1,2,3-Triazoles as Biomimetics in Peptide Science

Fragment-Based Design and Synthesis of Symmetrical bis-Peptidotriazoles Using Alkylidene bis-Amide Formations and Subsequent Triazole Ligation with β-Acetamido Carbonyl Scaffolds

A novel and efficient fragment-based assembly of symmetrical bis-peptidotraizoles has been developed based on double Sharpless azide-alkyne click chemistry. A new Cu(II) catalyzed protocol with a wide substrate scope was developed for accessing the symmetrical alkylidene bis-azidoamide fragment that yields the products in very good yields at room temperature without employing column purifications. The propargylated β-acetamido ketone fragment was accessed using another Cu(II) catalyzed room temperature MCR protocol. A fast double-click reaction (2 h) of symmetrical alkylidene bis-azidoamides with propargylated β-acetamido ketone fragments leads to the formation of unusual symmetrical bis-peptidotriazoles.

1,2,3-Triazole-Containing Azamacrocycles from Chiral Triazolopeptoids: Synthesis and Solid-State Studies

Two new chiral 1,2,3-triazole-containing macrocyclic oligoamides (i. e.: triazolopeptoid 4 and 5) were obtained through solid-phase synthesis of linear precursors followed by high dilution macrocyclization reaction. Theoretical (DFT) and spectroscopic (NMR) studies revealed the intricate interplay between the Nα-chiral side chains and their conformational attitudes. BH3-mediated reduction of the tertiary amide groups of known 1-3 and newly synthesized 4 gave novel azamacrocycles 6-9. Detection of borane complexes of azamacrocycles 6 and 9 (i. e.: 10 and 11), corroborated by X-ray diffraction studies, demonstrated the peculiar properties of 1,2,3-triazole-containing macrorings.

Click chemistry beyond metal-catalyzed cycloaddition as a remarkable tool for green chemical synthesis of antifungal medications

Click chemistry is widely used for the efficient synthesis of 1,4-disubstituted-1,2,3-triazole, a well-known scaffold with widespread biological activity in the pharmaceutical sciences. In recent years, this magic ring has attracted the attention of scientists for its potential in designing and synthesizing new antifungal agents. Despite scientific and medical advances, fungal infections still account for more than 1.5 million deaths globally per year, especially in people with compromised immune function. This increasing trend is definitely related to a raise in the incidence of fungal infections and prevalence of antifungal drug resistance. In this condition, an urgent need for new alternative antifungals is undeniable. By focusing on the main aspects of reaction conditions in click chemistry, this review was conducted to classify antifungal 1,4-disubstituted-1,2,3-triazole hybrids based on their chemical structures and introduce the most effective triazole antifungal derivatives. It was notable that in all reactions studied, Cu(I) catalysts generated in situ by the reduction in Cu(II) salts or used copper(I) salts directly, as well as mixed solvents of t-BuOH/H2O and DMF/H2O had most application in the synthesis of triazole ring. The most effective antifungal activity was also observed in fluconazole analogs containing 1,2,3-triazole moiety and benzo-fused five/six-membered heterocyclic conjugates with a 1,2,3-triazole ring, even with better activity than fluconazole. The findings of structure-activity relationship and molecular docking of antifungal derivatives synthesized with copper-catalyzed azide-alkyne cycloaddition (CuAAC) could offer medicinal chemistry scientists valuable data on designing and synthesizing novel triazole antifungals with more potent biological activities in their future research.

Iterative click reactions using trivalent platforms for sequential molecular assembly

A facile synthesis of multi(triazole)s by iterative click reactions is disclosed. Good functional group tolerance of sequential click assembly by sulfur-fluoride exchange (SuFEx), copper-catalyzed azide-alkyne cycloaddition (CuAAC), and thia-Michael reaction realizes the iterative click reactions. Diverse multi(triazole)-type mid-molecules can be synthesized easily from readily available modules through good chemoselective reactions without functional group transformation steps.

Stereochemical and Computational NMR Survey of 1,2,3-Triazoles: in Search of the Original Tauto-Conformers

The conformational analysis of nine functionalized 1,2,3-triazoles was carried out by the correlation of calculated and experimental high-level nuclear magnetic resonance (NMR) chemical shifts. In solution, the studied triazoles are in exchange dynamic equilibrium caused by their prototropic tautomerism of the NH-proton. The experimentally unresolved NMR signals were assigned for most of the compounds. A more thorough survey was conducted for 4-t-butyl-1,2,3-triazole-5-carbaldehyde oxime. The analysis performed within the framework of the DP4+ formalism completely confirmed the hypothesis of the predominance of the 2H-tautomer. Thus, the methodology for estimating stereochemical structures in the absence of some experimental data allowed the most stable conformations for dynamic systems with different tautomeric ratios to be reliably identified.

Trends in the Diversification of the Detergentome

Detergents are amphiphilic molecules that serve as enabling steps for today's world applications. The increasing diversity of the detergentome is key to applications enabled by detergent science. Regardless of the application, the optimal design of detergents is determined empirically, which leads to failed preparations, and raising costs. To facilitate project planning, here we review synthesis strategies that drive the diversification of the detergentome. Synthesis strategies relevant for industrial and academic applications include linear, modular, combinatorial, bio-based, and metric-assisted detergent synthesis. Scopes and limitations of individual synthesis strategies in context with industrial product development and academic research are discussed. Furthermore, when designing detergents, the selection of molecular building blocks, i. e., head, linker, tail, is as important as the employed synthesis strategy. To facilitate the design of safe-to-use and tailor-made detergents, we provide an overview of established head, linker, and tail groups and highlight selected scopes and limitations for applications. It becomes apparent that most recent contributions to the increasing chemical diversity of detergent building blocks originate from the development of detergents for membrane protein studies. The overview of synthesis strategies and molecular blocks will bring us closer to the ability to predictably design and synthesize optimal detergents for challenging future applications.

Novel Cu(ii) acidic deep eutectic solvent as an efficient and green multifunctional catalytic solvent system in base-free conditions to synthesize 1,4-disubstituted 1,2,3-triazoles

A novel green Cu(ii)-acidic deep eutectic solvent (Cu(ii)-ADES) bearing copper salt, choline chloride, and gallic acid ([ChCl]4[2GA-Cu(ii)]) was synthesized and thoroughly specified by physicochemical approaches such as FT-IR, EDX, XRD, Mapping, ICP, and UV-Vis analyses and physicochemical properties. After the detection of authentic data, the central composite design (CCD) was utilized to accomplish the pertaining tests and develop the optimum condition, and, in the following, [ChCl]4[2GA-Cu(ii)] was applied as a green multifunctional catalytic solvent system in reducing agent-free and base-free condition for the three-component click reaction from sodium azide, alkyl, allyl, ester, and benzyl halide, and terminal alkyne made from amines and caprolactam as a cyclic amide to furnish a successful new library of 1,4-disubstituted 1,2,3-triazoles with a yield of up to 98%. The Cu(ii)-ADES is stable and can comfortably be recovered and reused without a considerable decline in its acting for seven cycles. This triazole synthesizing methodology is distinguished via its atom economy, operational facility, short reaction times, diverse substrate scope, and high performance for large-scale synthesis of the desired products including: -CN and -NO2 as efficient functional groups.

"Click Chemistry": An Emerging Tool for Developing a New Class of Structural Motifs against Various Neurodegenerative Disorders

Click chemistry is a set of easy, atom-economical reactions that are often utilized to combine two desired chemical entities. Click chemistry accelerates lead identification and optimization, reduces the complexity of chemical synthesis, and delivers extremely high yields without undesirable byproducts. The most well-known click chemistry reaction is the 1,3-dipolar cycloaddition of azides and alkynes to form 1,2,3-triazoles. The resulting 1,2,3-triazoles can serve as both bioisosteres and linkers, leading to an increase in their use in the field of drug discovery. The current Review focuses on the use of click chemistry to identify new molecules for treating neurodegenerative diseases and in other areas such as peptide targeting and the quantification of biomolecules.

1,2,3-Triazoles in Biomolecular Crystallography: A Geometrical Data-Mining Approach

The 1,2,3-triazole scaffold has become very attractive to identify new chemical entities in drug discovery projects. Despite the widespread use of click chemistry to synthesize numerous 123Ts, there are few drugs on the market that incorporate this scaffold as a substructure. To investigate the true potential of 123Ts in protein-ligand interactions, we examined the noncovalent interactions between the 1,2,3-triazole ring and amino acids in protein-ligand cocrystals using a geometrical approach. For this purpose, we constructed a nonredundant database of 220 PDB IDs from available 123T-protein cocrystal structures. Subsequently, using the Protein Ligand Interaction Profiler web platform (PLIP), we determined whether 1,2,3-triazoles primarily act as linkers or if they can be considered interactive scaffolds. We then manually analyzed the geometrical descriptors from 333 interactions between 1,4-disubstituted 123T rings and amino acid residues in proteins. This study demonstrates that 1,2,3-triazoles exhibit diverse preferred interactions with amino acids, which contribute to protein-ligand binding.

Retinoic acid and evernyl-based menadione-triazole hybrid cooperate to induce differentiation of neuroblastoma cells

Neuroblastoma arises when immature neural precursor cells do not mature into specialized cells. Although retinoic acid (RA), a pro-differentiation agent, improves the survival of low-grade neuroblastoma, resistance to retinoic acid is found in high-grade neuroblastoma patients. Histone deacetylases (HDAC) inhibitors induce differentiation and arrest the growth of cancer cells; however, HDAC inhibitors are FDA-approved mostly for liquid tumors. Therefore, combining histone deacetylase (HDAC) inhibitors and retinoic acid can be explored as a strategy to trigger the differentiation of neuroblastoma cells and to overcome resistance to retinoic acid. Based on this rationale, in this study, we linked evernyl group and menadione-triazole motifs to synthesize evernyl-based menadione-triazole hybrids and asked if the hybrids cooperate with retinoic acid to trigger the differentiation of neuroblastoma cells. To answer this question, we treated neuroblastoma cells using evernyl-based menadione-triazole hybrids (6a-6i) or RA or both and examined the differentiation of neuroblastoma cells. Among the hybrids, we found that compound 6b inhibits class-I HDAC activity, induces differentiation, and RA co-treatments increase 6b-induced differentiation of neuroblastoma cells. In addition, 6b reduces cell proliferation, induces expression of differentiation-specific microRNAs leading to N-Myc downregulation, and RA co-treatments enhance the 6b-induced effects. We observed that 6b and RA trigger a switch from glycolysis to oxidative phosphorylation, maintain mitochondrial polarization, and increase oxygen consumption rate. We conclude that in evernyl-based menadione-triazole hybrid, 6b cooperates with RA to induce differentiation of neuroblastoma cells. Based on our results, we suggest that combining RA and 6b can be pursued as therapy for neuroblastoma. Schematic representation of RA and 6b in inducing differentiation of neuroblastoma cells.

Understanding the Fate of the Banert Cascade of Propargylic Azides: Sigmatropic versus Prototropic Pathway

The Banert cascade is an efficient synthetic strategy for obtaining 4,5-disubstituted 1,2,3-triazoles. The reaction can proceed via a sigmatropic or prototropic mechanism depending on the substrate and the conditions. In this work, the mechanisms of both pathways from propargylic azides with different electronic features were investigated using density functional theory, quantum theory of atoms in molecules, and natural bond orbital approaches. The calculated energy barriers were consistent with the experimental data. Three patterns of electron density distribution on the transition structures were observed, which reflected the behaviors of the reactants in the Banert cascade. The stronger conjugative effects were associated with lower/higher free activation energies of sigmatropic/prototropic reactions, respectively. A clear relationship between the accumulation of the charge at the C³ atom of propargylic azides with the energy barriers for prototropic reactions was found. Thus, the obtained results would allow the prediction of the reaction's course by evaluating reactants.

Synthesis, antimicrobial, antibiofilm and computational studies of isatin-semicarbazone tethered 1,2,3-triazoles

In present era, heterocyclic compounds containing two or three nitrogen atoms play a vital role in drug discovery. In this context, a new class of isatin-semicarbazone tethered 1,2,3-triazole hybrids was synthesized via Cu(I)-mediated azide alkyne cycloaddition reaction. Structural characteristics of the newly derived compounds were identified by various spectral techniques like FTIR, ¹H NMR, ¹³C NMR, HRMS and single crystal X-ray crystallography. Synthesized derivatives were also screened for in vitro antimicrobial and antibiofilm activity against different microbial species. Triazole hybrid 7e showed significant efficacy towards E. coli having MIC of 0.0063 µmol/mL, whereas 6a, 6b, 7a, 7c, 7e, and 7f showed highest percentage of biofilm inhibition against P. aeruginosa. Bioassay results suggested that these triazole hybrids could act as biomaterial for antimicrobial and antibiofilm applications and may constitute a new promising class of antimicrobial and antibiofilm agents. These results were further supported by in silico docking, DFT calculations and ADME studies.

Dendrimers in Alzheimer’s Disease: Recent Approaches in Multi-Targeting Strategies

Nanomaterials play an increasingly important role in current medicinal practice. As one of the most significant causes of human mortality, and one that is increasing year by year, Alzheimer’s disease (AD) has been the subject of a very great body of research and is an area in which nanomedicinal approaches show great promise. Dendrimers are a class of multivalent nanomaterials which can accommodate a wide range of modifications that enable them to be used as drug delivery systems. By means of suitable design, they can incorporate multiple functionalities to enable transport across the blood–brain barrier and subsequently target the diseased areas of the brain. In addition, a number of dendrimers by themselves often display therapeutic potential for AD. In this review, the various hypotheses relating to the development of AD and the proposed therapeutic interventions involving dendrimer–base systems are outlined. Special attention is focused on more recent results and on the importance of aspects such as oxidative stress, neuroinflammation and mitochondrial dysfunction in approaches to the design of new treatments.

Medicinal chemistry insights into antiviral peptidomimetics

The (re)emergence of multidrug-resistant viruses and the emergence of new viruses highlight the urgent and ongoing need for new antiviral agents. The use of peptidomimetics as therapeutic drugs has often been associated with advantages, such as enhanced binding affinity, improved metabolic stability, and good bioavailability profiles. The development of novel antivirals is currently driven by strategies of converting peptides into peptidomimetic derivatives. In this review, we outline different structural modification design strategies for developing novel peptidomimetics as antivirals, involving N- or C-cap terminal structure modifications, pseudopeptides, amino acid modifications, inverse-peptides, cyclization, and molecular hybridization. We also present successful recent examples of peptidomimetic designs.

Propargylamine Amino Acids as Constrained Nε-Substituted Lysine Mimetics

Herein, alkylated propargylamines are reported as constrained lysine mimetics and constructed in a single step using a copper(I)-catalyzed A³-coupling reaction. Using multiple secondary amines, the reaction allowed the generation of a structurally diverse set of N-Fmoc protected amino acid derivatives. In addition, the A³-reaction was applied on solid phase via the assembly of short model tripeptides. Moreover, the internal alkyne moiety allowed further functionalization toward novel 1,4,5-trisubstituted 1,2,3-triazole-based amino acids.

A dual-functional sulfone biscompound containing 1,2,3-triazole moiety for decolorization and disinfection of contaminated water

Water decontamination from toxic dyes and pathogenic microorganisms is critical for life on Earth. Herein, we report the synthesis of sulfone biscompound containing 1,2,3-triazole moiety and evaluation of its dye decolorization and biocidal and disinfection efficiencies. The decolorization efficiency was tested under different experimental conditions, while the biocidal action was examined against various types of waterborne pathogens, and the disinfection of some pathogenic microbes was executed in artificially contaminated water. The findindgs illustrated that the solution initial pH (pHi) affected the decolorization efficiency significantly. About complete removal of 10 mg/L malachite green (MG) dye was achieved after 10 min using 3 g/L of the sulfone biscompound at pHi 6. The pseudo-second-order equation suited the adsorption kinetics accurately, while the equilibrium data was suited by Langmuir isotherm model. Electrostatic, n-π, and π-π interactions brought about the adsorption of MG onto the sulfone biscompound. The biocidal results indicated that the sulfone biscompound had a powerful antibacterial potential against the tested bacterial species. Likewise, the distinction trail revealed that after 70-90 min of direct contact with an effective dose, the tested pathogens could be completely eliminated (6-log reduction). Overall, the newly synthesized sulfone biscompound can efficiently remove cationic dyes and disinfect contaminated water.

Macrocyclic Triazolopeptoids: A Promising Class of Extended Cyclic Peptoids

Head-to-tail cyclization of linear oligoamides containing 4-benzylaminomethyl-1H-1,2,3-triazol-1-yl acetic acid monomers afforded a novel class of "extended macrocyclic peptoids". The identification of the conformation in solution for a cyclodimer and the X-ray crystal structure of a cyclic tetraamide are reported.

In Vitro Antioxidant and Pancreatic Anticancer Activity of Novel 5-Fluorouracil-Coumarin Conjugates

Molecular hybridization consists of the combination of two or more non-identical pharmacophores in a single molecule. It has emerged as a promising strategy that allows the design of molecular frameworks with enhanced activity and affinity compared to their parent drugs. In this work, two novel hybrids that combine the well-known anticancer chemotherapeutic agent 5-fluorouracil with antioxidant coumarin derivatives have been synthesized and characterized by means of a copper-catalyzed azide-alkyne cycloaddition (CuAAC). The conjugates showed good antioxidant properties and a high tendency to aggregate and form stable nanoparticles in aqueous media, with regular shape and uniform size. These materials have proven to be preferential cytotoxic agents in vitro against human pancreatic cancer cells PANC-1, with an activity superior to free 5-fluorouracil. These results open up the possibility of exploiting the synergistic combination between 5-fluorouracil and coumarin derivatives and warrant further investigation of these hybrids as promising pancreatic anticancer agents.

Rational Design and Synthesis of New Selective COX-2 Inhibitors with In Vivo PGE2-Lowering Activity by Tethering Benzenesulfonamide and 1,2,3-Triazole Pharmacophores to Some NSAIDs

New selective COX-2 inhibitors were designed and synthesized by tethering 1,2,3-triazole and benzenesulfonamide pharmacophores to some NSAIDs. Compounds 6b and 6j showed higher in vitro COX-2 selectivity and inhibitory activity (IC₅₀ = 0.04 µM and S.I. = 329 and 312, respectively) than celecoxib (IC₅₀ = 0.05 µM and S.I. = 294). Compound 6e revealed equipotent in vitro COX-2 inhibitory activity to celecoxib. Furthermore, 6b and 6j expressed more potent relief of carrageenan-induced paw edema thickness in mice than celecoxib, with ED₅₀ values of 11.74 µmol/kg and 13.38 µmol/kg vs. 16.24 µmol/kg, respectively. Compounds 6b and 6j inhibited the production of PGE2 with a % inhibition of PGE2 production of 90.70% and 86.34%, respectively, exceeding celecoxib’s percentage (78.62%). Moreover, 6b and 6j demonstrated a gastric safety profile comparable to celecoxib. In conclusion, compounds 6b and 6j better achieved the target goal as more potent and selective COX-2 inhibitors than celecoxib in vitro and in vivo.

1,2,3-Triazole Tethered Hybrid Capsaicinoids as Antiproliferative Agents Active against Lung Cancer Cells (A549)

A series of novel 1,2,3-triazole derivatives of capsaicin and its structural isomer (new natural product hybrid capsaicinoid) were synthesized by exploiting one-/two-point modification of capsaicin without altering the amide linkage (neck). The newly synthesized compounds were screened for their antiproliferative activity against an NCI panel of 60 cancer cell lines at a single dose of 10 μM. Most of the compounds have demonstrated reduced growth between 55 and 95%, whereas capsaicin (10) has shown reduced growth between 0 and 24%. Compounds showing more than 50% growth inhibition were further evaluated for the IC50 value. Among the cell lines tested, lung cancer cell lines (A549, NCI-H460) were found to be more susceptible toward most of the synthesized compounds. Compounds 14g and 14j demonstrated good antiproliferative activity in NCI-H460 with IC50 values of 6.65 and 5.55 μM, respectively, while compounds 18b, 18c, 18f, and 18m demonstrated potential antiproliferative activity in A549 cell lines with IC50 values ranging between 2.9 and 10.5 μM. Among the compounds, compound 18f was found to demonstrate the best activity with an IC50 value of 2.91 μM against A549. Furthermore, 18f induces cell cycle arrest at the S-phase and disrupts the mitochondrial membrane potential, reducing cell migration potential by inducing cellular apoptosis and higher ROS generation along with a decrease in mitochondrial membrane potential in addition to surface and nuclear morphological alterations such as a reduction in the number and shrinkage of cells coupled with nuclear blabbing indicating the sign of apoptosis of A549 non-small cell lung cancer cell lines. Compound 18f has emerged as a lead molecule and may serve as a template for further discovery of capsaicinoid scaffolds.

MOF-Derived Cu@N-C Catalyst for 1,3-Dipolar Cycloaddition Reaction

Cu(im)2-derived Cu@N-C composites were used for the first time as efficient heterogeneous catalysts for one-pot 1,3-dipolar cycloaddition of terminal alkynes, aryl halides, and sodium azide to preparation of 1,4-disubstituted 1,2,3-triazoles with broad substrate scope and high yields. The catalyst can be easily reused without the changes of structure and morphology, and the heterogeneity nature was confirmed from the catalyst recyclability and metal leaching test.

5-Fluoro-1,2,3-triazole motif in peptides and its electronic properties

The 5-fluoro triazole amino acid has been prepared by halogen exchange between the 5-iodo triazole and fluoride salts and incorporated in peptides. X-ray crystallography reveals a cylindrical shape in its deformation electron density.

Secondary Structure Tuning of a Pseudoprotein Between β-Meander and α-Helical Forms in the Solid-State

Tuning the secondary structure of a protein or polymer in the solid-state is challenging. Here we report the topochemical synthesis of a pseudoprotein and its secondary structure tuning in the solid-state. We designed the dipeptide monomer N₃ -Leu-Ala-NH-CH₂ -C≡CH (1) for topochemical azide-alkyne cycloaddition (TAAC) polymerization. Dipeptide 1 adopts an anti-parallel β-sheet-like stacked arrangement in its crystals. Upon heating, the dipeptide undergoes quantitative TAAC polymerization in a crystal-to-crystal fashion yielding large polymers. The reaction occurs between the adjacent monomers in the H-bonded anti-parallel stack, yielding pseudoprotein having a β-meander structure. When dissolved in methanol, this pseudoprotein changes its secondary structure from β-meander to α-helical form and it retains the new secondary structure upon desolvation. This work demonstrates a novel paradigm for tuning the secondary structure of a polymer in the solid-state.

Facile construction of peptidomimetics by sequential C–S/C–N bond activation of Ugi-adducts

Diverse peptidomimetics containing a primary amide are prepared via the integration of an Ugi-4CR and sequential C–S/C–N bond activation.