NH-1,2,3-Triazole-based Inhibitors of the VIM-2 Metallo-β-Lactamase: Synthesis and Structure-Activity Studies

Elucidation of critical chemical moieties of metallo-β-lactamase inhibitors and prioritisation of target metallo-β-lactamases

The urgent demand for effective countermeasures against metallo-β-lactamases (MBLs) necessitates development of novel metallo-β-lactamase inhibitors (MBLIs). This study is dedicated to identifying critical chemical moieties within previously developed MBLIs, and critical MBLs should serve as the target in MBLI evaluations. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), a systematic literature analysis was conducted, and the NCBI RefSeq genome database was exploited to access the abundance profile and taxonomic distribution of MBLs and their variant types. Through the implementation of two distinct systematic approaches, we elucidated critical chemical moieties of MBLIs, providing pivotal information for rational drug design. We also prioritised MBLs and their variant types, highlighting the imperative need for comprehensive testing to ensure the potency and efficacy of the newly developed MBLIs. This approach contributes valuable information to advance the field of antimicrobial drug discovery.

I2/DMSO-mediated oxidative C-C and C-heteroatom bond formation: a sustainable approach to chemical synthesis

The I2/DMSO pair has emerged as a versatile, efficient, practical, and eco-friendly catalyst system, playing a significant role as a mild oxidative system, and thus employed as a good alternative to metal catalysts in synthetic chemistry. Presently, I2/DMSO is a thriving catalytic system that is used in preparing C-C and C-X (X = O/S/N/Se/Cl/Br) bonds, resulting in the formation of various bioactive molecules. Many processes utilize this system, including in situ glyoxal synthesis by diverse sp, sp2, and sp3 functionalities via iodination and subsequent Kornblum oxidation. Focusing on oxidation processes, this study examines the synergistic effect of dimethyl sulfoxide (DMSO) and molecular iodine in improving synthetic techniques. We provide a comprehensive overview of the research progress on the I2/DMSO catalytic system for the formation of C-C and C-heteroatom bonds from 2018 to the present. Additionally, the future prospects of this research field are discussed.

Azide-free cyclization reaction access to 4-aryl-NH-1,2,3-triazoles: P-toluenesulfonyl hydrazide and sulfamic acid as nitrogen sources

An iodine-mediated cyclization has been developed to 4-aryl-NH-1,2,3-triazoles, with p-toluenesulfonyl hydrazide and sulfamic acid used as nitrogen sources. Sulfamic acid plays a crucial role in this reaction by both acting as a substrate and providing an acidic environment. This reaction offers a metal- and azide-free strategy to access NH-1,2,3-triazoles.

Rapid Evolution of a Fragment-like Molecule to Pan-Metallo-Beta-Lactamase Inhibitors: Initial Leads toward Clinical Candidates

With the emergence and rapid spreading of NDM-1 and existence of clinically relevant VIM-1 and IMP-1, discovery of pan inhibitors targeting metallo-beta-lactamases (MBLs) became critical in our battle against bacterial infection. Concurrent with our fragment and high-throughput screenings, we performed a knowledge-based search of known metallo-beta-lactamase inhibitors (MBLIs) to identify starting points for early engagement of medicinal chemistry. A class of compounds exemplified by 11, discovered earlier as B. fragilis metallo-beta-lactamase inhibitors, was selected for in silico virtual screening. From these efforts, compound 12 was identified with activity against NDM-1 only. Initial exploration on metal binding design followed by structure-guided optimization led to the discovery of a series of compounds represented by 23 with a pan MBL inhibition profile. In in vivo studies, compound 23 in combination with imipenem (IPM) robustly lowered the bacterial burden in a murine infection model and became the lead for the invention of MBLI clinical candidates.

A three-component cyclocondensation reaction for the synthesis of new triazolo[1,5-a]pyrimidine scaffolds using 3-aminotriazole, aldehydes and ketene N,S-acetal

This study describes the use of 3-aminotriazole, different aldehydes and N-methyl-1-(methylthio)-2-nitroethenamine as a ketene N,S-acetal in a three-component condensation for the synthesis of a novel library of triazolo[1,5-a]pyrimidine scaffolds. The presence of trichloroacetic acid as a Brønsted-Lowry acidic promoter in acetonitrile or water solvent and room temperature condition resulting novel triazolo[1,5-a]pyrimidine systems named N-methyl-6-nitro-5-aryl-3,5-dihydro-[1, 2, 4]triazolo[1,5-a]pyrimidine-7-amine. The structure of products and direction of the N-cyclization could be confirmed using spectral data. The effect of various solvents on the progress of process was investigated in the paper. The presence of five nitrogen heteroatoms, the use of various aldehydes affording a range of skeletally distinct triazolo[1,5-a]pyrimidine-based heterocycles, the potency to create numerous hydrogen bonds in the product structure, and direction of cyclization are attractive features of this reaction.

Intercepting the Banert cascade with nucleophilic fluorine: direct access to α-fluorinated NH-1,2,3-triazoles

The treatment of propargylic azides with silver(i) fluoride in acetonitrile was found to yield α-fluorinated NH-1,2,3-triazoles via the Banert cascade. The reaction was regioselective and the products result from an initial [3,3] rearrangement. The reaction is demonstrated on >15 examples with yields ranging from 37% to 86%.

Silver Mediated Banert Cascade with Carbon Nucleophiles

The Banert cascade of propargylic azides can be promoted by simple silver salts, and the triazafulvene intermediate can be intercepted by carbon nucleophiles. Various indoles (>25 examples, up to 92% yield) and electron-rich heterocycles were effective. The Mayr nucleophilicity parameter (N) was found to correlate to the reaction efficiency, which enabled the formation of C_sp³-C_sp² and C_sp³-C_sp³ bonds under otherwise identical conditions from structurally dissimilar nucleophiles.

Development and biological applications of sulfur-triazole exchange (SuTEx) chemistry

Sulfur electrophiles constitute an important class of covalent small molecules that have found widespread applications in synthetic chemistry and chemical biology. Various electrophilic scaffolds, including sulfonyl fluorides and arylfluorosulfates as recent examples, have been applied for protein bioconjugation to probe ligand sites amenable for chemical proteomics and drug discovery. In this review, we describe the development of sulfonyl-triazoles as a new class of electrophiles for sulfur-triazole exchange (SuTEx) chemistry. SuTEx achieves covalent reaction with protein sites through irreversible modification of a residue with an adduct group (AG) upon departure of a leaving group (LG). A principal differentiator of SuTEx from other chemotypes is the selection of a triazole heterocycle as the LG, which introduces additional capabilities for tuning the sulfur electrophile. We describe the opportunities afforded by modifications to the LG and AG alone or in tandem to facilitate nucleophilic substitution reactions at the SO2 center in cell lysates and live cells. As a result of these features, SuTEx serves as an efficient platform for developing chemical probes with tunable bioactivity to study novel nucleophilic sites on established and poorly annotated protein targets. Here, we highlight a suite of biological applications for the SuTEx electrophile and discuss future goals for this enabling covalent chemistry.

Azo-triazolide bis-cyclometalated Ir(iii) complexes via cyclization of 3-cyanodiarylformazanate ligands

In this work we describe the synthesis of sterically encumbered 1,5-diaryl-3-cyanoformazanate bis-cyclometalated iridium(iii) complexes, two of which undergo redox-neutral cyclization during the reaction to produce carbon-bound 2-aryl-4-arylazo-2H-1,2,3-triazolide ligands. This transformation offers a method for accessing 2-aryl-4-arylazo-2H-1,2,3-triazolide ligands, a heretofore unreported class of chelating ligands. One formazanate complex and both triazolide complexes are structurally characterized by single-crystal X-ray diffraction, with infrared spectroscopy being the primary bulk technique to distinguish the formazanate and triazolide structures. All complexes are further characterized by UV-Vis absorption spectroscopy and cyclic voltammetry, with the triazolide compounds having similar frontier orbital energies to the formazanate complexes but much less visible absorption.

Divergent Mechanisms of the Banert Cascade with Propargyl Azides

Triazoles are privileged heterocycles for a variety of applications. The synthesis of 1H-triazoles can be accomplished by the Banert cascade from propargylic azides. Depending on the substrate and conditions, the Banert cascade can proceed by either a sigmatropic or prototropic mechanism. This report describes the first detailed kinetic analysis of the Banert cascade proceeding by both pathways including substituent effects and KIE. The analysis identified the inflection point in the divergent pathways, allowing future work to predict which Banert products are accessible.

Real-time monitoring and inhibition of the activity of carbapenemase in live bacterial cells: application to screening of β-lactamase inhibitors

Antibiotic resistance mediated by β-lactamases including metallo-β-lactamases (MβLs) has become an emerging threat.

Discovery of [1,2,4]Triazole Derivatives as New Metallo-β-Lactamase Inhibitors

The emergence and spread of metallo-β-lactamase (MBL)-mediated resistance to β-lactam antibacterials has already threatened the global public health. A clinically useful MBL inhibitor that can reverse β-lactam resistance has not been established yet. We here report a series of [1,2,4]triazole derivatives and analogs, which displayed inhibition to the clinically relevant subclass B1 (Verona integron-encoded MBL-2) VIM-2. 3-(4-Bromophenyl)-6,7-dihydro-5H-[1,2,4]triazolo [3,4-b][1,3]thiazine (5l) manifested the most potent inhibition with an IC₅₀ (half-maximal inhibitory concentration) value of 38.36 μM. Investigations of 5l against other B1 MBLs and the serine β-lactamases (SBLs) revealed the selectivity to VIM-2. Molecular docking analyses suggested that 5l bound to the VIM-2 active site via the triazole involving zinc coordination and made hydrophobic interactions with the residues Phe61 and Tyr67 on the flexible L1 loop. This work provided new triazole-based MBL inhibitors and may aid efforts to develop new types of inhibitors combating MBL-mediated resistance.

Metal-Free Cascade [4 + 1] Cyclization Access to 4-Aryl-NH-1,2,3-triazoles from N-Tosylhydrazones and Sodium Azide

A molecular iodine-mediated coupling cyclization reaction for the synthesis of 4-aryl-NH-1,2,3-triazoles has been developed from N-tosylhydrazones and sodium azide. This metal-free cascade [4 + 1] cyclization reaction could rapidly synthesize valuable compounds via a sequential C-N and N-N bond formation. Mechanistic studies demostrate that the nitrogen atoms of the 1,2,3-triazoles are not entirely from sodium azide.

Preparation of Carbon-14 Labeled 2-(2-mercaptoacetamido)-3-phenylpropanoic Acid as Metallo-beta-lactamases Inhibitor (MBLI), for Coadministration with Beta-lactam Antibiotics

Aim and Objective:

Bacteria could become resistant to β-lactam antibiotics through production of β- lactamase enzymes like metallo-β-lactamase. 2-(2-mercaptoacetamido)-3-phenylpropanoic acid was reported as a model inhibitor for this enzyme. In order to elucidate the mechanism of action in the body’s internal environment, preparation of a labeled version of 2-(2-mercaptoacetamido)-3-phenylpropanoic acid finds importance. In this regard, we report a convenient synthetic pathway for preparation of carbon-14 labeled 2-(2- mercaptoacetamido)-3-phenylpropanoic acid.

Materials and Methods:

This study was initiated by using non-radioactive materials. Then, necessary characterization was performed after each of the reactions. Finally, the synthesis steps were continued to produce the target labeled product. For labeled products, the process was started from benzoic acid-[carboxyl- 14C] which has been prepared from barium 14C-carbonate. Chromatography column and NMR spectroscopy were used for purifications and identification of desired products, respectively. Barium [14C]carbonate was purchased from Amersham Pharmacia Biotech and was converted to [14C]benzyl bromide. Radioactivity was determined using liquid scintillation spectrometer.

Results:

We used [14C]PhCH2Br which was previously prepared from [14C]BaCO3, H2SO4, PhMgI, LAH and HBr, respectively. To neutralize the [14C]phenylalanine in acidic condition and to reach an isoelectric point of phenylalanine (pH = 5.48), Pb(OH)2 was used. Next, thioacetic acid and bromo acetic acid were used to prepare (acetylthio) acetic acid. A peptide coupling reagent was used in this stage to facilitating amide bond formation reaction between [14C]methyl-2-amino-3-phenyl propanoate hydrochloride and (acetylthio) acetic acid.

Conclusion:

Carbon-14 labeled 2-(2-mercaptoacetamido)-3-phenylpropanoic acid via radioactive phenylalanine was obtained with overall chemical yield 73% and radioactivity 65.3 nCi. The labeled target product will be used for in vivo pharmacological studies.

Synthesis and identification of heteroaromatic N-benzyl sulfonamides as potential anticancer agents

Sulfonamides are a crucial class of bioisosteres that are prevalent in a wide range of pharmaceuticals, however, the available methods for their production directly from heteroaryl aldehyde reagents remains surprisingly limited. A new approach for regioselective incorporation of a sulfonamide unit to heteroarene scaffolds has been developed and is reported within. As a result, a variety of primary benzylic N-alkylsulfonamides have been prepared via a two-step (one pot) formation from the in situ reduction of an intermediate N-sulfonyl imine under mild, practical conditions. The compounds have been screened against a variety of cell lines for cytotoxicity effects using a Cell Titer Blue assay. The cell viability investigation identifies a subset of N-benzylic sulfonamides derived from the indole scaffold to be targeted for further development into novel molecules with potential therapeutic value. The most cytotoxic of the compounds prepared, AAL-030, exhibited higher potency than other well-known anticancer agents Indisulam and ABT-751.

Synthesis of 1,2,3-triazole-substituted 6,7-dihydroindolizin-8(5H)-one derivatives mediated by Selectfluor

The 1,2,3-triazole and 1 H-1,2,3-benzotriazole-substituted 6,7-dihydroindolizin-8(5 H)-one derivatives were synthesized by the reaction of ( E)-7-(arylmethylidene)-6,7-dihydroindolizin-8(5 H)-ones with 1,2,3-triazole and 1 H-1,2,3-benzotriazole in the presence of Selectfluor in moderate yield. The structures of all the products were characterized thoroughly by nuclear magnetic resonance, infrared, and high-resolution mass spectrometry together with X-ray crystallographic analysis.

Allylic azides: synthesis, reactivity, and the Winstein rearrangement

Organic azides are useful synthetic intermediates, which demonstrate broad reactivity. Unlike most organic azides, allylic azides can spontaneously rearrange to form a mixture of isomers. This rearrangement has been named the Winstein rearrangement. Using allylic azides can result in low yields and azide racemization in some synthetic contexts due to the Winstein rearrangement. Effort has been made to understand the mechanism of the Winstein rearrangement and to take advantage of this process. Several guiding principles can be used to identify which azides will produce a mixture of isomers and which will resist rearrangement. Selective reaction conditions can be used to differentiate the azide isomers in a dynamic manner. This review covers all aspects of allylic azides including their synthesis, their reactivity, the mechanism of the Winstein rearrangement, and reactions that can selectively elaborate an azide isomer. This review covers the literature from Winstein's initial report to early 2019.

Halogen-Substituted Triazolethioacetamides as a Potent Skeleton for the Development of Metallo-β-Lactamase Inhibitors

Metallo-β-lactamases (MβLs) are the target enzymes of β-lactam antibiotic resistance, and there are no effective inhibitors against MβLs available for clinic so far. In this study, thirteen halogen-substituted triazolethioacetamides were designed and synthesized as a potent skeleton of MβLs inhibitors. All the compounds displayed inhibitory activity against ImiS with an IC₅₀ value range of 0.032⁻15.64 μM except 7. The chlorine substituted compounds (1, 2 and 3) inhibited NDM-1 with an IC₅₀ value of less than 0.96 μM, and the fluorine substituted 12 and 13 inhibited VIM-2 with IC₅₀ values of 38.9 and 2.8 μM, respectively. However, none of the triazolethioacetamides exhibited activity against L1 at inhibitor concentrations of up to 1 mM. Enzyme inhibition kinetics revealed that 9 and 13 are mixed inhibitors for ImiS with K_i values of 0.074 and 0.27μM using imipenem as the substrate. Docking studies showed that 1 and 9, which have the highest inhibitory activity against ImiS, fit the binding site of CphA as a replacement of ImiS via stable interactions between the triazole group bridging ASP120 and hydroxyl group bridging ASN233.

Diversity and Proliferation of Metallo-β-Lactamases: a Clarion Call for Clinically Effective Metallo-β-Lactamase Inhibitors

The worldwide proliferation of life-threatening metallo-β-lactamase (MBL)-producing Gram-negative bacteria is a serious concern to public health. MBLs are compromising the therapeutic efficacies of β-lactams, particularly carbapenems, which are last-resort antibiotics indicated for various multidrug-resistant bacterial infections. Inhibition of enzymes mediating antibiotic resistance in bacteria is one of the major promising means for overcoming bacterial resistance. Compounds having potential MBL-inhibitory activity have been reported, but none are currently under clinical trials. The need for developing safe and efficient MBL inhibitors (MBLIs) is obvious, particularly with the continuous spread of MBLs worldwide. In this review, the emergence and escalation of MBLs in Gram-negative bacteria are discussed. The relationships between different class B β-lactamases identified up to 2017 are represented by a phylogenetic tree and summarized. In addition, approved and/or clinical-phase serine β-lactamase inhibitors are recapitulated to reflect the successful advances made in developing class A β-lactamase inhibitors. Reported MBLIs, their inhibitory properties, and their purported modes of inhibition are delineated. Insights into structural variations of MBLs and the challenges involved in developing potent MBLIs are also elucidated and discussed. Currently, natural products and MBL-resistant β-lactam analogues are the most promising agents that can become clinically efficient MBLIs. A deeper comprehension of the mechanisms of action and activity spectra of the various MBLs and their inhibitors will serve as a bedrock for further investigations that can result in clinically useful MBLIs to curb this global menace.

Semi-rational screening of the inhibitors and β-lactam antibiotics against the New Delhi metallo-β-lactamase 1 (NDM-1) producing E. coli

Bacteria containing bla NDM-1 gene are a growing threat to almost all clinically β-lactam antibiotics. Especially, the New Delhi metallo-β-lactamase (NDM-1) has become a potential public survival risk. In this study, a novel and efficient strategy for inhibitors and β-lactam antibiotics screening using recombinant New Delhi metallo-beta-lactamase (NDM-1) was developed. First, the gene of bla NDM-1 were identified and cloned from multi-drug resistance of Acinetobacter baumannii isolate; by the means of protein expression and purification, recombinant NDM-1 activity was up to 68.5 U ml-1, and high purity NDM-1 protein with activity of 347.4 U mg-1 was obtained. Finally, for NDM-1, the inhibitors (aspergillomarasmine A (AMA) and EDTA) with high affinity (HI) and the β-lactam antibiotics (imipenem) with low affinity (LA) were screened out. Surprisingly, the inhibition of the NDM-1 was enhanced by the use of inhibitor combinations (AMA-EDTA (1 : 2)), where the IC50 of AMA-EDTA was reduced by 88% and 95%, respectively, comparing to the AMA and EDTA alone. More interesting, AMA-EDTA could restore the activity of imipenem when tested against NDM-1 expressing strains (E. coli and Acinetobacter baumannii), with a working time of 120 min and 330 min, respectively. This method is expected to be used in high-throughput screening, drug redesign (including new inhibitors and drugs) and "old drug new use".

An efficient synthesis of 4,5-disubstituted-2H-1,2,3-triazoles from nitroallylic derivatives via a cycloaddition–denitration process

A variety of nitroallylic derivatives were smoothly reacted with sodium azide in the presence of p-TsOH to form synthetically-viable triazoles.

Rhodium-catalyzed triazole-directed C–H bond functionalization of arenes with diazo compounds

Rhodium(iii)-catalyzed alkylation reactions of arenes through triazole directed C–H activation that lead to a number of dialkylated and monoalkylated triazoles are described.

A One-Pot Procedure for the Synthesis of "Click-Ready" Triazoles from Ketones

A practical, straightforward, and highly regioselective Zn(OAc)₂-mediated method toward propargyl triazoles has been developed for the first time from commercially available enolizable ketones and propargyl amine. Postfunctionalization of this triazole leads to unique N- and C-linked bis-triazoles in excellent yields.

Design, Synthesis and Antifungal Activity of Novel Benzofuran-Triazole Hybrids

A series of novel benzofuran-triazole hybrids was designed and synthesized by click chemistry, and their structures were characterized by HRMS, FTIR and NMR. The in vitro antifungal activity of target compounds was evaluated using the microdilution broth method against five strains of pathogenic fungi. The result indicated that the target compounds exhibited moderate to satisfactory activity. Furthermore, molecular docking was performed to investigate the binding affinities and interaction modes between the target compound and N-myristoyltransferase. Based on the results, preliminary structure activity relationships (SARs) were summarized to serve as a foundation for further investigation.

A single-step acid catalyzed reaction for rapid assembly of NH-1,2,3-triazoles

NH-1,2,3-Triazole moieties are a part of the design of various biologically active compounds, pharmaceutical agents and functional materials.

Triazole: A Promising Antitubercular Agent

Tuberculosis is a contagious disease with comparatively high mortality worldwide. The statistics shows that around three million people throughout the world die annually from tuberculosis and there are around eight million new cases each year, of which developing countries showed major share. Therefore, the discovery and development of effective antituberculosis drugs with novel mechanism of action have become an insistent task for infectious diseases research programs. The literature reveals that, heterocyclic moieties have drawn attention of the chemists, pharmacologists, microbiologists, and other researchers owing to its indomitable biological potential as anti-infective agents. Among heterocyclic compounds, triazole (1,2,3-triazole/1,2,4-triazole) nucleus is one of the most important and well-known heterocycles, which is a common and integral feature of a variety of natural products and medicinal agents. Triazole core is considered as a privileged structure in medicinal chemistry and is widely used as 'parental' compounds to synthesize molecules with medical benefits, especially with infection-related activities. In the present review, we have collated published reports on this versatile core to provide an insight so that its complete therapeutic potential can be utilized for the treatment of tuberculosis. This review also explores triazole as a potential targeted core moiety against tuberculosis and various research ongoing worldwide. It is hoped that this review will be helpful for new thoughts in the quest for rational designs of more active and less toxic triazole-based antituberculosis drugs.