Unser 10. Leibniz Plant Biochemistry Symposium am 7. und 8. Mai war ein großer Erfolg. Thematisch ging es in diesem Jahr um neue Methoden und Forschungsansätze der Naturstoffchemie. Die exzellenten Vorträge über Wirkstoffe…
Omanische Heilpflanze im Fokus der Phytochemie IPB-Wissenschaftler und Partner aus Dhofar haben jüngst die omanische Heilpflanze Terminalia dhofarica unter die phytochemische Lupe genommen. Die Pflanze ist reich an…
Geschmack ist vorhersagbar: Mit FlavorMiner. FlavorMiner heißt das Tool, das IPB-Chemiker und Partner aus Kolumbien jüngst entwickelt haben. Das Programm kann, basierend auf maschinellem Lernen (KI), anhand der…
Müller, H.; Heinze, M.; Heinke, R.; Schmidt, J.; Roos, W.;Self-regulation of phytoalexin production: a non-biosynthetic enzyme controls alkaloid biosynthesis in cultured cells of Eschscholzia californicaPlant Cell Tiss. Organ Cult.119661-676(2014)DOI: 10.1007/s11240-014-0565-6
Benzophenanthridine alkaloids are strong antimicrobials of Papaveraceae and attractive lead compounds for drug development. The cytotoxicity of these compounds requires the producing plant to limit the pathogen-triggered burst of biosynthesis. Cells of Eschscholzia californica excrete early benzophenanthridines to the cell wall, followed by re-uptake and reduction in the cytoplasm by the detoxifying enzyme sanguinarine reductase. We now discovered that this enzyme is a core component of self-control in alkaloid production. RNAi-based silencing of sanguinarine reductase gave rise to mutants that either show a complete stop of elicitor-triggered alkaloid production or a burst of biosynthesis that severalfold surpasses the wild type level. These unexpected phenotypes reflect impacts of substrate or product of sanguinarine reductase: the substrate, sanguinarine, inhibits phospholipase A2 at the plasma membrane, an initial component of the signal path towards expression of biosynthetic enzymes. The product, dihydrosanguinarine, inhibits enzymes of early biosynthesis, prior to reticuline formation. By tuning these steady states, sanguinarine reductase adjusts the capacity of alkaloid biosynthesis: a minimum activity is sufficient to prevent the blockade of the induction pathway by sanguinarine, while the full activity of the same enzyme causes a limitation of the biosynthetic flow via dihydrosanguinarine.
Publikation
Bette, M.; Schmidt, J.; Steinborn, D.;Diacetylplatinum(II) and -platinum(IV) Complexes Bearing κ2- and κ3-Coordinated Tris(pyrazolyl)methane Ligands: Investigations on the Synthesis, Fluxionality, and Reactivity in Relation to the Substitution Pattern of the LigandsEur. J. Inorg. Chem.20132395-2410(2013)DOI: 10.1002/ejic.201201468
Reactions of the dinuclear platina‐β‐diketone [Pt2{(COMe)2H}2(μ‐Cl)2] (1) with HC(pz)3 and HC(3,5‐Me2pz)3 (pz = pyrazol‐1‐yl; 3,5‐Me2pz = 3,5‐dimethylpyrazol‐1‐yl) afforded cationic, thermally labile diacetyl(hydrido)platinum(IV) complexes [Pt(COMe)2H{(pz)3CH}]Cl (3a) and [Pt(COMe)2H{(3,5‐Me2pz)3CH}]Cl (3b) with κ3‐coordinated tris(pyrazolyl)methane ligands, which were found to react with NaOH or NEt3 to yield neutral diacetylplatinum(II) complexes with κ2‐coordinated tris(pyrazolyl)methane ligands {[Pt(COMe)2{(pz)3CH}] (4a); [Pt(COMe)2{(3,5‐Me2pz)3CH}] (4b)}. In 4a/b, a molecular rearrangement (decoordination of a pyrazolyl ring and coordination of the originally pendant one) has been found that has been investigated by variable‐temperature 1H NMR spectroscopic measurements (coalescence method) as well as by DFT calculations. Diacetylplatinum(II) complexes 4 were found to react in oxidative addition reactions with ROTf (R = H, Me; OTf = trifluoromethanesulfonate) and methyl iodide to yield cationic diacetylplatinum(IV) complexes of the type [Pt(COMe)2R{(pz)3CH}]X (R/X = H/OTf, 5a; Me/OTf, 6a; Me/I, 7a) and [Pt(COMe)2R{(3,5‐Me2pz)3CH}]X [R/X = H/OTf (5b), Me/OTf (6b), Me/I (7b)] with κ3‐bonded tris(pyrazolyl)methane ligands. Treatment of 4b with alkynyliodine(III) reagents of the type [IPh(C≡CR)]X (R/X = SiMe3/OTf, Ph/OTf, tBu/OTos, iPr/OTos; OTos = p‐toluenesulfonate) led to the formation of cationic diacetyl(alkynyl)platinum(IV) complexes [Pt(COMe)2(C≡CR){(3,5‐Me2pz)3CH}]X [R/X = SiMe3/OTf (8a), Ph/OTf (8b), tBu/OTos (8c), iPr/OTos (8d)]. The identities of all platinum complexes were unambiguously proven by high‐resolution mass spectrometric investigations, by NMR (1H, 13C, 195Pt) and IR spectroscopy, as well as by single‐crystal X‐ray diffraction analyses (4a, 4b, 7a, 8a/d). The constitution of the thermally labile complexes 3a/b has been confirmed by low‐temperature (–80 °C) NMR (1H, 13C) spectroscopic measurements. The electronic and steric influence of the additional methyl groups in HC(3,5‐Me2pz)3 on reactivity, stability, and properties of the investigated compounds will be discussed.