1,721,120 research outputs found
The Click Reaction as an Efficient Tool for the Construction of Macrocyclic Structures
Full text linkThe Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC, known as the click reaction) is an established tool used for the construction of complex molecular architectures. Given its efficiency it has been widely applied for bioconjugation, polymer and dendrimer synthesis. More recently, this reaction has been utilized for the efficient formation of rigid or shape-persistent, preorganized macrocyclic species. This strategy also allows the installment of useful functionalities, in the form of polar and function-rich 1,2,3-triazole moieties, directly embedded in the macrocyclic structures. This review analyzes the state of the art in this context, and provides some elements of perspective for future applications
Tagging Molecules with Linear Polymers: Biocatalytic Transformation of Substrates Anchored on Soluble Macromolecules
No full textWith the increasingly available technology in automated synthesis and screening protocols, the combination of polymer-supported chemistry and biocatalysis, with their respective advantages over classical organic synthesis, has become more scientifically attractive, yet remains challenging. Since the development of solid-phase synthesis and its rapid expansion in combination with the advent of combinatorial techniques, a variety of alternative methodologies have been proposed and demonstrated to be viable for applications in high-throughput and multistep syntheses of the desired products. These alternative methodologies overcome the disadvantages of crosslinked polymer beads, which, as a consequence of their insolubility and their being necessarily heterogeneous in the reaction mixture, do have operational drawbacks. They often rely on a common strategy: tagging the target substrate of interest with other fragments (fluorous synthons, macromolecules, "precipitons") in such a way that the tag-substrate covalent ensemble is then easily separated from the reaction mixture by physical methods (liquid-liquid extraction, precipitation, etc.). The efficiency of enzymes in transforming substrates is often enhanced when the stability limitations of the biocatalyst in unnatural conditions (i.e. organic solvents, high temperatures) are avoided by the use of immobilization-stabilization techniques. We comment here, with recent examples, on the use of linear macromolecules as recyclable tags capable of acting as covalent supports in combination with a biocatalyzed reactio
Supramolecular Self-Assembly of Fibres
No full textThis paper describes recent advances in the fields of unnatural supramolecular materials that are able to show polymer and/or gel properties by association through multiple weak, noncovalent bonds. The field is reviewed with a particular eye on materials science aspects, and on substrates which seem to hold promise for future applications
Synthesis of Macrocycles and Click Chemistry
No full textClick chemistry reactions are gaining increasing importance in the synthetic construction of complex nanoscale architectures. The Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) and the thiol–ene reaction are established click chemistry methodologies. Given their efficiencies, they have been widely applied for bioconjugation, polymer, and dendrimer synthesis. More recently, they have been utilized for the efficient formation of rigid or shape-persistent, preorganized macrocyclic species. This strategy also allows the installment of useful functionalities, such as thioethers, or polar and function-rich 1,2,3-triazole moieties, directly embedded in the macrocyclic structure. This chapter analyzes the state of the art in this context and provides some elements of perspective for future applications
Acentric Nanostructured Assembly as a Strategy for the Design of Organic Electrooptic Materials
No full textLinear vs. Crosslinked Macromolecules as Supports for Biocatalyzed Transformations: Recent Developments
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Anthradithiophene derivatives, process for the preparation thereof and polymers that contain them
No full textLocked Chromophores as CD and NMR Probes for the Helical Conformation of Tetraamidic Macrocycles
No full textA series of tetraamidic homochiral macrocycles have been built convergently upon the introduction in the covalent scaffold of two 1,1-binaphthyl-2,2-diol derivatives, joined by aromatic spacers of differing shapes and rigidity (p-phenyl, 4,4-biphenyl, 3,3-biphenyl) through aromatic amide functionalities, perfectly positioned to intramolecularly hydrogen bond the naphtholic oxygen acceptors of the binaphthyl units, in order to effectively lock the central chromophores in spatial proximity. The combination of several techniques, namely NMR and CD spectroscopies, and computational modeling, allows for a clear depiction of the structure and conformation of the macrocycles in solution. In the case of the shape unstable 3,3-biphenyl spacer, the preferred conformation of a wrapped form in a relatively polar (EtOH) solvent is clearly signalled by CD spectroscopy by analyzing the changes in the shape of the induced CD signal deriving from the central, achiral chromophore absorption band. The rigid, covalent scaffold in which the two central 3,3-biphenyl spacers are embedded raises the energetic barrier for the rotation around the aryl–aryl bonds of the spacers to a value (8.0 kcal mol-1) much higher than the value calculated in the case of unlocked biphenyls
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