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Carolina De Oliveira Bernardes - One of the best experts on this subject based on the ideXlab platform.

  • Semisynthetic Phenol Derivatives Obtained from Natural Phenols: Antimicrobial Activity and Molecular Properties.
    Journal of agricultural and food chemistry, 2017
    Co-Authors: Patrícia Fontes Pinheiro, Luciana Alves Parreira Menini, Patrícia Campos Bernardes, Sérgio Henriques Saraiva, José Walkimar De M. Carneiro, Adilson Vidal Costa, Társila Rodrigues Arruda, Mateus R. Lage, Patrícia Martins Gonçalves, Carolina De Oliveira Bernardes
    Abstract:

    Semisynthetic phenol derivatives were obtained from the natural phenols: thymol, carvacrol, eugenol, and guaiacol through catalytic oxychlorination, Williamson Synthesis, and aromatic Claisen rearrangement. The compounds characterization was carried out by 1H NMR, 13C NMR, and mass spectrometry. The natural phenols and their semisynthetic derivatives were tested for their antimicrobial activity against the bacteria: Staphylococcus aureus, Escherichia coli, Listeria innocua, Pseudomonas aeruginosa, Salmonella enterica Typhimurium, Salmonella enterica ssp. enterica, and Bacillus cereus. Minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values were determined using concentrations from 220 to 3.44 μg mL–1. Most of the tested compounds presented MIC values ≤220 μg mL–1 for all the bacteria used in the assays. The molecular properties of the compounds were computed with the PM6 method. Through principle components analysis, the natural phenols and their semisynthetic derivative...

  • Semisynthetic Phenol Derivatives Obtained from Natural Phenols: Antimicrobial Activity and Molecular Properties
    2017
    Co-Authors: Patrícia Fontes Pinheiro, Luciana Alves Parreira Menini, Adilson Vidal Costa, Mateus R. Lage, Patrícia Campos Bernardes, Sérgio Henriques Saraiva, José Walkimar Mesquita Carneiro, Társila Rodrigues Arruda, Patrícia Martins Gonçalves, Carolina De Oliveira Bernardes
    Abstract:

    Semisynthetic phenol derivatives were obtained from the natural phenols: thymol, carvacrol, eugenol, and guaiacol through catalytic oxychlorination, Williamson Synthesis, and aromatic Claisen rearrangement. The compounds characterization was carried out by 1H NMR, 13C NMR, and mass spectrometry. The natural phenols and their semisynthetic derivatives were tested for their antimicrobial activity against the bacteria: Staphylococcus aureus, Escherichia coli, Listeria innocua, Pseudomonas aeruginosa, Salmonella enterica Typhimurium, Salmonella enterica ssp. enterica, and Bacillus cereus. Minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values were determined using concentrations from 220 to 3.44 μg mL–1. Most of the tested compounds presented MIC values ≤220 μg mL–1 for all the bacteria used in the assays. The molecular properties of the compounds were computed with the PM6 method. Through principle components analysis, the natural phenols and their semisynthetic derivatives with higher antimicrobial potential were grouped

Dénes Szabó - One of the best experts on this subject based on the ideXlab platform.

  • Synthesis of optically active α-(nonafluoro-tert-butoxy)carboxylic acids
    Tetrahedron Letters, 2013
    Co-Authors: Tamás Csóka, Anikó Nemes, Dénes Szabó
    Abstract:

    Abstract Three novel α-(nonafluoro-tert-butoxy)carboxylic esters were synthesized by two methods: the Mitsunobu reaction of optically active (S)-α-hydroxycarboxylic esters and the Williamson Synthesis starting from the corresponding O-mesyl derivatives. Both procedures from ethyl (S)-lactate resulted in the formation of a fluorous optically active (R)-lactic acid ester derivative, while the reactions from methyl (S)-mandelate took place with racemization. The proposed mechanism of this racemization is described. The conversion of methyl (S)-phenyllactate under Mitsunobu conditions was also stereospecific, but the reaction of its O-mesyl derivative yielded a mixture of substitution and elimination products. The optical purity of the α-(nonafluoro-tert-butoxy)carboxylic acids prepared by the hydrolysis of the above esters was determined by 1H NMR spectroscopy.

Didier Le Cerf - One of the best experts on this subject based on the ideXlab platform.

  • Synthesis, physicochemical, structural and rheological characterizations of carboxymethyl xanthan derivatives
    Carbohydrate Polymers, 2016
    Co-Authors: Madiha Yahoum, Nadji Moulai-mostefa, Didier Le Cerf
    Abstract:

    The aim of this work was to synthesize a carboxymethylated xanthan (CMXG) via an etherification reaction between different ratios (2, 4, and 6) of xanthan gum (XG) and monochloroacetic acid (MCAA) using the Williamson Synthesis method. The synthetized products were characterized in terms of their physico-chemical and rheological properties. Both FTIR and proton nuclear magnetic resonance (H1 NMR) analyses confirmed the grafting of carboxymethyl groups on xanthan hydroxyl groups. The obtained results demonstrated that the degree of substitution was proportional to the chloroacetic acid and xanthan gum ratios. The obtained carboxymethyl derivatives presented greater hydrophilicity and lower molecular weights with increasing degrees of substitution than native xanthan gum. The rheological study revealed that the viscosity of the CMXG derivatives decreased with the degree of substitution and with the conservation of the shear-thinning and weak gel behaviours. The flow curves suggested the existence of two different populations of particles consisting of CMXG particles with a smaller average size and a second population formed by the residual fractions of native XG particles. It was also found that the elastic modulus of XG was largely higher than that of the CMXG derivatives and decreased with increasing DS. For the CMXG derivatives, two regions of viscoelastic behaviour were observed, which were separated by a crossover point corresponding to the critical frequency and relaxation time, i.e., the time required for stress relaxation.

Patrícia Fontes Pinheiro - One of the best experts on this subject based on the ideXlab platform.

  • Semisynthetic Phenol Derivatives Obtained from Natural Phenols: Antimicrobial Activity and Molecular Properties.
    Journal of agricultural and food chemistry, 2017
    Co-Authors: Patrícia Fontes Pinheiro, Luciana Alves Parreira Menini, Patrícia Campos Bernardes, Sérgio Henriques Saraiva, José Walkimar De M. Carneiro, Adilson Vidal Costa, Társila Rodrigues Arruda, Mateus R. Lage, Patrícia Martins Gonçalves, Carolina De Oliveira Bernardes
    Abstract:

    Semisynthetic phenol derivatives were obtained from the natural phenols: thymol, carvacrol, eugenol, and guaiacol through catalytic oxychlorination, Williamson Synthesis, and aromatic Claisen rearrangement. The compounds characterization was carried out by 1H NMR, 13C NMR, and mass spectrometry. The natural phenols and their semisynthetic derivatives were tested for their antimicrobial activity against the bacteria: Staphylococcus aureus, Escherichia coli, Listeria innocua, Pseudomonas aeruginosa, Salmonella enterica Typhimurium, Salmonella enterica ssp. enterica, and Bacillus cereus. Minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values were determined using concentrations from 220 to 3.44 μg mL–1. Most of the tested compounds presented MIC values ≤220 μg mL–1 for all the bacteria used in the assays. The molecular properties of the compounds were computed with the PM6 method. Through principle components analysis, the natural phenols and their semisynthetic derivative...

Hongchi Zhao - One of the best experts on this subject based on the ideXlab platform.

  • Preparation of the Water-Soluble Pyrene-Containing Fluorescent Polymer by One-Pot Method
    Polymers, 2015
    Co-Authors: Miaomiao Wang, Haijian Tan, Qingmin Yang, Aiqing Wang, Libin Bai, Hongchi Zhao
    Abstract:

    A new water-soluble pyrene-containing fluorescent polymer, 1-{3′-S-[poly(acryloyl ethylene diamine hydrochloride)-2′-methyl propionic acid]}propionyloxy hexyloxy pyrene (P3) with defined structure, was designed and synthesized using the click reaction between thiol and a carbon-carbon double bond. The intermediate products P1 (S-1-dodecyl-S′-[poly(N-Boc-acryloyl ethylene diamine)-2′-methyl propionic acid]trithiocarbonate) and AHP (1-(acryloyloxy hexyloxy)pyrene) were prepared via reversible addition fragmentation chain transfer (RAFT) polymerization and Williamson Synthesis, respectively. Conjugating AHP with P1, P2 (1-{3′-S-[poly(N-butoxycarbonyl-acryloyl ethylene diamine)-2″-methyl propionic acid]} propionyloxy hexyloxy pyrene) was synthesized, adopting both the reduction reaction of a trithioester bond of P1 to thiol and the click reaction between thiol and the carbon-carbon double bond of AHP simultaneously. P3 was obtained by the deprotection of the resulting Boc-protected polymer (P2) with aqueous HCl. The experiment results showed that P2 exhibited a bright blue-violet emission band at approximately 387–429 nm. After deprotection, P3 displayed good solubility in water and not only exhibited a blue-violet fluorescence emission band at approximately 387–429 nm in aqueous solution but also had the similar photoluminescent spectra to those of AHP and P2 in dichloromethane. The fluorescence quantum yields of P2 in dilute tetrahydrofuran and P3 in a dilute aqueous solution were 0.44 and 0.39, respectively. This experiment provided a novel insight into the study of water-soluble fluorescent polymers.

  • Preparation of the water-soluble fluorene-containing fluorescent polymer by one-pot method
    Macromolecular Research, 2015
    Co-Authors: Yuan Wang, Haijian Tan, Libin Bai, Yunxia Qian, Hongchi Zhao
    Abstract:

    A water-soluble fluorescent polymer, 2,7-di}4'-[3''-(S-poly(acryloyl ethylene diamine hydrochloride)-2'''- methyl propionic acid)propionyloxy hexyloxy]phenyl{-9,9-di(n-octyl)fluorene (P3) with regular and ordered structure, was designed and synthesized with high conversion using click reaction between thiols and carbon-carbon double bonds. Because the S-H bond is relatively weak, thiol groups are subject to rapid oxidation during purification and storage and thereby result in the low conversion in the following click reaction. To circumvent this limitation, the Synthesis of thiol groups and click reaction were simultaneously performed in one system (one-pot method). The intermediate products P1 (S-1-dodecyl-S'-[poly(N-Boc-acryloyl ethylene diamine)-2'-methyl propionic acid]trithiocarbonate) and M2 (2,7-di[4-(acryloyloxy hexyloxy)phenyl]-9,9-di(n-octyl)fluorene) were prepared via reversible addition fragmentation chain transfer (RAFT) polymerization and Williamson Synthesis, respectively. Then, 2,7- di}4'-[3''-(S-poly(N-Boc-acryloyl ethylene diamine)-2'''-methyl propionic acid)propionyloxy hexyloxy]phenyl{-9,9-di(n-octyl)fluorene (P2) was synthesized with high conversion (83%) by employing a click reaction with P1 and M2 as starting materials. Finally, water-soluble fluorescent polymer P3 was obtained after the deprotection of P2. M2, P1, P2 and P3 were characterized by Fourier transform infrared (FTIR) spectrum, nuclear magnetic resonance (NMR), high-resolution mass spectroscopy (MS), gel permeation chromatograph (GPC), UV-Visible (UV-Vis) spectrum, and fluorescence, respectively. The results revealed that P3 displayed good solubility in water and not only exhibited a blue fluorescence emission band in water but also had a similar photoluminescent spectra to those of M2 and P2 in dichloromethane. The fluorescence quantum yield of P3 in aqueous solution could reach 0.10. In addition, the result of cell cytotoxicity indicates that P3 has low cytotoxicity and exhibits potential for biomedical applications. This work provides a new insight into the study of water-soluble fluorescent polymer. Open image in new window