- Synthesis of Two Epimers of Pseudopaline
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Opines are a known group of compounds characterized by an elevated polarity. Recently, two new members of this class, staphylopine and pseudopaline, have been identified in Staphylococcus aureus and Pseudomonas aeruginosa, respectively. These molecules are metal chelators that contribute to the growth of bacteria in particularly metal-poor environment. Different evidences suggest that these molecules might have an important role in the development of pulmonary infections in humans. Considering the impact of P. aeruginosa infections in cystic fibrosis patients (prevalence up to 70 percent), pseudopaline has risen interest as potential source of new therapeutic intervention. We present herein a straightforward synthetic approach for the synthesis of the two epimers of pseudopaline. Starting from a chiral building block, we attribute the absolute configuration to the two obtained diasteroisomers.
- Arnoux, Pascal,Cavelier, Florine,Cullia, Gregorio,Fanelli, Roberto,Voulhoux, Romé
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- Combination strategy using pure enzymes and whole cells as biocatalysts for the preparation of 2-hydroxyesters and lactones from 2-oxoglutaric acid
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An innovative combination strategy that uses pure enzymes and whole microbial cells in the same process was used to prepare enantiomerically pure 3-carboxyalkyl-γ-butyrolactones and several alkyl esters of 2-hydroxyglutarate from 2-oxoglutaric acid. An innovative combination strategy that uses pure enzymes and whole microbial cells in the same process was used to prepare enantiomerically pure 3-carboxyalkyl-γ-butyrolactones and several alkyl esters of 2-hydroxyglutarates from 2-oxoglutaric acid. The method involves two consecutive biocatalytic steps. The first step, which converts the 2-oxoglutaric acid into the corresponding dialkyl esters, was catalyzed by a lipase. Then in the second step, by microbial reduction of the dialkyl-2-oxoglutarates, it is possible to obtain 3-carboxyalkyl-γ- butyrolactones or 2-hydroxyesters depending on the length of the chain in the alkyl moiety of the esters and on the fresh or lyophilized status of the cells.
- Rustoy, Eduardo M.,Pereyra, Elba N.,Moreno, Silvia,Baldessari, Alicia
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p. 3763 - 3768
(2007/10/03)
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- Synthesis of C1-C11 fragment of annonacin: A polyketide acetogenin of Annonaceae
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(4R, 10S)-Methyl tri-isopropylsilyloxy-4-tert-butyldimethylsilyloxy-10-tert-amyloxy-11- undecanoate 1 has been synthesized from L-glutamic acid. This compound is a key intermediate in the total synthesis of annonacin, an acetogenin of Annonaceae.
- Figadere,Franck,Cave
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p. 1637 - 1640
(2007/10/02)
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- On the factors controlling the structural specificity and stereospecificity of the L-lactate dehydrogenase from Bacillus stearothermophilus: Effects of Gln102→Arg and Arg171→Trp/Tyr double mutations
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The factors determining the L-stereospecificity of the L-lactate dehydrogenase from Bacillus stearolhermophilus have been probed by introducing Arg171Trp/Tyr and Gln 102Arg mutations. These changes preclude normal 2-keto acid substrate binding via an Arg171-COO- electrostatic interaction and are positioned to induce a reversal of the natural substrate binding mode, thereby leading to D-2-hydroxy acid formation. However, the L-stereospecificities of the mutant enzymes remain unchanged, showing that there are important fail-safe stereospecificity determinants that take over when the key Arg171-COO- binding interaction is removed. The effects of the mutations on structural specificity are approximately additive, resulting in the broad 2-keto acid specificity of the wild-type enzyme being changed to give catalysts highly selective for the dicarboxylic substrate oxalacetate.
- Kallwass, Helmut K.W.,Hogan, James K.,Macfarlane, Emma L.A.,Martichonok, Valeri,Partis, Wendy,Kay, Cyril M.,Gold, Marvin,Bryan Jones
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p. 10704 - 10710
(2007/10/02)
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- Reactivite du nitrite de sodium. V. Action sur les amino-acides, peptides et proteines
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The action of sodium nitrite on various amino-acids was re-examined in conditions approximating to a biological medium. 13C-NMR provides evidence of the existence of intramolecular ring closures and the formation of 5-membered rings with ornithine, citrulline and arginine.The reaction of cystine shows the opening of the sulphur bridges, whereas cysteine leads to the formation of carboxy-thiiran and 3-sulpho-lactic acid.The hydrolysis of the amide bonds of asparagine and glutamine is complete whereas the peptides studied - carnosine and aspartam - do not undergo hydrolysis of the peptide linkage.However, the first deamination of glutathion (γ-Glu-Cys-Gly) induces the peptide link to be broken and a cyclization with the formation of lactone to occur.A second deamination takes place on the cysteinyl residue released and allows the formation of a thiiran by intramolecular cyclization with the thiol group.The formation of thiiran was also observed with oxidized glutathion which has an S-S bridge.Finally, the formation of nitrosamines was detected by 15N-NMR during the reaction of sodium nitrite with two commercial products available to the general public.
- Gouesnard, Jean-Paul
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