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191.
Total Synthesis of Keramamides A and L from a Common Precursor by Late‐Stage Indole Synthesis and Configurational Revision
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Lukas Junk Prof. Dr. Uli Kazmaier 《Angewandte Chemie (International ed. in English)》2018,57(35):11432-11435
The marine natural products keramamide A and L, members of the class of anabaenopeptin‐type peptides, were synthesized for the first time by a convergent and flexible route. The installation of the substituted tryptophan moieties was accomplished at the very end of the synthesis on the cyclic peptides, and thus enabled the synthesis of both natural products from one common precursor. The preparation of several epimers clearly indicates that the originally proposed relative configurations of both Keramamides A and L were not correct. 相似文献
192.
Two Bacterial Diterpene Synthases from Allokutzneria albata Produce Bonnadiene,Phomopsene, and Allokutznerene
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Lukas Lauterbach Jan Rinkel Prof. Dr. Jeroen S. Dickschat 《Angewandte Chemie (International ed. in English)》2018,57(27):8280-8283
Two diterpene synthases from Allokutzneria albata were studied for their products, resulting in the identification of the new compound bonnadiene from the first enzyme. Although phylogenetically unrelated to fungal phomopsene synthase, the second enzyme produced a mixture of phomopsene and a biosynthetically linked new compound, allokutznerene, as well as spiroviolene. Both enzymes were subjected to in‐depth mechanistic studies involving isotopic labelling experiments, metal‐cofactor variation, and site‐directed mutagenesis. Oxidation products of phomopsene and allokutznerene are also discussed. 相似文献
193.
Vijayakumar EK Roy K Chatterjee S Deshmukh SK Ganguli BN Fehlhaber HW Kogler H 《The Journal of organic chemistry》1996,61(19):6591-6593
Arthrichitin (1), C(33)H(46)N(4)O(9), is a new cell wall active depsipeptide isolated from the fermentation broth of Arthrinium phaeospermum (HIL Y-903022). Its structure was elucidated on the basis of spectroscopic and chemical degradation studies. Arthrichitin consists of serine, beta-keto tryptophan, glutamic acid, and 2,4-dimethyl-3-hydroxydodecanoic acid units. 相似文献
194.
Henri Brunner Rainer Lukas Annamaria Woditsch 《Journal of organometallic chemistry》1978,161(2):C49-C52
(η-C5H5)(CO)2W[(η3-C5H5)(C5H5)2], I, containing two tilted five-membered rings, is converted into the bridged ferrocene derivative (η-C5H5)(CO)2W{(η3-C5H5)}[(η-C5 H4)2Fe]} II by successive reaction with Na and FeCl2. 相似文献
195.
Goossen LJ Koley D Hermann H Thiel W 《Chemical communications (Cambridge, England)》2004,(19):2141-2143
Based on DFT calculations, a new mechanism for the oxidative addition of aryl halides to Pd-catalysts is presented. The key intermediate is an anionic Pd-species in which the aryl halide coordinates to the palladium via the halide atom. 相似文献
196.
Huang HL Stasyk T Morandell S Mogg M Schreiber M Feuerstein I Huck CW Stecher G Bonn GK Huber LA 《Electrophoresis》2005,26(14):2843-2849
We present a simple protocol for affinity depletion to remove the two most abundant serum proteins, albumin and immunoglobulin G (IgG). Under native conditions, albumin/IgG were efficiently removed and several proteins were enriched as shown by two-dimensional electrophoresis (2-DE). Besides that, partly denaturing conditions were established by adding 5 or 20% acetonitrile (ACN) in order to disrupt the binding of low-molecular-weight (LMW) proteins to the carrier proteins albumin/IgG. 2-DE results showed that the total number of detected LMW proteins increased under denaturing conditions when compared to native conditions. Interestingly, the presence of 5% ACN in serum revealed better enrichment of LMW proteins when compared to 20% ACN condition. Seven randomly distributed spots in albumin/IgG depleted serum samples under 5% ACN condition were picked from the 2-DE gels and identified by mass spectrometry (MS). The intensity of five LMW protein spots increased under denaturing conditions when compared to native conditions. Three of the seven identified spots (serum amyloid P, vitamin D-binding protein, and transthyretin) belong to a group of relatively low-abundant proteins, which make up only 1% of all serum proteins. The method presented here improves the resolution of the serum proteome by increasing the number of visualized spots on 2-D gels and allowing the detection and MS identification of LMW proteins and proteins of lower abundance. 相似文献
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199.
Sebastian Preiß Ayla Päpcke Lukas Burkhardt Luca Großmann Prof. Dr. Stefan Lochbrunner Prof. Dr. Matthias Bauer Prof. Dr. Till Opatz Prof. Dr. Katja Heinze 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(23):5940-5949
In the context of solar-to-chemical energy conversion, inspired by natural photosynthesis, the synthesis, electrochemical properties and photoinduced electron-transfer processes of three novel zinc(II)-gold(III) bis(porphyrin) dyads [ZnII(P)–AuIII(P)]+ are presented (P: tetraaryl porphyrin). Time-resolved spectroscopic studies indicated ultrafast dynamics (k >1010 s−1) after visible-light excitation, which finally yielded a charge-shifted state [ZnII(P ⋅ +)–AuII(P)]+ featuring a gold(II) center. The lifetime of this excited state is quite long due to a comparably slow charge recombination (k ≈3×108 s−1). The [ZnII(P ⋅ +)–AuII(P)]+ charge-shifted state is reductively quenched by amines in bimolecular reactions, yielding the neutral zinc(II)–gold(II) bis(porphyrin) ZnII(P)–AuII(P). The electronic nature of this key gold(II) intermediate, prepared by chemical or photochemical reduction, is elucidated by UV/Vis, X-band EPR, gold L3-edge X-ray absorption near edge structure (XANES) and paramagnetic 1H NMR spectroscopy as well as by quantum chemical calculations. Finally, the gold(II) site in ZnII(P)–AuII(P) is thermodynamically and kinetically competent to reduce an aryl azide to the corresponding aryl amine, paving the way to catalytic applications of gold(III) porphyrins in photoredox catalysis involving the gold(III/II) redox couple. 相似文献
200.
Lukas Mai Nils Boysen David Zanders Dr. Teresa de los Arcos Dr. Felix Mitschker Dr. Bert Mallick Prof. Dr. Guido Grundmeier Prof. Dr. Peter Awakowicz Prof. Dr. Anjana Devi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(31):7489-7500
New precursor chemistries for the atomic layer deposition (ALD) of aluminium oxide are reported as potential alternatives to the pyrophoric trimethylaluminium (TMA) which is to date a widely used Al precursor. Combining the high reactivity of aluminium alkyls employing the 3-(dimethylamino)propyl (DMP) ligand with thermally stable amide ligands yielded three new heteroleptic, non-pyrophoric compounds [Al(NMe2)2(DMP)] ( 2 ), [Al(NEt2)2(DMP)] ( 3 , BDEADA) and [Al(NiPr2)2(DMP)] ( 4 ), which combine the properties of both ligand systems. The compounds were synthesized and thoroughly chemically characterized, showing the intramolecular stabilization of the DMP ligand as well as only reactive Al−C and Al−N bonds, which are the key factors for the thermal stability accompanied by a sufficient reactivity, both being crucial for ALD precursors. Upon rational variation of the amide alkyl chains, tunable and high evaporation rates accompanied by thermal stability were found, as revealed by thermal evaluation. In addition, a new and promising plasma enhanced (PE)ALD process using BDEADA and oxygen plasma in a wide temperature range from 60 to 220 °C is reported and compared to that of a modified variation of the TMA, namely [AlMe2(DMP)] (DMAD). The resulting Al2O3 layers are of high density, smooth, uniform, and of high purity. The applicability of the Al2O3 films as effective gas barrier layers (GBLs) was successfully demonstrated, considering that coating on polyethylene terephthalate (PET) substrates yielded very good oxygen transmission rates (OTR) with an improvement factor of 86 for a 15 nm film by using DMAD and a factor of 25 for a film thickness of just 5 nm by using BDEDA compared to bare PET substrates. All these film attributes are of the same quality as those obtained for the industrial precursor TMA, rendering the new precursors safe and potential alternatives to TMA. 相似文献