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  • Open access
  • 56 Reads
Density, Speed of Sound, and Refractive Index of Polyvinylpyrrolidone-K60 + N, N- Dimethylformamide / Dimethylacetamide Binary Mixtures at different Temperatures
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Densities, speeds of sound, and refractive indices for the binary mixtures of Polyvinylpyrrolidone-K60 in N, N- Dimethylformamide, and in Dimethylacetamide solvents have been measured as a function of the different concentrations of the polymer at (298.15, 308.15, and 318.15) K temperatures. The thermo physical parameters such as the acoustic impedance, adiabatic compressibility, specific refraction, space-filling factor, and relaxation strength have been evaluated over the entire composition range the concentrations and temperatures based on the experimental data. The results are discussed and interpreted by comparison between the both studied systems.

  • Open access
  • 64 Reads
Semisynthesis of 6β-acetoxyvouacapane derivates via the Ugi-azide multicomponent reaction

A semisynthesis of 6β-acetoxyvouacapane-1,5-disusbtituted tetrazoles derivates from the leaves of Caesalpinia platyloba by using the Ugi-azide multicomponent reaction as a key step reaction is described. To our knowledge, this is the first report where a non-natural product such as 1,5-disusbtituted tetrazole is linked to a natural product or derivate of a natural product, and beyond the biological relevance that the target molecules present, this work contributes to the area of natural products as well as multicomponent reactions

  • Open access
  • 30 Reads
Use of oxidative coupling strategy as a means to increase in vitro antioxidant activity of vanillin derivatives

The aim of this study was to investigate the antioxidant properties in vitro of three different vanillic dimers (Compounds 1a-c). They were synthesized through an oxidative coupling strategy in good yields. The targeted compounds were found to be highly active for the total antioxidant assay, as well as for the lipid peroxidation test. All investigated compounds exhibited superior or comparable antioxidant capacity in comparison to precursor vanillin, proving that the oxidative coupling is a great strategy to increase antioxidant behavior of vanillin derivatives

  • Open access
  • 39 Reads
Pyrene-4,5,9,10-tetrachalcogenone derivatives: a computational study of their potential use as materials for batteries

The family of polycyclic aromatic hydrocarbons (PAHs) are versatile building blocks for conjugated materials and can be applied in molecular electronics. Pyrenes are known as the best organic chromophores, and pyrene itself is known as an electron donor, being the properties of pyrene-4,5,9,10-tetraone extensively reported. Likewise quinones are promising electrode materials for lithium-ion batteries (LIBs), but their structure–electrochemical property relationship still remains unclear. The aim of this theoretical study is to disentangle the structural influence on the electrochemical properties of chalcogen derivatives of pyrene-4,5,9,10-tetraone. The calculations were performed with the hybrid functional B3LYP using LANL2DZ basis for the following compounds: pyrene-4,5,9,10-tetrathione, pyrene-4,5,9,10-tetraselenone and pyrene-4,5,9,10-tetratellurone and comparing the results with those of pyrene-4,5,9,10-tetraone. The results obtained indicate that the sulfur derivative is a suitable candidate to carry out experimental studies, since although those of selenium and tellurium compounds also present better prospects than 4,5,9,10-tetraoxopyrene, they require the improvement of available synthetic techniques or even the discovery of new ones.

  • Open access
  • 55 Reads
Analysis of the electron density of a water molecule encapsulated by two cholic acid residues

Cholic acid is a trihydroxy bile acid having three hydroxy groups at C-3, C-7 and C-12 carbon atoms, two methyl groups at C-10 and C-13 carbon atoms of the steroid nucleus, and a carboxylic group at C24 of the side alkyl chain. The distance between the oxygen atoms linked to C-7 and C-12 (~4.5 Å), perfectly matches with the edge distance between oxygen atoms in ice. This lead to a design of a cholic acid dimer in which one water molecule is encapsulated between two cholic residues, resembling an ice-like structure. The water molecule participates in four hydrogen bonds, the water simultaneously being acceptor from the O12-H hydroxy groups (two bonds with lengths of 2.177 Å and 2.114 Å) and the donor towards the O-7-H groups (two bonds with lengths of 1.866 Å and 1.920 Å).

It this communication we present the application of the “atoms in molecules” (AIM) theory to the former tetrahedral structure. The analysis of the calculated electron denstity, is performed through its gradient vector, and the Laplacian. The calculation of the complexation energy used correction of the basis set superposition error (BSSE) with the counterpoise method implemented in Gaussian 19. Laplacian of electronic density and critical points (AIM) were calculated using Multiwfn_3.8_dev software. As expected, four critical (3,-1) points located in the HO bond paths were identified. All calculated parameters are in concordance with those of similar systems and obey the proposed criteria for hydrogen bonds. The total energy for the interaction is -12.67 kcal/mol and is analyzed through proposed energy/electron density equations.

  • Open access
  • 38 Reads
Synthesis and Evaluation of an Azo Dye for the Chromogenic Detection of Metal Cations

Great efforts have been focused on developing selective and sensitive signaling probes for detecting metal ions because they are indispensable in most biological processes, but in abnormal levels these analytes may cause severe effects on human health and the environment. Among chromogenic probes, azo dyes are widely used as optical chemosensors due to their ease of synthesis, structural variability and color recognition with naked eye. A very popular azo dye is 4-[[4′-(N,N-dimethylamino)phenyl]diazenyl]benzoic acid, known as Dabcyl, a push−pull azobenzene functionalized at the para positions of the phenyl rings. Besides its biomolecular applications as a quencher in FRET-based probes, Dabcyl has also been used as a precursor in colorimetric probes for cation recognition. Following the research group´s work on optical chemosensors, we report herein the synthesis of Dabcyl, by an azocoupling reaction, as well as its evaluation as a potential colorimetric chemosensor for metal cations. Therefore, interaction studies of Dabcyl in the presence of environmentally and biologically important metal ions were performed in acetonitrile solutions. It was found that this receptor has potential application as a colorimetric chemosensor for Hg2+, Fe2+, Pd2+, Sn2+ and Al3+ with remarkable sensitivity and a marked color change from light yellow to pink in the presence of these cations.

  • Open access
  • 37 Reads
In silico analysis applied to the cytotoxic study of natural products

With the emergence of technological advances, computational analysis in research has become promising by enabling the emergence of scientific productions without the need for an experimental laboratory and began to be used in various sectors, including cytotoxicity. From this perspective, the main objective of this study is to understand the importance of computational analysis for the study of cytotoxicity in natural products, in addition to understanding scientific advances on this topic. Thus, this is a narrative-type bibliographic review, carried out between March and September 2022, through the digital databases Pubmed, SciELO and the Virtual Health Library with the adoption of the search formula configured with the available descriptors: “in silico analysis”, “cytotoxic” and “natural products”. This work reaffirmed the importance of computer simulations on cytotoxicity in natural products, allowing the verification that these analyzes are a source of knowledge about the structures of natural products, highlighting a great emphasis on the use of the analysis of cytotoxic agents, the anticancer action and treatment of other pathologies. With regard to effectiveness, it is clear that the software reflects results that are similar to studies carried out in vivo. It is noteworthy that the in silico method has an accentuated scientific importance as it allows for a greater adaptability and a lower cost of time and space for research. Thus, such methodology becomes essential in the process of cytotoxicity analysis, obtaining great potential in pharmacological research.

  • Open access
  • 42 Reads
Modified Algar-Flynn-Oyamada reaction for the synthesis of 3-hydroxy-2-styryl-chromen-4-ones under solvent-free conditions

A simple and efficient condition for Algar-Flynn-Oyamada reaction for the synthesis of 3-hydroxy-2-styryl-chromen-4-ones involving grinding of different 1-(2'-hydroxy-phenyl)-5-aryl-penta-2,4-dien-1-ones with UHP (urea-hydrogen peroxide), pulverized potassium hydroxide and few drops of ethanol at room temperature under solvent-free conditions has been described. A faster reaction and higher yields compared to the conventional methods are the advantages of present protocol. The structure of the synthesised compounds was identified from their spectral data (IR, 1H-NMR).

  • Open access
  • 22 Reads
Oxidation processes in a phosphine-thiocarbohydrazone ligand

In this work, we have isolated a pentadentate [P2N2S] phosphine-thiocarbohydrazone ligand, H2L, with a bulky phosphine group in both linker domains that undergoes an oxidation process in solution. This ligand was synthesized by direct reaction between two equivalents of 2-diphenylphosphinebenzaldehyde and one equivalent of thiocarbohydrazide. Two types of crystals derived from this ligand were obtained and studied by X-ray diffraction spectroscopy. One structure corresponds to the monooxidized ligand H2L(O) while the other indicates a dioxidation of the compound, H2L(OO).

  • Open access
  • 32 Reads
Synthesis of bis-amides employing a plant-derived triterpenoid as component in the Ugi reaction

Herein we describe the synthesis of a series of four novel triterpenoid-derived bis-amides employing masticadienonic acid from Pistacia mexicana, as carboxylic acid component in the Ugi reaction. Products were obtained via a facile and efficient one-pot procedure, under mild green conditions, with moderate yields (29-58%). The stereo-electronic nature of the aldehyde component influences the reaction yields.