Metal-Free Radical [3 + 2] Annulation of Tetraalkylthiuram Disulfide with Alkynes/Alkenes: An Approach of Synthesizing 1,3-Dithiole and 1,3-Ditholane Derivatives.

A novel and metal-free [3 + 2] annulation of tetraalkylthiuram disulfide with alkynes/alkenes has been developed using Selectfluor at room temperature. The formed 1,3-dithiol-2-ylium/1,3-dithiolan-2-ylium salts can be easily transformed into the corresponding 1,3-dithiol-2-ylidenes/1,3-ditholan-2-ylidenes by one-pot subsequent condensation with malononitrile. The present protocol features the use of easily accessible starting materials, mild reaction conditions, good tolerance with diverse functional groups, easy scale-up, and a wide substrate scope, affording the desired products in good yields. Importantly, this method is suitable for the late-stage modification of bioactive molecules. Furthermore, 1,3-dithiol-2-ylium salt can also be easily converted into various 1,3-dithiole derivatives by condensation, reduction, or hydrolysis. Mechanism studies show that this transformation involves radical annulation. Of note, this method presented a novel example using tetraalkylthiuram disulfide as a sulfur synthon in annulation, which greatly enriches the application of tetraalkylthiuram disulfides in organic synthesis. Biological evaluation indicates that these prepared compounds are promising candidates in terms of their antitumor activity.

Design, Synthesis, and Biological Evaluation of ß-Trifluoroethoxydimethyl Selenides as Potent Antiosteoporosis Agents.

An efficient protocol for the synthesis of ß-trifluoroethoxydimethyl selenides was achieved under mild reaction conditions, and 39 compounds were prepared. All compounds were evaluated for their abilities to inhibit RANKL-induced osteoclastogenesis, compound 4aa exhibited the most potent activity. Further investigations revealed that 4aa could inhibit F-actin ring generation, bone resorption, and osteoclast-specific gene expression in vitro. Western blot analyses demonstrated that compound 4aa abrogated the RANKL-induced mitogen-activated protein kinase and NF-kB-signaling pathways. In addition, 4aa also displayed a notable impact on the osteoblastogenesis of MC3T3-E1 preosteoblasts. In vivo experiments revealed that compound 4aa significantly ameliorated bone loss in an ovariectomized (OVX) mice model. Furthermore, the surface plasmon resonance experiment results revealed that 4aa probably bound to RANKL. Collectively, the above-mentioned findings suggested that compound 4aa as a potential RANKL inhibitor averted OVX-triggered osteoporosis by regulating the inhibition of osteoclast differentiation and stimulation of osteoblast differentiation.

3-methyl-1H-indol-1-yl dimethylcarbamodithioate attenuates periodontitis through targeting MAPK signaling pathway-regulated mitochondrial function.

Periodontitis, the second most common oral disease, is primarily initiated by inflammatory responses and osteoclast differentiation, in which the MAPK signaling pathway and mitochondrial function play important roles. 3-methyl-1H-indol-1-yl dimethylcarbamodithioate (3o), a hybrid of indole and dithiocarbamate, was first synthesized by our group. It has shown anti-inflammatory activity against lipopolysaccharide-induced acute lung injury. However, it is not known if 3o can exert effects in periodontitis. In vitro study: LPS-induced macrophage inflammation initiation and a receptor activator of nuclear factor κB ligand-stimulated osteoclast differentiation model were established. Cell viability, inflammatory cytokines, osteoclast differentiation, the MAPK signaling pathway, and mitochondrial function before and after treatment with 3o were investigated. In vivo study: Alveolar bone resorption, inflammatory cytokine expression, osteoclast differentiation, and the underlying mechanisms were assessed in mice with periodontitis. Inflammatory cytokine expression and osteoclast differentiation appeared downregulated after 3o treatment. 3o inhibited the MAPK signaling pathway and restored mitochondrial function, including mitochondrial reactive oxygen species, mitochondrial membrane potential, and ATP production. Meanwhile, 3o reduced inflammation activation and bone resorption in mice with periodontitis, reflected by the decreased expression of inflammatory cytokines and osteoclasts, implying that 3o inhibited the MAPK signaling pathway and the mitochondrial oxidative DNA damage marker 8-OHdG. These results highlight the protective role of 3o in periodontitis in mice and reveal an important strategy for preventing periodontitis.

Novel small-molecule compound YH7 inhibits the biofilm formation of Staphylococcus aureus in a sarX-dependent manner.

The emergence of antibiotic-resistant and biofilm-producing Staphylococcus aureus isolates presents major challenges for treating staphylococcal infections. Biofilm inhibition is an important anti-virulence strategy. In this study, a novel maleimide-diselenide hybrid compound (YH7) was synthesized and demonstrated remarkable antimicrobial activity against methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) in both planktonic cultures and biofilms. The minimum inhibitory concentration (MIC) of YH7 for S. aureus isolates was 16 µg/mL. Quantification of biofilms demonstrated that the sub-MIC (4 µg/mL) of YH7 significantly inhibits biofilm formation in both MSSA and MRSA. Confocal laser scanning microscopy analysis further confirmed the biofilm inhibitory potential of YH7. YH7 also significantly suppressed bacterial adherence to A549 cells. Moreover, YH7 treatment significantly inhibited S. aureus colonization in nasal tissue of mice. Preliminary mechanistic studies revealed that YH7 exerted potent biofilm-suppressing effects by inhibiting polysaccharide intercellular adhesin (PIA) synthesis, rather than suppressing bacterial autolysis. Real-time quantitative PCR data indicated that YH7 downregulated biofilm formation-related genes (clfA, fnbA, icaA, and icaD) and the global regulatory gene sarX, which promotes PIA synthesis. The sarX-dependent antibiofilm potential of YH7 was validated by constructing S. aureus NCTC8325 sarX knockout and complementation strains. Importantly, YH7 demonstrated a low potential to induce drug resistance in S. aureus and exhibited non-toxic to rabbit erythrocytes, A549, and BEAS-2B cells at antibacterial concentrations. In vivo toxicity assays conducted on Galleria mellonella further confirmed that YH7 is biocompatible. Overall, YH7 demonstrated potent antibiofilm activity supports its potential as an antimicrobial agent against S. aureus biofilm-related infections. IMPORTANCE Biofilm-associated infections, characterized by antibiotic resistance and persistence, present a formidable challenge in healthcare. Traditional antibacterial agents prove inadequate against biofilms. In this study, the novel compound YH7 demonstrates potent antibiofilm properties by impeding the adhesion and the polysaccharide intercellular adhesin production of Staphylococcus aureus. Notably, its exceptional efficacy against both methicillin-resistant and methicillin-susceptible strains highlights its broad applicability. This study highlights the potential of YH7 as a novel therapeutic agent to address the pressing issue of biofilm-driven infections.

Metal-Free Oxidative Dearomatization-Alkoxylation/Acyloxylation of Indoles: Synthesis of 2-Monosubstituted Indolin-3-ones.

A metal-free route for the preparation of 2-monosubstituted indolin-3-ones, including 2-alkoxyindolin-3-ones and 2-acyloxyindolin-3-ones from commercially available indoles, has been developed employing (bis(trifluoroacetoxy)iodo)benzene (PIFA) as an oxidant. The present protocol features mild reaction conditions, good tolerance with diverse functional groups, and a wide substrate scope, affording the desired products in good yields. This transformation is easy to scale up, and the desired products can be further modified. Most importantly, this method is suitable for the late-stage modification of bioactive molecules. Mechanism studies show that this transformation involves metal-free radical dearomatization and oxygenation. Furthermore, this method also provides a practical and efficient way to prepare indolin-3-ones from commercially available reagents in one step.

A novel small-molecule compound S-342-3 effectively inhibits the biofilm formation of Staphylococcus aureus.

IMPORTANCE: Biofilms are an important virulence factor in Staphylococcus aureus and are characterized by a structured microbial community consisting of bacterial cells and a secreted extracellular polymeric matrix. Inhibition of biofilm formation is an effective measure to control S. aureus infection. Here, we have synthesized a small molecule compound S-342-3, which exhibits potent inhibition of biofilm formation in both MRSA and MSSA. Further investigations revealed that S-342-3 exerts inhibitory effects on biofilm formation by reducing the production of polysaccharide intercellular adhesin and preventing bacterial adhesion. Our study has confirmed that the inhibitory effect of S-342-3 on biofilm is achieved by downregulating the expression of genes responsible for biofilm formation. In addition, S-342-3 is non-toxic to Galleria mellonella larvae and A549 cells. Consequently, this study demonstrates the efficacy of a biologically safe compound S-342-3 in inhibiting biofilm formation in S. aureus, thereby providing a promising antibiofilm agent for further research.

Metal-Free Thiocarbamation of Quinolinones: Direct Access to 3,4-Difunctionalized Quinolines and Quinolinonyl Thiocarbamates at Room Temperature.

A novel and practical method for the preparation of difunctionalized quinolines, bearing a thiocarbamate group at the C3-position and an acyloxyl group at the C4-position, and quinolinonyl thiocarbamates from quinolinones, tetraalkylthiuram disulfides, and hypervalent iodine(III) reagents has been developed via thiocarbamation of quinolinones at room temperature. The present method features mild reaction conditions, good tolerance with diverse functional groups, and a wide substrate scope, providing the desired products in good yields. Furthermore, this transformation is easy to scale up, and the desired products can be readily converted to heterocyclic thiols. Most importantly, this protocol allows for the late-stage thiocarbamation of bioactive compounds. Mechanistic studies show that radicals may be involved in this transformation, water is probably the oxygen source of thiocarbamates, and difunctionalized quinolines are possibly formed via nucleophilic attack of carboxylic anions, which derive from hypervalent iodine(III) reagents.

Small-Molecule Compound CY-158-11 Inhibits Staphylococcus aureus Biofilm Formation.

Staphylococcus aureus is an important human pathogen and brings about many community-acquired, hospital-acquired, and biofilm-associated infections worldwide. It tends to form biofilms, triggering the release of toxins and initiating resistance mechanisms. As a result of the development of S. aureus tolerance to antibiotics, there are few drugs can availably control biofilm-associated infections. In this study, we synthesized a novel small-molecule compound CY-158-11 (C22H14Cl2NO2Se2) and proved its inhibitory effect on the biofilm formation of S. aureus at a subinhibitory concentration (1/8 MIC). The subinhibitory concentration of CY-158-11 not only did not affect the growth of bacteria but also had no toxicity to A549 cells or G. mellonella. Total biofilm biomass was investigated by crystal violet staining, and the results were confirmed by SYTO 9 and PI staining through confocal laser scanning microscopy. Moreover, CY-158-11 effectively prevented initial attachment and repressed the production of PIA instead of autolysis. RT-qPCR analysis also exhibited significant suppression of the genes involved in biofilm formation. Taken together, CY-158-11 exerted its inhibitory effects against the biofilm formation in S. aureus by inhibiting cell adhesion and the expression of icaA related to PIA production. IMPORTANCE Most bacteria exist in the form of biofilms, often strongly adherent to various surfaces, causing bacterial resistance and chronic infections. In general, antibacterial drugs are not effective against biofilms. The small-molecule compound CY-158-11 inhibited the biofilm formation of S. aureus at a subinhibitory concentration. By hindering adhesion and PIA-mediated biofilm formation, CY-158-11 exhibits antibiofilm activity toward S. aureus. These findings point to a novel therapeutic agent for combating intractable S. aureus-biofilm-related infections.

C-H Diselenation and Monoselenation of Electron-Deficient Alkenes via Radical Coupling at Room Temperature.

A new, simple, and metal-free route for the diselenation of maleimides has been first developed employing (bis(trifluoroacetoxy)iodo)benzene (PIFA) at room temperature. The present method is compatible with different functional groups, and various diselenyl maleimides were obtained in moderate to excellent yields. Moreover, this protocol further highlights the unique practical application for the functionalization of biologically relevant molecules and amino acid derivatives. Preliminary mechanism studies suggest that radicals may be involved in this novel transformation. Additionally, this protocol is also applicable for the monoselenation of maleimides by switching the reaction conditions and selenation of other electron-deficient alkenes.

Small-molecule compound SYG-180-2-2 attenuates Staphylococcus aureus virulence by inhibiting hemolysin and staphyloxanthin production.

Multi-drug resistant Staphylococcus aureus infection is still a serious threat to global health. Therefore, there is an urgent need to develop new antibacterial agents based on virulence factor therapy to overcome drug resistance. Previously, we synthesized SYG-180-2-2 (C21H16N2OSe), an effective small molecule compound against biofilm. The aim of this study was to investigate the anti-virulence efficacy of SYG-180-2-2 against Staphylococcus aureus. MIC results demonstrated no apparent antibacterial activity of the SYG-180-2-2. The growth curve assay showed that SYG-180-2-2 had nonlethal effect on S. aureus. Besides, SYG-180-2-2 strongly inhibited the hemolytic activity and staphyloxanthin synthesis in S. aureus. Inhibition of staphyloxanthin by SYG-180-2-2 enhanced the sensitivity of S. aureus to oxidants and human whole blood. In addition, SYG-180-2-2 significantly decreased the expression of saeR-mediated hemolytic gene hlb and staphyloxanthin-related crtM, crtN and sigB genes by quantitative polymerase chain reaction (qPCR). Meanwhile, the expression of oxidative stress-related genes sodA, sodM and katA also decreased. Galleria Mellonella assay revealed that SYG-180-2-2 was not toxic to larvae. Further, the larvae infection model showed that the virulence of bacteria was significantly reduced after 4 µg/mL SYG-180-2-2 treatment. SYG-180-2-2 also reduced skin abscess formation in mice by reducing bacterial burden and subcutaneous inflammation. In conclusion, SYG-180-2-2 might be a promising agent to attenuate the virulence of S. aureus by targeting genes associated with hemolytic activity and staphyloxanthin synthesis.

Regioselective peri-C-H selenylation of aromatic compounds with weakly coordinating ketone groups.

A novel and versatile method for peri-C-H selenylation of aromatic compounds bearing ketone groups, including chromones, xanthones, acridinones, quinolinones and naphthoquinones with diselenides under Ru(II) catalysis is presented. Various chromones and diselenides are applicable for this transformation, affording 5-selenyl chromones in a highly regioselective manner in good to excellent yields. This transformation is easy to scale up and the desired products can be further modified. Most importantly, this transformation allows the late-stage selenylation of bioactive compounds. Mechanistic studies show that radicals may be involved in this novel transformation.

Design, synthesis and biological evaluation of novel chromone-maleimide hybrids as potent anti-inflammatory agents against LPS-induced acute lung injury.

Acute lung injury (ALI) is an acute inflammatory disease, which severely impacts lung function with a high lethality rate. Chromone and maleimide are very important moieties of anti-inflammatory agents. Here, forty new chromone-maleimide hybrids were readily synthesized using a Heck-type coupling strategy in good yields and were screened for their anti-inflammatory activity. A majority of these hybrids showed high inhibitory potency against LPS-stimulated release of pro-inflammatory cytokines in macrophages. Preliminary structure-activity relationship studies led to the discovery of highly potent inhibitors. Five of them were found to inhibit lipopolysaccharide (LPS)-induced IL-6 and TNF-α release in a dose-dependent manner with IC50 values in the nanomolar rang. Furthermore, in vivo administration of 5e and 5g resulted in distinctly attenuated LPS-induced ALI via inhibiting the inflammation. Thus it is evident from our study that these novel chromone-maleimide hybrids present promising therapeutic potential for ALI.

Chromone Derivatives CM3a Potently Eradicate Staphylococcus aureus Biofilms by Inhibiting Cell Adherence.

INTRODUCTION: The ability of Staphylococcus aureus to form biofilms is associated with high mortality and treatment costs. Established biofilms cannot be eradicated by many conventional antibiotics due to the development of antibiotic tolerance by S. aureus. Here we report the synthesis and biological characterization of novel small-molecule compounds with antibiofilm activity. Chromone 5-maleimide substitution compounds (CM3a) showed favorable antibacterial activity against S. aureus. METHODS: CM3A with antibacterial activity was synthesized and screened. The minimum inhibitory concentration (MIC) of CM3a were determined by the broth microdilution method. Biofilm eradication assay and colony count methods were used to investigate the effect of CM3a on S. aureus biofilm disruption and killing. Changes in biofilm architecture when subjected to CM3a, were visualized using confocal laser scanning microscopy (CLSM). CCK-8 assay and survival rate of Galleria mellonella larvae were used to test the toxicity of CM3a. RESULTS: The minimum inhibitory concentration (MIC) of CM3a against S. aureus was about 26.4 µM. Biofilm staining and laser scanning confocal microscopy analysis showed that CM3a eradicated S. aureus biofilms by reducing the viability of the constituent bacterial cells. On the other hand, CM3a showed negligible toxicity against mouse alveolar epithelial cells and Galleria mellonella larvae. CONCLUSION: Chromone derivatives CM3a has therapeutic potential as a safe and effective compound for the treatment of S. aureus infection.

The small molecule ZY-214-4 may reduce the virulence of Staphylococcus aureus by inhibiting pigment production.

BACKGROUND: In recent years, clinical Staphylococcus aureus isolates have become highly resistant to antibiotics, which has raised concerns about the ability to control infections by these organisms. The aim of this study was to clarify the effect of a new small molecule, ZY-214-4 (C19H11BrNO4), on S. aureus pigment production. RESULTS: At the concentration of 4 µg/mL, ZY-214-4 exerted a significant inhibitory effect on S. aureus pigment synthesis, without affecting its growth or inducing a toxic effect on the silkworm. An oxidant sensitivity test and a whole-blood killing test indicated that the S. aureus survival rate decreased significantly with ZY-214-4 treatment. Additionally, ZY-214-4 administration significantly reduced the expression of a pigment synthesis-related gene (crtM) and the superoxide dismutase genes (sodA) as determined by real-time quantitative polymerase chain reaction (RT-qPCR) analysis. ZY-214-4 treatment also improved the survival rate of S. aureus-infected silkworm larvae. CONCLUSIONS: The small molecule ZY-214-4 has potential for the prevention of S. aureus infections by reducing the virulence associated with this bacterium.

Antibiofilm Activity of Small-Molecule ZY-214-4 Against Staphylococcus aureus.

Staphylococcus aureus is the most important pathogenic bacteria in humans. As the resistance of S. aureus to existing antibiotics is increasing, there is an urgent need for new anti-infective drugs. S. aureus biofilms cause persistent infections and resist complete eradication with antibiotic therapy. The present study investigated the inhibitory effect of the novel small-molecule ZY-214-4 (C1 9H1 1BrNO4) on S. aureus biofilm formation. At a subinhibitory concentration (4 µg/ml), ZY-214-4 had no effect on the growth of S. aureus strains and also showed no cytotoxicity in human normal bronchial epithelial cells (Bease-2B). The results of a semi-quantitative biofilm test showed that ZY-214-4 prevented S. aureus biofilm formation, which was confirmed by scanning electron microscopy and confocal laser scanning microscopy. ZY-214-4 significantly suppressed the production of polysaccharide intercellular adhesion and prevented cell aggregation, and also inhibited the mRNA expression of icaA and other biofilm-related genes (eno, clfA/B, fnbB, fib, ebpS, psmα, and psmß) in clinical S. aureus isolates. Thus, at a subinhibitory concentration, ZY-214-4 inhibits biofilm formation by preventing cell aggregation, highlighting its clinical potential for preventing or treating S. aureus infections.

Ruthenium(II)-Catalyzed Direct C7-Selective Amidation of Indoles with Dioxazolones at Room Temperature.

A protocol for the preparation of 7-amido indoles via regioselective C-H bond functionalization has been first accomplished under Ru(II) catalysis. Indole derivatives and 4-aryl/heteroaryl/benzyl/alkyl dioxzaolines containing various substituents were applicable for this transformation, readily providing the amidated indoles in moderate to good yields. This novel process has many advantages, including good compatibility with diverse functional groups, broad substrate scopes, and mild reaction conditions. Deuteration studies and control experiments have been performed to understand the mechanism of this transformation.

Small-Molecule Compound SYG-180-2-2 to Effectively Prevent the Biofilm Formation of Methicillin-Resistant Staphylococcus aureus.

The resistance of methicillin-resistant Staphylococcus aureus (MRSA) has augmented due to the abuse of antibiotics, bringing about difficulties in the treatment of infection especially with the formation of biofilm. Thus, it is essential to develop antimicrobials. Here we synthesized a novel small-molecule compound, which we termed SYG-180-2-2 (C21H16N2OSe), that had antibiofilm activity. The aim of this study was to demonstrate the antibiofilm effect of SYG-180-2-2 against clinical MRSA isolates at a subinhibitory concentration (4 µg/ml). In this study, it was showed that significant suppression in biofilm formation occurred with SYG-180-2-2 treatment, the inhibition ranged between 65.0 and 85.2%. Subsequently, confocal laser scanning microscopy and a bacterial biofilm metabolism activity assay further demonstrated that SYG-180-2-2 could suppress biofilm. Additionally, SYG-180-2-2 reduced bacterial adhesion and polysaccharide intercellular adhesin (PIA) production. It was found that the expression of icaA and other biofilm-related genes were downregulated as evaluated by RT-qPCR. At the same time, icaR and codY were upregulated when biofilms were treated with SYG-180-2-2. Based on the above results, we speculate that SYG-180-2-2 inhibits the formation of biofilm by affecting cell adhesion and the expression of genes related to PIA production. Above all, SYG-180-2-2 had no toxic effects on human normal alveolar epithelial cells BEAS-2B. Collectively, the small-molecule compound SYG-180-2-2 is a safe and effective antibacterial agent for inhibiting MRSA biofilm.

Ruthenium(II)-Catalyzed C-H Activation of Chromones with Maleimides to Synthesize Succinimide/Maleimide-Containing Chromones.

An efficient route for the coupling of maleimides with chromones at the C5-position has been developed under Ru(II) catalysis. It could provide 1,4-addition products and oxidative Heck-type products by switching additives. Benzoic acid led to the formation of 1,4-addition products under solvent-free conditions, and silver acetate was promoted to the generation of oxidative Heck-type products. Various maleimides and chromones were suitable for this transformation, affording the desired products with good to excellent yields in a short reaction time. To understand the mechanism of this reaction, deuteration studies and control experiments have been performed.

Metal-free regioselective C-H chalcogenylation of coumarins/(hetero)arenes at ambient temperature.

A novel, practical and metal-free approach for the regioselective selenation of coumarins employing (bis(trifluoroacetoxy)iodo)benzene (PIFA) at room temperature is presented. The developed method is suitable for a wide substrate scope and affords 3-selenyl coumarins in good to excellent yields with high selectivity. A radical mechanism is proposed for this new transformation. Furthermore, the application of sulfenylation with coumarines and selenation with other (hetero)arenes in this transformation is successful.

Base promoted synthesis of novel indole-dithiocarbamate compounds as potential anti-inflammatory therapeutic agents for treatment of acute lung injury.

An efficient protocol for highly chemoselective introduction of dithiocarbamate groups to nitrogen position of indoles with bis(dialkylaminethiocarbonyl)disulfides was achieved by employing t-BuOK as a promoter. Based on this methodology, twenty nine novel indole-dithiocarbamate compounds were prepared in moderate to excellent yields at room temperature. All compounds were evaluated for their anti-inflammatory activity. Most of the compounds exhibited high potency on inhibiting the releasing of tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6). Four of them were found to suppress in vitro cytokine production in a dose-dependent manner with IC50 values in the nanomolar range. Additionally, 3-methyl-1H-indol-1-yl dimethylcarbamodithioate (3o) effectively ameliorated histopathological changes of lung tissues and attenuated lipopolysaccharides (LPS)-induced acute lung injury (ALI) in vivo. These data suggest that the new indole-dithiocarbamate derivatives could be particularly useful for further pharmaceutical development for the treatment of ALI.