Terminal Azide Research Articles

Cytotoxicity of Doxorubicin-Curcumin Nanoparticles Conjugated with Two Different Peptides (CKR and EVQ) against FLT3 Protein in Leukemic Stem Cells.

A targeted micellar formation of doxorubicin (Dox) and curcumin (Cur) was evaluated to enhance the efficacy and reduce the toxicity of these drugs in KG1a leukemic stem cells (LSCs) compared to EoL-1 leukemic cells. Dox-Cur-micelle (DCM) was developed to improve the cell uptake of both compounds in LSCs. Cur-micelle (CM) was produced to compare with DCM. DCM and CM were conjugated with two FLT3 (FMS-like tyrosine kinase)-specific peptides (CKR; C and EVQ; E) to increase drug delivery to KG1a via the FLT3 receptor (AML marker). They were formulated using a film-hydration technique together with a pH-induced self-assembly method. The optimal drug-to-polymer weight ratios for the DCM and CM formulations were 1:40. The weight ratio of Dox and Cur in DCM was 1:9. DCM and CM exhibited a particle size of 20-25 nm with neutral charge and a high %EE. Each micelle exhibited colloidal stability and prolonged drug release. Poloxamer 407 (P407) was modified with terminal azides and conjugated to FLT3-targeting peptides with terminal alkynes. DCM and CM coupled with peptides C, E, and C + E exhibited a higher particle size. Moreover, DCM-C + E and CM-C + E showed the highest toxicity in KG-1a and EoL-1 cells. Using two peptides likely improves the probability of micelles binding to the FLT3 receptor and induces cytotoxicity in leukemic stem cells.

Template Assisted Synthesis of Linear [5]Catenane by Post-Functionalization of Templated [2]Catenane and Using Click Reaction.

Polymers with all mechanically interlocked rings, such as linear [n]catenanes, have great potential as functional materials due to possible higher degrees of freedom that may contribute to their flexibility but remain elusive. All the synthetic methods used to prepare such a polymer yield mixtures of products. In the absence of higher molecular weight linear [n]catenanes, emphasis on synthesizing low molecular weight oligomers is being pursued. Here, we have described the synthesis of a linear [5]catenane by post-functionalizing a Co(III) templated [2]catenane having a pyridine-diamide unit free for further metal ion coordination. Two molecules were synthesized with suitable threading groups: one, two terminal azide groups, and two, with two terminal alkyne groups to form two [3]pseudorotaxane utilizing Co(III) coordination. These units were then joined, forming a macrocycle, using click reaction, giving the desired metalated linear [5]catenane in 40 % yield. Removal of metal ions leads to linear [5]catenane. In addition, the formation of linear [3] and [2]catenane are also observed. All synthesized structures have been isolated by column chromatographic technique and characterized by 1H-NMR, 13C-NMR, and mass spectroscopy.

Synthesis and crystal structure of the cluster (Et4N)[(Tp*)MoFe3S3(μ3-NSiMe3)(N3)3

The title compound, tetraethylammonium triazidotri-μ3-sulfido-[μ3-(trimethylsilyl)azanediido][tris(3,5-dimethylpyrazol-1-yl)hydroborato]triiron(+2.33)molybdenum(IV), (C8H20N)[Fe3MoS3(C15H22BN6)(C3H9NSi)(N3)3] or (Et4N)[(Tp*)MoFe3S3(μ3-NSiMe3)(N3)3] [Tp* = tris(3,5-dimethylpyrazol-1-yl)hydroborate(1−)], crystallizes as needle-like black crystals in space group P\overline{1}. In this cluster, the Mo site is in a distorted octahedral coordination model, coordinating three N atoms on the Tp* ligand and three μ3-bridging S atoms in the core. The Fe sites are in a distorted tetrahedral coordination model, coordinating two μ3-bridging S atoms, one μ3-bridging N atom from Me3SiN2−, and another N atom on the terminal azide ligand. This type of heterometallic and heteroleptic single cubane cluster represents a typical example within the Mo–Fe–S cluster family, which may be a good reference for understanding the structure and function of the nitrogenase FeMo cofactor. The residual electron density of disordered solvent molecules in the void space could not be reasonably modeled, thus the SQUEEZE [Spek (2015). Acta Cryst. C71, 9–18] function was applied. The solvent contribution is not included in the reported molecular weight and density.

Cu-Catalyzed Azide-Alkyne-Thiol Reaction Forms Ubiquitous Background in Chemical Proteomic Studies.

We report here a Cu-catalyzed azide-alkyne-thiol reaction forming thiotriazoles as the major byproduct under widely used bio-orthogonal protein labeling "click" conditions. The development of Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) had a tremendous impact on many biological discoveries. However, the considered chemoselectivity of CuAAC is hampered by the high reactivity of cysteine free thiols, yielding thiotriazole protein conjugates. The reaction byproducts generate false-positive protein hits in functional proteomic studies. The reported detail investigation of conjugates between chemical probes containing terminal alkynes, azide tags, and cell lysates reveals the formation of thiotriazoles, which can be readily detected by in-gel fluorescence scanning or after peptide and protein enrichment by mass spectrometry-based proteomics. In protein level identification and quantification experiments, the produced fluorescent bands or enriched proteins may not result from the important enzymatically driven reaction and can be falsely assigned as hits. This study provides a complete list of the most common background proteins. The knowledge of this previously overlooked reactivity now leads to the introduction of modified CuAAC conditions, which avoids the undesired product formation, diminishes the background, and hence improves the signal-to-noise ratio.

Copper-Catalyzed Azide-Alkyne Cycloaddition-Oriented Multifunctional Bio-Orthogonal Linker BPPA: Design, Synthesis and Evaluation.

The multifunctional linker molecules are crucial for the bio-orthogonal reaction for proteomic target profiling. Herein, we wish to present a novel type of biotin-based tetra-functional bio-orthogonal linkers 3a-3h named BPPA which, possessing a unique photolabile phenacyl ester motif, were readily prepared in 85-90% yields by a simple and green one-step protocol from commercially available and inexpensive reagents of biotin acids and 4'-ethynyl/azido 2-bromoacetophenones. The typical click reaction of BPPA linkers 3a and 3e via copper-catalyzed azide-alkyne cycloaddition (CuAAC) took place easily, resulting in the corresponding BPPA-triazole adducts 4a and 4b in nearly quantitative yields. A further cleavability evaluation of 4a and 4b demonstrated that the expected C-O bond detachment could be accomplished efficiently and rapidly by UV irradiation or by ammonia hydrolysis, respectively, resulting in the residual (hydroxyl)acetylphenyl triazole fragment supposed to be attached to proteins during biological manipulations. The BPPA linkers, with dual clickable options of either the terminal azide or alkyne clickable group, exhibit high potentials for various CuAAC-oriented bio-orthogonal reactions.

Copper(I)‐Catalyzed Interrupted Click Reaction: Synthesis of 1,4,5‐Trisubstituted 5‐Chloro‐1,2,3‐Triazoles

Abstract5‐Halo‐1,2,3‐triazoles are important scaffolds in organic chemistry, but current click reactions cannot produce 1,4,5‐trisubstituted 5‐chloro‐1,2,3‐triazoles in a simple way. Herein, we disclosed a Cu(I)‐catalyzed interrupted click reaction, using N‐chlorophthalimide as an electrophilic chlorine source, enabling the facile synthesis of 1,4,5‐trisubstituted 5‐chloro‐1,2,3‐triazoles in one step from readily available terminal alkynes and azides. Complete control of regioselectivities with a broad substrate scope was accomplished by this approach. Furthermore, a novel epoxidation was developed using 5‐chloro‐triazole as substrate, which could be further applied in various organic transformations.

Mononuclear Mn(III) complex with a terminal azide supported by phenol-based tetradentate N2O2 donor ligand: Synthesis, structure, properties, and catechol oxidase activity

Mixed ligand octahedral Mn(III) complex [Mn(L)(CH3OH)(N3)] (1) with sterically constrained phenol-based tetradentate N2O2 ligand, N,Nʹ-dimethyl-N,Nʹ-bis (2-hydroxy-3,5-dichlorobenzyl)-ethylenediamine (H2L) in association with azide ion and methanol as ancillary ligand has been synthesized. Synthesis, structure, properties, and catecholase activity of the mononuclear manganese complex (1) are described. Complex (1) crystallizes in triclinic space group P-1 with a = 10.5431(5) Å, b = 11.3731(6) Å and c = 22.9638(12) Å. The crystal structure reveals that complex (1) is an Mn (III) complex with flexible phenol-based ligand in association with azide as a terminal monodentate ligand. Electrochemical study of the mononuclear manganese complex (1) gives two quasi reversible oxidation peaks (E11/2≈ 0.18 V and E21/2≈ 0.23 V) in the positive potential range versus Ag/AgCl reference in acetonitrile due to ligand centered phenolate/phenoxyl couple. Complex (1) shows a strong emission band at 440 nm. The complex exhibits catechol oxidase activity in methanol. Oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone in methanol has been accelerated in presence of reported manganese complex (1) with a high Kcat value of 1.43 × 104h−1.

Interrupted Click Reaction with CuCF2CF3 Reagent: Synthesis of 5-Pentafluoroethyl 1,2,3-Triazoles.

We herein describe a three-component interrupted click reaction to synthesize novel 5-pentafluoroethyl 1,2,3-triazoles in one step from readily available terminal alkynes and azides. The key reagent [CuCF2CF3], prepared from the low-cost gas pentafluoroethane, demonstrates an orthogonal reactivity in facilitating cycloaddition rather than previously reported radical reactions. Reaction conditions are mild by using air as a green oxidant.

Synthesis of S-Adenosyl-L-Methionine Analogs with Extended Transferable Groups for Methyltransferase-Directed Labeling of DNA and RNA.

S-Adenosyl-L-methionine (AdoMet) is a ubiquitous methyl donor for a variety of biological methylation reactions catalyzed by methyltransferases (MTases). AdoMet analogs with extended propargylic chains replacing the sulfonium-bound methyl group can serve as surrogate cofactors for many DNA and RNA MTases, enabling covalent derivatization and subsequent labeling of their cognate target sites in DNA or RNA. Although AdoMet analogs with saturated aliphatic chains are less popular than propargylic ones, they can be useful for dedicated studies that require certain chemical derivatization. Here we describe synthetic procedures for the preparation of two AdoMet analogs, one with a transferable 6-azidohex-2-ynyl group (carrying an activating C≡C triple bond and a terminal azide functionality), and the other one with a transferable ethyl-2,2,2-d3 group (an isotope-labeled aliphatic moiety). Our synthetic approach is based on direct chemoselective alkylation of S-adenosyl-L-homocysteine at sulfur with a corresponding nosylate or triflate, respectively, under acidic conditions. We also describe synthetic routes to 6-azidohex-2-yn-1-ol and conversion of the alcohols to corresponding nosylate and triflate alkylators. Using these protocols, the synthetic AdoMet analogs can be prepared within 1 to 2 weeks. © 2023 Wiley Periodicals LLC. Basic Protocol 1: Synthesis of 6-azidohex-2-yn-1-ol Basic Protocol 2: Synthesis of 4-nitrobenzenesulfonate Basic Protocol 3: Synthesis of trifluoromethanesulfonates Basic Protocol 4: S-Alkylation of AdoHcy with sulfonates Basic Protocol 5: Purification and characterization of AdoMet analogs.

Influence of N-arylsulfonamido d-valine N-substituents on the selectivity and potency of matrix metalloproteinase inhibitors

To develop matrix metalloproteinase inhibitors (MMPIs) for both therapy and medicinal imaging by fluorescence-based techniques or positron-emission tomography (PET), a small library of eighteen N-substituted N-arylsulfonamido d-valines were synthesized and their potency to inhibit two gelatinases (MMP-2, and MMP-9), two collagenases (MMP-8, and MMP-13) and macrophage elastase (MMP-12) was determined in a Structure-Activity-Relation study with ({4-[3-(5-methylthiophen-2-yl)-1,2,4-oxadiazol-5-yl]phenyl}sulfonyl)-d-valine (1) as a lead. All compounds were shown to be more potent MMP-2/-9 inhibitors (nanomolar range) compared to other tested MMPs. This is a remarkable result considering that a carboxylic acid group is the zinc binding moiety. The compound with a terminal fluoropropyltriazole group at the furan ring (P1′ substituent) was only four times less potent in inhibiting MMP-2 activity than the lead compound 1, making this compound a promising probe for PET application (after using a prosthetic group approach to introduce fluorine-18). Compounds with a TEG spacer and a terminal azide or even a fluorescein moiety at the sulfonylamide N atom (P2′ substituent) were almost as active as the lead structure 1, making the latter derivative a suitable fluorescence imaging tool.

Mechanistic DFT Study of 1,3-Dipolar Cycloadditions of Azides with Guanidine

Density functional calculations SMD(chloroform)//B3LYP/6-311+G(2d,p) were employed in the computational study of 1,3-dipolar cycloadditions of azides with guanidine. The formation of two regioisomeric tetrazoles and their rearrangement to cyclic aziridines and open-chain guanidine products were modeled. The results suggest the feasibility of an uncatalyzed reaction under very drastic conditions since the thermodynamically preferred reaction path (a), which involves cycloaddition by binding the carbon atom from guanidine to the terminal azide nitrogen atom, and the guanidine imino nitrogen with the inner N atom from the azide, has an energy barrier higher than 50 kcal mol-1. The formation of the other regioisomeric tetrazole (imino nitrogen interacts with terminal N atom of azide) in direction (b) can be more favorable and proceed under milder conditions if alternative activation of the nitrogen molecule releases (e.g., photochemical activation), or deamination could be achieved because these processes have the highest barrier in the less favorable (b) branch of the mechanism. The introduction of substituents should favorably affect the cycloaddition reactivity of the azides, with the greatest effects expected for the benzyl and perfluorophenyl groups.

Three new zinc(II) 4′-chloro-2,2′:6′,2ʺ-terpyridine (4′-Cltpy)-based complexes: synthesis, spectroscopic and structural studies, thermal behavior, and Hirshfeld surface analysis

Three new ZnII complexes with the ligand 4′-chloro-2,2′:6′,2ʺ-terpyridine (4′-Cltpy), [Zn(4′-Cltpy)(N3)2] (1), [Zn(4′-Cltpy)(NCS)2] (2) (two 1:1 metal/ligand complexes) and a 1:2 metal/ligand complex, [Zn(4′-Cltpy)2](NO3)2·2H2O (3), have been synthesized and characterized by elemental analysis, IR, 1H NMR spectroscopy and single-crystal X-ray diffraction. The structures of 1 and 2 contain a ZnN5 coordination sphere, which includes coordination from three nitrogen donors of the 4′-Cltpy ligand and two nitrogen atoms of two terminal azide or two terminal thiocyanate ligands, respectively. Addison’s τ value suggests a distorted square pyramidal coordination of ZnII in 1 and intermediate between square pyramidal and trigonal bipyramidal in 2. In the complex cation of 3, the ZnII center is coordinated by six nitrogen atoms from two 4′-Cltpy ligands in a distorted octahedral coordination geometry. In this structure, two non-coordinating nitrate anions serve as counterions, and there are two non-coordinating solvent water molecules. Hirshfeld surface analysis was employed to clarify the nature and extent of intermolecular interactions. In addition, the thermal stabilities of the compounds were evaluated by thermogravimetric analysis (TGA).

Cyclization assisted iterative growth method for synthesizing monodisperse polymers

A fast iterative growth method is reported to prepare monodisperse polymers assisted by a cyclization technique. This novel method uses a di-functional and a tri-functional compounds as monomer pairs. The di-functional monomer is designed to have an azide and a hydroxyl end groups, while the tri-functional monomer is designed to have an alkyne and a sym-dibenzo-1,5-cyclooctadiene-3,7-diyne containing two strained alkynes. One iterative cycle of this novel method is composed by four step reactions. First, the self-accelerating double-strain-promoted azide-alkyne click reaction is used to couple two monomers/oligomers having an azide and a hydroxyl end group pairs with one tri-functional monomer by reacting the azide and strained alkyne groups. This coupling reaction increases chain length and produces an elongated oligomers having two hydroxyl end groups and one alkyne group in the middle position of main-chain. Second, the esterification between anhydride and hydroxyl is used to modify the hydroxyl end groups to endow the elongated oligomers with two azide end groups. Third, copper(I)-catalyzed azide-alkyne click reaction is then used to ring-close the elongated oligomers by reacting the middle alkyne and one terminal azide groups to prepare a tadpole-shaped oligomers with one azide end group. Fourth, the 2,3-dichloro-5,6-dicyano-p-benzoquinone oxidized deprotection reaction is used to cleave the preset methoxybenzyl ether bond in the ring of the tadpole-shaped oligomers and rebuild an azide and a hydroxyl end group pairs for the elongated oligomers. The repetition of above iterative cycle can synthesize the monodisperse polymers with a fast chain-growth manner of 2n+1-1.

Copper-on-Magnetically Activated Carbon-Catalyzed Azide-Alkyne Click Cycloaddition in Water

The copper-catalyzed cycloaddition of alkynes and azides (CuAAC) to give the corresponding 1,4-disubstituted-1,2,3-triazoles is the most successful and leading reaction within the click chemistry regime. Its heterogenization stands out as the innovative strategy to solve its environmental concerns and toxicity issue. In this report, magnetically retrievable activated carbon produced from biomass Persea Americana Nuts was loaded with a catalytically active copper(I) catalyst, resulting into a heterogeneous nanocatalyst, namely Cu-Fe3O4-PAC. This new compound was fully characterized using several techniques such as Powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray diffraction (EDX), Brunauer–Emmett–Teller (BET) analysis, and Raman spectroscopy. Cu-Fe3O4-PAC catalyzed the cycloaddition of a variety of substituted terminal alkynes and organic azides in water at room temperature with excellent yields and in a regioselective manner. The hot filtration test demonstrated that no significant leaching of catalytically active copper particles took place during the CuAAC process, a feature that supports the stability of Cu-Fe3O4-PAC and its heterogeneous action way. Cu-Fe3O4-PAC was magnetically separable by applying an external magnetic field and was recyclable up to five runs, with only an 8% decline in its activity after the 5th catalytic test. The hot filtration experiment heavily suggested that the present catalytic system would proceed in a heterogeneous manner in CuAAC. The electronic characteristics, nature of the intermediate complexes, and type of ligand-to-copper bonding interactions were studied by using quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) calculations, which enabled the confirmation of the proposed binuclear mechanism.

Tellurium-containing polymer for mass cytometry

Mass cytometry is a powerful analytical technique for high-dimensional single-cell analysis. In this technique, cells are stained with heavy isotope-tagged antibodies and are analyzed by an inductively coupled plasma time-of-flight mass spectrometer. While the current mass cytometer has more than 100 mass channels, only about 50 are used because reagents are only available for a fraction of the useful elements. Here we describe the synthesis of a tellurium-containing polymer based on poly-l-lysine and sulfated tellurophene. The polymer carried ca. 48 tellurophene units per chain and had a terminal azide group for antibody conjugation. While the polymer could be conjugated to antibodies, the resulting conjugates gave mixed results in mass cytometry immunoassays. For example, a goat anti-mouse (secondary) antibody and an anti-CD19 primary Ab labeled with polymers gave promising results in antibody titration experiments. However, an anti-CD20 Ab labeled with a 126Te-enriched polymer no longer recognized the antigen and showed significant non-specific binding in a 7-plex assay with human PBMCs.

Mononuclear cobalt(III) azido complex containing a tetradentate amine: one pot synthesis, structure and thermal behavior

One hexacoordinated mononuclear complex trans-[Co(L)(N3)2] PF6 (1) [L = N,N′-bis(3-aminopropyl)- 1,2-ethanediamine] is prepared by using one-pot reactions of the building units and characterized. X-ray analysis shows that cobalt center in 1 adopts a distorted octahedral geometry with CoN6 chromophore ligated through four N atoms of tetradentate amine (L) and the two N atoms of terminal azides in mutual trans orientation. In the crystalline state, double N-H…N and multiple N-H…F hydrogen bondings result in 2D sheet structure. The compound has a thermal stability up to 193°C.
 Bangladesh J. Sci. Ind. Res. 57(2), 109-116, 2022

Copper Catalyzed Inverse Electron Demand [4+2] Cycloaddition for the Synthesis of Oxazines

A copper catalyzed tandem CuAAC/ring cleavage/[4+2] annulation reaction of terminal ynones, sulfonyl azides, and imines has been developed to synthesize the functionalized oxazines under mild conditions. Particularly, the intermediate N-sulfonyl acylketenimines undergo cycloaddition of an inverse electron demand Diels–Alder reaction with imines and a series of 1,3-oxazine derivatives were obtained successfully in good yields.

Synthesis and hemagglutination inhibitory properties of mannose-tipped ligands: The effect of terminal phenyl groups and the linker between the mannose residue and the triazole moiety

Two families (A, B) of triazole conjugates derived from d-mannose possessing reversed linkage functionality were easily assembled by Cu(I) catalyzed azide-alkyne cycloaddition reaction (CuAAC). The mannose precursors were built with either 3-azidopropyl or propargyl aglycones whereas the phenyl moieties were built with terminal azide or propargyl groups, respectively. In a hemagglutination inhibition (HAI) assay, family A (7a-11a), where the linker between the mannose residue and the triazole ring is three carbons displayed a 3–5 fold enhancement in activity compared to family B (13a-17a) having methyl-triazolyl moiety. The representative ligand 7a, where the terminal phenyl ring is substituted with an ester group and Cl atom exhibited the highest inhibitory activity with an HAI titer of 8 μM. This compound could be a good candidate for the further design of potent mannosyl ligands targeting FimH fimbrial lectin.

Copper(II)-Bis-Cyclen Intercalated Graphene Oxide as an Efficient Two-Dimensional Nanocomposite Material for Copper-Catalyzed Azide-Alkyne Cycloaddition Reaction.

We report stable and heterogeneous graphene oxide (GO)–intercalated copper as an efficient catalyst for the organic transformations in green solvents. The GO-intercalated copper(II) complex of bis(1,4,7,10-tetraazacyclododecane) [Cu(II)-bis-cyclen] was prepared by a facile synthetic approach with a high dilution technique. The as-prepared GO-Cu(II)-bis-cyclen nanocomposite was used as a click catalyst for the 1,3 dipolar Huisgen cycloaddition reaction of terminal alkyne and azide substrates. On directing a great deal of attention toward the feasibility of the rapid electron transfer rate of the catalyst in proliferating the yield of 1,2,3-triazole products, the click catalyst GO-Cu(II)-bis-cyclen nanocomposite was designed and synthesized via non-covalent functionalization. The presence of a higher coordination site in an efficient 2D nanocomposite promotes the stabilization of Cu(I) L-acetylide intermediate during the catalytic cycle initiated by the addition of reductants. From the XRD analysis, the enhancement in the d-interlayer spacing of 1.04 nm was observed due to the intercalation of the Cu(II)-bis-cyclen complex in between the GO basal planes. It was also characterized by XPS, FT-IR, RAMAN, UV, SEM, AFM, and TGA techniques. The recyclability of the heterogeneous catalyst [GO-Cu(II)-cyclen] with the solvent effect has also been studied. This class of GO-Cu(II)-bis-cyclen nanocomposite paves the way for bioconjugation of macromolecules through the click chemistry approach.

Syntheses, characterization, and crystal structures of cobalt(III) complexes derived from 2-(((2-(pyrrolidin-1-yl)ethyl)imino)methyl)phenol with the antibacterial activity

A mononuclear cobalt(III) complex [CoL(NCS)2(OH2)] (1) and a trinuclear cobalt(III—II—III) complex [Co{CoLN3(m1,1-N3)2(CH3OH)}2] (2), derived from the Schiff base ligand 2-(((2-(pyrrolidin-1-yl)ethyl)imino)methyl)phenol (HL), are synthesized and characterized by IR and electronic spectra. The structures of both complexes are studied in detail by single crystal X-ray diffraction. In complex 1, the Co(III) atom is coordinated by three donor atoms of the Schiff base ligand, two thiocyanate N atoms, and one water O atom, forming an octahedral geometry. In complex 2, the terminal Co(III) atom is coordinated by three donor atoms of the Schiff base ligand, two end-on azide N atoms, and one terminal azide N atom, forming an octahedral geometry. The central Co(II) atom is coordinated by four end-on azide N atoms and two methanol O atoms, forming an octahedral geometry. The complexes exhibit interesting antibacterial activities against B. subtilis and E. coli.