For each category, an overview of the structural characteristics, biological prevalence, and function will be discussed. The biotechnological and therapeutic applications of these structural motifs are highlighted. Future perspectives focus on the addition of proteins and unnatural modifications to enhance structural stability for greater applicability.

    更新日期:2020-02-18
  • Theoretical Exploration and Electronic Applications of Conductive Two-Dimensional Metal–Organic Frameworks
    Top. Curr. Chem. (IF 6.721) Pub Date : 2020-02-18
    Jia Gao, Shubo Geng, Yao Chen, Peng Cheng, Zhenjie Zhang

    Abstract Two-dimensional (2D) metal–organic frameworks (MOFs) belong to a subgroup of MOFs reminiscent of graphite and covalent organic frameworks (COFs). In the past decade, conductive 2D MOFs have received increasing attention due to their relatively high charge carrier mobility and low resistivity that originate from in-plane charge delocalization and extended π conjugation within the layers. This review comprises the current state-of-the-art of the representative progress in theoretical exploration and electronic applications of conductive 2D MOFs. Special emphasis is placed on the intrinsic relations between the structural factors and the electronic properties of conductive 2D MOFs. This review will provide guidance for researchers to design and synthesize conductive 2D MOFs for advanced applications.

    更新日期:2020-02-18
  • Oligonucleotide–Polymer Conjugates: From Molecular Basics to Practical Application
    Top. Curr. Chem. (IF 6.721) Pub Date : 2020-02-17
    Fan Xiao, Zixiang Wei, Maggie Wang, Alexandra Hoff, Ying Bao, Leilei Tian

    Abstract DNA exhibits many attractive properties, such as programmability, precise self-assembly, sequence-coded biomedical functions, and good biocompatibility; therefore, DNA has been used extensively as a building block to construct novel nanomaterials. Recently, studies on oligonucleotide–polymer conjugates (OPCs) have attracted increasing attention. As hybrid molecules, OPCs exhibit novel properties, e.g., sophisticated self-assembly behaviors, which are distinct from the simple combination of the functions of DNA and polymer, making OPCs interesting and useful. The synthesis and applications of OPCs are highly dependent on the choice of the polymer block, but a systematic summary of OPCs based on their molecular structures is still lacking. In order to design OPCs for further applications, it is necessary to thoroughly understand the structure–function relationship of OPCs. In this review, we carefully categorize recently developed OPCs by the structures of the polymer blocks, and discuss the synthesis, purification, and applications for each category. Finally, we will comment on future prospects for OPCs.

    更新日期:2020-02-18
  • Construction of Biologically Important Biaryl Scaffolds through Direct C–H Bond Activation: Advances and Prospects
    Top. Curr. Chem. (IF 6.721) Pub Date : 2020-02-17
    Shuo Yuan, Junbiao Chang, Bin Yu

    Abstract Biaryl scaffolds are prevalent in natural products and drug molecules, and biaryl-containing compounds have been shown to exhibit diverse and interesting biological activities. To date, numerous synthetic methods, particularly direct C–H bond activation, have been developed for the construction of such scaffolds, due to their interesting structural features and biological profiles. We highlight herein recent advances in the construction of biologically important biaryl fragments through direct C–H bond activation and also demonstrate the application of direct C–H arylation in the total synthesis of biaryl-containing natural products and drug molecules. Graphic Abstract Selected biaryl-containing compounds

    更新日期:2020-02-18
  • Aptamer-Functionalized DNA Nanostructures for Biological Applications
    Top. Curr. Chem. (IF 6.721) Pub Date : 2020-02-07
    Xiaoyi Fu, Fangqi Peng, Jungyeon Lee, Qi Yang, Fei Zhang, Mengyi Xiong, Gezhi Kong, Hong-min Meng, Guoliang Ke, Xiao-Bing Zhang

    Abstract DNA nanostructures hold great promise for various applications due to their remarkable properties, including programmable assembly, nanometric positional precision, and dynamic structural control. The past few decades have seen the development of various kinds of DNA nanostructures that can be employed as useful tools in fields such as chemistry, materials, biology, and medicine. Aptamers are short single-stranded nucleic acids that bind to specific targets with excellent selectivity and high affinity and play critical roles in molecular recognition. Recently, many attempts have been made to integrate aptamers with DNA nanostructures for a range of biological applications. This review starts with an introduction to the features of aptamer-functionalized DNA nanostructures. The discussion then focuses on recent progress (particularly during the last five years) in the applications of these nanostructures in areas such as biosensing, bioimaging, cancer therapy, and biophysics. Finally, challenges involved in the practical application of aptamer-functionalized DNA nanostructures are discussed, and perspectives on future directions for research into and applications of aptamer-functionalized DNA nanostructures are provided.

    更新日期:2020-02-07
  • Recent Advances on the C2-Functionalization of Indole via Umpolung
    Top. Curr. Chem. (IF 6.721) Pub Date : 2020-02-07
    Bhaskar Deka, Mohit L. Deb, Pranjal K. Baruah

    Abstract Heterocyclic compounds having a nitrogen atom in the ring exhibit very interesting biological activities. Indole is the core structure of many bioactive compounds owing to its high affinity to bind with most biological targets. Indole is an electron-rich compound and generally prefers electrophilic rather than nucleophilic substitution. Hence, many important indole derivatives are difficult to synthesize through the conventional reactivity of indole. This limitation can be avoided by using the umpolung, from the German word meaning polarity inversion. In umpolung, the indole molecule, especially the C2 and C3 positions, behave as an electrophile. As C2-functionalized indoles have substantial importance in synthetic and pharmaceutical chemistry, this review focuses on the C2 umpolung of indoles via the indirect approach which is less explored. Unlike direct approaches of indole umpolung, indirect methods have several advantages and therefore a number of research articles have been published in this field. But no review is available up till now. This is the first review on this topic and we believe that it will surely motivate the readers to work in this area further.

    更新日期:2020-02-07
  • Why Design Matters: From Decorated Metal Oxide Clusters to Functional Metal–Organic Frameworks
    Top. Curr. Chem. (IF 6.721) Pub Date : 2020-02-03
    Alexander Schoedel, Sahar Rajeh

    Abstract The opportunity to generate functional solids with defined properties by deliberate design has not been materialized in traditional solid-state chemistry over many decades. The emergence of metal–organic frameworks (MOFs), permanently porous, crystalline solids with defined metrics, has allowed for studying design, synthesis, and properties, which then translated into new applications. Aggregates of metal ions stitched together by multidentate functional groups form such metal oxide clusters and represent the nodes of MOFs. These clusters, termed secondary building units (SBUs), are decorated with organic moieties that provide directionality and can be linked through geometric principles into extended nets using organic molecules (spacers). This concept of reticular chemistry has afforded permanently porous MOFs, and has resulted in over 20,000 structures over the past 20 years. However, there are still only a limited number of symmetric, discrete SBUs commonly used to design and synthesize MOFs. We herein introduce the most important SBUs that have emerged over time together with prototypal MOF structures and their fundamental applications. Both the discovery and the scientific impact will be highlighted alongside advantages and/or drawbacks. In addition, an outlook will be given on how the combination of multiple SBUs can lead to heterogeneous but ordered materials with higher complexity and functionality.

    更新日期:2020-02-03
  • High-performance biosensing based on autonomous enzyme-free DNA circuits
    Top. Curr. Chem. (IF 6.721) Pub Date : 2020-02-03
    Hong Wang, Huimin Wang, Itamar Willner, Fuan Wang

    Abstract Nucleic acids are considered not only extraordinary carriers of genetic information but also are perceived as the perfect elemental materials of molecular recognition and signal transduction/amplification for assembling programmable artificial reaction networks or circuits, which are similar to conventional electronic logic devices. Among these sophisticated DNA-based reaction networks, catalytic hairpin assembly (CHA), hybridization chain reaction (HCR), and DNAzyme represent the typical nonenzymatic amplification methods with high robustness and efficiency. Furthermore, their extensive hierarchically cascade integration into multi-layered autonomous DNA circuits establishes novel paradigms for constructing more different catalytic DNA nanostructures and for regenerating or replicating diverse molecular components with specific functions. Various DNA and inorganic nanoscaffolds have been used to realize the surface-confined DNA reaction networks with significant biomolecular sensing and signal-regulating functions in living cells. Especially, the specific aptamers and metal-ion-bridged duplex DNA nanostructures could extend their paradigms for detecting small molecules and proteins in even living entities. Herein, the varied enzyme-free DNA circuits are introduced in general with an extensive explanation of their underlying molecular reaction mechanisms. Challenges and outlook of the autonomous enzyme-free DNA circuits will also be discussed at the end of this chapter.

    更新日期:2020-02-03
  • DNA-Driven Nanoparticle Assemblies for Biosensing and Bioimaging
    Top. Curr. Chem. (IF 6.721) Pub Date : 2020-02-03
    Yuan Zhao, Lixia Shi, Hua Kuang, Chuanlai Xu

    Abstract DNA molecules with superior flexibility, affinity and programmability have garnered considerable attention for the controllable assembly of nanoparticles (NPs). By controlling the density, length and sequences of DNA on NPs, the configuration of NP assemblies can be rationally designed. The specific recognition of DNA enables changes to be made to the spatial structures of NP assemblies, resulting in differences in tailorable optical signals. Comprehensive information on the fabrication of DNA-driven NP assemblies would be beneficial for their application in biosensing and bioimaging. This review analyzes the progress of DNA-driven NP assemblies, and discusses the tunable configurations determined by the structural parameters of DNA skeletons. The collective optical properties, such as chirality, fluorescence and surface enhanced Raman resonance (SERS), etc., of DNA-driven NP assemblies are explored, and engineered tailorable optical properties of these spatial structures are achieved. We discuss the development of DNA-directed NP assemblies for the quantification of DNA, toxins, and heavy metal ions, and demonstrate their potential application in the biosensing and bioimaging of tumor markers, RNA, living metal ions and phototherapeutics. We hihghlight possible challenges in the development of DNA-driven NP assemblies, and further direct potential prospects in the practical applications of macroscopical materials and photonic devices.

    更新日期:2020-02-03
  • Metal–Organic Frameworks Towards Desulfurization of Fuels
    Top. Curr. Chem. (IF 6.721) Pub Date : 2020-01-29
    Leiduan Hao, Matthew J. Hurlock, Guodong Ding, Qiang Zhang

    Abstract Petroleum is an essential source of energy for our daily life. However, crude oil contains various kinds of sulfur-containing compounds that will form sulfur oxides upon combustion and cause severe environmental problems. To reduce the environmental impact of petroleum energy, the desulfurization of fuels is necessary. Metal–organic frameworks (MOFs), an emerging class of porous materials, have shown great potential in a variety of applications. In this review, we summarize the use of MOFs in the desulfurization of fuels. The scope of this review includes MOFs and MOF-derived materials that have been applied in oxidative desulfurization and adsorptive desulfurization processes. We aim to provide an overview of the progress of MOFs in fuel desulfurization as well as shed light on the development of superior MOF-based materials in the field of desulfurization.

    更新日期:2020-01-29
  • Tertiary Amine Lewis Base Catalysis in Combination with Transition Metal Catalysis
    Top. Curr. Chem. (IF 6.721) Pub Date : 2020-01-16
    Gary J. Knox, Luke S. Hutchings-Goetz, Colin M. Pearson, Thomas N. Snaddon

    Abstract The cooperation between two orthogonal catalytic events during the formation of carbon–carbon and carbon–heteroatom bonds has emerged as an effective strategy for enantioselective chemical synthesis. In recent years, a number of pioneering investigations have described useful chemical synthesis methods whereby the reactivity or nucleophile–electrophile combinations can be fine-tuned or extended far beyond the effect and influence of a single catalyst. The recognition of this has had profound implications for the development cooperative catalysis as a field and has provided a foundation for the development of broadly useful chemical synthesis methods. This chapter focuses on the combination of tertiary amine Lewis base and transition metal catalysts, which the authors hope will simulate further developments and advances.

    更新日期:2020-01-16
  • Carbon Nanotubes in Biomedicine
    Top. Curr. Chem. (IF 6.721) Pub Date : 2020-01-14
    Viviana Negri, Jesús Pacheco-Torres, Daniel Calle, Pilar López-Larrubia

    Nowadays, biomaterials have become a crucial element in numerous biomedical, preclinical, and clinical applications. The use of nanoparticles entails a great potential in these fields mainly because of the high ratio of surface atoms that modify the physicochemical properties and increases the chemical reactivity. Among them, carbon nanotubes (CNTs) have emerged as a powerful tool to improve biomedical approaches in the management of numerous diseases. CNTs have an excellent ability to penetrate cell membranes, and the sp2 hybridization of all carbons enables their functionalization with almost every biomolecule or compound, allowing them to target cells and deliver drugs under the appropriate environmental stimuli. Besides, in the new promising field of artificial biomaterial generation, nanotubes are studied as the load in nanocomposite materials, improving their mechanical and electrical properties, or even for direct use as scaffolds in body tissue manufacturing. Nevertheless, despite their beneficial contributions, some major concerns need to be solved to boost the clinical development of CNTs, including poor solubility in water, low biodegradability and dispersivity, and toxicity problems associated with CNTs’ interaction with biomolecules in tissues and organs, including the possible effects in the proteome and genome. This review performs a wide literature analysis to present the main and latest advances in the optimal design and characterization of carbon nanotubes with biomedical applications, and their capacities in different areas of preclinical research.

    更新日期:2020-01-14
  • Insights into the Gas Adsorption Mechanisms in Metal–Organic Frameworks from Classical Molecular Simulations
    Top. Curr. Chem. (IF 6.721) Pub Date : 2020-01-13
    Tony Pham, Brian Space

    Classical molecular simulations can provide significant insights into the gas adsorption mechanisms and binding sites in various metal–organic frameworks (MOFs). These simulations involve assessing the interactions between the MOF and an adsorbate molecule by calculating the potential energy of the MOF–adsorbate system using a functional form that generally includes nonbonded interaction terms, such as the repulsion/dispersion and permanent electrostatic energies. Grand canonical Monte Carlo (GCMC) is the most widely used classical method that is carried out to simulate gas adsorption and separation in MOFs and identify the favorable adsorbate binding sites. In this review, we provide an overview of the GCMC methods that are normally utilized to perform these simulations. We also describe how a typical force field is developed for the MOF, which is required to compute the classical potential energy of the system. Furthermore, we highlight some of the common analysis techniques that have been used to determine the locations of the preferential binding sites in these materials. We also review some of the early classical molecular simulation studies that have contributed to our working understanding of the gas adsorption mechanisms in MOFs. Finally, we show that the implementation of classical polarization for simulations in MOFs can be necessary for the accurate modeling of an adsorbate in these materials, particularly those that contain open-metal sites. In general, molecular simulations can provide a great complement to experimental studies by helping to rationalize the favorable MOF–adsorbate interactions and the mechanism of gas adsorption.

    更新日期:2020-01-13
  • DNA–Iron Oxide Nanoparticles Conjugates: Functional Magnetic Nanoplatforms in Biomedical Applications
    Top. Curr. Chem. (IF 6.721) Pub Date : 2020-01-10
    José Raúl Sosa-Acosta, Claudia Iriarte-Mesa, Greter A. Ortega, Alicia M. Díaz-García

    Abstract The use of magnetic nanoparticles (MNPs), such as iron oxide nanoparticles (IONPs), in biomedicine is considered to be a valuable alternative to the more traditional materials due to their chemical stability, cost-effectiveness, surface functionalization, and the possibility to selectively attach and transport targeted species to the desired location under a magnetic field. One of the many main applications of MNPs is DNA separation, which enables genetic material manipulation; consequently, MNPs are used in numerous biotechnological methods, such as gene transfection and molecular recognition systems. In addition, the interaction between the surfaces of MNPs and DNA molecules and the magnetic nature of the resulting composite have facilitated the development of safe and effective gene delivery vectors to treat significant diseases, such as cancer and neurological disorders. Furthermore, the special recognition properties of nucleic acids based on the binding capacity of DNA and the magnetic behavior of the nanoparticles allowing magnetic separation and concentration of analytes have led to the development of biosensors and diagnostic assays; however, both of these applications face important challenges in terms of the improvement of selective nanocarriers and biosensing capacity. In this review, we discuss some aspects of the properties and surface functionalization of MNPs, the interactions between DNA and IONPs, the preparation of DNA nanoplatforms and their biotechnological applications, such as the magnetic separation of DNA, magnetofection, preparation of DNA vaccines, and molecular recognition tools.

    更新日期:2020-01-10
  • MOFs-Based Catalysts Supported Chemical Conversion of CO 2
    Top. Curr. Chem. (IF 6.721) Pub Date : 2020-01-06
    Ying Shi, Shengli Hou, Xiaohang Qiu, Bin Zhao

    The dramatic increase in atmospheric carbon dioxide (CO2) concentrations has attracted human attention and many strategies about converting CO2 into high-value chemicals have been put forward. Metal–organic frameworks (MOFs), as a class of versatile materials, have been widely used in CO2 capture and chemical conversion, due to their unique porosity, multiple active centers and good stability and recyclability. Herein, we focused on the processes of chemical conversion of CO2 by MOFs-based catalysts, including the coupling reactions of epoxides, aziridines or alkyne molecules, CO2 hydrogenation, and other CO2 conversion reactions. The synthesized methods and high catalytic activity of MOFs-based materials were also analyzed systematically. Finally, a brief perspective on feasible strategies is presented to improve the catalytic activity of novel MOFs-based materials and explore the new CO2 conversion reactions.

    更新日期:2020-01-06
  • DNA Strand Displacement Reaction: A Powerful Tool for Discriminating Single Nucleotide Variants
    Top. Curr. Chem. (IF 6.721) Pub Date : 2020-01-02
    Weiyang Tang, Weiye Zhong, Yun Tan, Guan A. Wang, Feng Li, Yizhen Liu

    Abstract Single-nucleotide variants (SNVs) that are strongly associated with many genetic diseases and tumors are important both biologically and clinically. Detection of SNVs holds great potential for disease diagnosis and prognosis. Recent advances in DNA nanotechnology have offered numerous principles and strategies amenable to the detection and quantification of SNVs with high sensitivity, specificity, and programmability. In this review, we will focus our discussion on emerging techniques making use of DNA strand displacement, a basic building block in dynamic DNA nanotechnology. Based on their operation principles, we classify current SNV detection methods into three main categories, including strategies using toehold-mediated strand displacement reactions, toehold-exchange reactions, and enzyme-mediated strand displacement reactions. These detection methods discriminate SNVs from their wild-type counterparts through subtle differences in thermodynamics, kinetics, or response to enzymatic manipulation. The remarkable programmability of dynamic DNA nanotechnology also allows the predictable design and flexible operation of diverse strand displacement probes and/or primers. Here, we offer a systematic survey of current strategies, with an emphasis on the molecular mechanisms and their applicability to in vitro diagnostics.

    更新日期:2020-01-02
  • Gold, Silver and Iron Oxide Nanoparticles: Synthesis and Bionanoconjugation Strategies Aimed at Electrochemical Applications
    Top. Curr. Chem. (IF 6.721) Pub Date : 2020
    Claudia Iriarte-Mesa,Yeisy C. López,Yasser Matos-Peralta,Karen de la Vega-Hernández,Manuel Antuch

    Nanomaterials have revolutionized the sensing and biosensing fields, with the development of more sensitive and selective devices for multiple applications. Gold, silver and iron oxide nanoparticles have played a particularly major role in this development. In this review, we provide a general overview of the synthesis and characteristics of gold, silver and iron oxide nanoparticles, along with the main strategies for their surface functionalization with ligands and biomolecules. Finally, different architectures suitable for electrochemical applications are reviewed, as well as their main fabrication procedures. We conclude with some considerations from the authors’ perspective regarding the promising use of these materials and the challenges to be faced in the near future.

    更新日期:2020-01-01
  • Recent Progress in Asymmetric Relay Catalysis of Metal Complex with Chiral Phosphoric Acid
    Top. Curr. Chem. (IF 6.721) Pub Date : 2019-12-27
    Pu-Sheng Wang, Dian-Feng Chen, Liu-Zhu Gong

    Asymmetric metal/organo relay catalysis, utilizing a metal complex and a chiral organocatalyst in a one-pot cascade reaction, is aimed to sequentially impart activation on multiple steps by distinct catalysts. Such a catalysis merges the advantages of both metal catalysis and organocatalysis, providing step-economy, and, more importantly, the potential to achieve inaccessible reactivity by a single catalyst. Chiral phosphoric acids are among the most robust organocatalysts, rendering a broad range of enantioselective bond-forming reactions. The combination of metal complexes and chiral phosphoric acids in a single vessel has been well documented. In particular, the asymmetric relay catalysis of metal complex with chiral phosphoric acid has grown rapidly since 2008. Several excellent reviews have been published to cover almost all examples in this area from 2008 to early 2014; therefore, in this chapter, we will mainly highlight progress from 2014 to mid-2019.

    更新日期:2019-12-27
  • Bioconjugated Plasmonic Nanoparticles for Enhanced Skin Penetration
    Top. Curr. Chem. (IF 6.721) Pub Date : 2019-12-16
    David Alba-Molina, Juan J. Giner-Casares, Manuel Cano

    Plasmonic nanoparticles (NPs) are one of the most promising and studied inorganic nanomaterials for different biomedical applications. Plasmonic NPs have excellent biocompatibility, long-term stability against physical and chemical degradation, relevant optical properties, well-known synthesis methods and tuneable surface functionalities. Herein, we review recently reported bioconjugated plasmonic NPs using different chemical approaches and loading cargoes (such as drugs, genes, and proteins) for enhancement of transdermal delivery across biological tissues. The main aim is to understand the interaction of the complex skin structure with biomimetic plasmonic NPs. This knowledge is not only important in enhancing transdermal delivery of pharmaceutical formulations but also for controlling undesired skin penetration of industrial products, such as cosmetics, sunscreen formulations and any other mass-usage consumable that contains plasmonic NPs.

    更新日期:2019-12-17
  • Limitations and Prospects for Wastewater Treatment by UV and Visible-Light-Active Heterogeneous Photocatalysis: A Critical Review
    Top. Curr. Chem. (IF 6.721) Pub Date : 2019-12-16
    Giuseppina Iervolino, Ian Zammit, Vincenzo Vaiano, Luigi Rizzo

    Heterogeneous photocatalysis (HPC) has been widely investigated in recent decades for the removal of a number of contaminants from aqueous matrices, but its application in real wastewater treatment at full scale is still scarce. Indeed, process and technological limitations have made HPC uncompetitive with respect to consolidated processes/technologies so far. In this manuscript, these issues are critically discussed and reviewed with the aim of providing the reader with a realistic picture of the prospective application of HPC in wastewater treatment. Accordingly, consolidated and new photocatalysts (among which the visible active ones are attracting increasing interest among the scientific community), along with preparation methods, are reviewed to understand whether, with increased process efficiency, these methods can be realistically and competitively developed at industrial scale. Precipitation is considered as an attractive method for photocatalyst preparation at the industrial scale; sol–gel and ultrasound may be feasible only if no expensive metal precursor is used, while hydrothermal and solution combustion synthesis are expected to be difficult (expensive) to scale up. The application of HPC in urban and industrial wastewater treatment and possible energy recovery by hydrogen production are discussed in terms of current limitations and future prospects. Despite the fact that HPC has been studied for the removal of pollutants in aqueous matrices for two decades, its use in wastewater treatment is still at a “technological research” stage. In order to accelerate the adoption of HPC at full scale, it is advisable to focus on investigations under real conditions and on developing/improving pilot-scale reactors to better investigate scale-up conditions and the potential to successfully address specific challenges in wastewater treatment through HPC. In realistic terms, the prospective use of HPC is more likely as a tertiary treatment of wastewater, particularly if more stringent regulations come into force, than as pretreatment for industrial wastewater to improve biodegradability.

    更新日期:2019-12-17
  • Ferrite Materials for Photoassisted Environmental and Solar Fuels Applications
    Top. Curr. Chem. (IF 6.721) Pub Date : 2019-12-16
    Patricia Garcia-Muñoz, Fernando Fresno, Víctor A. de la Peña O’Shea, Nicolas Keller

    Ferrites are a large class of oxides containing Fe3+ and at least another metal cation that have been investigated for and applied to a wide variety of fields ranging from mature technologies like circuitry, permanent magnets, magnetic recording and microwave devices to the most recent developments in areas like bioimaging, gas sensing and photocatalysis. In the last respect, although ferrites have been less studied than other types of semiconductors, they present interesting properties such as visible light absorption, tuneable optoelectronic properties and high chemical and photochemical stability. The versatility of their chemical composition and of their crystallographic structure opened a playground for developing new catalysts with enhanced efficiency. This article reviews the recent development of the application of ferrites to photoassisted processes for environmental remediation and for the synthesis of solar fuels. Applications in the photocatalytic degradation of pollutants in water and air, photo-Fenton, and solar fuels production, via photocatalytic and photoelectrochemical water splitting and CO2 reduction, are reviewed paying special attention to the relationships between the physico-chemical characteristics of the ferrite materials and their photoactivated performance.

    更新日期:2019-12-17
  • Functionalized Dynamic Metal–Organic Frameworks as Smart Switches for Sensing and Adsorption Applications
    Top. Curr. Chem. (IF 6.721) Pub Date : 2019-12-11
    Binbin Qian, Ze Chang, Xian-He Bu

    Over the past two decades, metal–organic frameworks (MOFs) with flexible structures or dynamic behavior have shown great potential as functional materials in many fields. This paper presents a review of these dynamic and functional MOFs, which can undergo controllable and reversible transformation, with regard to their application as smart switches. Trigger conditions, which include physical/chemical stimuli (e.g., guest molecules, light, temperature, pressure), are also discussed. Research methods for investigating the dynamic processes and mechanisms involving experimental characterization and computational modeling are briefly mentioned as well. The emphasis is on the aspects of the design and functionalization of dynamic MOFs. The pre-design of metal nodes, organic linkers, and topology, as well as post-modification of components, increases the possibility of obtaining functionalized dynamic materials. Recent advances with regard to potential applications for dynamic frameworks as smart switches for adsorption and sensing are also reviewed.

    更新日期:2019-12-11
  • Regulation of the Degree of Interpenetration in Metal–Organic Frameworks
    Top. Curr. Chem. (IF 6.721) Pub Date : 2019-12-02
    Gaurav Verma, Sydney Butikofer, Sanjay Kumar, Shengqian Ma

    Interpenetration in metal–organic frameworks (MOFs) can have significant impacts on the structure, porous nature, and functional applications of MOFs. Considered to be disadvantageous in the initial phases leading to a decrease in surface area, interpenetration has proved to be highly useful for modulation of pore size and selective separation of gases. The importance of interpenetration has been realized over the last decade, and numerous approaches to graft interpenetration and utilize it for improved functions and applications have been achieved. Several factors such as temperature, solvent system, time duration and steric aspects of the ligands have been utilized to regulate the degree of interpenetration (DOI). In this review, we summarize recent advances in regulating the DOI in MOFs and its impact on the resulting properties.

    更新日期:2019-12-02
  • Waste-derived Materials: Opportunities in Photocatalysis
    Top. Curr. Chem. (IF 6.721) Pub Date : 2019-11-28
    Daily Rodríguez-Padrón, Rafael Luque, Mario J. Muñoz-Batista

    Waste-derived materials have been gaining increased attention in recent years due to their great potential and environmentally friendly nature. Several contributions in the literature have covered the advances achieved so far in this area. Nonetheless, to the best of our knowledge, no review has been dedicated specifically to waste-derived or templated photocatalytic materials. Both photocatalysis and (bio)waste-inspired design yield materials of a remarkably green nature. Therefore, the partnership between them may open promising possibilities for both waste valorization and photocatalytic processes, which in turn will lead to sustainable development globally, with the potential for full utilization of renewable energy sources such as biomass and sunlight. Several photocatalytic waste-derived materials, synthetic procedures, and applications will be described throughout this work, including waste-derived/templated TiO2, ZnO, and metal sulfide materials. Special attention will be given to biomass-inspired carbonaceous materials, including carbon quantum dots and graphitic carbon nitride (g-C3N4).

    更新日期:2019-11-28
  • Asymmetric Reactions Enabled by Cooperative Enantioselective Amino- and Lewis Acid Catalysis
    Top. Curr. Chem. (IF 6.721) Pub Date : 2019-11-25
    Pier Giorgio Cozzi, Andrea Gualandi, Simone Potenti, Francesco Calogero, Giacomo Rodeghiero

    Organocatalysis—the branch of catalysis featuring small organic molecules as the catalysts—has, in the last decade, become of central importance in the field of asymmetric catalysis, so much that it is now comparable to metal catalysis and biocatalysis. Organocatalysis is rationalized and classified by a number of so-called activation modes, based on the formation of a covalent or not-covalent intermediate between the organocatalyst and the organic substrate. Among all the organocatalytic activation modes, enamine and iminium catalysis are widely used for the practical preparation of valuable products and intermediates, both in academic and industrial contexts. In both cases, chiral amines are employed as catalysts. Enamine activation mode is generally employed in the reaction with electrophiles, while nucleophiles require the iminium activation mode. Commonly, in both modes, the reaction occurs through well-organized transitions states. A large variety of partners can react with enamines and iminium ions, due to their sufficient nucleophilicity and electrophilicity, respectively. However, despite the success, organocatalysis still suffers from narrow scopes and applications. Multicatalysis is a possible solution for these drawbacks because the two different catalysts can synergistically activate the substrates, with a simultaneous activation of the two different reaction partners. In particular, in this review we will summarize the reported processes featuring Lewis acid catalysis and organocatalytic activation modes synergically acting and not interfering with each other. We will focus our attention on the description of processes in which good results cannot be achieved independently by organocatalysis or Lewis acid catalysis. In these examples of cooperative dual catalysis, a number of new organic transformations have been developed. The review will focus on the possible strategies, the choice of the Lewis acid and the catalytic cycles involved in the effective reported combination. Additionally, some important key points regarding the rationale for the effective combinations will be also included. π-Activation of organic substrates by Lewis acids, via formation of electrophilic intermediates, and their reaction with enamines will be also discussed in this review.

    更新日期:2019-11-26
  • Mechanochemical Forces as a Synthetic Tool for Zero- and One-Dimensional Titanium Oxide-Based Nano-photocatalysts
    Top. Curr. Chem. (IF 6.721) Pub Date : 2019-11-25
    Dimitrios A. Giannakoudakis, Gregory Chatel, Juan Carlos Colmenares

    A new field where the utilization of mechanochemistry can create new opportunities is materials chemistry, and, more interestingly, the synthesis of novel nanomaterials. Ball-milling procedures and ultrasonic techniques can be regarded as the most important mechanochemical synthetic tools, since they can act as attractive alternatives to the conventional methods. It is also feasible for the utilization of mechanochemical forces to act synergistically with the conventional synthesis (as a pre-treatment step, or simultaneously during the synthesis) in order to improve the synthetic process and/or the material’s desired features. The usage of ultrasound irradiation or ball-milling treatment is found to play a crucial role in controlling and enhancing the structural, morphological, optical, and surface chemistry features that are important for heterogeneous photocatalytic practices. The focus of this article is to collect all the available examples in which the utilization of sonochemistry or ball milling had unique effects as a synthesis tool towards zero- or one-dimensional nanostructures of a semiconductor which is assumed as a benchmark in photocatalysis, titanium dioxide.

    更新日期:2019-11-26
  • Fused Heteroaromatic Rings via Metal-Mediated/Catalyzed Intramolecular C–H Activation: A Comprehensive Review
    Top. Curr. Chem. (IF 6.721) Pub Date : 2019-07-23
    Angel H. Romero

    The present review highlights the most important recent contributions toward the synthesis of functionalized fused heteroaromatic rings via intramolecular C–H activation mediated or catalyzed by transition metals. This type of reaction constitutes a versatile strategy to obtain a great variety of fused heterocyclic systems through the formation of carbon–carbon (C–C) and C–heteroatom bonds from direct coupling between two adjacent C–H bonds or C–H/H–X bonds. The revision is focused on the synthesis of fused heterocycles through two chemical processes: (1) metal-catalyzed intramolecular oxidative C–H activation, and (2) intramolecular C–H activation mediated by metallic Lewis acids.

    更新日期:2019-11-18
  • Cross-Dehydrogenative Coupling Reactions Between C(sp)–H and X–H (X = N, P, S, Si, Sn) Bonds: An Environmentally Benign Access to Heteroatom-Substituted Alkynes
    Top. Curr. Chem. (IF 6.721) Pub Date : 2019-07-04
    Wanxi Peng, Esmail Vessally, Sattar Arshadi, Aazam Monfared, Akram Hosseinian, Ladan Edjlali

    Form a green and sustainable chemistry point of view, cross-dehydrogenative coupling (or oxidative cross-coupling) reactions have been recognized as environmentally sustainable and atom economical synthetic routes for the construction of new carbon–carbon and carbon–heteroatom bonds, since no pre-functionalization of starting materials is required. In the past few years, the direct coupling of sp-hybridized C–H bonds with heteroatom–H bonds has received much attention because of the importance of heteroatom-substituted alkynes in organic and medicinal chemistry. This review examines the recent developments in cross-dehydrogenative coupling reactions between C(sp)–H and X–H (X = N, P, S, Si, Sn) bonds, with a particular focus on the mechanistic aspects of the reactions.

    更新日期:2019-11-18
  • In the Search of Glycoside-Based Molecules as Antidiabetic Agents
    Top. Curr. Chem. (IF 6.721) Pub Date : 2019-06-05
    Aleksandra Pałasz, Dariusz Cież, Bartosz Trzewik, Katarzyna Miszczak, Grzegorz Tynor, Bartłomiej Bazan

    This review is an effort to summarize recent developments in synthesis of O-glycosides and N-, C-glycosyl molecules with promising antidiabetic potential. Articles published after 2000 are included. First, the O-glycosides used in the treatment of diabetes are presented, followed by the N-glycosides and finally the C-glycosides constituting the largest group of antidiabetic drugs are described. Within each group of glycosides, we presented how the structure of compounds representing potential drugs changes and when discussing chemical compounds of a similar structure, achievements are presented in the chronological order. C-Glycosyl compounds mimicking O-glycosides structure, exhibit the best features in terms of pharmacodynamics and pharmacokinetics. Therefore, the largest part of the article is concerned with the description of the synthesis and biological studies of various C-glycosides. Also N-glycosides such as N-(β-d-glucopyranosyl)-amides, N-(β-d-glucopyranosyl)-ureas, and 1,2,3-triazolyl derivatives belong to the most potent classes of antidiabetic agents. In order to indicate which of the compounds presented in the given sections have the best inhibitory properties, a list of the best inhibitors is presented at the end of each section. In summary, the best inhibitors were selected from each of the summarizing figures and the results of the ranking were placed. In this way, the reader can learn about the structure of the compounds having the best antidiabetic activity. The compounds, whose synthesis was described in the article but did not appear on the figures presenting the structures of the most active inhibitors, did not show proper activity as inhibitors. Thus, the article also presents studies that have not yielded the desired results and show directions of research that should not be followed. In order to show the directions of the latest research, articles from 2018 to 2019 are described in a separate Sect. 5. In Sect. 6, biological mechanisms of action of the glycosides and patents of marketed drugs are described.

    更新日期:2019-11-18
  • Enamine/Transition Metal Combined Catalysis: Catalytic Transformations Involving Organometallic Electrophilic Intermediates
    Top. Curr. Chem. (IF 6.721) Pub Date : 2019-11-16
    Samson Afewerki, Armando Córdova

    The concept of merging enamine activation catalysis with transition metal catalysis is an important strategy, which allows for selective chemical transformations not accessible without this combination. The amine catalyst activates the carbonyl compounds through the formation of a reactive nucleophilic enamine intermediate and, in parallel, the transition metal activates a wide range of functionalities such as allylic substrates through the formation of reactive electrophilic π-allyl-metal complex. Since the first report of this strategy in 2006, considerable effort has been devoted to the successful advancement of this technology. In this chapter, these findings are highlighted and discussed.

    更新日期:2019-11-17
  • Organocatalysis Combined with Photocatalysis
    Top. Curr. Chem. (IF 6.721) Pub Date : 2019-11-15
    Yi-Yin Liu, Jing Liu, Liang-Qiu Lu, Wen-Jing Xiao

    Over the past decade, the combination of visible light photocatalysis and organocatalysis has made remarkable progress in modern chemical synthesis. In these dual catalysis system, photocatalysts or photosensitizers absorb visible light to induce their photoexcited states which can activate unreactive substrates via electron or energy transfer mechanisms, and organocatalysts are usually employed to regulate the chemical reactivity of the other substrates. By doing so, two reactive species react with each in a selective—especially enantioselective—way, to provide the final products. This article summarizes the recent development of cooperative catalysis by the combination of organocatalysis and photocatalysis in asymmetric organic synthesis. These reactions are classified according to the manner of activation of the organocatalysts. Enamine/iminium catalysts are used to activate unreactive carbonyl molecules. Nucleophilic catalysts including nitrogen heterocycle carbene catalysts and tertiary amine catalysts are employed to reverse the reactivity of electrodeficient substrates including aldehydes and enals. Chiral Brønsted acid catalysts are used to activate substrates by forming key H-bonding complexes between substrates and catalysts.

    更新日期:2019-11-15
  • Heterogeneous Catalyzed Thermochemical Conversion of Lignin Model Compounds: An Overview
    Top. Curr. Chem. (IF 6.721) Pub Date : 2019-11-14
    Mikel Oregui-Bengoechea, Ion Agirre, Aitziber Iriondo, Alexander Lopez-Urionabarrenechea, Jesus M. Requies, Iker Agirrezabal-Telleria, Kepa Bizkarra, V. Laura Barrio, Jose F. Cambra

    Thermochemical lignin conversion processes can be described as complex reaction networks involving not only de-polymerization and re-polymerization reactions, but also chemical transformations of the depolymerized mono-, di-, and oligomeric compounds. They typically result in a product mixture consisting of a gaseous, liquid (i.e., mono-, di-, and oligomeric products), and solid phase. Consequently, researchers have developed a common strategy to simplify this issue by replacing lignin with simpler, but still representative, lignin model compounds. This strategy is typically applied to the elucidation of reaction mechanisms and the exploration of novel lignin conversion approaches. In this review, we present a general overview of the latest advances in the principal thermochemical processes applied for the conversion of lignin model compounds using heterogeneous catalysts. This review focuses on the most representative lignin conversion methods, i.e., reductive, oxidative, pyrolytic, and hydrolytic processes. An additional subchapter on the reforming of pyrolysis oil model compounds has also been included. Special attention will be given to those research papers using “green” reactants (i.e., H2 or renewable hydrogen donor molecules in reductive processes or air/O2 in oxidative processes) and solvents, although less environmentally friendly chemicals will be also considered. Moreover, the scope of the review is limited to those most representative lignin model compounds and to those reaction products that are typically targeted in lignin valorization.

    更新日期:2019-11-14
  • N -Heterocyclic Carbene (NHC)/Metal Cooperative Catalysis
    Top. Curr. Chem. (IF 6.721) Pub Date : 2019-11-13
    Kazunori Nagao, Hirohisa Ohmiya

    N-Heterocyclic carbene (NHC) catalysis can access umpolung reactivity of carbonyl compounds as acyl anions, enolates and homoenolates. Considerable progress has been made in asymmetric transformation by the introduction of chirality to the NHC scaffold. However, the single catalyst system has limitations in chemo-, regio- and stereoselectivity. A solution to these problems has recently emerged with the synergistic combination of NHC catalysis and metal catalysis. A number of NHC/metal combinations have been found not only to improve reactivity and stereoselectivity, but also to enable access to unprecedented transformations. This paper highlights examples of successful asymmetric NHC/metal cooperative catalysis.

    更新日期:2019-11-13
  • Twin and triplet drugs in opioid research.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2011-06-02
    Hideaki Fujii

    Twin and triplet drugs are defined as compounds that contain respectively two and three pharmacophore components exerting pharmacological effects in a molecule. The twin drug bearing the same pharmacophores is a "symmetrical twin drug", whereas that possessing different pharmacophores is a "nonsymmetrical twin drug." In general, the symmetrical twin drug is expected to produce more potent and/or selective pharmacological effects, whereas the nonsymmetrical twin drug is anticipated to show both pharmacological activities stemming from the individual pharmacophores (dual action). On the other hand, nonsymmetrical triplet drugs, which have two of the same pharmacophores and one different moiety, are expected to elicit both increased pharmacological action and dual action. The two identical portions could bind the same receptor sites simultaneously while the third portion could bind a different receptor site or enzyme. This review will mainly focus on the twin and triplet drugs with an evaluation of their in vivo pharmacological effects, and will also include a description of their pharmacology and synthesis.

    更新日期:2019-11-01
  • Synthesis of neoclerodane diterpenes and their pharmacological effects.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2011-06-02
    Kimberly M Lovell,Katherine M Prevatt-Smith,Anthony Lozama,Thomas E Prisinzano

    Salvinorin A is a neoclerodane diterpene that has been shown to be an agonist at kappa opioid receptors. Its unique structure makes it an attractive target for synthetic organic chemists due to its seven chiral centers and diterpene scaffold. This molecule is also interesting to pharmacologists because it is a non-serotonergic hallucinogen, and the first opioid ligand discovered that lacks a basic nitrogen. There have been several total synthesis approaches to salvinorin A, and these will be detailed within this chapter. Additionally, research efforts have concentrated on structure modification of the salvinorin A scaffold through semi-synthetic methods. Most modifications have focused on the manipulation of the acetate at C-2 and the furan ring. However, chemistry has also been developed to generate analogs at the C-1 ketone, the C-4 methyl ester, and the C-17 lactone. The synthetic methodologies developed for the salvinorin A scaffold will be described, as well as specific analogs with interesting biological activities.

    更新日期:2019-11-01
  • 14-Amino-4,5-epoxymorphinan derivatives and their pharmacological actions.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2011-06-02
    John W Lewis,Stephen M Husbands

    14-Hydroxy-7,8-dihydromorphinone (oxymorphone) and its derivatives (oxycodone, naloxone, naltrexone) have become among the most important clinical agents to have been produced from opium. 14-Aminocodeinone and its 7,8-dihydro and morphinone derivatives are of more recent origin thanks to the work of Professor Gordon Kirby and his collaborators. The 14-amino parent compounds have proved of limited interest but their 14-acylamino- and 14-alkylamino derivatives have been extensively studied. The 4'-substituted cinnamoylamino-17-cyclopropylmethyl-7,8-dihydronormorphinones, C-CAM and M-CAM are the best available selective MOR irreversible antagonists and the related dihydrocodeinone MC-CAM, 4'-chloro-cinnamoylamino-17-cyclopropylmethyl-7,8-dihydronorcodeinone, is a long-acting MOR partial agonist with extended MOR-pseudoirreversible antagonist activity that could be a candidate for pharmacotherapy of opiate abuse/dependence.

    更新日期:2019-11-01
  • Opioids in preclinical and clinical trials.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2011-06-02
    Hiroshi Nagase,Hideaki Fujii

    Since 1952, when Gates determined the stereo structure of morphine, numerous groups have focused on discovering a nonnarcotic opioid drug. Although several natural, semisynthetic, and synthetic opioid ligands (alkaloids and peptides) have been developed in clinical studies, very few were nonnarcotic opioid drugs. One of the most important studies in the opioid field appeared in 1976, when Martin and colleagues established types of opioid receptors (these are now classified into mu, delta, and kappa types). Later, Portoghese discovered a highly selective mu type opioid receptor antagonist, beta-funaltrexamine. This led to the finding that the mu type opioid receptor was correlated to drug dependence. Consequently, delta, and particularly kappa, opioid agonists were expected to lead to ideal opioid drugs. Moreover, opioid antagonists were evaluated for the treatment of symptoms related to undesirable opioid system activation. In this chapter, we provide a short survey of opioid ligands in development and describe the discovery of the two most promising drugs, TRK-851 and TRK-820 (nalfurafine hydrochloride).

    更新日期:2019-11-01
  • 3D-pharmacophore identification for kappa-opioid agonists using ligand-based drug-design techniques.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2011-06-02
    Noriyuki Yamaotsu,Shuichi Hirono

    A selective kappa-opioid receptor (KOR) agonist might act as a powerful analgesic without the side effects of micro-opioid receptor-selective drugs such as morphine. The eight classes of known KOR agonists have different chemical structures, making it difficult to construct a pharmacophore model that takes them all into account. Here, we summarize previous efforts to identify the pharmacophore for kappa-opioid agonists and propose a new three-dimensional pharmacophore model that encompasses the kappa-activities of all classes. This utilizes conformational sampling of agonists by high-temperature molecular dynamics and pharmacophore extraction through a series of molecular superpositions.

    更新日期:2019-11-01
  • Synthesis of novel basic skeletons derived from naltrexone.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2011-06-02
    Hiroshi Nagase,Hideaki Fujii

    We will describe eight interesting reactions using naltrexone derivatives. Almost all these reactions are characteristic of naltrexone derivatives, and can lead to the synthesis of many novel skeletons that provide new interesting pharmacological data. Some of the new reactions that were found with naltrexone derivatives were expanded into general reactions. For example, the reaction of 6alpha-hydroxyaldehyde derived from naltrexone led to the oxazoline dimer and the 1,3,5-trioxazatriquinane skeleton (triplet drug); this reaction was applied to general ketones which were converted to alpha-hydroxyaldehydes, followed by conversion to dimers and trimers, as described in Sect. 7.

    更新日期:2019-11-01
  • Nonpeptidic delta (delta) opioid agonists and antagonists of the diarylmethylpiperazine class: what have we learned?
    Top. Curr. Chem. (IF 6.721) Pub Date : 2011-06-02
    Silvia N Calderon

    The discovery of the selective delta (delta) opioid agonists SNC 80 and BW373U86, which possess a diarylmethylpiperazine structure unique among opioids, represented a major advance in the field of delta-opioid ligands. Extensive research has recently been performed to uncover the structure-activity relationships (SAR) of this class of ligands, thereby providing valuable tools for the pharmacological characterization of the delta opioid receptor. This review focuses on the SAR of this unique series of ligands, and provides an overview of the various chemical routes that have been developed and optimized through the years to allow the syntheses of these ligands on a multigram scale. The search for selective delta opioid agonists and antagonists, as well as for those with mixed opioid agonist properties with potential therapeutic value, continues. Several questions regarding the interaction at the molecular level of diphenylmethylpiperazine derivatives and related analogs with opioid receptors and in particular with the delta opioid system still remain unanswered. Indeed, the development and pharmacological characterization of novel nonpeptidic delta opioid ligands remains an active area of research, as it may provide a better understanding of the role of this receptor in multiple disease states and disorders.

    更新日期:2019-11-01
  • Synthesis of 14-alkoxymorphinan derivatives and their pharmacological actions.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2011-06-02
    Helmut Schmidhammer,Mariana Spetea

    Among opioids, morphinans play an important role as therapeutically valuable drugs. They include pain relieving agents such as naturally occurring alkaloids (e.g. morphine, codeine), semisynthetic derivatives (e.g. oxycodone, oxymorphone, buprenorphine), and synthetic analogs (e.g. levorphanol). Currently used opioid analgesics also share a number of severe side effects, limiting their clinical usefulness. The antagonist morphinans, naloxone and naltrexone are used to treat opioid overdose, opioid dependence, and alcoholism. All these opioid drugs produce their biological actions through three receptor types, mu, delta, and kappa, belonging to the G-protein-coupled receptor family. Considerable effort has been put forward to understand the appropriate use of opioid analgesics, while medicinal chemistry and opioid pharmacology have been continuously engaged in the search for safer, more efficacious and nonaddicting opioid compounds, with the final goal to reduce complications and to improve patient compliance. Toward this goal, recent advances in chemistry, ligand-based structure activity relationships and pharmacology of 14-alkoxymorphinans are reviewed in this chapter. Current developments of different structural patterns of 14-alkoxymorphinans as research tools and their potential therapeutic opportunities are also summarized.

    更新日期:2019-11-01
  • Recent advances in the synthesis of morphine and related alkaloids.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2011-06-02
    Noritaka Chida

    Morphine, an alkaloid isolated from the opium poppy, has been widely used as an analgesic, and has been a fascinating synthetic target of organic chemists. After the first total synthesis reported in 1952, a number of synthetic studies toward morphine have been reported, and findings obtained in such studies have greatly contributed to the progress of synthetic organic chemistry as well as medicinal chemistry. This review provides an overview of recent studies toward the total synthesis of morphine and related alkaloids. Work reported in the literature since 2004 will be reviewed.

    更新日期:2019-11-01
  • From natural polysaccharides to materials for catalysis, adsorption, and remediation.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2010-01-01
    Françoise Quignard,Francesco Di Renzo,Eric Guibal

    Polysaccharides display most of the properties needed for applications in catalysis, adsorption or remediation. Requisites common to these applications are appropriate surface functions to ensure substrate-material interactions, accessibility of the functional groups, and proper shaping for easy manipulation. Natural polysaccharides are well known as supports for enzymatic catalysts and gelling agents in aqueous phase, due to the high level of dispersion of hydrocolloids. However, they suffer from diffusional limitations in the dry state, due to the low surface area of the dried materials generally used, xerogels or lyophilized solids. This chapter deals with the proper methods to prepare dry materials which retain the dispersion of the polymer hydrogel, namely polysaccharide aerogels. The materials whose properties are described here are stable in most organic solvents and present numerous and diverse surface functionalities (like hydroxy, carboxy, or amino groups). Shaping and appropriate drying of gelling polysaccharides provide a new opportunity to obtain materials from one of the less energy-intensive sources of biomass. Their application in catalysis and adsorption could open substantial markets for products of seaweed harvesting and coproducts of the seafood industry.

    更新日期:2019-11-01
  • Oligomannuronates from seaweeds as renewable sources for the development of green surfactants.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2010-01-01
    Thierry Benvegnu,Jean-François Sassi

    The development of surfactants based on natural renewable resources is a concept that is gaining recognition in detergents, cosmetics, and green chemistry. This new class of biodegradable and biocompatible products is a response to the increasing consumer demand for products that are both "greener", milder, and more efficient. In order to achieve these objectives, it is necessary to use renewable low-cost biomass that is available in large quantities and to design molecular structures through green processes that show improved performance, favorable ecotoxicological properties and reduced environmental impact. Within this context, marine algae represent a rich source of complex polysaccharides and oligosaccharides with innovative structures and functional properties that may find applications as starting materials for the development of green surfactants or cosmetic actives. Thus, we have developed original surfactants based on mannuronate moieties derived from alginates (cell-wall polyuronic acids from brown seaweeds) and fatty hydrocarbon chains derived from vegetable resources. Controlled chemical and/or enzymatic depolymerizations of the algal polysaccharides give saturated and/or unsaturated functional oligomannuronates. Clean chemical processes allow the efficient transformation of the oligomers into neutral or anionic amphiphilic molecules. These materials represent a new class of surface-active agents with promising foaming/emulsifying properties.

    更新日期:2019-11-01
  • Olive pomace, a source for valuable arabinan-rich pectic polysaccharides.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2010-01-01
    Manuel A Coimbra,Susana M Cardoso,José A Lopes-da-Silva

    Cell wall polysaccharides account for nearly one third of olive pomace dry matter produced by the environment friendly biphasic system. These polysaccharides are mainly cellulose, glucuronoxylans, and arabinan-rich pectic polysaccharides, in equivalent proportions. The structural features of pectic polysaccharides are unique concerning the arabinan moiety due to the occurrence of a beta-(1-->5)-terminally-linked arabinose residue. This odd feature tends to disappear with olive ripening and can be used as a diagnostic tool in the evaluation of the stage of ripening of this fruit, as well as a marker for the presence of olive pulp in matrices containing pectic polysaccharides samples. These pectic polysaccharides have the ability to form elastic gels with calcium. The critical gelling calcium and galacturonic acid concentrations are higher than that observed for commercial citrus low-methoxyl pectic material. Nevertheless, they present a syneresis occurring for much higher calcium concentration and, consequently, show a much larger zone in which homogeneous gels are formed. In addition, olive pomace pectic polysaccharides gels are more resistant to temperature than the low-methoxyl pectin/calcium gels. These properties show that olive pomace can be a potential source of gelling pectic material with useful properties for particular applications.

    更新日期:2019-11-01
  • Cellulose and derivatives from wood and fibers as renewable sources of raw-materials.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2010-01-01
    J A Figueiredo,M I Ismael,C M S Anjo,A P Duarte

    Cellulose is the most important biopolymer in Nature and is used in preparation of new compounds. Molecular structure of cellulose is a repeating unit of beta-D-glucopyranose molecules forming a linear chain that can have a crystallographic or an amorphous form. Cellulose is insoluble in water, but can dissolve in ionic liquids. Hemicelluloses are the second most abundant polysaccharides in Nature, in which xylan is one of the major constituents of this polymer. There are several sources of cellulose and hemicelluloses, but the most important source is wood. Typical chemical modifications are esterifications and etherifications of hydroxyl groups. TEMPO-mediated oxidation is a good method to promote oxidation of primary hydroxyl groups to aldehyde and carboxylic acids, selectively. Modified cellulose can be used in the pharmaceutical industry as a metal adsorbent. It is used in the preparation of cellulosic fibers and biocomposites such as nanofibrils and as biofuels.

    更新日期:2019-11-01
  • Development of agriculture left-overs: fine organic chemicals from wheat hemicellulose-derived pentoses.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2010-01-01
    Frédéric Martel,Boris Estrine,Richard Plantier-Royon,Norbert Hoffmann,Charles Portella

    This review is dedicated to wheat hemicelluloses and its main components D-xylose and L-arabinose as raw materials for fine organic chemistry. The context of the wheat agro-industry, its by-products, and extraction and hydrolysis of hemicelluloses to produce the pentoses are considered. The straightforward preparation of pentose-based surfactants, their properties, and their situation in the field of carbohydrate-based surfactants are addressed. Multistep transformations of pentoses are also described, first from a methodology point of view, with the aim of producing multifunctional enantiopure building-blocks, then considering targeted natural and/or bioactive products. Selected reactions of furfural, an important dehydration product of pentoses, are also presented.

    更新日期:2019-11-01
  • Difructose dianhydrides (DFAs) and DFA-enriched products as functional foods.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2010-01-01
    Carmen Ortiz Mellet,José M García Fernández

    This review provides an overview of the current status of the chemistry and biology of di-D-fructose dianhydrides (DFAs) with a focus on their potential as functional foods. The history of this family of cyclic ketodisaccharides has expanded for almost 100 years and offers a paradigmatic example of artificial synthetic molecules that were identified as natural products later on and finally encountered in our own table. Issued from fundamental investigations on the reactivity of carbohydrates in strongly acidic media, DFAs remained laboratory curiosities for decades. Early reports on their isolation from plants raised doubts, until the formation of some DFA representatives by the action of microorganisms on fructans was reported in the middle 1980s. Since then, research on DFAs has run in parallel in the areas of microbiology and carbohydrate chemistry. Evidence of the potential of these compounds as functional food was accumulated from both sides, with the development of biotechnological processes for mass production of selected candidates and of chemical methodologies to prepare DFA-enriched products from sucrose or inulin. In 1994 a decisive discovery in the field took place in the laboratory of Jacques Defaye in Grenoble, France: the presence of DFAs in a commercial sucrose caramel was evidenced in a quite significant 18% mass proportion! The development of an efficient analytical protocol for DFAs and the stereoselective synthesis of individual standards allowed one to demonstrate that DFAs and their glycosylated derivatives (glycosyl-DFAs) are universally formed during caramelization reactions. They are not potential food products; they have actually always been in our daily food. Most important, they seem to exert beneficial effects: they are acariogenic, low-caloric, and promote the growth of beneficial microflora in the gut. Most recent evidence indicates that DFAs can even protect the intestinal tract against agressive agents favor the assimilation of antioxidants, and act as a drug-like food for the treatment of colon ailments such as inflammatory bowel disease (Crohn disease). The development of efficient methodologies for the preparation of DFA-enriched caramels, compatible with the food and agricultural industry regulations, may lead to new natural functional foods and nutraceuticals based on DFAs in the near future.

    更新日期:2019-11-01
  • Sucrose-utilizing transglucosidases for biocatalysis.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2010-01-01
    Isabelle André,Gabrielle Potocki-Véronèse,Sandrine Morel,Pierre Monsan,Magali Remaud-Siméon

    Sucrose-utilizing transglucosidases are valued tools in chemistry to generate glycodiversification. Not only do these enzymes use as substrate an abundant agroresource, sucrose, but they also share a remarkable versatility regarding the acceptor substrate, allowing the structurally-controlled synthesis of diverse glucosylated products. Latest research has demonstrated the potential of enzyme engineering to tailor novel sucrose-utilizing transglucosidases that give access to original carbohydrate-based structures. This chapter gives an overview of the recent achievements in biocatalysis using these enzymes.

    更新日期:2019-11-01
  • Sucrose: A prospering and sustainable organic raw material.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2010-01-01
    Siegfried Peters,Thomas Rose,Matthias Moser

    Sucrose (alpha-D-glucopyranosyl-(1-->2)-beta-D-fructofuranoside) is an inexpensive chemical produced by sugar cane and sugar beet cultivation. Chemical and/or biochemical transformations convert it into highly valuable synthetic intermediates such as 5-hydroxymethylfurfural (HMF), bioethylene, 1,2-propylene glycol and levulinic acid. Sucrose can also be converted into biodegradable polymers such as polyesters and polyurethanes, as well as into novel carbohydrates such as isomaltulose, trehalulose, inulin, levan, Neo-amylose, and dextran, highly valuable additives for food and cosmetics and materials for separation and purification technologies.

    更新日期:2019-11-01
  • Synthesis and applications of ionic liquids derived from natural sugars.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2010-01-01
    Cinzia Chiappe,Alberto Marra,Andrea Mele

    Aiming to develop environmentally compatible chemical syntheses, the replacement of traditional organic solvents with ionic liquids (ILs) has attracted considerable attention. ILs are special molten salts with melting points below 100 degrees C that are typically constituted of organic cations (imidazolium, pyridinium, sulfonium, phosphonium, etc.) and inorganic anions. Due to their ionic nature, they are endowed with high chemical and thermal stability, good solvent properties, and non-measurable vapor pressure. Although the recovery of unaltered ILs and recycling partly compensate their rather high cost, it is important to develop new synthetic approaches to less expensive and environmentally sustainable ILs based on renewable raw materials. In fact, most of these alternative solvents are still prepared starting from fossil feedstocks. Until now, only a limited number of ILs have been prepared from renewable sources. Surprisingly, the most available and inexpensive raw material, i.e., carbohydrates, has been hardly exploited in the synthesis of ILs. In 2003 imidazolium-based ILs were prepared from o-fructose and used as solvents in Mizoroki-Heck and Diels-Alder reactions. Later on, the first chiral ILs derived from sugars were prepared from methyl D-glucopyranoside. In the same year, a family of new chiral ILs, obtained from commercial isosorbide (dianhydro-D-glucitol), was described. A closely related approach was followed by other researchers to synthesize mono- and bis-ammonium ILs from isomannide (dianhydro-D-mannitol). Finally, a few ILs bearing a pentofuranose unit as the chiral moiety were prepared using sugar phosphates as glycosyl donors and 1-methylimidazole as the acceptor.

    更新日期:2019-11-01
  • Synthetic polymers from readily available monosaccharides.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2010-01-01
    J A Galbis,M G García-Martín

    The low degradability of petroleum-based polymers and the massive use of these materials constitute a serious problem because of the environmental pollution that they can cause. Thus, sustained efforts have been extensively devoted to produce new polymers based on natural renewing resources and with higher degradability. Of the different natural sources, carbohydrates stand out as highly convenient raw materials because they are inexpensive, readily available, and provide great stereochemical diversity. New polymers, analogous to the more accredited technical polymers, but based on chiral monomers, have been synthesized from natural and available sugars. This chapter describes the potential of sugar-based monomers as precursors to a wide variety of macromolecular materials.

    更新日期:2019-11-01
  • Palladium-catalyzed telomerization of butadiene with polyols: from mono to polysaccharides.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2010-01-01
    Sandrine Bouquillon,Jacques Muzart,Catherine Pinel,Franck Rataboul

    The telomerization of butadiene with alcohols is an elegant way to synthesize ethers with minimal environmental impact since this reaction is 100% atom efficient. Besides telomerization of butadiene with methanol and water that is industrially developed, the modification of polyols is still under development. Recently, a series of new substrates has been involved in this reaction, including diols, pure or crude glycerol, protected or unprotected monosaccharides, as well as polysaccharides. This opens up the formation of new products having specific physicochemical properties. We will describe recent advances in this field, focusing on the reaction of renewable products and more specifically on saccharides. The efficient catalytic systems as well as the optimized reaction conditions will be described and some physicochemical properties of the products will be reported.

    更新日期:2019-11-01
  • Heterogeneously-catalyzed conversion of carbohydrates.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2010-01-01
    Karine De Oliveira Vigier,François Jérôme

    Polyfunctionality of carbohydrates and their low solubility in conventional organic solvents make rather complex their conversion to higher value added chemicals. Therefore, innovative processes are now strongly needed in order to increase the selectivity of these reactions. Here, we report an overview of the different heterogeneously-catalyzed processes described in the literature. In particular, hydrolysis, dehydration, oxidation, esterification, and etherification of carbohydrates are presented. We shall discuss the main structural parameters that need to be controlled and that permit the conversion of carbohydrates to bioproducts with good selectivity. The conversion of monosaccharides and disaccharides over solid catalysts, as well as recent advances in the heterogeneously-catalyzed conversion of cellulose, will be presented.

    更新日期:2019-11-01
  • Carbohydrate-based lactones: synthesis and applications.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2010-01-01
    Nuno M Xavier,Amélia P Rauter,Yves Queneau

    The synthesis and uses of different kinds of carbohydrate-based lactones are described. This group of compounds includes aldonolactones, other related monocyclic lactones and bicyclic systems. The latter can arise from uronic acids, carboxymethyl ethers or glycosides, or from C-branched sugars.

    更新日期:2019-11-01
  • Knoevenagel reaction of unprotected sugars.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2010-01-01
    Marie-Christine Scherrmann

    The Knoevenagel reaction of unprotected sugars was investigated in the 1950s using zinc chloride as promoter. The so-called Garcia Gonzalez reaction had been almost forgotten for 50 years, until the emergence of new water tolerant catalysts having Lewis acid behavior. The reaction was thus reinvestigated and optimal conditions have been found to prepare trihydroxylated furan derivatives from pentose or beta-tetrahydrofuranylfuran from hexoses with non-cyclic beta-keto ester or beta-diketones. Other valuable compounds such as beta-linked tetrahydrobenzofuranyl glycosides or hydroxyalkyl-3,3,6,6,-tetramethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione can be obtained using cyclic beta-dicarbonylic derivatives. Apart from one report in the 1950s, the Knoevenagel reaction of unprotected carbohydrate in basic condition has been studied only in the mid-1980s to prepare C-glycosyl barbiturates from barbituric acids and, later on, from non-cyclic beta-diketones, beta-C-glycosidic ketones. The efficient method exploited to prepare such compounds has found an industrial development in cosmetics.

    更新日期:2019-11-01
  • Magnetic and porous molecule-based materials.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2010-01-01
    Nans Roques,Veronica Mugnaini,Jaume Veciana

    In this chapter, we give an overview of the recent state-of-the-art research of porous and magnetic molecule-based materials. The subject is introduced by a section devoted to the fundamentals of magnetism in molecular magnets, with special attention to the design strategies to prepare molecular magnetic materials. We will then focus on the two main families of materials combining porosity and magnetism: the purely organic and the metal-organic porous magnetic materials. For both families, a selection of the most representative examples has been made. A complete section is devoted to magnetic and porous materials with flexible frameworks, an area of emerging importance in this field, because of their wide range of applications. Finally, we conclude with a brief overview on the most recent approaches for the future development of these materials.

    更新日期:2019-11-01
  • Designing metal-organic frameworks for catalytic applications.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2010-01-01
    Liqing Ma,Wenbin Lin

    Metal-organic frameworks (MOFs) are constructed by linking organic bridging ligands with metal-connecting points to form infinite network structures. Fine tuning the porosities of and functionalities within MOFs through judicious choices of bridging ligands and metal centers has allowed their use as efficient heterogeneous catalysts. This chapter reviews recent developments in designing porous MOFs for a variety of catalytic reactions. Following a brief introduction to MOFs and a comparison between porous MOFs and zeolites, we categorize catalytically active achiral MOFs based on the types of catalytic sites and organic transformations. The unsaturated metal-connecting points in MOFs can act as catalytic sites, so can the functional groups that are built into the framework of a porous MOF. Noble metal nanoparticles can also be entrapped inside porous MOFs for catalytic reactions. Furthermore, the channels of porous MOFs have been used as reaction hosts for photochemical and polymerization reactions. We also summarize the latest results of heterogeneous asymmetric catalysis using homochiral MOFs. Three distinct strategies have been utilized to develop homochiral MOFs for catalyzing enantioselective reactions, namely the synthesis of homochiral MOFs from achiral building blocks by seeding or by statistically manipulating the crystal growth, directing achiral ligands to form homochiral MOFs in chiral environments, and incorporating chiral linker ligands with functionalized groups. The applications of homochiral MOFs in several heterogeneous asymmetric catalytic reactions are also discussed. The ability to synthesize value-added chiral molecules using homochiral MOF catalysts differentiates them from traditional zeolite catalysis, and we believe that in the future many more homochiral MOFs will be designed for catalyzing numerous asymmetric organic transformations.

    更新日期:2019-11-01
  • Controlled polymerization by incarceration of monomers in nanochannels.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2010-01-01
    Takashi Uemura,Susumu Kitagawa

    Porous Coordination Polymers (PCPs) composed of transition metal ions and bridging organic ligands have been extensively studied. The characteristic features of PCPs are highly regular channel structures, controllable channel sizes approximating molecular dimensions, designable surface potentials and functionality, and flexible frameworks responsive to guest molecules. Owing to these advantages, successful applications of PCPs range from molecular storage and separation to heterogeneous catalysts. In particular, use of their regulated and tunable nanochannels in the field of polymerization has allowed multi-level control of polymerization via control of stereoregularlity, molecular weight, etc. In this chapter, we focus on recent progress in polymerization utilizing the nanochannels of PCPs, and demonstrate why this polymerization system is attractive and promising from the viewpoint of precision control of polymeric structures.

    更新日期:2019-11-01
  • Chiral metal-organic porous materials: synthetic strategies and applications in chiral separation and catalysis.
    Top. Curr. Chem. (IF 6.721) Pub Date : 2010-01-01
    Kimoon Kim,Mainak Banerjee,Minyoung Yoon,Sunirban Das

    In the light of growing demand for chiral purity in biological and chemical processes, the synthesis of chiral metal-organic porous materials (CMOPMs) have become immensely important because of their potential applications in chiral separation and asymmetric catalysis. In this chapter, the synthetic strategies for CMOPMs are discussed briefly keeping the focus on their applications. Two distinct approaches have been taken to synthesize a wide variety of chiral structures with different topologies and accessible cavities. Several CMOPMs have shown catalytic activity and enantioselectivity toward a number of chemical transformations. On many occasions, the chiral pores of the MOPMs have been utilized in order to achieve separation of enantiomers from racemates. Recent applications of homochiral MOPMs in heterogeneous asymmetric catalysis and chiral separations are also presented here.

    更新日期:2019-11-01
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