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1.
Angew Chem Int Ed Engl ; 60(12): 6451-6456, 2021 Mar 15.
Article in English | MEDLINE | ID: mdl-33320996

ABSTRACT

The TeII /TeIII -catalyzed dehydrogenative C-H phenothiazination of challenging phenols featuring electron-withdrawing substituents under mild aerobic conditions and with high yields is described. These unexpected TeII /TeIII radical catalytic properties were characterized by cyclic voltammetry, EPR spectroscopy, kinetic experiments, and DFT calculations.

2.
Chem Commun (Camb) ; 55(91): 13749-13752, 2019 Nov 12.
Article in English | MEDLINE | ID: mdl-31663087

ABSTRACT

Highly π-extended hetero-cyclic/aromatic skeletons are of great importance as they can be utilized in many organic material based technologies. Therefore, developing efficient, pre-activation-free, synthetic procedures for the rapid build-up of these complex structures remains a high priority objective. The herein presented approach delivers highly fused carbazole skeletons from simple naphthylamine derivatives.

3.
Org Lett ; 21(17): 6830-6834, 2019 Sep 06.
Article in English | MEDLINE | ID: mdl-31429294

ABSTRACT

A silver-tetrafluoroborate- or HBF4-catalyzed ortho-alkylation reaction of phenols and diarylamines with styrenes has been explored. A broad substrate scope is presented as well as mechanistic experiments and discussion.

4.
Chemistry ; 24(57): 15178-15184, 2018 Oct 12.
Article in English | MEDLINE | ID: mdl-29928784

ABSTRACT

The mechanism of a trinuclear cooperative dehydrogenative C-N bond-forming reaction is investigated in this work, which avoids the use of chelate-assisting directing groups. Two new highly efficient Ru/Cu co-catalyzed systems were identified, allowing orders of magnitude greater TOFs than the previous state of the art. In-depth kinetic studies were performed in combination with advanced DFT calculations, which reveal a decisive rate-determining trinuclear Ru-Cu cooperative reductive elimination step (CRE).

5.
Metabolites ; 2(1): 39-56, 2012 Jan 05.
Article in English | MEDLINE | ID: mdl-24957367

ABSTRACT

Aspergillus oryzae and A. flavus are important species in industrial biotechnology and food safety and have been some of the first aspergilli to be fully genome sequenced. Bioinformatic analysis has revealed 99.5% gene homology between the two species pointing towards a large coherence in the secondary metabolite production. In this study we report on the first comparison of secondary metabolite production between the full genome sequenced strains of A. oryzae (RIB40) and A. flavus (NRRL 3357). Surprisingly, the overall chemical profiles of the two strains were mostly very different across 15 growth conditions. Contrary to previous studies we found the aflatrem precursor 13-desoxypaxilline to be a major metabolite from A. oryzae under certain growth conditions. For the first time, we additionally report A. oryzae to produce parasiticolide A and two new analogues hereof, along with four new alkaloids related to the A. flavus metabolites ditryptophenalines and miyakamides. Generally the secondary metabolite capability of A. oryzae presents several novel end products likely to result from the domestication process from A. flavus.

6.
J Nat Prod ; 74(11): 2338-48, 2011 Nov 28.
Article in English | MEDLINE | ID: mdl-22026385

ABSTRACT

Dereplication, the rapid identification of known compounds present in a mixture, is crucial to the fast discovery of novel natural products. Determining the elemental composition of compounds in mixtures and tentatively identifying natural products using MS/MS and UV/vis spectra is becoming easier with advances in analytical equipment and better compound databases. Here we demonstrate the use of LC-UV/vis-MS-based dereplication using data from UV/vis diode array detection and ESI+/ESI- time-of-flight MS for assignment of 719 microbial natural product and mycotoxin reference standards. ESI+ was the most versatile ionization method, detecting 93% of the compounds, although with 12% ionizing poorly. Using ESI+ alone, 56.1% of the compounds could be unambiguously assigned based on characteristic patterns of multiple adduct ions. Using ESI-, 36.4% of the compounds could have their molecular mass assigned unambiguously using multiple adduct ions, while a further 41% of the compounds were detected only as [M - H]-. The most reliable interpretations of conflicting ESI+ and ESI- data on a chromatographic peak were from the ionization polarity with the most intense ionization. Poor ionization was most common with small molecules (<200 Da). In ESI-, these were often polar and basic, while in ESI+ they were small aromatic acids or anthraquinones. No single ion-source settings could be applied over a m/z 60-2000 range. However, continuous switching among three settings (e.g., for 0.5 s each) during the chromatographic run allowed MS of both small labile molecules and large peptides, and pseudo MS/MS data on labile molecules since the settings for large molecules often induce fragmentation into small molecules.


Subject(s)
Biological Products , Biological Products/analysis , Biological Products/chemistry , Biological Products/metabolism , Molecular Structure , Molecular Weight , Spectrometry, Mass, Electrospray Ionization , Tandem Mass Spectrometry
7.
FEMS Microbiol Lett ; 321(2): 157-66, 2011 Aug.
Article in English | MEDLINE | ID: mdl-21658102

ABSTRACT

Fungi possess an advanced secondary metabolism that is regulated and coordinated in a complex manner depending on environmental challenges. To understand this complexity, a holistic approach is necessary. We initiated such an analysis in the important model fungus Aspergillus nidulans by systematically deleting all 32 individual genes encoding polyketide synthases. Wild-type and all mutant strains were challenged on different complex media to provoke induction of the secondary metabolism. Screening of the mutant library revealed direct genetic links to two austinol meroterpenoids and expanded the current understanding of the biosynthetic pathways leading to arugosins and violaceols. We expect that the library will be an important resource towards a systemic understanding of polyketide production in A. nidulans.


Subject(s)
Aspergillus nidulans/enzymology , Aspergillus nidulans/genetics , Gene Knockout Techniques , Phenols/metabolism , Polyketide Synthases/genetics , Terpenes/metabolism , Aspergillus nidulans/metabolism , Fungal Proteins/genetics , Fungal Proteins/metabolism , Gene Library , Genes, Fungal/genetics , Metabolic Networks and Pathways , Multigene Family , Phenotype , Polyketide Synthases/metabolism
8.
Fungal Biol ; 115(4-5): 406-20, 2011.
Article in English | MEDLINE | ID: mdl-21530923

ABSTRACT

During the last 50y, the carcinogenic mycotoxin sterigmatocystin (ST) has been reported in several phylogenetically and phenotypically different genera: Aschersonia, Aspergillus, Bipolaris, Botryotrichum, Chaetomium, Emericella, Eurotium, Farrowia, Fusarium, Humicola, Moelleriella, Monocillium and Podospora. We have reexamined all available strains of the original producers, in addition to ex type and further strains of each species reported to produce ST and the biosynthetically derived aflatoxins. We also screened strains of all available species in Penicillium and Aspergillus for ST and aflatoxin. Six new ST producing fungi were discovered: Aspergillus asperescens, Aspergillus aureolatus, Aspergillus eburneocremeus, Aspergillus protuberus, Aspergillus tardus, and Penicillium inflatum and one new aflatoxin producer: Aspergillus togoensis (=Stilbothamnium togoense). ST was confirmed in 23 Emericella, four Aspergillus, five Chaetomium, one Botryotrichum and one Humicola species grown on a selection of secondary metabolite inducing media, and using multiple detection methods: HPLC-UV/Vis DAD, - HRMS and - MS/MS. The immediate precursor for aflatoxin, O-methylsterigmatocystin was found in Chaetomium cellulolyticum, Chaetomium longicolleum, Chaetomium malaysiense and Chaetomium virescens, but aflatoxin was not detected from any Chaetomium species. In all 55 species, representing more than 11 clades throughout the Pezizomycotina, can be reliably claimed to be ST producers and 13 of these can also produce aflatoxins. It is not known yet whether the ST/aflatoxin pathway has been developed independently 11 times, or is the result of partial horizontal gene transfer.


Subject(s)
Aflatoxins/metabolism , Aspergillus/metabolism , Penicillium/metabolism , Sterigmatocystin/biosynthesis , Aflatoxins/analysis , Aflatoxins/biosynthesis , Aspergillus/chemistry , Aspergillus/genetics , DNA, Fungal , Fungi/metabolism , Penicillium/chemistry , Penicillium/genetics , Phylogeny , Sterigmatocystin/metabolism , Talaromyces/chemistry
9.
Med Mycol ; 47 Suppl 1: S53-71, 2009.
Article in English | MEDLINE | ID: mdl-18763205

ABSTRACT

Aspergillus fumigatus is the most important species in Aspergillus causing infective lung diseases. This species has been reported to produce a large number of extrolites, including secondary metabolites, acids, and proteins such as hydrophobins and extracellular enzymes. At least 226 potentially bioactive secondary metabolites have been reported from A. fumigatus that can be ordered into 24 biosynthetic families. Of these families we have detected representatives from the following families of secondary metabolites: fumigatins, fumigaclavines, fumiquinazolines, trypacidin and monomethylsulochrin, fumagillins, gliotoxins, pseurotins, chloroanthraquinones, fumitremorgins, verruculogen, helvolic acids, and pyripyropenes by HPLC with diode array detection and mass spectrometric detection. There is still doubt whether A. fumigatus can produce tryptoquivalins, but all isolates produce the related fumiquinazolines. We also tentatively detected sphingofungins in A. fumigatus Af293 and in an isolate of A. lentulus. The sphingofungins may have a similar role as the toxic fumonisins, found in A. niger. A further number of mycotoxins, including ochratoxin A, and other secondary metabolites have been reported from A. fumigatus, but in those cases either the fungus or its metabolite appear to be misidentified.


Subject(s)
Aspergillus fumigatus/chemistry , Aspergillus fumigatus/metabolism , Metabolomics , Organic Chemicals/analysis , Aspergillosis/microbiology , Aspergillus fumigatus/isolation & purification , Chromatography, High Pressure Liquid , Humans , Organic Chemicals/classification , Plants/microbiology , Soil Microbiology
10.
Org Lett ; 10(3): 401-4, 2008 Feb 07.
Article in English | MEDLINE | ID: mdl-18179222

ABSTRACT

Novofumigatonin (1), a new metabolite, has been isolated from Aspergillus novofumigatus. The structure and relative stereochemistry were determined from HR ESI MS, one- and two-dimensional NMR, and single-crystal X-ray analysis. The absolute configuration was assigned using vibrational circular dichroism in combination with density functional calculations.


Subject(s)
Aspergillus/chemistry , Terpenes/chemistry , Terpenes/isolation & purification , Circular Dichroism/methods , Crystallography, X-Ray , Molecular Conformation , Molecular Structure
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