Search Results (75)

This study aims to develop a robust and reproducible method for fabricating efficient ultrathin antifouling coatings on gold surfaces by leveraging hydroxylation-based surface modifications. An ultrathin antifouling coating of a monoethylene glycol silane derivative, known to reduce fouling by at least 90% on flat hydroxylated surfaces, was successfully replicated on flat gold (reducing fouling by ~75%) by hydroxylating its surface with β-mercaptoethanol. This tandem coating contains the monoethylene glycol silane layer on top of the β-mercaptoethanol on the gold. Characterization was performed using contact angle goniometry, atomic force microscopy, x-ray photoelectron spectroscopy, and antifouling measurements. The results from these techniques, consistent with the literature, confirmed the successful and reproducible application of the tandem coating. Through heterogeneities, including defects and incomplete coverage, the AFM data revealed distinct visible layers of the tandem coating. The direct application of monoethylene glycol silane onto gold resulted in superior antifouling performance (88% reduction), demonstrating that direct silylation exploits pre-existing oxygen-containing species on the gold surface for a more effective antifouling layer. These findings offer a scalable approach for engineering antifouling coatings on gold substrates, with potential applications in biosensing and implantable device antifouling technologies. Full article

Background/Objectives: While various nucleoside and nucleotide analogs have been approved as anticancer and antiviral drugs, their limitations, including low bioavailability and chemotherapeutic resistance, encourage the development of novel structures. In this context, and motivated by our previous findings on bioactive 3′-O-substituted xylofuranosyl nucleosides and 5-guanidine xylofuranose derivatives, we present herein the synthesis and biological evaluation of 5′-guanidino furanosyl nucleosides comprising 6-chloropurine and uracil moieties and a 3-O-benzyl xylofuranosyl unit. Methods: The synthetic methodology was based on the N-glycosylation of a 5-azido 3-O-benzyl xylofuranosyl acetate donor with the silylated nucleobase and a subsequent one-pot sequential two-step protocol involving Staudinger reduction of the thus-obtained 5-azido uracil and N⁷/N⁹-linked purine nucleosides followed by guanidinylation with N,N′-bis(tert-butoxycarbonyl)-N′′-triflylguanidine. The molecules were evaluated for their anticancer and anti-neurodegenerative diseases potential. Results: 5′-Guanidino 6-chloropurine nucleosides revealed dual anticancer and butyrylcholinesterase (BChE)-inhibitory effects. Both N⁹/N⁷-linked nucleosides exhibited mixed-type and selective submicromolar/micromolar BChE inhibiton. The N⁹ regioisomer was the best inhibitor (K_i/K_i′ = 0.89 μM/2.96 μM), while showing low cytotoxicity to FL83B hepatocytes and no cytotoxicity to human neuroblastoma cells (SH-SY5Y). Moreover, the N⁹-linked nucleoside exhibited selective cytotoxicity to prostate cancer cells (DU-145; IC₅₀ = 27.63 μM), while its N⁷ regioisomer was active against all cancer cells tested [DU-145, IC₅₀ = 24.48 μM; colorectal adenocarcinoma (HCT-15, IC₅₀ = 64.07 μM); and breast adenocarcinoma (MCF-7, IC₅₀ = 43.67 μM)]. In turn, the 5′-guanidino uracil nucleoside displayed selective cytotoxicity to HCT-15 cells (IC₅₀ = 76.02 μM) and also showed neuroprotective potential in a Parkinson’s disease SH-SY5Y cells’ damage model. The active molecules exhibited IC₅₀ values close to or lower than those of standard drugs, and comparable, or not significant, neuro- and hepatotoxicity. Conclusions: These findings demonstrate the interest of combining guanidine moieties with nucleoside frameworks towards the search for new therapeutic agents. Full article

In the field of medicinal chemistry, the introduction of silylated groups is an important strategy to alter the activity, selectivity, and pharmacokinetics of compounds based on the diverse traits of silicon, including atomic size, electronegativity, and hydrophobicity. The hydroxy group on C-9 or C-9 and C-10 of hydroxystearic acids have been functionalized as t-butyl dimethyl silyl ether. The target compounds have been fully characterized and tested for in vitro cytotoxicity in tumor cells HT29, HCT116, CaCo2, HeLa, MCF7, U2OS, and Jurkat J6 and normal I407 cells. In particular, the silyl derivative of (R)-9-hydroxystearic acid was more active in colon cancer cells. Analyses of cell proliferation, oxidative cell status, histones post-translational modifications, protein phosphorylation, gene expression, and DNA damage were performed to obtain information on the antitumor properties of the new molecules in comparison with the unmodified (R)-9-hydroxystearic acid’s previously studied effects. Our results suggest that the incorporation of a silyl functionality may be a useful tool for the structural development of new pharmaceutically active compounds against colon cancer. Full article

The current research is devoted to integrating naturally renewable cardanol derivatives into one-component silyl-terminated-polyether-based prepolymer systems to improve climatic resistance and obtain materials with versatile mechanical properties that could be significant to various sectors of the economy. Various cardanol-type products are used in industries that require high climatic resistance, and thus combining cardanol with commercially available silyl-terminated polyether prepolymers would improve its material climatic resistance, maintaining its market and application value as well as improving material sustainability. The results obtained in this work show that depending on how the cardanol prepolymer Ultra Lite 513 is modified, it is possible to increase the elasticity (670%) or tensile strength (104%) of the material as well as significantly increase the climatic resistance of the material, thus improving the quality and sustainability of the adhesive compared to existing silyl-terminated-prepolymer-based adhesives on the market. Full article

Experimentally accessible stable polyhedral clusters of gallium differ from clusters of its lighter homologue boron by having sterically demanding external groups such as tBu₃Si, (Me₃Si)₃Si, (Me₃Si)₃C, (Me₃Si)₂N, and fluorenyl. This restricts closo deltahedral [Ga_nR_n]^z gallane chemistry to octahedral derivatives such as Ga₆R₆²⁻ (R = SiBuPh₂, SiBu^t₃) and Ga₆R₆ (R = SiMe(SiMe₃)₂) in which the bulky external silyl groups are spread out because of the relatively high local curvature of the degree 4 vertices of the central Ga₆ octahedron. The structures of larger gallium clusters are based on alternatives to closo deltahedra having exclusively high local curvature degree 4 vertices such as the 8-vertex square antiprismatic Ga₈R₈ (R = fluorenyl) or, more commonly, larger polyhedra or fused polyhedra with some bare gallium vertices. Some of the larger gallium clusters can be considered to be spherically aromatic systems with closed shells according to the jellium model. Examples include [Ga₁₃(SitBu₃)₆]⁻ with 8 cluster electrons corresponding to a filled 1S²1P⁶ shell as well as [Ga@Ga₁₈{C(SiMe₃)₃}₆]⁻ with 52 cluster electrons, Ga₂₂{E(SiMe₃)₃]₈, (E = C, Si) and Ga@Ga₁₁{GaN(SiMe₃)₂}₁₁ with 58 skeletal electrons, and [Ga₂₆{Si(SiMe₃)₃}₈]²⁻ with 72 cluster electrons. The 10-vertex species Ga₁₀{Si(SiMe₃)₃}₆, [Ga₁₀(SitBu₃)₆]⁻, and Ga₁₀(SitBu₃)₆ have structures consisting of a fusion of two polyhedra sharing bare gallium vertices with skeletal electron counts, suggesting a multicenter core bond in each of the two polyhedral cavities. Full article

Silylation is a widely used derivatization technique for the gas chromatographic analysis of benzodiazepines, a class of psychoactive drugs commonly encountered in forensic and biological samples. This study investigated the optimal experimental conditions for the silylation of benzodiazepines using N,O-bis(trimethylsilyl)trifluoroacetamide containing 1% trimethylchlorosilane (BSTFA + 1% TMCS), a widely employed silylating agent. Ten structurally different benzodiazepines, including variations within the classic 1,4-benzodiazepine core and triazolo ring derivatives, were selected to address the effect of structural diversity on silylation. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used to optimize the silylation of benzodiazepines by means of GC-MS analysis. PCA identified key experimental factors influencing silylation efficiency and distinct response patterns of different benzodiazepines. HCA further categorized the benzodiazepines based on their silylation behavior, highlighting the need for tailored derivatization strategies. The results indicated that the BSTFA + 1% TMCS concentration and solvent volume were pivotal for achieving high silylation efficiency, whereas the temperature, reaction time, and catalyst were less critical. The optimized method was successfully applied to 30 real forensic samples, demonstrating its efficacy in detecting and identifying various benzodiazepines, including designer drugs like etizolam. This study provides a foundation for improving drug detection methodologies in forensic toxicology and provides useful insights into the dynamics of benzodiazepine silylation and the use of individualized analysis parameters. Full article

This study examined the chemoselectivity and diastereoselectivity of silyl nitronate alkenyn-nitroethers in Intramolecular Silyl Nitronate Cycloadditions (ISNCs) to produce isoxazole derivatives with interesting medicinal properties. These reactions resulted in the formation of either dihydrofuro[3,4-c]isoxazolines/isoxazolidines and/or alkynyl moieties attached to 2,5-dihydrofuryl carbonyls. This study also discerned the diastereoselectivities of the resulting cyclic adducts and compared them to previous findings. The reactions were also investigated with Spartan molecular modeling computations to aid in the understanding of any displayed chemo- and/or stereoselectivity. These [3+2]-cycloaddition reactions demonstrated excellent to complete chemospecificity. The cycloadditions also demonstrated remarkable diastereospecificity in that each diastereomer of the nitroethers resulted in the formation of only one of four possible diastereomeric outcomes. The stereochemistry of the major diastereomers did not agree with previously published findings. Full article

Alkynylallenes offer the varied reactivity patterns of two different multiple bond linkages either separately or in concert. Initially, a short overview of their syntheses, structures, rearrangement mechanisms and synthetic utility, especially when treated with transition metal reagents such as gold(I), silver(I), platinum metals or metal carbonyls, is presented. Subsequently, we focus on the particular case of 1,2-dien-5-ynes (propargylallenes), whereby the shortness of the single atom bridge, and the consequent proximity of the allenyl and alkynyl moieties, facilitates metal-mediated interactions between them. It is shown how these metals can coordinate to either the alkyne or the allene fragment, thus leading to different cyclisation or rearrangement products, dependent also on whether it is the proximal or the distal double bond of the allene that participates in the reaction. Dimerisation of bromo-substituted fluorenylideneallenes bearing silyl or ferrocenyl substituents can occur in either head-to-head or head-to-tail fashion, thereby yielding propargylallene derivatives that undergo unexpected and novel rearrangements, including the formation of molecules possessing unusually long carbon–carbon single bonds. Fluorenyl-bearing propargylallenes react with silver nitrate or iron carbonyl to form novel organic polycyclic systems. Finally, suggestions are offered for future advances in the area. Full article

Background: Retinitis pigmentosa (RP), the leading cause of inherited blindness in adults, is marked by the progressive degeneration of rod photoreceptors in the retina. While gene therapy has shown promise in treating RP in patients with specific mutations, no effective therapies currently exist for the majority of patients with diverse genetic backgrounds. Additionally, no intervention can yet prevent or delay photoreceptor loss across the broader RP patient population. Resveratrol (RES), a naturally occurring polyphenol, has shown cytoprotective effects in various neurodegenerative disease models; however, its therapeutic potential is limited by low bioavailability. Methods: In this study, we synthesized novel RES derivatives and assessed their retinoprotective effects in a murine model of RP (rd10 mice). Results: Among these derivatives, piceid octanoate (PIC-OCT) significantly delayed photoreceptor degeneration in the RP model, demonstrating superior efficacy compared to RES. Conclusions: PIC-OCT shows strong potential as a leading candidate for developing new therapeutic strategies for RP. Full article

Protection of the hydroxy group in monoterpenoids borneol and isoborneol with various silyl-protective groups containing a different number of phenyl groups enabled complete assignments of the ¹H chemical shifts. In particular, a wider range of the protons in isoborneol and its silyl-protected derivatives were influenced than those in borneol and its silyl-protected derivatives, which is likely to be due to the anisotropic effects from the phenyl groups. Understanding these effects allows for the interpretation of the ¹H NMR spectra and provides information about how silyl-protecting groups affect these spectra. Full article

Selenium-containing molecules represent a valuable class of compounds with a variety of applications in chemical and biological fields. Selenated reagents are used as intermediates to introduce functional groups (e.g., double bonds) onto different substrates or in the synthesis of various selenated derivatives. Among the variety of selenium-containing reagents, silyl selenides are frequently used to transfer a selenated moiety due to the smooth functionalization of the Se-Si bond, which allows for the generation of selenium nucleophilic species under mild conditions. While the use of the analogous sulfur nucleophiles, namely silyl sulfides, has been widely explored, a relatively limited number of reports on selenosilanes have been provided. This contribution will focus on the application of selenosilanes as nucleophiles in a variety of organic transformations, as well as under radical and redox conditions. The use of silyl selenides to prepare metal complexes and as selenium precursors of materials for atomic layer deposition will also be discussed. Full article

Nitrilotris(methylenephenylphosphinic) acid (NTPAH₃) was silylated using hexamethyldisilazane to produce the tris(trimethylsilyl) derivative NTPA(SiMe₃)₃. From the latter, upon alcoholysis in chloroform, NTPAH₃ could be recovered. Thus, a new modification of that phosphinic acid formed. Meanwhile, NTPAH₃ synthesized in aqueous hydrochloric acid crystallized in the space group P3c1 with the formation of O-H⋅⋅⋅O H-bonded networks (NTPAH₃^P), in chloroform crystals in the space group R3c formed (NTPAH₃^M), the constituents of which are individual molecules with exclusively intramolecular O-H⋅⋅⋅O hydrogen bonds. Both solids, NTPAH₃^P and NTPAH₃^M, were characterized by single-crystal X-ray diffraction, multi-nuclear (¹H, ¹³C, ³¹P) solid-state NMR spectroscopy, and IR spectroscopy as well as quantum chemical calculations (both of their individual constituents as isolated molecules as well as in the periodic crystal environment). In spite of the different stabilities of their constituting molecular conformers, the different crystal packing interactions rendered the modifications of NTPAH₃^P and NTPAH₃^M similarly stable. In both solids, the protons of the acid are engaged in cyclic (O=P–O–H)₃ H-bond trimers. Thus, the trialkylamine N atom of this compound is not protonated. IR and ¹H NMR spectroscopy of these solids indicated stronger H-bonds in the (O=P–O–H)₃ H-bond trimers of NTPAH₃^M over those in NTPAH₃^P. Full article

In this study, we report the preparation of neutral Au(I), Ag(I), and Cu(I) derivatives [(hyp)₂P₇M]_n (M = Au, n = 2; M = Ag, Cu, n = 4) of a heptaphospha-nortricyclane cage. Synthesis was conducted via a halodesilylation route under the cleavage of the sterically less shielded trimethyl silyl group, starting from the heteroleptic cage (hyp)₂(tms)P₇. All coinage metal derivatives exhibit short metal–metal distances of 2.9542(2) Å (Au), 2.8833(6) Å (Ag), and 2.654(1) Å (Cu), respectively. The same synthetic methodology was also applied for the preparation of a zinc derivative, [{(hyp)₂P₇}₂Zn]*Et₂O, for which full multinuclear NMR characterization could be conducted. Full article

The aromatic character of silolyl and germolyl anions markedly depends on the substituents in the 2,5-positions; carbon-substituted derivatives are nonaromatic, whereas silyl-substituted ones tend to exhibit an aromatic character. However, only carbon-substituted derivatives have been reported for stannolyl anions. In this study, we present the synthesis and structure of a 2,5-disilylated stannolyl anion. Transmetalation of a 2,5-disilyl-1-zirconacyclopentadiene with SnCl₄ gave a dichlorostannole 1, which reacted with potassium tris(trimethylsilyl)silanide to introduce a bulky silyl group on the tin atom. Reduction of the 1-chloro-1-silylstannole 2 with lithium generated the lithium salt of the desired stannolyl anion 3 that adopts an η¹-coordination to the lithium atom. We concluded that the stannolyl anion 3 is nonaromatic based on the pyramidalized tin center and the C–C bond alternation in the five-membered ring as well as the NMR properties. Full article

Cholesterol present in food of animal origin is a precursor of oxysterols (COPs), whose high intake through diet can be associated with health implications. Evaluation of the content of these contaminants in food is associated with many analytical problems. This work presents a GC-TOF/MS method for the simultaneous determination of squalene, cholesterol and seven COPs (7-ketocholesterol, 7α-hydroxycholesterol, 7β-hydroxycholesterol, 25-hydroxycholesterol, 5,6α-epoxycholesterol, 5,6β-epoxycholesterol, cholestanetriol). The sample preparation procedure includes such steps as saponification, extraction and silylation. The method is characterized by high sensitivity (limit of quantification, 0.02–0.25 ng mL⁻¹ for instrument, 30–375 μg kg of sample), repeatability (RSD 2.3–6.2%) and a wide linearity range for each tested compound. The method has been tested on eight different animal-origin products. The COP to cholesterol content ratio in most products is about 1%, but the profile of cholesterol derivatives differs widely (α = 0.01). In all the samples, 7-ketocholesterol is the dominant oxysterol, accounting for 31–67% of the total COPs level. The levels of the other COPs range between 0% and 21%. In none of the examined products are cholestanetriol and 25-hydroxycholesterol present. The amount of squalene, which potentially may inhibit the formation of COPs in food, ranges from 2 to 57 mg kg⁻¹. Full article