The development of collagen hydrogels with tailored properties for improved applications in biomedicine represents an area of opportunity for materials science. The collagen can form semi-interpenetrated networks (semi-IPN) with various natural and/or synthetic polymers. This work aims the preparation of novel hydrogels generated from a collagen matrix cross-linked with polyurethane (PU), and the subsequent inclusion of polysaccharide chains to form semi-IPN systems with improved properties. The choice of polysaccharides for this purpose is related to their ability to modulate the biocompatibility and the antibacterial capacity in various biomedical strategies. The work
In this work, a series of phenacyl bromide derivatives was synthesized and employed as key intermediate for the synthesis of substituted imidazo [1,2-a]pyridines. First, phenacyl bromide molecules were obtained from the bromination reaction of acetophenones assisted by microwave irradiation, obtaining the products 4a-v in a 15 minutes reaction with yields in the range of 50% to 99%. Subsequently, the conjugation of these molecules with 2-aminopyridine conduced to the production of imidazo[1,2-a]pyridine derivatives (7a-v) in a 60-second reaction with yields of 24% to 99%. Improved yields were determined with respect to those obtained with more tedious methodologies like thermally and mechanically assisted routes. Intense luminescence emissions in the purple and blue regions of the electromagnetic spectra were observed under UV excitation according to the nature of the substituents. This environmentally friendly methodology is expected to constitute an important class of organic compounds for the development of biomarkers, photochemical sensors, and medicinal applications.
In this paper, we present a brief review of quinoid systems, focusing on their chemical synthesis over the last decade. We address not only major methods of synthesizing quinoids, but also their involvement in biological processes. We highlight their medical relevance and versatility, including antitumor, antiretroviral, or antihypertensive agents, properties determined by their various patterns of substitution.
Graphical AbstractKeywords Quinone Á Synthesis Á Cytotoxicity Á Natural products Á Pharmacology Á Redox Abbreviations 3a-HSD 3a-Hydroxysteroid dehydrogenase AIDS Acquired Immune Deficiency Syndrome AlnA Alnumycin A AlnB Alnumycin B BAQ Benzanthracene quinone (7,12-benzo[a] anthraquinone) BPQ Benzo[a]pyrene-7,8-dione CAN Ceric ammonium nitrate CC 50 50 % Cytotoxic concentration CDC25 Cell division cycle phosphatases Cyt Ferricytochrome d-A 2 0 -Deoxyadenosine DBU 1,8-Diazabicyclo[5.4.0]undec-7-ene DDQ 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone d-G, d-Guo 2'-Deoxyguanosine DMF N,N-dimethylformamide DMP Dess-Martin periodinane DMSO
The
development of practical and sensitive tools for detecting
phosphate deficiency could facilitate engineering approaches to enhance
crop yield and quality in phosphate-stressed environments, reducing
the misuse of nonrenewable fertilizers and their consequent ecological
impact. Herein, a 975 nm-activated method based on ZrO2:Yb,Er@ZrO2 core@shell upconversion nanoparticles is presented
for rapid visualization and determination of the phosphate ions in
aqueous solutions and extracts. At optimized thickness, the nondoped
ZrO2 shell not only enhances the emission of the ZrO2:Yb,Er but also provides an active surface for the intense
interaction with the phosphate group, allowing a “label-free”
determination that avoids the use of additional phosphate-recognizing
elements like ligands or antibodies. According to the experimental
evidence, the optical output of the ZrO2:Yb,Er@ZrO2 nanoparticles specifically matches with the absorption spectrum
of the fast green alimentary dye (FG) electrostatically attached to
the nanoparticle surface, activating the Förster resonance
energy transfer (FRET) and thereby the upconversion luminescence quenching.
Upon addition of the phosphate ions and the covalent interaction with
the ZrO2:Yb,Er@ZrO2–FG nanocomplex, the
FG is gradually removed, displaying a fast and reproducible “turn-on”
luminescence which allows measurements in a few minutes. This rapid
response is due to the stronger coordination between the ZrO2 shell and the phosphate compared to the FG molecules (−31.97
and −5.99 eV, respectively). The detection method was then
effectively modulated in a 20–1000 nM linear response range
without interfering effects of commonly coexisting ions, achieving
a detection limit up to 15 times lower than that obtained with the
conventionally used colorimetric methods.
An efficient and simple synthesis of novel and densely substituted N-benzyl-1H-pyrroles 6a-r is described by a 1,4-addition/isomerization/ring closure/demetalation cascade process of alkynyl Fischer carbene complexes 1a-f and 2a and α-imino glycine methyl esters 3a, b, d, g, h, and k promoted with LDA.
The unprecedented reaction of ketone‐containing aromatic pyridinium salts 3a‐e and alkynyl Fischer complexes 1a‐f proceeds via a mild domino process to provide 4,6‐disubstituted pyran‐2‐ones 5a‐k and 2,3,5‐trisubstituted furans 6a‐h (45‐97%). According of the results of isotopic labeling experiments, a mechanism involving an initial Michael addition appears to be the key step, obtaining a mesomeric structure responsible for the formation of both products.
<p>An alternative is presented for promoting a reaction with infrared irradiation to obtain different 4-aryl-3-cyano-5-ethoxycarbonyl-6-methyl-2-pyridone derivatives <strong>9a-k</strong>. The process was carried out with a green approach from the corresponding 4<em>H</em>-pyrans, using mild reaction conditions and infrared irradiation as the energy source. In the first stage, the reaction produced 1,2,3,4-tetrahydropyridin-2-one derivatives <strong>8a-k</strong>, followed by an oxidative step to afford the target molecules in good yields. The structure of products <strong>9a-k</strong> was confirmed by FT-IR, <sup>1</sup>H NMR and <sup>13</sup>C NMR spectroscopic techniques and X-ray diffraction. It was found that the efficiency of the reaction depends on the catalyst and the solvent, as well as on the aldehyde substituents.</p>
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