Synthesis and in vitro/in vivo antibacterial activity of oxazolidinones having thiocarbamate at C-5 on the A-ring and an amide- or urea-substituted [1,2,5]triazepane or [1,2,5]oxadiazepane as the C-ring

Radical N2-Retention Cyclizations of Aryl Diazoniums: Access to 7/8/9-Membered Heterocycles

We report herein a modular approach to synthesizing diverse functionalized 7/8/9-membered poly-N-containing heterocycles via oxidative radical N2-retention cyclizations of allylic aryl diazonium salts using CF3SO2Na as a CF3 radical source. A range of trifluoromethylated benzotriazepines, benzotriazocines, and benzotriazonines were obtained in moderate to good yields. This transition-metal-free protocol demonstrates atom economy, safe conditions, broad functional group tolerance, and availability of readily accessible reagents.

Direct C-H Sulfuration: Synthesis of Disulfides, Dithiocarbamates, Xanthates, Thiocarbamates and Thiocarbonates

In light of the important biological activities and widespread applications of organic disulfides, dithiocarbamates, xanthates, thiocarbamates and thiocarbonates, the continual persuit of efficient methods for their synthesis remains crucial. Traditionally, the preparation of such compounds heavily relied on intricate multi-step syntheses and the use of highly prefunctionalized starting materials. Over the past two decades, the direct sulfuration of C-H bonds has evolved into a straightforward, atom- and step-economical method for the preparation of organosulfur compounds. This review aims to provide an up-to-date discussion on direct C-H disulfuration, dithiocarbamation, xanthylation, thiocarbamation and thiocarbonation, with a special focus on describing scopes and mechanistic aspects. Moreover, the synthetic limitations and applications of some of these methodologies, along with the key unsolved challenges to be addressed in the future are also discussed. The majority of examples covered in this review are accomplished via metal-free, photochemical or electrochemical approaches, which are in alignment with the overraching objectives of green and sustainable chemistry. This comprehensive review aims to consolidate recent advancements, providing valuable insights into the dynamic landscape of efficient and sustainable synthetic strategies for these crucial classes of organosulfur compounds.

Oxazolidinones as versatile scaffolds in medicinal chemistry

Oxazolidinone is a five-member heterocyclic ring with several biological applications in medicinal chemistry. Among the three possible isomers, 2-oxazolidinone is the most investigated in drug discovery. Linezolid was pioneered as the first approved drug containing an oxazolidinone ring as the pharmacophore group. Numerous analogues have been developed since its arrival on the market in 2000. Some have succeeded in reaching the advanced stages of clinical studies. However, most oxazolidinone derivatives reported in recent decades have not reached the initial stages of drug development, despite their promising pharmacological applications in a variety of therapeutic areas, including antibacterial, antituberculosis, anticancer, anti-inflammatory, neurologic, and metabolic diseases, among other areas. Therefore, this review article aims to compile the efforts of medicinal chemists who have explored this scaffold over the past decades and highlight the potential of the class for medicinal chemistry.

Design, synthesis and antibacterial evaluation of pleuromutilin derivatives

We report herein the design, synthesis, and structure-activity relationship studies of pleuromutilin derivatives containing urea/thiourea functionalities. The antibacterial activities of these new pleuromutilin derivatives were evaluated in vitro against Gram-positive pathogens (GPPs) (Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecium) and Mycoplasma pneumoniae by the broth dilution method. Most of the targeted compounds exhibit good potency in inhibiting the growth of pathogens including Methicillin-susceptible S. aureus (MSSA, ATCC29213, MIC: 0.0625-16 μg/mL), Methicillin-resistant S. aureus (MRSA, ATCC43300, MIC: 0.125-16 μg/mL) and M. pneumoniae (ATCC15531 MIC: 0.125-1 μg/mL, ATCC29342 MIC: 0.0625-0.25 μg/mL and drug resistant strain MIC: 0.5-2 μg/mL). In particular, the compounds 6m and 6n containing phenyl-urea group showed excellent activity with the MIC value less than 0.0625 μg/mL against S. aureus ATCC29213. The compound 6h exhibited better activity than tiamulin against Methicillin-resistant S. aureus ATCC43300.

Synthesis and application of thiocarbamates via thiol-dioxazolone modified Lossen rearrangement

Thiocarbamates afforded from thiol-dioxazolone modified Lossen rearrangement under mild conditions were further applied to prepare polythiocarbamates with self-healing properties.

Installation of an aryl boronic acid function into the external section of N-aryl-oxazolidinones: Synthesis and antimicrobial evaluation

N-aryl-oxazolidinones is a prominent family of antimicrobials used for treating infections caused by clinically prevalent Gram-positive bacteria. Recently, boron-containing compounds have displayed intriguing potential in the antibiotic discovery setting. Herein, we report the unprecedented introduction of a boron-containing moiety such as an aryl boronic acid in the external region of the oxazolidinone structure via a chemoselective acyl coupling reaction. As a result, we accessed a series of analogues with a distal aryl boronic pharmacophore on the oxazolidinone scaffold. We identified that a peripheric linear conformation coupled with freedom of rotation and no further substitution on the external aryl boronic ring, an amido linkage with hydrogen bonding character, in addition to a para-relative disposition between boronic group and linker, are the optimal combination of structural features in this series for antimicrobial activity. In comparison to linezolid, the analogue comprising all those features, compound 20b, displayed levels of antimicrobial activity augmented by an eight-fold to a thirty-two-fold against a panel of Gram-positive strains, and a near one hundred-fold against Escherichia coli JW5503, a Gram-negative mutant strain with a defective efflux capability.

1,2,3-Triazole-containing hybrids with potential antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA)

Methicillin-resistant Staphylococcus aureus (MRSA), as a classic reason for genuine skin and flimsy tissues diseases, is a worldwide general wellbeing risk and has already tormented humanity for a long history, creating a critical need for the development of new classes of antibacterials. 1,2,3-Triazole moiety, readily interact with diverse enzymes and receptors in organisms through weak bond interaction, is among the most common frameworks present in the bioactive molecules. 1,2,3-Triazole derivatives, especially 1,2,3-triazole-containing hybrids, possess broad-spectrum activity against a panel of clinically important bacteria including drug-resistant pathogens, so rational design of 1,2,3-triazole derivatives may open a door for the opportunities on the development of novel anti-MRSA agents. This review is an endeavour to highlight the current scenario of 1,2,3-triazole-containing hybrids with potential anti-MRSA activity, covering articles published between 2010 and 2020.

Original synthesis of radiolabeling precursors for batch and on resin one-step/late-stage radiofluorination of peptides

Radiolabeling of peptides with fluorine-18 is hurdled by their chemical sensitivity and complicated processes. Original triflyl-pyridine intermediates afforded ammonium precursors that were radiolabeled at low temperature. From that study, a generic tag has been designed to allow a simple one-step/late-stage radiolabelling of peptides. The strategy has been transposed to an automated "on-resin" radiolabelling.

Urea Derivatives in Modern Drug Discovery and Medicinal Chemistry

The urea functionality is inherent to numerous bioactive compounds, including a variety of clinically approved therapies. Urea containing compounds are increasingly used in medicinal chemistry and drug design in order to establish key drug-target interactions and fine-tune crucial drug-like properties. In this perspective, we highlight physicochemical and conformational properties of urea derivatives. We provide outlines of traditional reagents and chemical procedures for the preparation of ureas. Also, we discuss newly developed methodologies mainly aimed at overcoming safety issues associated with traditional synthesis. Finally, we provide a broad overview of urea-based medicinally relevant compounds, ranging from approved drugs to recent medicinal chemistry developments.

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

Research activities on the oxazolidinone antibacterial class of compounds continue to focus on developing newer derivatives with improved potency, broad-spectrum activity and safety profiles superior to linezolid. Among the safety concerns with the oxazolidinone antibacterial agents is inhibition of monoamine oxidases (MAO) resulting from their structural similarity with toloxatone, a known MAO inhibitor. Diverse substitution patterns at the C-5 position of the oxazolidinone ring have been shown to significantly affect both antibacterial activity and MAO inhibition to varying degrees. Also, the antibacterial activity of compounds containing iron-chelating functionalities, such as the hydroxamic acids, 8-hydroxyquinolines and catechols have been correlated to their ability to alter iron intake and/or metabolism. Hence a series of novel 5-(hydroxamic acid)methyl oxazolidinone derivatives were synthesized and evaluated for their antibacterial and MAO-A and -B inhibitory activities. The compounds were devoid of significant antibacterial activity but most demonstrated moderate MAO-A and -B inhibitory activities. Computer modeling studies revealed that the lack of potent antibacterial activity was due to significant steric interaction between the hydroxamic acid N-OH oxygen atom and one of the G2540 5'-phosphate oxygen atoms at the bacterial ribosomal binding site. Therefore, the replacement of the 5-acetamidomethyl group of linezolid with the 5-(N-hydroxyacetamido)methyl group present in the hydroxamic acid oxazolidinone derivatives was concluded to be detrimental to antibacterial activity. Furthermore, the 5-(hydroxamic acid)methyl oxazolidinone derivatives were also less active as MAO-A and -B inhibitors compared with linezolid and the selective inhibitors clorgyline and pargyline. In general, the 5-(hydroxamic acid)methyl oxazolidinone derivatives demonstrated moderate but selective MAO-B inhibitory activity.

Crystal structure of 1-(2,4-di-methyl-phen-yl)urea

In the title urea derivative, C₉H₁₂N₂O, the dihedral angle between the benzene ring and the mean plane of the urea group, N—C(=O)—N, is 86.6 (1)°. In the crystal, the urea O atom is involved in three N—H⋯O hydrogen bonds. Mol­ecules are linked via pairs of N—H⋯O hydrogen bonds, forming inversion dimers with an R²₂(8) ring motif. The dimers are linked by further N—H⋯O hydrogen bonds, forming two-dimensional networks lying parallel to (100).

Oxazolidinone derivatives: cytoxazone-linezolid hybrids induces apoptosis and senescence in DU145 prostate cancer cells

In this study, we report the synthesis of novel oxazolidinone derivatives derived from linezolid 3 having p-methoxyphenyl group at C-4 position. In vitro evaluation for their anticancer activity toward cultured A549, DU145, HELA, and MCF7 were carried out. The series of compounds prepared displayed wide range of cytotoxicity in MTT assays (10-70 μM) across the cell lines tested. Of the all tested compounds 16 and 17 displayed good anticancer potential against A549 (lung) and DU145 (prostate) cancer cells. Further, to determine their anticancer potential, in the present study we have assessed effect of 17 on DU145 cells growth in in vitro assays. The results clearly demonstrated that the exposure of DU145 cells to 17 inhibits cell proliferation and induces apoptosis by activation of caspase-3 and -9. Long term exposure of DU145 cells to 17 induced cellular senescence confirmed by senescence marker β-galactosidase staining of cells on post exposure to 17. The results from this current report support that the oxazolidinone derivatives with ethyl and acryl substitutions showed promising anticancer activity which will be helpful to develop further novel anticancer agents with better therapeutic potential.