Role of catechol in the radical reduction of B-alkylcatecholboranes in presence of methanol

Povie, Guillaume; Villa, Giorgio; Ford, Leigh; Pozzi, Davide; Schiesser, Carl H.; Renaud, Philippe

doi:10.1039/b917004a

Cited by 46 publications

(31 citation statements)

References 36 publications

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“…Due to their low radical reduction potentials, catechols can act as hydrogen atom donors and efficiently terminate radical chain reactions [40]. This ability requires hydroxyl moieties to be available for radical scavenging [41].…”

Section: Resultsmentioning

confidence: 99%

The Alternative Role of Enterobactin as an Oxidative Stress Protector Allows Escherichia coli Colony Development

et al. 2014

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Numerous bacteria have evolved different iron uptake systems with the ability to make use of their own and heterologous siderophores. However, there is growing evidence attributing alternative roles for siderophores that might explain the potential adaptive advantages of microorganisms having multiple siderophore systems. In this work, we show the requirement of the siderophore enterobactin for Escherichia coli colony development in minimal media. We observed that a strain impaired in enterobactin production (entE mutant) was unable to form colonies on M9 agar medium meanwhile its growth was normal on LB agar medium. Given that, neither iron nor citrate supplementation restored colony growth, the role of enterobactin as an iron uptake-facilitator would not explain its requirement for colony development. The absence of colony development was reverted either by addition of enterobactin, the reducing agent ascorbic acid or by incubating in anaerobic culture conditions with no additives. Then, we associated the enterobactin requirement for colony development with its ability to reduce oxidative stress, which we found to be higher in media where the colony development was impaired (M9) compared with media where the strain was able to form colonies (LB). Since oxyR and soxS mutants (two major stress response regulators) formed colonies in M9 agar medium, we hypothesize that enterobactin could be an important piece in the oxidative stress response repertoire, particularly required in the context of colony formation. In addition, we show that enterobactin has to be hydrolyzed after reaching the cell cytoplasm in order to enable colony development. By favoring iron release, hydrolysis of the enterobactin-iron complex, not only would assure covering iron needs, but would also provide the cell with a molecule with exposed hydroxyl groups (hydrolyzed enterobactin). This molecule would be able to scavenge radicals and therefore reduce oxidative stress.

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Section: Resultsmentioning

confidence: 99%

The Alternative Role of Enterobactin as an Oxidative Stress Protector Allows Escherichia coli Colony Development

et al. 2014

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“…Because of their low radical reduction potentials, catechols can act as hydrogen atom donors and efficiently terminate radical chain reactions [29]. Fig.…”

Section: Resultsmentioning

confidence: 99%

Catecholate Siderophores Protect Bacteria from Pyochelin Toxicity

et al. 2012

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BackgroundBacteria produce small molecule iron chelators, known as siderophores, to facilitate the acquisition of iron from the environment. The synthesis of more than one siderophore and the production of multiple siderophore uptake systems by a single bacterial species are common place. The selective advantages conferred by the multiplicity of siderophore synthesis remains poorly understood. However, there is growing evidence suggesting that siderophores may have other physiological roles besides their involvement in iron acquisition.Methods and Principal FindingsHere we provide the first report that pyochelin displays antibiotic activity against some bacterial strains. Observation of differential sensitivity to pyochelin against a panel of bacteria provided the first indications that catecholate siderophores, produced by some bacteria, may have roles other than iron acquisition. A pattern emerged where only those strains able to make catecholate-type siderophores were resistant to pyochelin. We were able to associate pyochelin resistance to catecholate production by showing that pyochelin-resistant Escherichia coli became sensitive when biosynthesis of its catecholate siderophore enterobactin was impaired. As expected, supplementation with enterobactin conferred pyochelin resistance to the entE mutant. We observed that pyochelin-induced growth inhibition was independent of iron availability and was prevented by addition of the reducing agent ascorbic acid or by anaerobic incubation. Addition of pyochelin to E. coli increased the levels of reactive oxygen species (ROS) while addition of ascorbic acid or enterobactin reduced them. In contrast, addition of the carboxylate-type siderophore, citrate, did not prevent pyochelin-induced ROS increases and their associated toxicity.ConclusionsWe have shown that the catecholate siderophore enterobactin protects E. coli against the toxic effects of pyochelin by reducing ROS. Thus, it appears that catecholate siderophores can behave as protectors of oxidative stress. These results support the idea that siderophores can have physiological roles aside from those in iron acquisition.

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“…[15] We have reported that catechols can be used as as ource of hydrogen atoms in radical reactions involving organoborane radical precursors. [16] Fori nstance,amild procedure for the protonolysis of organoboranes has been developed based on ah ighly efficient radical chain process. [16a] Interestingly,c atechols are excellent H-donors for alkyl radicals with rate constants in the desired range (gray region in Figure 1).…”

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confidence: 99%

Catechols as Sources of Hydrogen Atoms in Radical Deiodination and Related Reactions

et al. 2016

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When used with trialkylboranes, catechol derivatives, which are low-cost and low toxicity, are valuable hydrogen atom donors for radical chain reactions involving alkyl iodides and related radical precursors. The system 4-tert-butylcatechol/triethylborane has been used to reduce a series of secondary and tertiary iodides, a xanthate, and a thiohydroxamate ester. Catechol derivatives are right in the optimal kinetic window for synthetic applications, as demonstrated by highly efficient radical cyclizations. Cyclizations leading to the formation of quaternary centers can be performed in an all-at-once process (no slow addition of the hydrogen atom donor) at standard concentrations. The H-donor properties of catechol derivatives can be fine-tuned by changing their substitution pattern. In slow radical cyclization processes, an enhanced ratio of cyclized/uncyclized products was obtained by using 3-methoxycatechol instead of 4-tert-butylcatechol.

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Role of catechol in the radical reduction of B-alkylcatecholboranes in presence of methanol

Cited by 46 publications

References 36 publications

The Alternative Role of Enterobactin as an Oxidative Stress Protector Allows Escherichia coli Colony Development

The Alternative Role of Enterobactin as an Oxidative Stress Protector Allows Escherichia coli Colony Development

Catecholate Siderophores Protect Bacteria from Pyochelin Toxicity

Catechols as Sources of Hydrogen Atoms in Radical Deiodination and Related Reactions

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