January 2025
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13 Reads
Zeitschrift fur Naturforschung B
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January 2025
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13 Reads
Zeitschrift fur Naturforschung B
June 2024
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38 Reads
The pH‐dependent UV/Vis absorption and fluorescence of several analogs of the marine natural product ageladine A were investigated. Besides ageladine A itself, its BF2 complex and the corresponding debrominated analogs were included, as were the chloro analog of the debromoageladine‐BF2 complex, an imidazolone analog, and a triazole derivative, which lack the free amino group. Importantly, the pH‐dependence of the fluorescence of the chloro analog closely resembles that of the natural product ageladine A, but with about 25‐fold higher fluorescence intensity and a maximum between pH 3 and 6. The imidazolone derivative behaves in a complementary manner and shows fluorescence only above pH 6, but with less intensity than ageladine A. The calculated Stokes shifts agree well with the experiment, which underlines the accuracy of the DFT calculation method (ωB97XD/TApr‐cc‐pVDZ, PCM). The conformational fixation of arylated imidazo[4,5‐c]pyridines by BF2 units seems to be promising with regard to the development of novel, pH‐dependent fluorescent probes.
February 2024
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141 Reads
Nachrichten aus der Chemie
Unter anderem das hat die Organik im letzten Jahr bewegt: milde Oxidation mit Elektrochemie, Oxidation zu enantiomerenreinen Sulfonylverbindungen, Flüssigkristallphasen erkennen mit maschinellem Lernen, CO 2 reagiert zu Succinat und Carbamaten, eine Alternative zu Bisphenol A, Subporphyrine, photoschaltbare Spinmaterialien, photochemische Thiophen‐Ringerweiterung, und Peptide werden mit Bor versehen und cyclisiert. Die Zusammenstellung des Trendberichts koordiniert hat Martin Breugst, Universität Chemnitz.
November 2023
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11 Reads
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1 Citation
Organic & Biomolecular Chemistry
The tetracyclic core structure of the majority of indole diterpenoids features a trans-hydrindane moiety that is fused to an indole unit. We report here a novel synthetic route that includes...
November 2023
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14 Reads
Synthesis
The first synthesis of the marine natural product cyanogramide D is reported. The key step is the acetylation of a β-carboline N-oxide, followed by acetyl migration. Since in this particular case it was not possible to incorporate the styryl side chain by Buchwald coupling, a phenylethanolamine side chain was attached, which was dehydrated with Martin's sulfurane after assembly of the tetracycle. Pentacyclic products were obtained under Appel conditions. The synthesis will facilitate the exploration of the biomimetic oxidative spirocyclization of cyanogramide D to the spirooxindole cyanogramide.
March 2023
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15 Reads
Zeitschrift fur Naturforschung B
As part of our program on the synthesis and reactivity of the pyrrole-imidazole alkaloids from marine sponges, the synthesis of the 2-azido analog of the key marine natural product oroidin is reported. In addition, desaminooroidin and its alkyne analog were synthesized. Red-Al reduction of a 4-alkynylimidazole intermediate afforded the ( E )-alkene, without having to pass via the ( Z )-alkene. Coupling of 4,5-dibromopyrrole-2-carboxylic acid with 2-azidoimidazolylprop-2-en-1-amine was best achieved by EDCI-mediated coupling, which was superior to using the corresponding trichloromethylketone. Use of t- BuOK in acetonitrile can be recommended for the coupling of non-azidated alkenyl and alkynylimidazoles. The azido analog of oroidin underwent click cycloadditions to imidazolyltriazoles.
March 2023
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145 Reads
Nachrichten aus der Chemie
Polystyrolproben werden mit Eisen(III)chlorid und weißen LEDs zu Oligomeren und Benzoylprodukten; ein Wolframatkatalysator invertiert die Absolutkonfiguration an sp3‐Kohlenstoffzentren; gelöstes Rätsel um eine symmetrieverbotene konrotatorische 14‐Elektronen‐Elektrocyclisierung; Polycarbonate, die sich ohne Lösungsmittel recyceln lassen: Highlights von Oktober 2021 bis 2022.
March 2022
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7 Reads
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3 Citations
Organic Letters
Marinacarboline E and cyanogramides B and C from the marine-derived bacterium Actinoalloteichus cyanogriseus have been synthesized. The key step is the Baeyer-Villiger oxidation of marinacarboline E to a ketene aminal via O → N acetyl migration, followed by addition of water or MeOH. Replacing the phenylethyl by a styryl side chain afforded dehydromarinacarboline E that was oxidized to a tetracyclic aminal. This study contributes to the chemical understanding of the enzymatic conversions in the biosynthesis of the cyanogramides.
February 2022
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12 Reads
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4 Citations
Organic Letters
The marine natural product ageladine A was synthesized by exploiting novel aza-BODIPY-type boron complexes that allowed the regioselective dibromination of the pyrrole unit, as confirmed by quantum chemical calculation (ωB97XD/TApr-cc-pVDZ). The parent tricycle was accessed by Suzuki-Miyaura cross-coupling employing Buchwald's precatalyst. The boron complex of ageladine A exhibited strong fluorescence that was greater than that of the natural product by a factor of ∼30 and that disappeared in the presence of 2-azido groups.
February 2022
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152 Reads
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2 Citations
Nachrichten aus der Chemie
Flüssigkristalle als responsive Materialien etwa in der organischen Elektronik, erste Nanogürtel mit Acencharakter, direkt aus der Atmosphäre entferntes CO2, Disauerstoff wird organokatalytisch zu Wasserstoffperoxid, und Chinazolinone lassen sich biokatalytisch herstellen.
... [23] In recent years, photochemical strategies were increasely applied in the synthesis of natural products. [24] Photo-Nazarov reactions were reported in the construction of cyclopentane-fused heteroaromatic scaffolds in several polycyclic natural products, [25] such as the indeno [1,2-b]indole scaffolds in 16-epi-terpendole E [26] and Janthitrem B [27] (Scheme 1, b). However, photochemical construction strategy of indeno[2, 1b]indole has never been reported until now. ...
November 2023
Organic & Biomolecular Chemistry
... 73 Marinacarboline E 35 is the precursor for the synthesis of cyanogramide B 38 and C 39. Sarnes and companions in 2022, presented the synthesis of marinacarboline E 35, cyanogramides B 38 and C 39 by employing Baeyer-Villiger oxidation as a basic step. 70 In the rst step of synthesis, L-tryptophan methyl ester 32 was converted into the natural product stellarine C 33 in 61% yield via Pictet-Spengler reaction with an aldehyde in the presence of iodine, p-toluene sulfonic acid and methanol. In the next step, methylation of b-carboline 33 in the presence of NaH, MeI in DMF followed by saponication with LiOH in THF to generate the compound 34 in 90% yield. ...
March 2022
Organic Letters
... Indazapyroxamet (X) (Fig. 20) is a novel active ingredient from FMC, [76][77][78][79] and was first discovered by DuPont in 2013. 80 It contains a pyridine linked in the 3-position to an indazolylcarboxamide. ...
February 2022
Nachrichten aus der Chemie
... In our total synthesis of ageladine A (1), we came across aza-BODIPY-type BF 2 -complexes of ageladine A and precursors. [10] In particular, we obtained the BF 2 -complex 3 of ageladine A, which exhibited much stronger fluorescence. In this paper, we report on the pH-dependent fluorescence of several of our ageladine analogs, assessing the preferred protonation states and tautomers with the help of absorption and emission spectra and also quantum chemical calculations. ...
February 2022
Organic Letters
... Therefore, CASE systems have a high relevance by integrating all existing computational methods, for example, structure generation by structure assembly [361][362][363][364] and reduction [365], stochastic structure generators [366], combinatorial structure generation with restraints [367,368], convergent structure generation [369,370], fuzzy structure generation [371], chemical graph generators [42], logic engines [372], combinatorial brute force [373][374][375][376], databases of 13 C NMR chemical shifts and fragments [377,378], genetic algorithms [379,380], simulated annealing [381], evolutionary algorithms [382], expert systems [44,383], and expert systems with Density Functional Theory (DFT) [43][44][45]. In Figure 7, the main achievements of CASE systems are highlighted [39][40][41]43,384,385]. The evolution of the CASE systems in the past fifty years clearly highlights three approaches, shown in Figure 7. Phase I between 1969 and 1994 is represented in light blue, Phase II between 1991 and 2016 in blue, and Phase III between 2016 and 2023 in purple. ...
August 2021
Molecules
... Moco biosynthesis is essential for various cellular functions across eukaryotic organisms 56 . The incorporation of Mo into MPT to form Moco is a critical step catalyzed by the Mo insertase 57 . While this process is wellcharacterized in many organisms, the structural and functional diversity of Mo insertases across species remains intriguing. ...
December 2019
Bioscience Reports
... It was assumed that the chair-like transition state 97a is favored compared with the boat or twist-boat 97b. [41] Lindel and coworkers [42] recently reported the synthesis of the indol alkaloid raputimonoindole A including the assignment of the absolute configuration. They used as the key step our domino Heck Suzuki protocol that proved to be a reliable method (Scheme 30). ...
June 2019
... Commercial (-)-methyl (S)-3-bromo-2-methylpropionate (6) served as convenient point of departure, which was treated with Et 2 Zn in the presence of catalytic amounts of MnBr 2 and CuCl in DMPU (Scheme 2). [23,24] The resulting zinc homoenolate was coupled with 1-bromo-2-methyl-1-propene (7) under palladium catalysis to afford 8. Although this product can also be made more conventionally by asymmetric prenylation of a propionate derivative under the aegis of a chiral auxiliary (see the Supporting Information), the new route based on the alkyl-Negishi reaction [25] is catalytic in nature, shorter overall, higher yielding, and scalable; as it resorts to the "chiral pool", the optical purity of the product was impeccable (ee � 99.8 %). ...
February 2019
Beilstein Journal of Organic Chemistry
... Salarins are marine macrolides extracted from Madagascan sponge (Facaplysinopsis sp.) comprising of 17-membered lactone set with a trisubstituted oxazole or a trisacylamine core. Salarin C 181 (a nitrogenous macrolide) isolated by Kashman and coworkers belongs to this class and acts as antiproliferative agent (Fig. 26) [96,97]. ...
October 2018
Organic Letters
... Eunicellin-based diterpenes (Figures 2 and 3) are marine natural products that consist of a six-membered ring moiety fused to a ten-membered ring moiety. In many compounds, an additional ether bridge is formed between C-2 and C-9 or C-4 and C-7 [23]. ...
September 2018
Beilstein Journal of Organic Chemistry