Further studies on the biosynthesis of the boron-containing antibiotic aplasmomycin

Lee, J. J.; Dewick, Paul M.; Gorst-Allman, Charles P.; Spreafico, F.; Kowal, C.; Chang, Chin-Jer; McInnes, A. G.; Walter, Josef; Keller, Paul J.; Floss, Heinz G.

doi:10.1021/ja00252a019

Cited by 28 publications

(14 citation statements)

References 2 publications

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“…The potential starter unit, D-lactate, most probably is derived from pyruvate which originates from glycerol based on feeding studies of structurally related compounds (28,36,37). Analyses of domain composition of modular PKSs showed that TrtKS1, in addition to BT2KS1 from B. thailandensis and BryKS1 from Candidatus E. sertula (38), also is preceded by the same catalytic organization, making this KS group a new clade.…”

Section: Discussionmentioning

confidence: 99%

Boronated tartrolon antibiotic produced by symbiotic cellulose-degrading bacteria in shipworm gills

Elshahawi

Trindade-Silva

Hanora

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

114

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Shipworms are marine wood-boring bivalve mollusks (family Teredinidae) that harbor a community of closely related Gammaproteobacteria as intracellular endosymbionts in their gills. These symbionts have been proposed to assist the shipworm host in cellulose digestion and have been shown to play a role in nitrogen fixation. The genome of one strain of Teredinibacter turnerae, the first shipworm symbiont to be cultivated, was sequenced, revealing potential as a rich source of polyketides and nonribosomal peptides. Bioassay-guided fractionation led to the isolation and identification of two macrodioloide polyketides belonging to the tartrolon class. Both compounds were found to possess antibacterial properties, and the major compound was found to inhibit other shipworm symbiont strains and various pathogenic bacteria. The gene cluster responsible for the synthesis of these compounds was identified and characterized, and the ketosynthase domains were analyzed phylogenetically. Reverse-transcription PCR in addition to liquid chromatography and high-resolution mass spectrometry and tandem mass spectrometry revealed the transcription of these genes and the presence of the compounds in the shipworm, suggesting that the gene cluster is expressed in vivo and that the compounds may fulfill a specific function for the shipworm host. This study reports tartrolon polyketides from a shipworm symbiont and unveils the biosynthetic gene cluster of a member of this class of compounds, which might reveal the mechanism by which these bioactive metabolites are biosynthesized.symbiosis | biosynthesis | natural products | acyl-transferase | cecum

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Section: Discussionmentioning

confidence: 99%

Boronated tartrolon antibiotic produced by symbiotic cellulose-degrading bacteria in shipworm gills

Elshahawi

Trindade-Silva

Hanora

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

114

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“…Instead it was found to derive from an intact glycerol molecule (Fig. 4) [7,9,29]. Several experiments suggested either phosphoglyceric acid or phosphoenolpyruvate as the starter unit [29].…”

Section: Glycerol Derived Starter Unitsmentioning

confidence: 99%

“…Incorporation experiments have established the origin of the carbon skeleton of aplasmomycin (Fig. 4) [7,9,29]. Each half of the molecule contains a polyketide chain made up of a starter unit, and seven acetate-derived extension units.…”

Section: Glycerol Derived Starter Unitsmentioning

confidence: 99%

“…4) [7,9,29]. Several experiments suggested either phosphoglyceric acid or phosphoenolpyruvate as the starter unit [29]. Phosphoenolpyruvate was deemed an attractive possibility because an addition-elimination ring closure mechanism can be postulated (Scheme 4) [29].…”

Section: Glycerol Derived Starter Unitsmentioning

confidence: 99%

“…This process has analogies with the reaction catalysed by 5-enoylpyruvylshikimate-3-phosphate synthase. A second hypothetical mechanism for ring closure involves a S N 2-type displacement of phosphate from C-16 by the C-13 hydroxyl group (Scheme 4) [29]. An analogous mechanism can be postulated using phosphoglycerate as the starter unit [29].…”

Section: Glycerol Derived Starter Unitsmentioning

confidence: 99%

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Mechanisms for incorporation of glycerol-derived precursors into polyketide metabolites

Walton¹,

Corre²,

Challis³

2005

J IND MICROBIOL BIOTECHNOL

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Several polyketide secondary metabolites are shown by feeding experiments to incorporate glycerol-derived 3-carbon starter units, 2-carbon extender units, or 3-carbon branches into their hydrocarbon chains. In recent years, genetic studies have begun to elucidate the mechanisms by which this occurs. In this article we review the incorporation of glycerol-derived precursors into polyketides and propose new mechanisms for the incorporation processes.

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The Oxidation of Alcohols by Modified Oxochromium( VI )–Amine Reagents

Luzzio

1998

Organic Reactions

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The development of oxochromium(VI)‐amine reagents as oxidants in organic synthesis has evolved since the early studies of Sisler which described the use of adducts of heterocyclic nitrogen bases and chromium(VI) oxide. The later work of Sarrett and coworkers in steroid synthesis soon established the utility of chromium(VI) oxide‐pyridine adducts as the first selective oxochromium(VI)‐amine reagents. Several modifications of the Sarrett oxidation followed. The present concern with the toxicity and environmental implications of oxochromium(VI) has provided encouragement for the study and use of catalytic oxochromium reagents in conjunction with stoichiometric co‐oxidants such as peroxides. Such technology is welcome, particularly when applied to the large‐scale preparations found in industry where the disposal of byproducts is a constant problem. Modified oxochromium(VI)‐amine reagents on polymer supports have been prepared and examined with the objective of providing a regenerable reagent system which is serviceable on a practical scale. A significant improvement in routine oxidations utilizing PCC and PDC entails the addition of adsorbents such as Celite®, alumina, silica gel, molecular sieves, or zeolites. The distinct advantages associated with the use of adsorbents in oxochromium(VI)‐amine‐mediated oxidations are discussed. The importance of buffers and desiccants in oxochromium(VI) oxidations is discussed. Virtually any number of oxochromium(VI)‐amine reagents may be prepared by varying the amine ligand and/or acid species associated with oxochromium(VI), and many of these compounds have been tested using simple substrate alcohols for oxidation to carbonyl compounds. The search for a milder and more efficient oxidant than the Sarrett‐type oxochromium(VI) reagent systems as well as the nonchromium oxidants based on dimethyl sulfoxide or dimethyl sulfide led to an examination of the utility of pyridinium chlorochromate (PCC) in selective oxidations of alcohols. PCC was superior in terms of ease of preparation, shelf stability and economy. Since the introduction of PCC in 1975 the reagent has become a commercially available “textbook” compound and is usually the reagent of choice for routine large and small scale oxidations of alcohols to carbonyl compounds. Unlike the oxochromium(VI)‐pyridine adducts, PCC is an acid salt, and its properties have proven advantageous in a number of tandem oxidative reactions such as oxidative transpositions and oxidative cationic cyclizations. Several reviews address the versatility of PCC and its extension to many different types of oxidative conversions in single and multistep organic syntheses. While PCC was gaining widespread use, the utility of pyridinium dichromate (PDC) in solvents such as dimethylformamide (DMF) and dichloromethane was reported. PDC/DMF was useful for oxidizing allylic alcohols to the corresponding, α,β‐unsaturated carbonyl compounds and non‐conjugated aldehydes and primary alcohols to the corresponding carboxylic acids. The utilization of beyond the simple oxidation of alcohols, and it is now employed for various transformations. Many other types of substituted pyridines, nitrogen heterocycles and amines form chromates, dichromates, and chlorochromates which allow many different types of oxidative processes for a wide range of substrate molecules. This chapter surveys the many applications of oxochromium(VI) complexes in oxidative conversions of alcohols to carbonyl compounds. Alternative reagent systems based on modifications involving ligands, buffering agents, or adsorbents, as well as nonchromium(VI) oxidants are discussed. A variety of substrates have been included in the Tables so as to guide the synthetic chemist in selecting reagents and conditions that will be optimal for a given transformation. Oxidative conversions of alcohols through transpositions and cationic cyclizations giving carbonyl compounds as endproducts are included.

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Further studies on the biosynthesis of the boron-containing antibiotic aplasmomycin

Cited by 28 publications

References 2 publications

Boronated tartrolon antibiotic produced by symbiotic cellulose-degrading bacteria in shipworm gills

Boronated tartrolon antibiotic produced by symbiotic cellulose-degrading bacteria in shipworm gills

Mechanisms for incorporation of glycerol-derived precursors into polyketide metabolites

The Oxidation of Alcohols by Modified Oxochromium( VI )–Amine Reagents

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