The Biocatalytic Repertoire of Natural Biaryl Formation

Aldemir, Hülya; Richarz, René; Gulder, Tobias A. M.

doi:10.1002/anie.201401075

Cited by 136 publications

(100 citation statements)

References 97 publications

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“…19,20 Consistent with the underlying biochemical logic for the oxidative coupling of aryl rings, 21 our studies revealed that naturally produced OH-BDEs and di-OH-BDEs are assembled via the biradical homo- and heterocoupling of bromophenol and bromocatechol monomers mediated by cytochrome P450 enzymes. Recently, additional biotic 22 and abiotic 23 radical coupling processes have been reported for OH-BDE syntheses.…”

Section: Introductionsupporting

confidence: 76%

Complexity of Naturally Produced Polybrominated Diphenyl Ethers Revealed via Mass Spectrometry

Agarwal¹,

Li²,

Rahman³

et al. 2015

Environ. Sci. Technol.

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Polybrominated diphenyl ethers (PBDEs) are persistent and bioaccumulative anthropogenic and natural chemicals that are broadly distributed in the marine environment. PBDEs are potentially toxic due to inhibition of various mammalian signaling pathways and enzymatic reactions. PBDE isoforms vary in toxicity in accordance with structural differences, primarily in the number and pattern of hydroxyl moieties afforded upon a conserved core structure. Over four decades of isolation and discovery-based efforts have established an impressive repertoire of natural PBDEs. Based on our recent reports describing the bacterial biosyntheses of PBDEs, we predicted the presence of additional classes of PBDEs to those previously identified from marine sources. Using mass spectrometry and NMR spectroscopy, we now establish the existence of new structural classes of PBDEs in marine sponges. Our findings expand the chemical space explored by naturally produced PBDEs, which may inform future environmental toxicology studies. Furthermore, we provide evidence for iodinated PBDEs and direct attention toward the contribution of promiscuous halogenating enzymes in further expanding the diversity of these polyhalogenated marine natural products.

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Section: Introductionsupporting

confidence: 76%

Complexity of Naturally Produced Polybrominated Diphenyl Ethers Revealed via Mass Spectrometry

Agarwal¹,

Li²,

Rahman³

et al. 2015

Environ. Sci. Technol.

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show abstract

“…The pioneering work of Zenk as well as subsequent studies showed that intramolecular phenol coupling during alkaloid biosynthesis is catalyzed regioselectively and stereoselectively by cytochrome P450 enzymes (Gerardy and Zenk, 1992;Gesell et al, 2009). Furthermore, there is a growing number of examples also for bimolecular couplings that are mediated by cytochrome P450s, laccases, or peroxidases in a stereospecific manner (Schlauer et al, 1998;Niemetz and Gross, 2003;Fang et al, 2012;Aldemir et al, 2014;Mazzaferro et al, 2015). Stereochemical control by the oxidizing enzymes alleviates the need for any DIR activity.…”

mentioning

confidence: 99%

Dirigent Protein Mode of Action Revealed by the Crystal Structure of AtDIR6

et al. 2016

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Dirigent proteins impart stereoselectivity to phenoxy radical coupling reactions in plants and, thus, play an essential role in the biosynthesis of biologically active natural products. This includes the regioselective and enantioselective coupling and subsequent cyclization of two coniferyl alcohol radicals to pinoresinol as the committed step of lignan biosynthesis. The reaction is controlled by dirigent proteins, which, depending on the species and protein, direct the reaction to either (+)-or (2)-pinoresinol. We present the crystal structure of the (2)-pinoresinol forming DIRIGENT PROTEIN6 (AtDIR6) from Arabidopsis (Arabidopsis thaliana) with data to 1.4 Å resolution. The structure shows AtDIR6 as an eight-stranded antiparallel b-barrel that forms a trimer with spatially well-separated cavities for substrate binding. The binding cavities are two lobed, exhibiting two opposing pockets, each lined with a set of hydrophilic and potentially catalytic residues, including essential aspartic acids. These residues are conserved between (+) and (2)-pinoresinol-forming DIRs and required for activity. The structure supports a model in which two substrate radicals bind to each of the DIR monomers. With the aromatic rings fixed in the two pockets, the propionyl side chains face each other for radical-radical coupling, and stereoselectivity is determined by the exact positioning of the side chains. Extensive mutational analysis supports a previously unrecognized function for DIRs in catalyzing the cyclization of the bis-quinone methide reaction intermediate to yield (+)-or (2)-pinoresinol.

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“…The involvement of the flavoenzyme suggests an electrophilic aromatic substitution as the biosynthetic mechanism for the homocoupling. Such a biosynthesis is in clear contrast to the phenol oxidative coupling usually observed for C , C ‐coupled biaryls 5. Rotation around the heterobiaryl axis in 1 and 2 is hampered at ambient temperatures, leading to separable enantiomers, of which only the ( M ) isomer has been found in the bacterial producer.…”

Section: Introductionmentioning

confidence: 89%

Thermal Evaluation of Diesel/Hydrogen Peroxide Fuel Blend

et al. 2015

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Thermal properties of fossil fuel are the key fundamental characteristics, which can distinguish any compound as a potential fuel. The performance of diesel fuel blend along with stability and solubility parameter designs are evaluated. The results from the experimental study indicate that the increase in hydrogen peroxide (H2O2) amount enhances the cetane number of diesel fuel blend significantly. However, the calorific value decreases as compared to pure diesel fuel. All values performed well according to the ASTM D‐975 diesel testing method. The thermodynamics of the prepared fuel blends also revealed that substantial solubility and diesel/H2O2 blend stability are provided even at lower temperatures. Such blends can be used as a feasible replacement of pure diesel fuel.

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The Biocatalytic Repertoire of Natural Biaryl Formation

Cited by 136 publications

References 97 publications

Complexity of Naturally Produced Polybrominated Diphenyl Ethers Revealed via Mass Spectrometry

Complexity of Naturally Produced Polybrominated Diphenyl Ethers Revealed via Mass Spectrometry

Dirigent Protein Mode of Action Revealed by the Crystal Structure of AtDIR6

Thermal Evaluation of Diesel/Hydrogen Peroxide Fuel Blend

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