Discovery of novel anti-HIV agents via Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click chemistry-based approach

In vitro α-glucosidase, docking and density functional theory studies on novel azide metal complexes

Aim: The goal of this study is to synthesize new metal complexes containing N-methyl-1-(pyridin-2-yl)methanimine and azide ligands as α-glucosidase inhibitors for Type 2 diabetes. Materials & methods: The target complexes (12-16) were synthesized by reacting N-methyl-1-(pyridin-2-yl)methanimine (L1) with sodium azide in the presence of corresponding metal salts. The investigation of target protein interactions, vibrational, electronic and nonlinear optical properties for these complexes was performed by molecular docking and density functional theory studies. Results: Among these complexes, complex 13 (IC50 = 0.2802 ± 0.62 μM) containing Hg ion showed the highest α-glucosidase inhibitory property. On the other hand, significant results were detected for complexes containing Cu and Ag ions. Conclusion: Complex 13 may be an alternate anti-diabetic inhibitor according to in vitro/docking results.

Advances in drug structure-activity-relationships for the development of selenium-based compounds against HIV

INTRODUCTION

Selenium possesses numerous advantageous properties in the field of medicine, and a variety of selenium-containing compounds have been documented to exhibit anti-HIV activity. This paper aims to categorize these compounds and conduct SAR analysis to offer guidance for drug design and optimization.

AREAS COVERED

The authors present a comprehensive review of the reported SAR analysis conducted on selenium-based compounds against HIV, accompanied by a concise discussion regarding the pivotal role of selenium in drug development.

EXPERT OPINION

In addition to the conventional bioisosterism strategy, advanced strategies such as covalent inhibition, fragment-based growth and drug repositioning can also be incorporated into research on selenium-containing anti-HIV drugs. Ebselen, which acts as an HIV capsid inhibitor, serves as a valuable probe compound for the discovery of novel HIV integrase inhibitors. Furthermore, it is crucial not to underestimate the potential toxicity associated with organic selenium compounds despite no reported instances of severe toxicity.

Accelerated Diffusion of a Copper(I)-Functionalized COF Packed Bed Reactor for Efficient Continuous Flow Catalysis

Flow chemistry provides a neo-orientation for the research and development of chemical technology, in which heterogeneous continuous catalysis based on packed beds can realize rapid separation and recycling. However, options for heterogeneous catalysts are still limited. In this work, we gradually grow covalent organic frameworks (COFs, TpBpy) on the surface of a silica gel (SiO2)-supported substrate to obtain a stable copper(I)-chelated high-loading heterogeneous catalyst (SiO2@CuI-TpBpy). SiO2@CuI-TpBpy shows high catalytic activity in three-component Huisgen 1,3-dipolar cycloaddition, giving the corresponding triazoles with excellent yields and reposeful recyclability under batch conditions. The structures of the catalysts remain steady, and the copper contents are basically unchanged after five cycles. Then, the catalysts are successfully applied for three-component heterogeneous catalysis in a one-pot continuous flow to prepare rufinamide in 89% yield for 24 h stably and efficiently with mere traces of copper ions remaining. More importantly, the catalytic system reveals a minuscule effect of catalyst particle size on internal diffusion. This COF encapsulation strategy presents a new possibility for the design of industrial heterogeneous catalysts with high metal loading and low internal diffusion resistance.

Click chemistry inspired syntheses of new amide linked 1,2,3-triazoles from naphthols: biological evaluation and in silico computational study

In search of new active molecules, a small focused library of new 1,2,3-triazoles derived from naphthols were efficiently prepared via the click chemistry approach. The synthesized triazole derivatives were evaluated for their antifungal, antioxidant and antitubercular activities. Furthermore, to rationalize the observed biological activity data, the molecular docking study has also been carried out against the active site of cytochrome P450 lanosterol 14α-demethylase of C. albicans to understand the binding affinity and binding interactions of enzyme and synthesized derivatives, which revealed a significant correlation between the binding score and biological activity for these compounds. The results of the in vitro and In Silico study suggest that the 1,2,3-triazole derivatives may possess the ideal structural requirements for the further development of novel therapeutic agents.

Investigation of 1,4-Substituted 1,2,3-Triazole Derivatives as Antiarrhythmics: Synthesis, Structure, and Properties

Here, we investigated the reaction of 1,3-dipolar cycloaddition of 1,3-diazido-2-nitro-2- azapropane (DANP) to propargyl alcohol over a copper-based catalyst and identified the optimum reaction conditions that enable the synthesis of 2-nitro-1,3-bis(4,4'-dihydroxymethyl)-1,2,3-triazolyl-2-azapropane (1) in more than 84% yield. The reaction between DANP, 1,5-diazido-3-nitrazapentane, and phenylacetylene produced the respective 1,2,3-triazole derivatives in 83% and 71% yields, respectively. The structures of the resultant compounds were validated by infrared and NMR spectroscopies and elemental analysis. The structure of 1 was proved by single-crystal X-ray diffraction. This study demonstrated that 1 exhibits a dose-dependent antiarrhythmic activity towards calcium-chloride-induced arrhythmia and refers to Class III: moderately hazardous substances.

Click reaction in the synthesis of dendrimer drug-delivery systems

Drug delivery systems are technologies designed for the targeted delivery and controlled release of medicinal agents. Among the materials employed as drug delivery systems, dendrimers have gained increasing interest in recent years because of their properties and structural characteristics. The use of dendrimer-nanocarrier formulations enhances the safety and bioavailability, increases the solubility in water, improves stability and pharmacokinetic profile, and enables efficient delivery of the target drug to a specific site. However, the synthesis of dendritic architectures through convergent or divergent methods has drawbacks and limitations that disrupt aspects related to design and construction and consequently slow down the transfer from academia to industry. In that sense, the implementation of click chemistry has been received increasing attention in the last years, because offers new efficient approaches to obtain dendritic species in good yields and higher monodispersity. This review focuses on recent strategies for building dendrimer drug delivery systems using click reactions from 2015 to early 2021. The dendritic structures showed in this review are based on β-cyclodextrins (β-CD), poly(amidoamine) (PAMAM), dendritic poly (lysine) (PLLD), dimethylolpropionic acid (bis-MPA), phosphoramidate (PAD), and poly(propargyl alcohol-4-mercaptobutyric (PPMA).

Therapeutic potential of indole derivatives as anti-HIV agents: A mini-review

Acquired immunodeficiency syndrome (AIDS), caused by human immunodeficiency virus (HIV), is one of the leading causes of human deaths. The advent of different anti-HIV drugs over different disease progress has made AIDS/HIV from a deadly infection to chronic and manageable disease. However, the development of multidrug-resistant viruses, together with the severe side effects of anti-HIV agents, compromised their efficacy and limited the treatment options. Indoles, the most common frameworks in the bioactive molecules, represent attractive scaffolds for the design and development of novel drugs. Indole derivatives are potential inhibitors of HIV enzymes such as reverse transcriptase, integrase and protease, and some indole-based agents like Delavirdine have already been applied in clinics or under clinical evaluations for the treatment of AIDS/HIV, revealing that indole moiety is a useful template for the development of anti-HIV agents. This review focuses on the recent advancement of indole derivatives including indole alkaloids, hybrids, and dimers with anti-HIV potential, covering articles published between 2010 and 2020. The chemical structures, structure-activity relationship and mechanisms of action are also discussed.

Cu(I)-Catalyzed Click Chemistry in Glycoscience and Their Diverse Applications

Copper(I)-catalyzed 1,3-dipolar cycloaddition between organic azides and terminal alkynes, commonly known as CuAAC or click chemistry, has been identified as one of the most successful, versatile, reliable, and modular strategies for the rapid and regioselective construction of 1,4-disubstituted 1,2,3-triazoles as diversely functionalized molecules. Carbohydrates, an integral part of living cells, have several fascinating features, including their structural diversity, biocompatibility, bioavailability, hydrophilicity, and superior ADME properties with minimal toxicity, which support increased demand to explore them as versatile scaffolds for easy access to diverse glycohybrids and well-defined glycoconjugates for complete chemical, biochemical, and pharmacological investigations. This review highlights the successful development of CuAAC or click chemistry in emerging areas of glycoscience, including the synthesis of triazole appended carbohydrate-containing molecular architectures (mainly glycohybrids, glycoconjugates, glycopolymers, glycopeptides, glycoproteins, glycolipids, glycoclusters, and glycodendrimers through regioselective triazole forming modular and bio-orthogonal coupling protocols). It discusses the widespread applications of these glycoproducts as enzyme inhibitors in drug discovery and development, sensing, gelation, chelation, glycosylation, and catalysis. This review also covers the impact of click chemistry and provides future perspectives on its role in various emerging disciplines of science and technology.

1,2,3-Triazole hybrids with anti-HIV-1 activity

The human immunodeficiency virus type 1 (HIV-1) is the major etiological agent responsible for the acquired immunodeficiency syndrome (AIDS), which is a serious infectious disease and remains one of the most prevalent problems at present. Currently, combined antiretroviral therapy is the primary modality for the treatment and management of HIV/AIDS, but the long-term use can result in major drawbacks such as the development of multidrug-resistant viruses and multiple side effects. 1,2,3-Triazole is the common framework in the development of new drugs, and its derivatives have the potential to inhibit various HIV-1 enzymes such as reverse transcriptase, integrase, and protease, consequently possessing a potential anti-HIV-1 activity. This review covers the recent advances regarding the 1,2,3-triazole hybrids with potential anti-HIV-1 activity; it focuses on the chemical structures, structure-activity relationship, and mechanisms of action, covering articles published from 2010 to 2020.

Design, synthesis and structure-activity relationships of 4-phenyl-1H-1,2,3-triazole phenylalanine derivatives as novel HIV-1 capsid inhibitors with promising antiviral activities

HIV-1 CA is involved in different stages of the viral replication cycle, performing essential roles in both early (uncoating, reverse transcription, nuclear import, integration) and late events (assembly). Recent efforts have demonstrated HIV-1 CA protein as a prospective therapeutic target for the development of new antivirals. The most extensively studied CA inhibitor, PF-3450074 (PF-74, discovered by Pfizer), that targets an inter-protomer pocket within the CA hexamer. Herein we reported the design, synthesis, and biological evaluation of a series of 4-phenyl-1H-1,2,3-triazole phenylalanine derivatives as HIV-1 CA inhibitors based on PF-74 scaffold. Most of the analogues demonstrated potent antiviral activities, among them, the anti-HIV-1 activity of 6a-9 (EC50 = 3.13 μM) is particularly prominent. The SPR binding assay of selected compounds (6a-9, 6a-10, 5b) suggested direct and effective interaction with recombinant CA proteins. The mechanism of action studies also demonstrated that 6a-9 displays the effects in both the early and late stages of HIV-1 replication. To explore the potential binding mode of the here presented analogues, 6a-9 was analyzed by MD simulation to predict its binding to the active site of HIV-1 CA monomer. In conclusion, this novel series of antivirals can serve as a starting point for the development of a new generation of HIV-1 treatment regimen and highlights the potentiality of CA as a therapeutic target.

Discovery of novel 1,4-disubstituted 1,2,3-triazole phenylalanine derivatives as HIV-1 capsid inhibitors

The HIV-1 capsid (CA) protein plays crucial roles in both early and late stages of the viral life cycle, which has intrigued researchers to target it to develop anti-HIV drugs. Accordingly, in this research, we report the design, synthesis and biological evaluation of a series of novel phenylalanine derivatives as HIV-1 CA protein inhibitors using the Cu(I)-catalyzed azide and alkyne 1,3-dipolar cycloaddition (CuAAC) reaction. Among this series of inhibitors, compound II-10c displayed a remarkable anti-HIV activity (EC₅₀ = 2.13 μM, CC₅₀ > 35.49 μM). Furthermore, surface plasmon resonance (SPR) binding assays showed that compounds II-10c and PF-74 (lead compound) have similar affinities to HIV-1 CA monomer. Further investigation showed that the weak permeability and water solubility of representative compounds were probably the important factors that restricted their cell-based activity. Preliminary structure-activity relationships (SARs) were inferred based on the activities of these compounds, and their known structure. The most promising new compound was studied with molecular dynamics simulation (MD) to determine the preferred interactions with the drug target. Finally, the activities of members of this series of inhibitors were deeply inspected to find the potential reasons for their anti-HIV-1 activity from various perspectives. This highlights the important factors required to design compounds with improved potency.

Overview of Recent Strategic Advances in Medicinal Chemistry

Introducing novel strategies, concepts, and technologies that speed up drug discovery and the drug development cycle is of great importance both in the highly competitive pharmaceutical industry as well as in academia. This Perspective aims to present a "big-picture" overview of recent strategic innovations in medicinal chemistry and drug discovery.

Recent applications of click chemistry in drug discovery

Introduction: Click chemistry has been exploited widely in the past to expedite lead discovery and optimization. Indeed, Copper-catalyzed azide-alkyne cycloaddition (CuAAC) click chemistry is a bioorthogonal reaction of widespread utility throughout medicinal chemistry and chemical biology. Areas covered: The authors review recent applications of CuAAC click chemistry to drug discovery based on the literature published since 2013. Furthermore, the authors provide the reader with their expert perspectives on the area including their outlook on future developments. Expert opinion: Click chemistry reactions are an important part of the medicinal chemistry toolbox and offer substantial advantages to medicinal chemists in terms of overcoming the limitations of useful chemical synthesis, increasing throughput, and improving the quality of compound libraries. To explore new chemical spaces for drug-like molecules containing a high degree of structural diversity, it may be useful to merge the diversity-oriented synthesis and 'privileged' substructure-based strategy with bioorthogonal reactions using sophisticated automation and flow systems to improve productivity. Large compound libraries obtained in this way should be of great value for the discovery of bioactive compounds and therapeutic agents.

Catalyst-free cycloaddition of 1,3-diene-1-carbamates with azodicarboxylates: A rapid click reaction

Novel click reactions are of continued interest in many scientific research areas and applications. Herein, we report a novel practical, catalyst-free, azo-Diels-Alder reaction between dienecarbamates and azodicarboxylates exhibiting a remarkable functional group tolerance. The availability of starting materials, mild reaction conditions, chemoselectivity and scalability make this cycloaddition a viable supplement to the other reactions in "click" chemistry.

1-Iodobuta-1,3-diynes in Copper-Catalyzed Azide-Alkyne Cycloaddition: A One-Step Route to 4-Ethynyl-5-iodo-1,2,3-triazoles

Cu-catalyzed 1,3-dipolar cycloaddition of iododiacetylenes with organic azides using iodotris(triphenylphosphine)copper(I) as a catalyst was found to be an efficient one-step synthetic route to 5-iodo-4-ethynyltriazoles. The reaction is tolerant to various functional groups in both butadiyne and azide moieties. The synthetic application of 5-iodo-4-ethynyl triazoles obtained was also evaluated: the Sonogashira coupling with alkynes resulted in unsymmetrically substituted triazole-fused enediyne systems, while the Suzuki reaction yielded the corresponding 5-aryl-4-ethynyl triazoles.

Targeting the hydrophobic channel of NNIBP: discovery of novel 1,2,3-triazole-derived diarylpyrimidines as novel HIV-1 NNRTIs with high potency against wild-type and K103N mutant virus

Novel 1,2,3-triazole-derived diarylpyrimidines were discovered as potent HIV-1 NNRTIs.

Targeting the entrance channel of NNIBP: Discovery of diarylnicotinamide 1,4-disubstituted 1,2,3-triazoles as novel HIV-1 NNRTIs with high potency against wild-type and E138K mutant virus

Inspired by our previous efforts on the modifications of diarylpyrimidines as HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTI) and reported crystallography study, novel diarylnicotinamide derivatives were designed with a "triazole tail" occupying the entrance channel in the NNRTI binding pocket of the reverse transcriptase to afford additional interactions. The newly designed compounds were then synthesized and evaluated for their anti-HIV activities in MT-4 cells. All the compounds showed excellent to good activity against wild-type HIV-1 strain with EC₅₀ of 0.02-1.77 μM. Evaluations of selected compounds against more drug-resistant strains showed these compounds had advantage of inhibiting E138K mutant virus which is a key drug-resistant mutant to the new generation of NNRTIs. Among this series, propionitrile (3b2, EC_50(IIIB) = 0.020 μM, EC_50(E138K) = 0.015 μM, CC₅₀ = 40.15 μM), pyrrolidin-1-ylmethanone (3b8, EC_50(IIIB) = 0.020 μM, EC_50(E138K) = 0.014 μM, CC₅₀ = 58.09 μM) and morpholinomethanone (3b9, EC_50(IIIB) = 0.020 μM, EC_50(E138K) = 0.027 μM, CC₅₀ = 180.90 μM) derivatives are the three most promising compounds which are equally potent to the marketed drug Etravirine against E138K mutant strain but with much lower cytotoxicity. Furthermore, detailed SAR, inhibitory activity against RT and docking study of the representative compounds are also discussed.

Current insights into anti-HIV drug discovery and development: a review of recent patent literature (2014-2017)

INTRODUCTION

To deal with the rapid emergence of drug resistance challenges, together with the difficulty to eradicate the virus, off-target effects and significant cumulative drug toxicities, it is still imperative to develop next-generation anti-HIV agents with novel chemical classes or new mechanisms of action.

AREAS COVERED

We primarily focused on current strategies to discover novel anti-HIV agents. Moreover, examples of anti-HIV lead compounds were mainly selected from recently patented publications (reported between 2014 and 2017). In particular, 'privileged structure'-focused substituents decorating approach, scaffold hopping, natural-product diversification and prodrug are focused on. Furthermore, exploitation of new compounds with unexplored mechanisms of action and medicinal chemistry strategies to deplete the HIV reservoir were also described. Perspectives that could inspire future anti-HIV drug discovery are delineated.

EXPERT OPINION

Even if a large number of patents have been disclosed recently, additional HIV inhibitors are still required, especially novel chemical skeletons displaying a unexploited mechanism of action. Current medicinal chemistry strategies are inadequate, and appropriate and new methodologies and technologies should be exploited to identify novel anti-HIV drug candidates in a time- and cost- effective manner.

Design, synthesis and biological evaluation of tacrine-1,2,3-triazole derivatives as potent cholinesterase inhibitors

We report herein the design and synthesis of a series of 11 novel tacrine-1,2,3-triazole derivatives via a Cu(i)-catalyzed alkyne-azide 1,3-dipolar cycloaddition (CuAAC) reaction. The newly synthesized compounds were evaluated for their inhibition activity against Electrophorus electricus acetylcholinesterase (AChE) and horse serum butyrylcholinesterase (BChE) as potential drug targets for Alzheimer's disease (AD). Among the designed compounds, compound 8a2 exhibited potent inhibition against AChE and BChE with IC₅₀ values of 4.89 μM and 3.61 μM, respectively. Further structure-activity relationship (SAR) and molecular modeling studies may provide valuable insights into the design of better tacrine-triazole analogues with potential therapeutic applications for AD.

7-Methylguanosine monophosphate analogues with 5'-(1,2,3-triazoyl) moiety: Synthesis and evaluation as the inhibitors of cNIIIB nucleotidase

The hydrolysis of nucleoside 5'-monophosphates to the corresponding nucleosides and inorganic phosphate is catalysed by 5'-nucleotidases, thereby contributing to the control of endogenous nucleotide turnover and affecting the fate of exogenously delivered nucleotide- and nucleoside-derived therapeutics in cells. A recently identified nucleotidase cNIIIB shows preference towards 7-methylguanosine monophosphate (m⁷GMP) as a substrate, which suggests its potential involvement in mRNA degradation. However, the extent of biological functions and the significance of cNIIIB remains to be elucidated. Here, we synthesised a series of m⁷GMP analogues carrying a 1,2,3-triazole moiety at the 5' position as the potential inhibitors of human cNIIIB. The compounds were synthesised by using the copper-catalysed azide-alkyne cycloaddition (CuAAC) between 5'-azido-5'-deoxy-7-methylguanosine and different phosphate or phosphonate derivatives carrying terminal alkyne. The analogues were evaluated as cNIIIB inhibitors using HPLC and malachite green assays, demonstrating that compound 1a, carrying a 1,2,3-triazoylphosphonate moiety, inhibits cNIIIB activity at micromolar concentrations (IC₅₀ 87.8 ± 7.5 µM), while other analogues showed no activity. In addition, compound 1d was identified as an artifical substrate for ^HscNIIIB. Further characterization of inhibitor 1a revealed that it is poorly recognised by other m⁷G-binding proteins, eIF4E and DcpS, indicating its selectivity towards cNIIIB. The first inhibitor (1a) and unnatural substrate (1d) of cNIIIB, identified here, can be used as molecular probes for the elucidation of biological roles of cNIIIB, including the verification of its proposed function in mRNA metabolism.

Mechanistic applications of click chemistry for pharmaceutical drug discovery and drug delivery

The concept of click chemistry (CC), first introduced by K.B. Sharpless, has been widely adopted for use in drug discovery, novel drug delivery systems (DDS), polymer chemistry, and material sciences. In this review, we outline novel aspects of CC related to drug discovery and drug delivery, with a brief overview of molecular mechanisms underlying each click reaction commonly used by researchers, and the main patents that paved the way for further diverse medicinal applications. We also describe recent progress in drug discovery and polymeric and carbon material-based drug delivery for potential pharmaceutical applications and advancements based on the CC approach, and discuss some intrinsic limitations of this popular conjugation reaction. The use of CC is likely to significantly advance drug discovery and bioconjugation development.