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Ken S Feldman - One of the best experts on this subject based on the ideXlab platform.
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ellagitannin chemistry evolution of a three component coupling strategy for the synthesis of the dimeric ellagitannin coriariin a and a dimeric gallotannin analogue
Journal of Organic Chemistry, 2000Co-Authors: Ken S Feldman, And Michael D Lawlor, Kiran SahasrabudheAbstract:The total synthesis of the dimeric ellagitannin coriariin A is reported. The key reaction to access the dimeric framework was realized early in the synthesis pathway via a bis acylation reaction of a dehydrodigalloyl diacid with 2 equiv of a glucopyranose trichloroacetimidate. The glucose rings were subsequently functionalized, culminating in a double oxidative cyclization to form stereoselectively both (S)-HHDP ester units. This bis acylation strategy was also employed to prepare a gallotannin analogue of coriariin A whose earlier synthesis by orthoquinone dimerization was plagued by yield-limiting side reactions.
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probing the role of polyphenol oxidation in mediating insect pathogen interactions galloyl derived electrophilic traps for the lymantria dispar nuclear polyhedrosis virus matrix protein polyhedrin
Journal of Organic Chemistry, 1999Co-Authors: Ken S Feldman, Aruna Sambandam, Katherine E Bowers, Heidi M AppelAbstract:Galloyl-derived orthoquinone probes have been designed, synthesized, and utilized in an ongoing study of insect−pathogen interactions. A stable galloyl-derived orthoquinone O-methyl ether modified with both acidic and fluorescent appendages was successful in trapping the model nucleophile cysteine, a test protein bearing a single cysteine residue, and the viral occlusion body matrix protein polyhedrin from Lymantria dispar nuclear polyhedrosis virus (LdNPV), a pathogen of the gypsy moth caterpillar (GMc). This latter observation may be related to the molecular mechanism by which gallotannins decrease LdNPV infectivity in GMc's. Sufficient site isolation was not achieved with a polymer-bound reactive galloyl hydroxyorthoquinone electrophile to permit similar nucleophile trapping to compete with oligomerization.
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ellagitannin chemistry syntheses of tellimagrandin ii and a dehydrodigalloyl ether containing dimeric gallotannin analogue of coriariin a
Journal of Organic Chemistry, 1999Co-Authors: Ken S Feldman, Kiran SahasrabudheAbstract:The first chemical synthesis of the naturally occurring ellagitannin tellimagrandin II is reported. Key steps of the synthesis include the atropselective oxidative coupling of suitably protected galloyl rings at the O(4) and O(6) positions of a glucopyranose core, and the stereoselective acylation of the derived anomeric alcohol with a galloyl chloride. In addition, the synthesis of a novel gallotannin−ellagitannin hybrid is described. This dimeric construct relied on a hetero Diels−Alder cycloaddition/reductive rearrangement sequence to deliver the intact skeleton from a monomeric pentagalloylglucose-based orthoquinone.
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galloyl derived Orthoquinones as reactive partners in nucleophilic additions and diels alder dimerizations a novel route to the dehydrodigalloyl linker unit of agrimoniin type ellagitannins
Journal of Organic Chemistry, 1996Co-Authors: Ken S Feldman, Stephane Quideau, Heidi M AppelAbstract:Orthochloranil-mediated oxidation of galloyl monoethers furnishes the derived Orthoquinones in excellent yield. These reactive electrophiles participate in a variety of nucleophilic addition reactions with heteroatomic and carbanionic partners. In addition, Lewis acid-mediated dimerization of the Orthoquinones provides an efficient route to dehydrodigalloyl-type diaryl ether units characteristic of several ellagitannin natural products. The implications for ellagitannin biosynthesis and gallotannin-protein covalent attachment are discussed.
Heidi M Appel - One of the best experts on this subject based on the ideXlab platform.
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probing the role of polyphenol oxidation in mediating insect pathogen interactions galloyl derived electrophilic traps for the lymantria dispar nuclear polyhedrosis virus matrix protein polyhedrin
Journal of Organic Chemistry, 1999Co-Authors: Ken S Feldman, Aruna Sambandam, Katherine E Bowers, Heidi M AppelAbstract:Galloyl-derived orthoquinone probes have been designed, synthesized, and utilized in an ongoing study of insect−pathogen interactions. A stable galloyl-derived orthoquinone O-methyl ether modified with both acidic and fluorescent appendages was successful in trapping the model nucleophile cysteine, a test protein bearing a single cysteine residue, and the viral occlusion body matrix protein polyhedrin from Lymantria dispar nuclear polyhedrosis virus (LdNPV), a pathogen of the gypsy moth caterpillar (GMc). This latter observation may be related to the molecular mechanism by which gallotannins decrease LdNPV infectivity in GMc's. Sufficient site isolation was not achieved with a polymer-bound reactive galloyl hydroxyorthoquinone electrophile to permit similar nucleophile trapping to compete with oligomerization.
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galloyl derived Orthoquinones as reactive partners in nucleophilic additions and diels alder dimerizations a novel route to the dehydrodigalloyl linker unit of agrimoniin type ellagitannins
Journal of Organic Chemistry, 1996Co-Authors: Ken S Feldman, Stephane Quideau, Heidi M AppelAbstract:Orthochloranil-mediated oxidation of galloyl monoethers furnishes the derived Orthoquinones in excellent yield. These reactive electrophiles participate in a variety of nucleophilic addition reactions with heteroatomic and carbanionic partners. In addition, Lewis acid-mediated dimerization of the Orthoquinones provides an efficient route to dehydrodigalloyl-type diaryl ether units characteristic of several ellagitannin natural products. The implications for ellagitannin biosynthesis and gallotannin-protein covalent attachment are discussed.
Kiran Sahasrabudhe - One of the best experts on this subject based on the ideXlab platform.
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ellagitannin chemistry evolution of a three component coupling strategy for the synthesis of the dimeric ellagitannin coriariin a and a dimeric gallotannin analogue
Journal of Organic Chemistry, 2000Co-Authors: Ken S Feldman, And Michael D Lawlor, Kiran SahasrabudheAbstract:The total synthesis of the dimeric ellagitannin coriariin A is reported. The key reaction to access the dimeric framework was realized early in the synthesis pathway via a bis acylation reaction of a dehydrodigalloyl diacid with 2 equiv of a glucopyranose trichloroacetimidate. The glucose rings were subsequently functionalized, culminating in a double oxidative cyclization to form stereoselectively both (S)-HHDP ester units. This bis acylation strategy was also employed to prepare a gallotannin analogue of coriariin A whose earlier synthesis by orthoquinone dimerization was plagued by yield-limiting side reactions.
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ellagitannin chemistry syntheses of tellimagrandin ii and a dehydrodigalloyl ether containing dimeric gallotannin analogue of coriariin a
Journal of Organic Chemistry, 1999Co-Authors: Ken S Feldman, Kiran SahasrabudheAbstract:The first chemical synthesis of the naturally occurring ellagitannin tellimagrandin II is reported. Key steps of the synthesis include the atropselective oxidative coupling of suitably protected galloyl rings at the O(4) and O(6) positions of a glucopyranose core, and the stereoselective acylation of the derived anomeric alcohol with a galloyl chloride. In addition, the synthesis of a novel gallotannin−ellagitannin hybrid is described. This dimeric construct relied on a hetero Diels−Alder cycloaddition/reductive rearrangement sequence to deliver the intact skeleton from a monomeric pentagalloylglucose-based orthoquinone.
Martinelli, Fernanda Rodrigues - One of the best experts on this subject based on the ideXlab platform.
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Cinchonaínas - método cromatográfico e produção de padrões para contrôle de qualidade de extratos polares de catuaba (Trichilia catigua Adr. Juss.)
Universidade Estadual Paulista (UNESP), 2010Co-Authors: Martinelli, Fernanda RodriguesAbstract:A espécie Trichilia catigua, é uma árvore de 3 a 5 metros de altura, de distribuição ampla nos países da América do Sul, é conhecida como catuaba ou catiguá ou Angelim rosa, é utilizada popularmente como tônico mental e físico e especialmente como estimulante sexual. Cinchonaínas A e B foram escolhidas como marcadores químicos para a padronização do extrato hidroalcóolico de cascas de catuaba por serem as substâncias majoritárias desse extrato e também possuírem atividades antioxidante e antibacteriana. Como os padrões de cinchonaínas ainda não são comercializados foi realizado, neste trabalho, o isolamento, identificação, determinação de pureza absoluta e estudo de estabilidade destes compostos para que possam ser utilizados adequadamente como padrões de trabalho. A purificação das cinchonaínas foi feita em CLAE preparativo, utilizando coluna de fase reversa C18 e gradiente linear de CH3COOH (0,1%) em H2O/MeOH e a identificação foi realizada através da análise dos espectros de massas de alta resolução e RMN de 1H e 13C. Foram realizados também estudos de estabilidade em solução para cinchonaína A, B e extrato hidroalcóolico da casca de catuaba em diferentes condições de armazenamento. Os estudos de estabilidade acelerada foram realizados de acordo com RE 398 da ANVISA em condições de temperatura (40ºC) e umidade (75% UR). Estes estudos indicaram que os padrões de cinchonaína A e B são estáveis quando mantidos secos sob condições ambientais, com prazo de validade estimado de dois anos. No entanto, em solução hidrometanólica (MeOH:H2O 1:1) ocorre rápida oxidação com formação das di - orto – quinonas, indicando que as soluções mães desses padrões não podem ser estocados por mais de 1 dia. O estudo de estabilidade em solução, mostrou que o perfil cromatográfico das soluções hidroalcóolicas da planta não apresentou...Trichilia catigua, is a tree which grows 6.56 to 13.12 feet, widely distributed in South America, and is known as catuaba, catiguá or Angelim renders rose-colored and is popular used as mental and physical tonic and especially as sexual stimulant. Cinchonains A and B were chosen as chemical markers to standardize the extract in focus due the major concentration of those substances in the hydroalcoholic extract from bark of catuaba and also due to antioxidant and anti bacterial activities related to them. Since the cinchonains standards are not commercialized, we had to perform the isolation, identification, absolute purity and stability study of these compounds, so that they could be properly used as standards. The cinchonains purification was performed in HPLC using preparative C-18 reverse phase column and H2O/MeOH as solvent, by running a linear gradient. The identification was obtained through high resolution mass spectrum and 1H e 13C NMR (Nuclear Magnetic Resonance). Stability studies were executed in solution of cinchonain A, B and hydroalcoholic extract from bark of catuaba in different storage conditions. The accelerated stability studies were performed according to RE 398, November 12nd of 2004 - ANVISA under temperature of 40 °C and humidity of 75% UR. These studies indicated that standards of cinchonain A and B are stable when they are dried and kept under ambient conditions, having a shelf life estimated of two years. However, in hydromethanol solution (MeOH:H2O 1:1), rapid oxidation occurs leading to di-Orthoquinones formation, indicating that stock standards solutions cannot be stored more than 1 day. The stability study on solution showed that the chromatographic profile of the plant hydroalcoholic solution did not present alteration within 7 days, indicating that samples can be prepared and stored during this period. The parameters... (Complete abstract click electronic access below)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES
Martinelli, Fernanda Rodrigues [unesp] - One of the best experts on this subject based on the ideXlab platform.
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Cinchonaínas - método cromatográfico e produção de padrões para contrôle de qualidade de extratos polares de catuaba (Trichilia catigua Adr. Juss.)
Universidade Estadual Paulista (UNESP), 2010Co-Authors: Martinelli, Fernanda Rodrigues [unesp]Abstract:A espécie Trichilia catigua, é uma árvore de 3 a 5 metros de altura, de distribuição ampla nos países da América do Sul, é conhecida como catuaba ou catiguá ou Angelim rosa, é utilizada popularmente como tônico mental e físico e especialmente como estimulante sexual. Cinchonaínas A e B foram escolhidas como marcadores químicos para a padronização do extrato hidroalcóolico de cascas de catuaba por serem as substâncias majoritárias desse extrato e também possuírem atividades antioxidante e antibacteriana. Como os padrões de cinchonaínas ainda não são comercializados foi realizado, neste trabalho, o isolamento, identificação, determinação de pureza absoluta e estudo de estabilidade destes compostos para que possam ser utilizados adequadamente como padrões de trabalho. A purificação das cinchonaínas foi feita em CLAE preparativo, utilizando coluna de fase reversa C18 e gradiente linear de CH3COOH (0,1%) em H2O/MeOH e a identificação foi realizada através da análise dos espectros de massas de alta resolução e RMN de 1H e 13C. Foram realizados também estudos de estabilidade em solução para cinchonaína A, B e extrato hidroalcóolico da casca de catuaba em diferentes condições de armazenamento. Os estudos de estabilidade acelerada foram realizados de acordo com RE 398 da ANVISA em condições de temperatura (40ºC) e umidade (75% UR). Estes estudos indicaram que os padrões de cinchonaína A e B são estáveis quando mantidos secos sob condições ambientais, com prazo de validade estimado de dois anos. No entanto, em solução hidrometanólica (MeOH:H2O 1:1) ocorre rápida oxidação com formação das di - orto – quinonas, indicando que as soluções mães desses padrões não podem ser estocados por mais de 1 dia. O estudo de estabilidade em solução, mostrou que o perfil cromatográfico das soluções hidroalcóolicas da planta não apresentou...Trichilia catigua, is a tree which grows 6.56 to 13.12 feet, widely distributed in South America, and is known as catuaba, catiguá or Angelim renders rose-colored and is popular used as mental and physical tonic and especially as sexual stimulant. Cinchonains A and B were chosen as chemical markers to standardize the extract in focus due the major concentration of those substances in the hydroalcoholic extract from bark of catuaba and also due to antioxidant and anti bacterial activities related to them. Since the cinchonains standards are not commercialized, we had to perform the isolation, identification, absolute purity and stability study of these compounds, so that they could be properly used as standards. The cinchonains purification was performed in HPLC using preparative C-18 reverse phase column and H2O/MeOH as solvent, by running a linear gradient. The identification was obtained through high resolution mass spectrum and 1H e 13C NMR (Nuclear Magnetic Resonance). Stability studies were executed in solution of cinchonain A, B and hydroalcoholic extract from bark of catuaba in different storage conditions. The accelerated stability studies were performed according to RE 398, November 12nd of 2004 - ANVISA under temperature of 40 °C and humidity of 75% UR. These studies indicated that standards of cinchonain A and B are stable when they are dried and kept under ambient conditions, having a shelf life estimated of two years. However, in hydromethanol solution (MeOH:H2O 1:1), rapid oxidation occurs leading to di-Orthoquinones formation, indicating that stock standards solutions cannot be stored more than 1 day. The stability study on solution showed that the chromatographic profile of the plant hydroalcoholic solution did not present alteration within 7 days, indicating that samples can be prepared and stored during this period. The parameters... (Complete abstract click electronic access below