Synthesis and biological evaluation of novel 5-(hydroxamic acid)methyl oxazolidinone derivatives

Structural toxicity relationship (STR) of linezolid to mitigate myelosuppression and serotonergic toxicity

Tuberculosis (TB) remains a significant global health challenge, with multidrug-resistant (MDR-TB) and extensively drug-resistant (XDR-TB) strains posing severe threats to treatment efficacy. Linezolid, a key component of the BPaL (Bedaquiline, Pretomanid and Linezolid) regimen, has demonstrated substantial efficacy against MDR-TB and XDR-TB. However, its clinical utility is often limited by side effects such as myelosuppression and monoamine oxidase (MAO) inhibition, linked to its mechanism of action. This perspective centres on the structural toxicity relationship (STR) of Linezolid and its analogues, exploring modifications to the C-ring and C-5 position that aim to reduce these toxicities while maintaining or enhancing antibacterial activity. Several promising analogues have been identified that exhibit reduced myelosuppression and MAO inhibition, highlighting the potential for developing safer Linezolid derivatives. The findings underscore the importance of continued research into the structure toxicity relationships of oxazolidinones to improve the therapeutic profiles of these essential drugs in combating drug-resistant TB.

Design and Synthesis of the Linezolid Bioisosteres to Resolve the Serotonergic Toxicity Associated with Linezolid

Serotonergic toxicity due to MAO enzyme inhibition is a significant concern when using linezolid to treat MDR-TB. To address this issue, we designed linezolid bioisosteres with a modified acetamidomethyl side chain at the C-5 position of the oxazolidine ring to balance activity and reduce toxicity. Among these bioisosteres, R7 emerged as a promising candidate, demonstrating greater effectiveness against M. tuberculosis (Mtb) H37Rv cells with an MIC of 2.01 μM compared to linezolid (MIC = 2.31 μM). Bioisostere R7 also exhibited remarkable activity (MIC50) against drug-resistant Mtb clinical isolates, with values of 0.14 μM (INHR, inhA+), 0.53 μM (INHR, katG+), 0.24 μM (RIFR, rpoB+), and 0.92 μM (INHR INHR, MDR). Importantly, it was >6.52 times less toxic as compared to the linezolid toward the MAO-A and >64 times toward the MAO-B enzyme, signifying a substantial improvement in its drug safety profile.

Design, Synthesis, Molecular Docking, and In Vitro Antibacterial Evaluation of Benzotriazole-Based β-Amino Alcohols and Their Corresponding 1,3-Oxazolidines

In the present study, a series of benzotriazole-based β-amino alcohols were efficiently synthesized in excellent yields via aminolysis of benzotriazolated epoxides under catalyst- and solvent-free conditions. Further these β-amino alcohols were successfully utilized to synthesize the corresponding benzotriazole-based oxazolidine heterocyclic derivatives. All the synthesized compounds were characterized by various spectroscopic techniques such as 1H NMR, 13C NMR, and mass spectroscopy for structure elucidation. The compounds were subjected to a microtiter plate-based antimicrobial assay. The antimicrobial activity results reveal that the compounds 4a, 4e, and 5f were found to be active against Staphylococcus aureus (ATCC-25923) with minimum inhibitory concentrations (MICs) of 32, 8, and 64 μM, respectively. Also, the compounds 4a, 4e, 4k, 4i, 4m, 4n, 4o, 5d, 5e, 5f, 5g, and 5h showed effective activity against Bacillus subtilis (ATCC 6633) with MICs of 64, 16, 16, 16, 64, 16, 64, 64, 32, 64, 8, and 16 μM, respectively. A biological investigation was conducted, including molecular docking of two compounds with several receptors to identify and confirm the best ligand-protein interactions. Hence, this study found a significant strategy to diversify the chemical molecules. The synthesized compounds play a potential role as an antibacterial intensifier against some pathogenic bacteria for the development of antibacterial substances.

Optimization and Antibacterial Evaluation of Novel 3-(5-Fluoropyridine-3-yl)-2-oxazolidinone Derivatives Containing a Pyrimidine Substituted Piperazine

In this study, a series of novel 3-(5-fluoropyridine-3-yl)-2-oxazolidinone derivatives were designed and synthesized based on compounds previously reported, and their antibacterial activity was investigated. Then their antibacterial activity was investigated for the first time. Preliminary screening results showed that all these compounds exhibited antibacterial activity against gram-positive bacteria, including 7 drug-sensitive strains and 4 drug-resistant strains, among which compound 7j exhibited an 8-fold stronger inhibitory effect than linezolid, with a minimum inhibitory concentration (MIC) value of 0.25 µg/mL. Further molecular docking studies predicted the possible binding mode between active compound 7j and the target. Interestingly, these compounds could not only hamper the formation of biofilms, but also have better safety, as confirmed by cytotoxicity experiments. All these results indicate that these 3-(5-fluoropyridine-3-yl)-2-oxazolidinone derivatives have the potential to be developed into novel candidates for the treatment of gram-positive bacterial infections.

Synthesis, DFT study, theoretical and experimental spectroscopy of fatty amides based on extra-virgin olive oil and their antibacterial activity

Medication products from natural materials are preferred due to their minimal side effects. Extra-virgin olive oil (EVOO) is a highly acclaimed Mediterranean diet and a common source of lipids that lowers morbidity and disease severity. This study synthesised two fatty amides from EVOO: hydroxamic fatty acids (FHA) and fatty hydrazide hydrate (FHH). The Density Functional Theory (DFT) was applied to quantum mechanics computation. Nuclear magnetic resonance (NMR), Fourier transforms infrared (FTIR), and element analysis were used to characterise fatty amides. Likewise, the minimum inhibitory concentration (MIC) and timing kill assay were determined. The results revealed that 82 % for FHA and 80 % for FHH conversion were achieved. The amidation reagent/EVOO ratio (mmol: mmol) was 7:1, using the reaction time of 12 h and hexane as an organic solvent. The results further revealed that fatty amides have high antibacterial activity with low concentration at 0.04 μg/mL during eight h of FHA and 0.3 μg/mL during ten h of FHH. This research inferred that FHA and FHH could provide an alternative and effective therapeutic strategy for bacterial diseases. Current findings could provide the basis for the modernisation/introduction of novel and more effective antibacterial drugs derived from natural products.

Synthesis and structure-activity relationships of novel 5-(hydroxamic acid)methyl oxazolidinone derivatives as 5-lipoxygenase inhibitors

Oxazolidinone hydroxamic acid derivatives were synthesised and evaluated for inhibitory activity against leukotriene (LT) biosynthesis in three in vitro cell-based test systems and on direct inhibition of recombinant human 5-lipoxygenase (5-LO). Thirteen of the 19 compounds synthesised were considered active ((50% inhibitory concentration (IC₅₀) ≤ 10 µM in two or more test systems)). Increasing alkyl chain length on the hydroxamic acid moiety enhanced activity and morpholinyl-containing derivatives were more active than N-acetyl-piperizinyl derivatives. The IC₅₀ values in cell-based assay systems were comparable to those obtained by direct inhibition of 5-LO activity, confirming that the compounds are direct inhibitors of 5-LO. Particularly, compounds PH-249 and PH-251 had outstanding potencies (IC₅₀ < 1 µM), comparable to that of the prototype 5-LO inhibitor, zileuton. Pronounced in vivo activity was demonstrated in zymosan-induced peritonitis in mice. These novel oxazolidinone hydroxamic acid derivatives are, therefore, potent 5-LO inhibitors with potential application as anti-allergic and anti-inflammatory agents.

Synthesis and Characterization of N-Methyl Fatty Hydroxamic Acids from Ketapang Seed Oil Catalyzed by Lipase

N-methyl fatty hydroxamic acid (N-MFHA), which is a derivative of hydroxamic acid (HA), was synthesized from ketapang seed oil (Terminalia catappa L.). In general, HAs have wide applications due to their chelating properties and biological activities. N-MFHAs were synthesized using immobilized lipase (Lipozyme TL IM) in biphasic medium which was the ketapang seed oil dissolved in hexane and N-methylhydroxylamine dissolved in water. The products were characterized through color testing and FT-IR spectroscopy after purification. Various factors affecting the enzyme activity investigated in the study included the effect of incubation time, the amount of lipase used, and the temperature. On the basis of the results, the optimum conditions for the synthesis of N-MFHA obtained are 25 h of incubation time, a temperature of 40 °C, and a ratio of 1:100 for the amount of enzyme (g)/oil (g). At the optimum conditions of the reaction, 59.7% of the oils were converted to N-MFHA.

Novel approaches to the discovery of selective human monoamine oxidase-B inhibitors: is there room for improvement?

Introduction: Selective monoamine oxidase-B (MAO-B) inhibitors are currently used as coadjuvants for the treatment of early motor symptoms in Parkinson's disease. They can, based on their chemical structure and mechanism of inhibition, be categorized into reversible and irreversible agents. Areas covered: This review provides a comprehensive update on the development state of selective MAO-B inhibitors describing the results, structures, structure-activity relationships (SARs) and Medicinal chemistry strategies as well as the related shortcomings over the past five years. Expert opinion: Researchers have explored and implemented new and old chemical scaffolds achieving high inhibitory potencies and isoform selectivity. Most of them were characterized and proposed as multitarget agents able to act at different levels (including AChE inhibition, H3R or A_2AR antagonism, antioxidant and chelating properties, Aβ_1-42 aggregation reduction) in the network of aetiologies of neurodegenerative disorders. These results can also be used to avoid 'cheese-reaction' effects and the occurrence of serotonergic syndrome in patients.

Monoamine oxidase-B inhibitors as potential neurotherapeutic agents: An overview and update

Monoamine oxidase (MAO) inhibitors have made significant contributions and remain an indispensable approach of molecular and mechanistic diversity for the discovery of antineurodegenerative drugs. However, their usage has been hampered by nonselective and/or irreversible action which resulted in drawbacks like liver toxicity, cheese effect, and so forth. Hence, the search for selective MAO inhibitors (MAOIs) has become a substantial focus in current drug discovery. This review summarizes our current understanding on MAO-A/MAO-B including their structure, catalytic mechanism, and biological functions with emphases on the role of MAO-B as a potential therapeutic target for the development of medications treating neurodegenerative disorders. It also highlights the recent developments in the discovery of potential MAO-B inhibitors (MAO-BIs) belonging to diverse chemical scaffolds, arising from intensive chemical-mechanistic and computational studies documented during past 3 years (2015-2018), with emphases on their potency and selectivity. Importantly, readers will gain knowledge of various newly established MAO-BI scaffolds and their development potentials. The comprehensive information provided herein will hopefully accelerate ideas for designing novel selective MAO-BIs with superior activity profiles and critical discussions will inflict more caution in the decision-making process in the MAOIs discovery.

Synthesis and Biological Evaluation of Novel Dehydroabietic Acid-Oxazolidinone Hybrids for Antitumor Properties

Novel representatives of the important group of biologically-active, dehydroabietic acid-bearing oxazolidinone moiety were synthesized to explore more efficacious and less toxic antitumor agents. Structures of all the newly target molecules were confirmed by IR, ¹H-NMR, ¹³C-NMR, and HR-MS. The inhibitory activities of these compounds against different human cancer cell lines (MGC-803, CNE-2, SK-OV-3, NCI-H460) and human normal liver cell line LO2 were evaluated and compared with the commercial anticancer drug cisplatin, using standard MTT (methyl thiazolytetrazolium) assay in vitro. The pharmacological screening results revealed that most of the hybrids showed significantly improved antiproliferative activities over dehydroabietic acid and that some displayed better inhibitory activities compared to cisplatin. In particular, compound 4j exhibited promising cytotoxicity with IC₅₀ values ranging from 3.82 to 17.76 µM against all the test cell lines and displayed very weak cytotoxicity (IC₅₀ > 100 µM) on normal cells, showing good selectivity between normal and malignant cells. Furthermore, the action mechanism of the representative compound 4j was preliminarily investigated by Annexin-V/PI dual staining, Hoechst 33258 staining, which indicated that the compound can induce cell apoptosis in MGC-803 cells in a dose-dependent manner and arrest the cell cycle in G1 phase. Therefore, 4j may be further exploited as a novel pharmacophore model for the development of anticancer agents.

Crystal structure of catena-poly[diaqua-bis(di(N 2,N 6-dihydroxypyridine-2,6-dicarboxamide))potassium(I)]tetrahydrate, C14H25N6O14K

C14H25N6O14K, triclinic, P1̅ (no. 2), a = 6.9630(15) Å, b = 9.2770(17) Å, c = 9.6100(18) Å, α = 69.822(2)°, β = 87.225(2)°, γ = 85.559(2)°, V = 580.8(2) Å3, Z = 1, R gt(F) = 0.0366, wR ref(F 2) = 0.1052, T = 293(2) K.

The Current Status of O-Heterocycles: A Synthetic and Medicinal Overview

O-Heterocycles have been explored in the field of medicinal chemistry for a long time, but their significance has not been duly recognised and they are often shunned in favour of N-heterocycles. The design of bioactive molecules for nearly every pathophysiological condition is primarily focused on novel N-heterocycles. The main reasons for such bias include the ease of synthesis and possible mimicking of physiological molecules by N-heterocycles. But considering only this criterion rarely provides breakthrough molecules for a given disease condition, and instead the risks of toxicity or side effects are increased with such molecules. On the other hand, owing to improved synthetic feasibility, O-heterocycles have established themselves as equally potent lead molecules for a wide range of pathophysiological conditions. In the last decade there have been hundreds of reports validating the fact that equally potent molecules can be designed and developed by using O-heterocycles, and these are also expected to have comparably low toxicity. Even so, researchers tend to remain biased toward the use of N-heterocycles over O-heterocycles. Thus, this review provides a critical analysis of the synthesis and medicinal attributes of O-heterocycles, such as pyrones, oxazolones, furanones, oxetanes, oxazolidinones, and dioxolonones, and others, reported in the last five years, underlining the need for and the advantages guiding researchers toward them.

Synthesis of oxazolidinones: rhodium-catalyzed C-H amination of N-mesyloxycarbamates

N-Mesyloxycarbamates undergo intramolecular C-H amination reactions to afford oxazolidinones in good to excellent yields in the presence of rhodium(ii) carboxylate catalysts. The reaction is performed under green conditions and potassium carbonate is used, forming biodegradable potassium mesylate as a reaction by-product. This method enables the production of electron-rich, electron-deficient, aromatic and heteroaromatic oxazolidinones in good to excellent yields. Conformationally restricted cyclic secondary N-mesyloxycarbamates furnish cis-oxazolidinones in high yields and selectivity; DFT calculations are provided to account for the observed selectivity. trans-Oxazolidinones were prepared from acyclic secondary N-mesyloxycarbamates using Rh₂(oct)₄. The selectivity was reverted with a cytoxazone N-mesyloxycarbamate precursor using large chiral rhodium(ii) carboxylate complexes, affording the corresponding cis-oxazolidinone. This orthogonal selectivity was used to achieve the formal synthesis of (-)-cytoxazone.

Privileged scaffolds as MAO inhibitors: Retrospect and prospects

This review aims to be a comprehensive, authoritative, critical, and readable review of general interest to the medicinal chemistry community because it focuses on the pharmacological, chemical, structural and computational aspects of diverse chemical categories as monoamine oxidase inhibitors (MAOIs). Monoamine oxidases (MAOs), namely MAO-A and MAO-B represent an enormously valuable class of neuronal enzymes embodying neurobiological origin and functions, serving as potential therapeutic target in neuronal pharmacotherapy, and hence we have coined the term "Neurozymes" which is being introduced for the first time ever. Nowadays, therapeutic attention on MAOIs engrosses two imperative categories; MAO-A inhibitors, in certain mental disorders such as depression and anxiety, and MAO-B inhibitors, in neurodegenerative disorders like Alzheimer's disease (AD) and Parkinson's disease (PD). The use of MAOIs declined due to some potential side effects, food and drug interactions, and introduction of other classes of drugs. However, curiosity in MAOIs is reviving and the recent developments of new generation of highly selective and reversible MAOIs, have renewed the therapeutic prospective of these compounds. The initial section of the review emphasizes on the detailed classification, structural and binding characteristics, therapeutic potential, current status and future challenges of the privileged pharmacophores. However, the chemical prospective of privileged scaffolds such as; aliphatic and aromatic amines, amides, hydrazines, azoles, diazoles, tetrazoles, indoles, azines, diazines, xanthenes, tricyclics, benzopyrones, and more interestingly natural products, along with their conclusive SARs have been discussed in the later segment of review. The last segment of the article encompasses some patents granted in the field of MAOIs, in a simplistic way.

Antibiotics: where to throw the spanner in the ribosomal machinery?

The sheer molecular scale of the ribosome is intimidating to the traditional drug designer. By analyzing the ribosome as a series of 12 key target sites, this review seeks to make the ribosome ligand design process more manageable. Analysis of recently evaluated ribosomal structures, particularly those with bound antibiotics, indicates where the ligand target sites are located. This review employs current research data to map antibiotic binding across the ribosome. A number of neighboring ligand-binding sites are often contiguous and can be combined. Ligands that bind in close proximity can be combined into hybrid structures. The different ways antibiotics disrupt ribosomal function are also discussed. Antibiotics tend to inhibit conformational changes that are essential to the ribosomal mechanism.

Oxazolidinone antimicrobials: a patent review (2012-2015)

INTRODUCTION

Antimicrobial resistance in Gram-positive bacteria is a major health care issue. This review summarizes patent publications from 2012 to 2015 that divulged novel oxazolidinones as antibacterial agents.

AREAS COVERED

A total of 25 patents obtained from Espacenet, WIPO Patentscope and FreePatentsOnline, and AcclaimIP search engines were reviewed. The patents were scrutinized based on the novelty of the compounds, their antibacterial activity (MIC, µg/mL), and the process of preparation. The oxazolidinones with promising antibacterial activity were classified according to the following structural diversities, as biaryl heterocyclic, fused heteroaryl rings containing oxazolidinones, and others. The biaryl heterocyclic, fused heteroaryl, benzoxazine, and the 1H-pyrazol-1-yl containing oxazolidinone derivatives demonstrated potent antibacterial activities superior to linezolid against Gram-positive bacteria. Some derivatives were effective against standard strains of Gram-negative bacteria, namely Moraxella catarrhalis ATCC A894, and Escherichia coli ATCC 25922. In addition, a patent disclosed a structural isomer of linezolid with marginal activity against the aerobic Gram-negative bacteria MDR Stenotrophomonas (Xanthomonas) maltophilia, while linezolid and vancomycin did not inhibit growth. Finally, some derivatives showed activity against respiratory infectious diseases' causative agents, such as B. anthracis, B. mallei, Y. pestis, and M. pneumoniae.

EXPERT OPINION

Overall, there is limited in vivo data to support the potential clinical advancement of the currently reported novel derivatives.