Construction of Eight-Membered Cyclic Diaryl Sulfides via Domino Reaction of Arynes with Thioaurone Analogues and DFT Study on the Reaction Mechanism

Eight-membered cyclic and [5,5]-bicyclic sulfides were synthesized via a domino reaction between thioaurone analogues and arynes. Density functional theory calculations were performed to elucidate the reaction mechanism, which involves the elementary steps of the [3 + 2] cycloaddition, 1,2-hydrogen shift, and C­(sp2)–S bond cleavage as well as the substituent effect

Proximity Binding-Triggered Assembly of Two MNAzymes for Catalyzed Release of G‑Quadruplex DNAzymes and an Ultrasensitive Homogeneous Bioassay of Platelet-Derived Growth Factor

When the target biorecognition-triggered assembly of two Mg2+-dependent DNAzymes (MNAzymes) is employed for dually catalytic release of peroxidase-mimicking G-quadruplex DNAzymes (G-DNAzymes), this work develops a novel homogeneous colorimetric method for an ultrasensitive bioassay of platelet-derived growth factor-BB (PDGF-BB). The first MNAzyme assembly is realized through a highly specific aptamer biorecognition-driven proximity ligation reaction. Its catalytic cleavage toward the two designed hairpin substrates not only releases a large amount of G-DNAzymes for colorimetric signal transduction but also enables the spontaneous assembly of another MNAzyme for signal amplification. This leads to the successful detection of PDGF-BB in a wide linear range from 2.0 pg mL–1 to 20 ng mL–1 with a very low detection down to 0.088 pg mL–1. As the whole reactions including aptamer biorecognitions, DNA hybridizations, and catalytic cleavages of MNAzymes are conducted in a homogeneous solution, this method has very simple manipulations and also has high repeatability. In addition, the high specificity of the aptamer biorecognition-triggered signal transduction decides the excellent selectivity of the method. This bioassay does not require an expensive instrument and nucleic acid labeling for signal readout or any nanomaterial, enzyme, or nuclease for signal amplification. Thus, it displays an extensive potential for clinical diagnostic applications

Phosphine-Catalyzed Domino Reaction of Thioaurones and Allenoate: Synthesis of Benzothiophene-Fused Dioxabicyclo[3.3.1]nonane Derivatives

The reaction of thioaurone derivatives with allenoate catalyzed by tris­(4-methoxyphenyl)­phosphane (P­(4-MeOC₆H₄)₃) resulted in a domino annulation reaction to produce a benzothiophene-fused bridged bicyclic ring, with 40–91% yields. The advantages of the methodology include diastereoselective formation of a bridged bicyclic ring in a single step, very mild reaction conditions, and success resulting from a broad functional group. The proposed mechanism was tested and supported by DFT calculations

Phosphine-Catalyzed Domino Reaction of Thioaurones and Allenoate: Synthesis of Benzothiophene-Fused Dioxabicyclo[3.3.1]nonane Derivatives

The reaction of thioaurone derivatives with allenoate catalyzed by tris­(4-methoxyphenyl)­phosphane (P­(4-MeOC₆H₄)₃) resulted in a domino annulation reaction to produce a benzothiophene-fused bridged bicyclic ring, with 40–91% yields. The advantages of the methodology include diastereoselective formation of a bridged bicyclic ring in a single step, very mild reaction conditions, and success resulting from a broad functional group. The proposed mechanism was tested and supported by DFT calculations

Antibiofilm Activity of Eugenol-Loaded Chitosan Coatings against Common Medical-Device-Contaminating Bacteria

The formation of pathogenic biofilms on medical devices is a major public health concern accounting for over 65% of healthcare-associated infections and causing high infection morbidity, mortality, and a great burden to patients and the healthcare system due to its resistance to treatment. In this study, we developed a chitosan-based antimicrobial coating with embedded mesoporous silica nanoparticles (MSNs) to load and deliver eugenol, an essential oil component, to inhibit the biofilm formation of common bacteria in medical-device-related infections. The eugenol-loaded MSNs were dispersed in a chitosan solution, which was then cross-linked with glutaraldehyde and drop-casted to obtain coatings. The MSNs and coatings were characterized by dynamic light scattering, Brunauer–Emmett–Teller analysis, attenuated-total-reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, 3D optical profilometry, and scanning electron microscopy. The release behavior of eugenol-loaded MSNs and coatings and the antibiofilm and antimicrobial activity of the coatings against adherent Staphylococcus aureus, methicillin-resistant S. aureus, and Pseudomonas aeruginosa were investigated. Eugenol was released from the MSNs and coatings in aqueous conditions in a controlled manner with an initial low release, followed by a peak release, a decrease, and a plateau. While the chitosan coatings alone or with unloaded MSNs demonstrated limited antimicrobial effects and still supported biofilm formation after 24 h, the coating containing eugenol not only reduced biofilm formation but also killed the majority of the attached bacteria. It also showed biocompatibility in indirect contact with NIH/3T3 fibroblasts and a high percentage of live cells in direct contact. However, further investigations into cell proliferation in direct contact are recommended. The findings indicated that the chitosan-based coating with eugenol-loaded MSNs could be developed into an effective strategy to inhibit biofilm formation on medical devices

Multilayer Nanostructured Porphyrin Arrays Constructed by Layer-by-Layer Self-Assembly

UV−vis absorption, atomic force microscopy (AFM), contact angle, and X-ray reflectivity experiments were performed on thin films deposited on crystalline silicon substrates as alternating layers of a porphyrin with anionic functionality, tetra-5,10,15,20-(4-sulfonatophenyl)porphine (TSPP) or the metalated version, Cu(II)TSPP, and the cationic polyelectrolyte, poly(diallyldimethylammonium chloride) (PDDA). The films were made by dipping in alternating aqueous solutions containing film components (layer-by-layer deposition). Modeling of the X-ray reflectivity data revealed differences in the films’ thickness depending on the method of film deposition. An unusual decrease in film thickness after each polyelectrolyte dip was also observed for films using TSSP. UV−vis measurements revealed that a similar amount of TSSP was included within films despite the method of formation. UV−vis measurements also revealed the presence of free-base, H-aggregate, and J-aggregate forms of the porphyrin after TSPP dipping, and the subsequent disappearance of the J-aggregate after dipping in the PDDA solution. A model of film formation was proposed on the basis of the concept of two different types of porphyrin aggregates being present after dipping in porphyrin solution. A layer of porphyrin molecules initially attach to the Si surface such that the planar molecules are arranged side by side as H-aggregates with an excess of J-aggregated material on top. The J-aggregate is then removed and replaced by a layer of PDDA. A change in contact angle of 14° was observed between porphyrin and polyelectrolyte layers due to the more hydrophobic nature of the polymer. The presence of the J-aggregate was confirmed in AFM images obtained from the porphyrin layer. Exposure of the films to solutions of alternating pHs of 10 and 1.8 resulted in reproducible switching of the UV−vis spectra, indicating a possible sensing application

Substrate-Controlled Domino Reactions of Crotonate-Derived Sulfur Ylides: Synthesis of Benzothiophene Derivatives

Substrate-controlled domino reactions between thioaurones or their analogues and crotonate-derived sulfur ylides were developed and produced a broad spectrum of benzothiophene-fused pyran derivatives, substituted chromene derivatives. In these reactions, crotonate-derived sulfur ylides acting as two-carbon synthons (α and β carbons or β and γ carbons) in annulation reactions are reported for the first time. These investigations nicely complement and expand previously studied reactions of crotonate-derived sulfur ylides. In addition, reaction mechanisms for these domino reactions are proposed, one of which is supported by DFT calculations

Substrate-Controlled Domino Reactions of Crotonate-Derived Sulfur Ylides: Synthesis of Benzothiophene Derivatives

Substrate-controlled domino reactions between thioaurones or their analogues and crotonate-derived sulfur ylides were developed and produced a broad spectrum of benzothiophene-fused pyran derivatives, substituted chromene derivatives. In these reactions, crotonate-derived sulfur ylides acting as two-carbon synthons (α and β carbons or β and γ carbons) in annulation reactions are reported for the first time. These investigations nicely complement and expand previously studied reactions of crotonate-derived sulfur ylides. In addition, reaction mechanisms for these domino reactions are proposed, one of which is supported by DFT calculations

Substrate-Controlled Domino Reactions of Crotonate-Derived Sulfur Ylides: Synthesis of Benzothiophene Derivatives

Substrate-controlled domino reactions between thioaurones or their analogues and crotonate-derived sulfur ylides were developed and produced a broad spectrum of benzothiophene-fused pyran derivatives, substituted chromene derivatives. In these reactions, crotonate-derived sulfur ylides acting as two-carbon synthons (α and β carbons or β and γ carbons) in annulation reactions are reported for the first time. These investigations nicely complement and expand previously studied reactions of crotonate-derived sulfur ylides. In addition, reaction mechanisms for these domino reactions are proposed, one of which is supported by DFT calculations

Substrate-Controlled Domino Reactions of Crotonate-Derived Sulfur Ylides: Synthesis of Benzothiophene Derivatives

Substrate-controlled domino reactions between thioaurones or their analogues and crotonate-derived sulfur ylides were developed and produced a broad spectrum of benzothiophene-fused pyran derivatives, substituted chromene derivatives. In these reactions, crotonate-derived sulfur ylides acting as two-carbon synthons (α and β carbons or β and γ carbons) in annulation reactions are reported for the first time. These investigations nicely complement and expand previously studied reactions of crotonate-derived sulfur ylides. In addition, reaction mechanisms for these domino reactions are proposed, one of which is supported by DFT calculations