Search Results (46)

The paper focuses on the synthesis and characterization of the spectroscopic and electrochemical properties of novel oxime esters. Six benzothiazole-based compounds were synthesized using a simple three-step procedure. The chemical structure of novel oxime esters was confirmed by Nuclear Magnetic Resonance spectroscopy (¹H and ¹³C NMR), as well as FT-IR spectroscopy and elemental analysis. The melting point of these compounds was also determined. The spectroscopic properties were studied in 10 solvents with different polarity. The fluorescence quantum yield was determined using Coumarin I as a reference. Additionally, the E_0→0 transition energy was determined. The electrochemical properties were determined using cyclic voltammetry. To justify their use as potential photoinitiators, preliminary studies were conducted to assess their utility in initiating light-induced polymerization. Based on the results, the proposed oxime esters are potential Type I photoinitiators for free radical polymerization. Full article

The development of new photoinitiators for photocurable systems has gained increasing interest in response to regulatory and environmental requirements, including efficient absorption in the UV/Vis range and reduced toxicity. Among emerging light-sensitive compounds, oxime esters have attracted growing attention as efficient radical photoinitiators. In this paper, five series of oxime esters based on carbazole, coumarin, carbazole–coumarin, phenothiazine, and triphenylamine scaffolds were described. Their high performance in photopolymerization processes was presented, demonstrating their ability to act as both type I and type II photoinitiators, as confirmed by high monomer conversion degrees. These data highlight oxime esters as versatile photoinitiating systems and provide a basis for further structural optimization aimed at improving water solubility and enabling comprehensive cytotoxicity assessment. Full article

Photoinitiators (PIs) are pivotal in enabling energy-efficient, spatiotemporally controlled photopolymerization for coatings. To address application-specific demands of coatings, diverse systems of Norrish-Type I (e.g., oxime esters, acylphosphine oxides) and Type II (e.g., onium salts, ketones) PIs have been engineered through systematic molecular design strategies. A comprehensive review necessitates highlighting recent achievements in designing PIs by various molecular engineering approaches. The π-conjugation extension, push–pull structures, and auxochrome incorporation boost strong and long-wavelength absorption; unimolecular PI systems with hydrogen-donor modifications improve reactivity and reduce oxygen inhibition; photobleaching via cleavable bonds and blocking conjugation enables colorless coating and deep-penetration curing; polymerizable macromolecular designs enhance migration resistance; organosilicon-functionalized structures optimize monomer compatibility. These strategies bridge molecular innovations with advanced applications in biomedical and deep-cured coatings. Full article

The current paper reports the asymmetric synthesis of a focused library of enantiostructured triacylglycerols (TAGs) constituting a potent drug of the NSAID type (ibuprofen or naproxen) along with a pure bioactive n-3 polyunsaturated fatty acid (PUFA) intended as a novel type of prodrug. In this second category, a TAG prodrug of the terminal sn-1 or sn-3 position of the glycerol skeleton is acylated with a single saturated medium-chain fatty acid (C6, C8, C10, or C12), and another with the drug entity; the PUFA (EPA or DHA) is located in the sn-2 position. This was accomplished by a six-step chemoenzymatic approach, two of which were promoted by a lipase, starting from enantiopure (R)- and (S)-solketals. The highly regioselective immobilized Candida antarctica lipase (CAL-B) played a crucial role in the regiocontrol of the synthesis. The most challenging key step involved the incorporation of the drugs that were activated as oxime esters by the lipase exclusively in the terminal position of glycerol that is protected as a benzyl ether. All combinations, a total of 32 such prodrug TAGs, were prepared, isolated, and fully characterized, along with 24 acylglycerol intermediates, obtained in very-high-to-excellent yields in the majority of cases. Full article

Fusidic acid is a translation inhibitor with activity against major Gram-positive bacterial pathogens such as S. aureus. However, its activity against Gram-negatives is poor based on an inability to access its cytoplasmic target in these organisms. Opportunities for functionalization of the fusidic acid scaffold to enhance activity against Gram-negative pathogens have not been explored. Using an activity-guided synthetic strategy, the tolerance of the tetracyclic natural product to derivatization at the A- and C-rings and its carboxylic acid side chain was explored with the goal of enhancing its activity spectrum and pharmacological properties. All side-chain carboxylic acid esters were inactive. Oxidation of the C-ring alcohol and oxime were not tolerated either. A number of esters of the A-ring alcohol retained modest activity against Gram-positive bacteria and were informative for future activity-guided studies. For the A-ring esters, differences in antibacterial activity relative to inhibitory activity in a ribosome in vitro translation assay suggested the possibility of a pro-druglike effect for the fusidic acid pyrazine-2-carboxylate. This study furthers the understanding of the activity of the fusidic acid scaffold against Gram-positive bacteria. These results suggest promise for future modification of the A-ring alcohol of fusidic acid in the advancement of its antibiotic properties. Full article

Reducing photoinitiator migration from photocured coatings remains a critical challenge, particularly for applications in food packaging and healthcare products. Here, we report a series of novel UV-LED sensitive oxime ester photoinitiators that possess self-anchoring ability through incorporating polymerizable double bonds into the coumarin chromophore. All photoinitiators exhibit strong absorption around 340 nm and efficient photolysis under 365 nm LED irradiation, showing good initiating efficiency in acrylates and thiol-ene formulations. Migration studies show that the incorporation of polymerizable groups at the oxime ester terminus reduces the migration rate of the residual photoinitiator from 81% to 16.3%, while introducing an allyl group into the coumarin structure further decreases it to 5% and potentially suppresses the migration of low-molecular-weight photolysis products. The dual-functionalized derivative achieves the lowest migration rate of 3%. This molecular design strategy provides an effective approach toward safe UV-LED curable coatings with minimal photoinitiator migration. Full article

Hydroxylation of aryl sulfonium salts could be realized by utilizing acetohydroxamic acid and oxime as hydroxylative agents in the presence of cesium carbonate as a base, leading to a variety of structurally diverse hydroxylated arenes in 47–95% yields. In addition, the reaction exhibited broad functionality tolerance, and a range of important functional groups (e.g., cyano, nitro, sulfonyl, formyl, keto, and ester) could be well amenable to the mild reaction conditions. Full article

A series of novel diterpene-type 1,3-aminoalcohols and their regioisomers have been synthesised from natural stevioside in a stereoselective manner. The key intermediate β-keto alcohol was prepared using Wagner–Meerwein rearrangement of the epoxide derived from steviol methyl ester. The primary aminoalcohol was formed via Raney-nickel-catalysed hydrogenation of an oxime, and a versatile library of aminoalcohols was synthesised using a Schiff base with the primary amines. The aminoalcohol regioisomers were prepared from the mesylate of the β-keto alcohols. The corresponding primary aminoalcohol was formed via the palladium-catalysed hydrogenation of hydroxyl-azide, and click reactions of the latter were also carried out. The new compounds were characterised using 1D- and 2D-NMR techniques and HRMS measurements. The in vitro investigations showed high inhibition of cell growth in human cancer cell lines (HeLa, SiHa, A2780, MCF-7 and MDA-MB-231) in the case of naphthalic N-substituted derivatives. The antiproliferative effects were assayed using the MTT method. Full article

Bacillus species produce different classes of antimicrobial and antioxidant substances: peptides or proteins with different structural compositions and molecular masses and a broad range of volatile organic compounds (VOCs), some of which may serve as biomarkers for microorganism identification. The aim of this study is the identification of biologically active compounds synthesized by five Bacillus species using gas chromatography coupled to mass spectrometry (GC–MS). The current study profoundly enhances the knowledge of antibacterial and antioxidant metabolites ensuring the unambiguous identification of VOCs produced by some Bacillus species, which were isolated from vegetable samples of potato, carrot, and tomato. Phylogenetic and biochemical studies were used to identify the bacterial isolates after culturing. Phylogenetic analysis proved that five bacterial isolates BSS12, BSS13, BSS16, BSS21, and BSS25 showed 99% nucleotide sequence similarities with Bacillus safensis AS-08, Bacillus cereus WAB2133, Bacillus acidiproducens NiuFun, Bacillus toyonesis FORT 102, and Bacillus thuringiensis F3, respectively. The crude extract was prepared from bacterial isolates to assess the antibiotic resistance potency and the antimicrobial potential against various targeted multidrug-resistant strains, including yeast strains such as Candida albicans, Candida krusei, and bacterial strains of Enterococcus hirae, Escherichia coli, Klebsiella aerogenes, Klebsiella pneumoniae, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus group B, Streptococcus mutans, Shigella sonnei, Salmonella enteritidis, Serratia marcescens, Pseudomonas aeruginosa, and Proteus vulgaris. GC–MS analysis of bacterial strains found that VOCs from Bacillus species come in a variety of chemical forms, such as ketones, alcohols, terpenoids, alkenes, etc. Overall, 69 volatile organic compounds were identified from five Bacillus species, and all five were found to share different chemical classes of volatile organic components, which have a variety of pharmacological applications. However, eight antibacterial compounds with different concentrations were commonly found in all five species: acetoin, acetic acid, butanoic acid, 2-methyl-, oxime-, methoxy-phenyl, phenol, 1,2-benzenedicarboxylic acid, bis(2-methylpropyl) ester, nonanoic acid, and hexadecanoic acid, methyl. The present study has demonstrated that bacterial isolates BSS25, BSS21, and BSS16 display potent inhibitory effects against Candida albicans, while BSS25, BSS21, and BSS13 exhibit the ability to restrain the growth and activity of Candida krusei. Notably, BSS25 and BSS21 are the only isolates that demonstrate substantial inhibitory activity against Klebsiella aerogenes. This disparity in inhibitory effects could be attributed to the higher concentrations of acetoin in BSS25 and BSS21, whereas BSS16 and BSS13 have relatively elevated levels of butanoic acid, 2-methyl-. Certainly, the presence of acetoin and butanoic acid, 2-methyl-, contributes to the enhanced antibacterial potential of these bacterial strains, in conjunction with other organic volatile compounds and peptides, among other factors. The biology and physiology of Bacillus can be better understood using these results, which can also be used to create novel biotechnological procedures and applications. Moreover, because of its exceptional ability to synthesize and produce a variety of different antibacterial compounds, Bacillus species can serve as natural and universal carriers for antibiotic compounds in the form of probiotic cultures and strains to fight different pathogens, including mycobacteria. Full article

Sour bamboo shoot is a Chinese fermented vegetable with unique flavors and is favored by local consumers. In this study, at different fermentation times, the texture of bamboo shoots and the changing rules of pH, titratable acid (TA), reduced sugar, and nitrite in bamboo shoot fermentation broth were explored. Headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) and orthogonal partial least squares discriminant analysis (OPLS-DA) were used to investigate the dominant aroma compounds. 16S rRNA high-throughput sequencing technology (HTS) was employed to investigate the core microbial communities. The results show that the chewiness, fracturability, hardness, and pH decreased, while TA increased during the 60-day fermentation. The contents of reducing sugar and nitrite peaked on the 14th day of fermentation and then decreased. A total of 80 volatile compounds were detected during sour bamboo shoot fermentation, with 2,4-Di-tert-butylphenol having the highest concentration. Among them, 12 volatile compounds (VIP ≥ 1) were identified as characteristic aroma substances of sour bamboo shoots. The dominant bacterial phyla in sour bamboo shoots were Firmicutes and Proteobacteria, while Bacillus and Acinetobacter were the dominant genus. Correlation analysis showed that Firmicutes exhibited a positive correlation with 3,6-Nonadien-1-ol, (E,Z)-, Oxalic acid, isobutyl hexyl ester, and (-)-O-Acetylmalic anhydride, whereas Bacillus exhibited a negative correlation with Silanediol, dimethyl-, and Oxime-, methoxy-phenyl-. A detailed picture of the microbial community of fermented bamboo shoots has been provided by this study, and it may provide insight into the Chinese traditional fermented vegetable microbial structure. Full article

The carbon–nitrogen bond is one of the most prevalent chemical bonds in natural and artificial molecules, as many naturally existing organic molecules, pharmaceuticals, agrochemicals, and functional materials contain at least one nitrogen atom. Radical decarboxylative carbon–nitrogen bond formation from readily available carboxylic acids and their derivatives has emerged as an attractive and valuable tool in modern synthetic chemistry. The promising achievements in this research topic have been demonstrated via utilizing this strategy in the synthesis of complex natural products. In this review, we will cover carbon–nitrogen bond formation via radical decarboxylation of carboxylic acids, Barton esters, MPDOC esters, N–hydroxyphthalimide esters (NHP esters), oxime esters, aryliodine(III) dicarboxylates, and others, respectively. This review aims to bring readers a comprehensive survey of the development in this rapidly expanding field. We hope that this review will emphasize the knowledge, highlight the proposed mechanisms, and further disclose the fascinating features in modern synthetic applications. Full article

Two series of novel sophoridine derivatives were designed, synthesized, and evaluated for their anti-mosquito activity. SOP-2g, SOP-2q, and SOP-2r exhibited potential larvicidal activity against Aedes albopictus larva with LC₅₀ values of 330.98, 430.53, and 411.09 ppm, respectively. Analysis of structure–activity relationships indicated that the oxime ester group was beneficial for improving the larvicidal biological activity, whereas the long-chain aliphatic group and fused-ring group were introduced. Furthermore, the larvicidal mechanism was also investigated based on the inhibition assay of acetylcholinesterase (AChE) and the morphological observation of dead larva treated with derivatives. Results indicated that the AChE inhibitory activity of the preferred three derivatives were 63.16%, 46.67%, and 35.11%, respectively, at 250 ppm concentration. Additionally, morphological evidence demonstrated that SOP-2q and SOP-2r induced changes in the larva’s intestinal cavity, caudal gill, and tail, thereby displaying larvicidal action against Ae. albopictus together with AChE inhibition. Therefore, this study implied that sophoridine and its novel derivatives could be used to control the population of mosquito larva, which may also be effective alkaloids to reduce the mosquito population density. Full article

The synthetic strategies of oxime derivatives participating in radical-type reactions have been rapidly developed in the last few decades. Among them, the N–O bond cleavage of oxime esters leading to formation of nitrogen-centered radicals triggers adjacent C–C bond cleavage to produce carbon-centered free radicals, which has been virtually used in organic synthesis in recent years. Herein, we summarized the radical reactions involving oxime N–O bond and C–C bond cleavage through this special reaction form, including those from acyl oxime ester derivatives and cyclic ketoxime ester derivatives. These contents were systematically classified according to different reaction types. In this review, the free radical reactions involving acyl oxime esters and cyclic ketoxime esters after 2021 were included, with emphasis on the substrate scope and reaction mechanism. Full article

Photopolymerization is an active research field enabling to polymerize in greener conditions than that performed with traditional thermal polymerization. At present, a great deal of effort is devoted to developing visible light photoinitiating systems. Indeed, the traditional UV photoinitiating systems are currently the focus of numerous safety concerns so alternatives to UV light are being actively researched. However, visible light photons are less energetic than UV photons so the reactivity of the photoinitiating systems should be improved to address this issue. In this field, furane constitutes an interesting candidate for the design of photocatalysts of polymerization due to its low cost and its easy chemical modification. In this review, an overview concerning the design of furane-based photoinitiators is provided. Comparisons with reference systems are also established to demonstrate evidence of the interest of these photoinitiators in innovative structures. Full article

Nanomaterials have been extensively used in several applications in the past few decades related to biomedicine and healthcare. Among them, nanogels (NGs) have emerged as an important nanoplatform with the properties of both hydrogels and nanoparticles for the controlled/sustained delivery of chemo drugs, nucleic acids, or other bioactive molecules for therapeutic or diagnostic purposes. In the recent past, significant research efforts have been invested in synthesizing NGs through various synthetic methodologies such as free radical polymerization, reversible addition-fragmentation chain-transfer method (RAFT) and atom transfer radical polymerization (ATRP), as well as emulsion techniques. With further polymeric functionalizations using activated esters, thiol–ene/yne processes, imines/oximes formation, cycloadditions, nucleophilic addition reactions of isocyanates, ring-opening, and multicomponent reactions were used to obtain functionalized NGs for targeted delivery of drug and other compounds. NGs are particularly intriguing for use in the areas of diagnosis, analytics, and biomedicine due to their nanodimensionality, material characteristics, physiological stability, tunable multi-functionality, and biocompatibility. Numerous NGs with a wide range of functionalities and various external/internal stimuli-responsive modalities have been possible with novel synthetic reliable methodologies. Such continuous development of innovative, intelligent materials with novel characteristics is crucial for nanomedicine for next-generation biomedical applications. This paper reviews the synthesis and various functionalization strategies of NGs with a focus on the recent advances in different biomedical applications of these surface modified/functionalized single-/dual-/multi-responsive NGs, with various active targeting moieties, in the fields of cancer theranostics, immunotherapy, antimicrobial/antiviral, antigen presentation for the vaccine, sensing, wound healing, thrombolysis, tissue engineering, and regenerative medicine. Full article