Copper-catalyzed Azide Alkyne Research Articles

Controlling the Kinetics of Self-Reproducing Micelles by Catalyst Compartmentalization in a Biphasic System.

Compartmentalization of reactions is ubiquitous in biochemistry. Self-reproducing lipids are widely studied as chemical models of compartmentalized biological systems. Here, we explore the effect of catalyst location on copper-catalyzed azide–alkyne cycloadditions which drive the self-reproduction of micelles from phase-separated components. Tuning the hydrophilicity of the copper-ligand complex, so that hydro-phobic or -philic catalysts are used in combination with hydro-philic and -phobic coupling partners, provides a wide range of reactivity patterns. Analysis of the kinetic data shows that reactions with a hydrophobic catalyst are faster than with a hydrophilic catalyst. Diffusion-ordered spectroscopy experiments suggest compartmentalization of the hydrophobic catalyst inside micelles while the hydrophilic catalyst remains in the bulk aqueous phase. The autocatalytic effects observed can be tuned by varying reactant structure and coupling a hydrophilic alkyne and hydrophobic azide results in a more pronounced autocatalytic effect. We propose and test a model that rationalizes the observations in terms of the phase behavior of the reaction components and catalysts.

Strong Inhibition of Cholera Toxin B Subunit by Affordable, Polymer-Based Multivalent Inhibitors.

Cholera is a potentially fatal bacterial infection that affects a large number of people in developing countries. It is caused by the cholera toxin (CT), an AB5 toxin secreted by Vibrio cholera. The toxin comprises a toxic A-subunit and a pentameric B-subunit that bind to the intestinal cell surface. Several monovalent and multivalent inhibitors of the toxin have been synthesized but are too complicated and expensive for practical use in developing countries. Meta-nitrophenyl α-galactoside (MNPG) is a known promising ligand for CT, and here mono- and multivalent compounds based on MNPG were synthesized. We present the synthesis of MNPG in greatly improved yields and its use while linked to a multivalent scaffold. We used economical polymers as multivalent scaffolds, namely, polyacrylamide, dextran, and hyperbranched polyglycerols (hPGs). Copper-catalyzed alkyne azide cycloaddition reaction (CuAAC) produced the inhibitors that were tested in an ELISA-type assay and an intestinal organoid swelling inhibition assay. The inhibitory properties varied widely depending on the type of polymer, and the most potent conjugates showed IC50 values in the nanomolar range.

Comb Polymers with Triazole Linkages under Thermal and Mechanical Stress

Assessing the stability of molecular bonds in polymer architectures is of critical importance for determining conditions for extrusion, molding, and processing. The topological complexity of branched polymers defines their strain hardening and consequently their melt strength properties, critical parameters for their exploitation in applications. Their molecular architecture is defined by the grafting density and the chain length of the backbone as well as branches. Herein, we introduce a set of polymer combs to establish an understanding of the above parameters on the stability of the popular triazole linkage—often exploited in tethering the branches to the backbone—during thermal treatment and shearing. We exploit a combination of reversible deactivation radical polymerization (RDRP) and copper-catalyzed alkyne–azide cycloaddition (CuAAC) to construct comb polymers (ranging in backbone number-average molecular weight from 39.9 to 55.6 kg mol–1 and a branch length from 3.3 to 18 kg mol–1) with statistically located branches tethered via triazole-based ligation to the backbone. These polymer combs were subsequently thermally challenged at 150 °C (or 180 °C) in an inert atmosphere as well as subjected to shearing at the same temperature. The resulting molecular cleavage processes were analyzed via size exclusion chromatography (SEC) as well as SEC coupled to high-resolution electrospray ionization mass spectrometry (SEC-HR ESI MS) to establish a mechanistic image of branch debonding when it occurs. In addition, by virtue of this approach, we establish an in-depth understanding of how the comb architecture dictates its stability under otherwise unchanged chemical bonding conditions via triazole units, allowing to adopt design criteria for generating thermally and mechanically stable comb structures.

Expedient synthesis of a symmetric cycloheptyne-Co2(CO)6 complex for orthogonal Huisgen cycloadditions

A cycloheptyne dicobalt-carbonyl complex with a terminal alkyne was synthesized by a short procedure, and was able to react selectively in Strain Promoted Alkyne Azide Cycloaddition (SPAAC) or Copper Catalysed Alkyne Azide Cycloaddition (CuAAC) depending on the conditions.

Photo-responsive liposomes composed of spiropyran-containing triazole-phosphatidylcholine: investigation of merocyanine-stacking effects on liposome-fiber assembly-transition.

A spiropyran-containing triazole-phosphatidylcholine (SPTPC) was synthesized through a copper-catalyzed azide alkyne cyclo-addition (CuAAC) reaction. In water, SPTPCs self-assembled and a spontaneous spiropyran-to-merocyanine (SP-to-MC) isomerization occurred, resulting in coexistence of liposomes and fibers, and switching from the spiropyran (SP) to the merocyanine (MC) isomeric structure induced a reversible transition between these molecular assemblies. Study of the self-assembly of SPTPCs and photo-induced liposome-fiber assembly-transition revealed that the presence of MC enabled additional inter-membrane interaction during self-assembly and that the MC-stacking effect was the driving force for the assembly-transition. Exposure to UV light induced switching from SP to MC, where the planar structure of MC and the confinement of MC led to enhanced MC-stacking. The effect of MC-stacking was both advantageous and disadvantageous: MC-stacking perturbed the hydrophobic phase in the bilayer membrane and facilitated the liposome-to-fiber transition, otherwise the MC-stacking retarded switching of MC to SP, and caused an incomplete recovery of MC to SP during fiber-to-liposome recovery, thus a fatigue of SP was induced by MC-stacking during the liposome-to-fiber transition cycle. To decrease the intermolecular interactions and suppress MC-stacking, photo-inert triazole-phosphatidylcholine (TPC) was incorporated to prepare two-component TPC/SPTPC-liposomes, which exhibited better recovery kinetics. The photo-adaptive behavior of TPC/SPTPC-liposomes confirmed the disturbance of bilayer membranes by inter-membrane MC-stacking and the formation of MCTPC-enriched phases in the bilayer membrane.

Synthesis of pyramidal tetraarylborate pentads

Tetrahedral tetraarylborate pentads were synthesized by a typical click reaction, copper-catalyzed azide–alkyne cyclization, which exhibited interesting ionic dissociation in low polar organic solvents.

Copper-Catalyzed Alkyne-Azide Cycloaddition on the Solid Phase for the Preparation of Fully Click-Modified Nucleic Acids.

Click chemistry has become a widely used method to insert modifications into DNA. Due to its commercial availability, 5'-ethynyl-deoxyuridine (EdU) is commonly incorporated into the DNA for subsequent modification by click reaction. However, it is partially oxidized during deprotection during solid-phase synthesis, resulting in a ketone that is no longer accessible for click modification. To enable the high-fidelity solid-phase synthesis of EdU-containing DNA, this protocol describes a procedure to perform the click reaction on the solid phase before deprotection. Afterwards, the DNA can be deprotected and purified according to standard procedures, and the full modification of EdU with the azide of choice can be analyzed by HPLC and HPLC/MS.

Nanoparticle Assembling through Click Chemistry Directed by Mixed SAMs for Magnetic Applications

“Click” chemistry, used to promote nanoparticle assemblies, is a powerful strategy which has emerged very recently to control the spatial arrangement of nanoparticles onto surfaces. Such a strategy may be of high interest for applications such as magnetic recording media or magnetic sensors which are based on the fine control of the collective properties of nanoparticles. Nevertheless, self-assembly driven by clickable functional groups still remains to be understood. Mixed self-assembled monolayers (SAMs) of alkane–thiol molecules were used to control the spatial arrangement of nanoparticles onto gold substrates. This approach was combined with click chemistry in order to control the immobilization of nanoparticles on selective areas through specific copper catalyzed alkyne–azide cycloaddition (CuAAC) reaction. Mixed SAMs consist of co-adsorbed 11-(undec-1-ynyl)thiol (S-CC) and 12-(dodecane)thiol (S-CH3) molecules. The variation of the molar ratio between both molecules resulted in significant modulation of the structure of nanoparticle assemblies. The spatial arrangement of nanoparticles revealed the very complex structure of alkyne/methylene terminated mixed SAMs. Alkyne terminal groups could not be only studied by the usual characterization surface techniques such as PM-IRRAS and XPS. Therefore, azido-terminated nanoparticles acted as probing agents to determine the spatial distribution of alkyne groups at the surface of mixed SAMs. This approach was combined with scanning tunneling microscopy (STM) and DFT calculations to get a deeper insight into the structure of mixed SAMs of S-CC and S-CH3 molecules. Gold substrate topography, chemical affinity of molecules, intermolecular interactions and length of alkyl chains were found to be critical parameters that rule the SAM structure.

Mechanistic Study in Click Reactions by Using (N-Heterocyclic carbene)Copper(I) Complexes: Anionic Effects

A series of Cu complexes bearing N-heterocyclic carbene were synthesized, and their application for the copper-catalyzed azide–alkyne cycloaddition reaction was studied. The catalytic results demonstrated that [L2Cu]Br exhibited the most activity, and the trend of the other complexes was I > Br > Cl ∼ BF4 > PF6. The 1H NMR spectrum of the reaction of LCuCl and phenylacetylene demonstrated that the NHC ligand dissociated from the Cu atom and deprotonated phenylacetylene to produce phenylacetylide. The conductivity study also proved this phenomenon. According to the density functional theory calculations, a mechanism was proposed in which acetylide copper halide was formed after NHC ligand dissociation and phenylacetylene deprotonation. Then, the six-membered metallacycle from the cycloadditions of methyl azide with mononuclear copper acetylide reacted with the second copper catalyst, (NHC)CuX, to form the dinuclear intermediate, which in turn underwent a rapid ring contraction to form another more stable d...

Theoretical Study of Copper Acetonitrile Effects on Parr Functions Indices and Regioselectivity Using Density Functional Theory (DFT)

Copper-catalyzed azide–alkyne cycloaddition (CuAAC) is a straightforward way for making covalent connections between building blocks containing various functional groups. It is widely used in organic synthesis, medicinal chemistry, polymer chemistry, and bioconjugation applications. Using copper acetonitrile as catalyst for click reactions (CuAAC) lead to a non-concerted reaction, and affect Parr functions indices to determine the polar sites, therefore predict the favorable regioisomer (1,4-regioisomer) and explain the contradiction obtained to the experimental results. The huge difference of activation barriers between catalyzed and uncatalyzed reaction indicate that is a selective reaction.

Synthesis and antibacterial activity of new 1,2,3-triazolylmethyl-2H-1,4-benzothiazin-3(4H)-one derivatives

BackgroundA novel series of 1,2,3-triazole derivatives containing 1,4-benzothiazin-3-one ring (7a–9a, 7b–9b), (10a–12a, 10b–12b) and (13–15) were synthesized by 1,3-dipolar cycloaddition reactions of azides α-d-galactopyranoside azide F, 2,3,4,6-tetra-O-acetyl-(d)-glucopyranosyl azide G and methyl-N-benzoyl-α-azidoglycinate H with compounds 4–6.FindingsInitially, the reactions were conducted under thermal conditions in ethanol. The reaction leads, each time, to the formation of two regioisomers: (Schemes 2, 3) with yields of 17 to 21% for 1,5-disubstituted 1,2,3-triazole-regioisomers (7b–12b) and yields ranging from 61 to 65% for the 1,4-disubstituted regioisomers (7a–12a). In order to report an unequivocal synthesis of the 1,4-regioisomers and confirm the structures of the two regioisomers obtained in thermal conditions (Huisgen reactions), the method click chemistry (Copper-Catalyzed Azide-Alkyne Cycloaddition) has been used.ConclusionsThe newly synthesized compounds using cycloaddition reactions were evaluated in vitro for their antibacterial activities against some Gram positive and Gram negative microbial strains. Among the compounds tested, the compound 8a showed excellent antibacterial activities against PA ATCC and Acin ESBL (MIC = 31.2 μg/ml).

Screening of a Library of Oligosaccharides Targeting Lectin LecB of Pseudomonas Aeruginosa and Synthesis of High Affinity Oligoglycoclusters.

The Gram negative bacterium Pseudomonas aeruginosa (PA) is an opportunistic bacterium that causes severe and chronic infection of immune-depressed patients. It has the ability to form a biofilm that gives a selective advantage to the bacteria with respect to antibiotherapy and host defenses. Herein, we have focused on the tetrameric soluble lectin which is involved in bacterium adherence to host cells, biofilm formation, and cytotoxicity. It binds to l-fucose, d-mannose and glycan exposing terminal fucose or mannose. Using a competitive assay on microarray, 156 oligosaccharides and polysaccharides issued from fermentation or from the biomass were screened toward their affinity to LecB. Next, the five best ligands (Lewisa, Lewisb, Lewisx, siayl-Lewisx and 3-fucosyllactose) were derivatized with a propargyl aglycon allowing the synthesis of 25 trivalent, 25 tetravalent and 5 monovalent constructions thanks to copper catalyzed azide alkyne cycloaddition. The 55 clusters were immobilized by DNA Directed immobilization leading to the fabrication of a glycocluster microarray. Their binding to LecB was studied. Multivalency improved the binding to LecB. The binding structure relationship of the clusters is mainly influenced by the carbohydrate residues. Molecular simulations indicated that the simultaneous contact of both binding sites of monomer A and D seems to be energetically possible.

Copper(I)-catalyzed tandem reaction: synthesis of 1,4-disubstituted 1,2,3-triazoles from alkyl diacyl peroxides, azidotrimethylsilane, and alkynes.

A copper-catalyzed azide–alkyne cycloaddition (CuAAC) reaction for the synthesis of 1,4-disubstituted 1,2,3-triazoles from alkyl diacyl peroxides, azidotrimethylsilane, and terminal alkynes is reported. The alkyl carboxylic acids is for the first time being used as the alkyl azide precursors in the form of alkyl diacyl peroxides. This method avoids the necessity to handle organic azides, as they are generated in situ, making this protocol operationally simple. The Cu(I) catalyst not only participates in the alkyl diacyl peroxides decomposition to afford alkyl azides but also catalyzes the subsequent CuAAC reaction to produce the 1,2,3-triazoles.

Synthesis, crystal structure, Hirshfeld surface analysis, and DFT calculations of new 1-[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]-6-methoxy-1H-benzimidazol-2(3H)-one

Abstract Benzimidazole derivatives are of substantial importance because of their wide array of pharmacological activities. These nitrogen-containing heterocycles are used as therapeutic agents in medicinal chemistry. The title compound has been prepared using click chemistry (Copper-Catalyzed Azide-Alkyne Cycloaddition (CuAAC)) involving 1-propargyl-6-methoxy benzimidazolone as the dipolarophile and benzylazide as the dipole. The crystallographic study showed that the compound with formula C18H17N5O2 adopts a pincer-like conformation in the crystal. Inversion-related N H⋯O hydrogen bonds form dimers which are elaborated into layers parallel to (10–2) by C H⋯O and C H⋯N hydrogen bonds and C H⋯π(ring) and π-stacking interactions. The Hirshfeld surface analysis of the title compound was performed using the Crystal Explorer program while the density functional theory (DFT) calculation was performed by the hybrid B3LYP method.

Synthesis of Molecular Dyads and Triads Based Upon N‐Annulated Perylene Diimide Monomers and Dimers

The synthesis of N‐annulated perylene diimides (NPDIs) with grafted electron donating phenothiazine (PTZ) groups is presented. The synthetic strategy takes advantage of the N‐annulation at the PDI bay position, which allows for the facile installation of the pendant donors. Three new molecular materials are reported, a dyad consisting of an NPDI monomer tethered to a PZT unit (4), a dyad consisting of an NPDI dimer with one PZT unit tethered (9), and a triad consisting of an NPDI dimer with two PTZ units tethered (10). The PTZ and NPDI were “clicked” together using copper catalyzed alkyne–azide cycloaddition chemistry. Analysis of optical absorption/emission spectra and electrochemical data reveal that the electronic structure of each individual aromatic system remains distinct, but through‐space interactions occur, as is evident by fluorescence quenching in both solution and the solid state.

Decoration of Coiled-Coil Peptides with N-Cysteine Peptide Thioesters As Cyclic Peptide Precursors Using Copper-Catalyzed Azide-Alkyne Cycloaddition (CuAAC) Click Reaction.

The development of a copper-catalyzed azide-alkyne cycloaddition (CuAAC) protocol for the decoration of coiled coils with N-cysteine peptide thioesters as cyclic peptide precursors is presented. The reaction conditions include tert-butanol/PBS as the solvent and CuSO4/THPTA/ascorbate as the catalytic system. During these studies, partial formylation of N-terminal cysteine peptides is observed. Mechanistic analysis leads to identification of the formyl source and, hence, to the development of reaction conditions, under which the undesired side reaction was suppressed.

Measuring Bacterial Glycosyl Hydrolase Activity with a Soluble Capture Probe by Mass Spectrometry.

A solution-phase enzymatic assay has been developed to track bacterial glycosyl hydrolase activity by surface-assisted MALDI-TOF mass spectrometry. Lactose was equipped with an azide-functionalized linker and was supplemented to bacterial cultures as an artificial substrate for bacterial β-galactosidase enzyme. The azide linked glycoside probe was then covalently captured on an alkyne-functionalized indium tin oxide sample plate via a bio-orthogonal copper-catalyzed azide alkyne cycloaddition (CuAAC). The noncovalent immobilization of the alkyne capture tag via hydrophobic interactions on the ITO-sample plate allowed the analysis of the probe conjugate by surface-based mass spectrometry. The ratio of digested to nondigested lactose probe was then employed as a measure for bacterial hydrolase activity, which correlated well with bacterial growth measured by optical density. In addition, we established in a proof of concept experiment that the setup was well suited to identify antibiotic susceptibility of bacterial strains with a performance comparable to current state-of-the-art methods. While the proof of concept version is limited to the identification of a single enzyme activity, we envisage that the use of multiple substrate probes in a multiplexed version will allow the quantification of various glycosyl hydrolase activities with clinical relevance in a single experiment.

Synthesis and insecticidal activities of novel solanidine derivatives.

Potato (Solanum tuberosum) is the fourth culture in the world and is widely used in the agri-food industries. They generate by-products in which α-chaconine and α-solanine, the two major solanidine-based glycoalkaloids of potato, are present. As secondary metabolites, they play an important role in the protection system of potato and are involved in plant protection against insects. To add value to these by-products, we described here new glycoalkaloids that could have phytosanitary properties. Solanidine, as a renewable source, was modified with an azido linker and coupled by copper-catalyzed alkyne azide cycloaddition to alkynyl derivatives of the monosaccharides found in the natural potato glycoalkakoids: D-glucose, D-galactose and L-rhamnose. The efficacy of our compounds was evaluated on the potato aphid Macrosiphum euphorbiae. The synthetic compounds have stronger aphicidal properties against nymphs than unmodified solanidine. They also showed strong aphicidal activities on adults and a negative impact on fecundity. Our synthetic neoglycoalkaloids affected Macrosiphum euphorbiae survival at the nymphal stage as well as at the adult stage. Furthermore, they induced a decrease in fecundity. Our results show that chemical modifications of by-products may afford new sustainable compounds for crop and plant protection. © 2018 Society of Chemical Industry.

Ultrasound Assisted High-Throughput Synthesis of 1,2,3-Triazoles Libraries: A New Strategy for “Click” Copper-Catalyzed Azide-Alkyne Cycloaddition Using Copper(I/II) as a Catalyst

A series of 1,4-disubstituted 1,2,3-triazoles were prepared by a parallel synthesis protocol utilizing the 3D-supramolecular coordination polymer (SCP) {[CuI(CN)(phen)2·CuII(CN)2(phen)]·5H2O}, 1 as a catalyst under ultrasonic irradiations. This work establishes the synergistic action between the mixed valance copper catalyst SCP 1 and ultrasonic irradiation to yield a high-throughput synthesis of 1,4-disubstituted 1,2,3-triazoles libraries. This mixed valance copper(I/II) supramolecular coordination polymer catalyzed azide alkyne cycloaddition reaction protocol allowed a rapid synthesis of the target compounds (10 min) in a parallel fashion with good to excellent yields. Twelve reactions were performed in a single deep well microtiter plate, employing three alkynes and four different azide reagents. From this effort, a total of twelve 1,2,3-triazole were obtained in useful isolated yields. Moreover, unambiguous structural assignment of the obtained regioisomers was determined utilizing Heteronuclear Multiple Bond Correlation (HMBC) 2D NMR techniques as a valuable. A series of 1,4-disubstituted 1,2,3-triazoles were prepared by a parallel synthesis protocol utilizing the 3D-supramolecular coordination polymer (SCP) {[CuI(CN)(phen)2·CuII(CN)2(phen)]·5H2O}, 1 as a catalyst under ultrasonic irradiations.

Synthesis of carboxylated derivatives of poly(isobutylene-co-isoprene) by azide–alkyne “click” chemistry

The synthesis of carboxylated derivatives of poly(isobutylene-co-isoprene) (isobutylene–isoprene rubber, IIR) with substitution levels ranging from 1 to 4 mol% and different spacer lengths was accomplished through azide–alkyne Huisgen cycloaddition. Azido-functionalized IIR was first prepared by reacting brominated IIR with sodium azide to full conversion in a 90:10 tetrahydrofuran/N,N-dimethylacetamide mixture. The click reaction of azido-functionalized IIR with acetylenic acids, which was carried out using the copper(I) bromide/N,N,N′,N″,N″-pentamethyldiethylenetriamine catalyst system in tetrahydrofuran, yielded carboxylated IIRs. The products were characterized by 1H NMR and FT-IR spectroscopy, and their molecular weight was determined by size exclusion chromatography analysis. The conversion to carboxylated groups reached up to 100% as determined by NMR spectroscopy but was highly dependent on the type of solvent and the amounts of catalysts and reactants used in the procedures. The synthesis of carboxylated IIR was achieved in high yield starting from brominated substrates, which were first converted to azides and used in the copper-catalyzed azide–alkyne Huisgen cycloaddition reaction with acetylenic acids containing different aliphatic spacer lengths. Optimization of the reaction conditions was critical to avoid the formation of gel particles in the reactions and to achieve full conversion of the bromide to carboxylate derivatives.