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Hans-joachim Knölker - One of the best experts on this subject based on the ideXlab platform.
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first total synthesis and investigation of the x ray crystal structure of the pyrano 3 2 a Carbazole Alkaloid clausenalansine a
Synthesis, 2021Co-Authors: Valerie Losle, O N Kataeva, Hans-joachim KnölkerAbstract:We describe the first total synthesis of the recently discovered pyrano[3,2-a]Carbazole Alkaloid clausenalansine A. The synthetic strategy for the construction of this formylpyrano[3,2-a]Carbazole is based on a sequence of Buchwald–Hartwig coupling, palladium(II)-catalyzed oxidative cyclization, Lewis acid promoted annulation of the pyran ring, and chemoselective oxidation of a methyl to a formyl group.
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Enantioselective Total Synthesis and Assignment of the Absolute Configuration of the Furo[3,2- a]Carbazole Alkaloid Furoclausine-B.
The Journal of organic chemistry, 2018Co-Authors: Benedikt Spindler, Olga Kataeva, Hans-joachim KnölkerAbstract:We describe the first enantioselective total synthesis and the assignment of the absolute configuration of the furo[3,2-a]Carbazole Alkaloid furoclausine-B. As key steps for our approach we used a ...
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first total synthesis of the cytotoxic Carbazole Alkaloid excavatine a and regioselective annulation to pyrano 2 3 a Carbazoles and 1 4 oxazepino 2 3 4 jk Carbazoles
European Journal of Organic Chemistry, 2017Co-Authors: Christian Brütting, Arndt W. Schmidt, Olga Kataeva, Hans-joachim KnölkerAbstract:We describe the first total synthesis of the cytotoxic Carbazole Alkaloid excavatine-A (1). The Carbazole framework was constructed via double C-H bond activation of a diarylamine using our palladium(II)-catalyzed oxidative cyclization. Treatment of the intermediate 8-hydroxyCarbazoles 8 with prenal (7) and different additives led either to the pyrano[2,3-a]Carbazoles 6 or the [1,4]oxazepino[2,3,4-jk]Carbazoles 15. The pyran annulation was investigated to determine the influence of substitution pattern, additives, and reaction time on the selectivity.
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First Total Synthesis of the Cytotoxic Carbazole Alkaloid Excavatine‐A and Regioselective Annulation to Pyrano[2,3‐a]Carbazoles and [1,4]Oxazepino[2,3,4‐jk]Carbazoles
European Journal of Organic Chemistry, 2017Co-Authors: Christian Brütting, Arndt W. Schmidt, Olga Kataeva, Hans-joachim KnölkerAbstract:We describe the first total synthesis of the cytotoxic Carbazole Alkaloid excavatine-A (1). The Carbazole framework was constructed via double C-H bond activation of a diarylamine using our palladium(II)-catalyzed oxidative cyclization. Treatment of the intermediate 8-hydroxyCarbazoles 8 with prenal (7) and different additives led either to the pyrano[2,3-a]Carbazoles 6 or the [1,4]oxazepino[2,3,4-jk]Carbazoles 15. The pyran annulation was investigated to determine the influence of substitution pattern, additives, and reaction time on the selectivity.
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Synthesis of the Pyrano[3,2-a]Carbazole Alkaloids Koenine, Koenimbine, Koenigine, Koenigicine, and Structural Reassignment of Mukonicine
Synthesis, 2015Co-Authors: Christian Schuster, Arndt W. Schmidt, Anne Jager, Marika Rönnefahrt, Konstanze K. Julich-gruner, Hans-joachim KnölkerAbstract:Using the palladium(II)-catalyzed oxidative cyclization of a diarylamine and the annulation of a dimethylpyran ring by Lewis acid promoted reaction with prenal as key steps, the total syntheses of the 6-oxygenated pyrano[3,2-a]Carbazole Alkaloids koenine and koenimbine, and of the 6,7-dioxygenated pyrano[3,2-a]Carbazole Alkaloids koenigine and koenigicine (koenimbidine, koenidine) were achieved. Moreover, these studies led to an improved synthetic route to the 2,6-dioxygenated Carbazole Alkaloid glycozolidol. Mukonicine, originally published as 6,8-dimethoxypyrano[3,2-a]Carbazole, was found to be identical with koenigicine.
Olga Kataeva - One of the best experts on this subject based on the ideXlab platform.
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Enantioselective Total Synthesis and Assignment of the Absolute Configuration of the Furo[3,2- a]Carbazole Alkaloid Furoclausine-B.
The Journal of organic chemistry, 2018Co-Authors: Benedikt Spindler, Olga Kataeva, Hans-joachim KnölkerAbstract:We describe the first enantioselective total synthesis and the assignment of the absolute configuration of the furo[3,2-a]Carbazole Alkaloid furoclausine-B. As key steps for our approach we used a ...
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Enantioselective Total Synthesis and Assignment of the Absolute Configuration of the Furo[3,2‑a]Carbazole Alkaloid Furoclausine‑B
2018Co-Authors: Benedikt Spindler, Olga Kataeva, Hans-joachim KnölkerAbstract:We describe the first enantioselective total synthesis and the assignment of the absolute configuration of the furo[3,2-a]Carbazole Alkaloid furoclausine-B. As key steps for our approach we used a palladium(II)-catalyzed double C–H-bond activation for the construction of the Carbazole framework, a Shi epoxidation, and an intramolecular opening of the epoxide for annulation of the dihydrofuran moiety
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first total synthesis of the cytotoxic Carbazole Alkaloid excavatine a and regioselective annulation to pyrano 2 3 a Carbazoles and 1 4 oxazepino 2 3 4 jk Carbazoles
European Journal of Organic Chemistry, 2017Co-Authors: Christian Brütting, Arndt W. Schmidt, Olga Kataeva, Hans-joachim KnölkerAbstract:We describe the first total synthesis of the cytotoxic Carbazole Alkaloid excavatine-A (1). The Carbazole framework was constructed via double C-H bond activation of a diarylamine using our palladium(II)-catalyzed oxidative cyclization. Treatment of the intermediate 8-hydroxyCarbazoles 8 with prenal (7) and different additives led either to the pyrano[2,3-a]Carbazoles 6 or the [1,4]oxazepino[2,3,4-jk]Carbazoles 15. The pyran annulation was investigated to determine the influence of substitution pattern, additives, and reaction time on the selectivity.
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First Total Synthesis of the Cytotoxic Carbazole Alkaloid Excavatine‐A and Regioselective Annulation to Pyrano[2,3‐a]Carbazoles and [1,4]Oxazepino[2,3,4‐jk]Carbazoles
European Journal of Organic Chemistry, 2017Co-Authors: Christian Brütting, Arndt W. Schmidt, Olga Kataeva, Hans-joachim KnölkerAbstract:We describe the first total synthesis of the cytotoxic Carbazole Alkaloid excavatine-A (1). The Carbazole framework was constructed via double C-H bond activation of a diarylamine using our palladium(II)-catalyzed oxidative cyclization. Treatment of the intermediate 8-hydroxyCarbazoles 8 with prenal (7) and different additives led either to the pyrano[2,3-a]Carbazoles 6 or the [1,4]oxazepino[2,3,4-jk]Carbazoles 15. The pyran annulation was investigated to determine the influence of substitution pattern, additives, and reaction time on the selectivity.
Arndt W. Schmidt - One of the best experts on this subject based on the ideXlab platform.
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first total synthesis of the cytotoxic Carbazole Alkaloid excavatine a and regioselective annulation to pyrano 2 3 a Carbazoles and 1 4 oxazepino 2 3 4 jk Carbazoles
European Journal of Organic Chemistry, 2017Co-Authors: Christian Brütting, Arndt W. Schmidt, Olga Kataeva, Hans-joachim KnölkerAbstract:We describe the first total synthesis of the cytotoxic Carbazole Alkaloid excavatine-A (1). The Carbazole framework was constructed via double C-H bond activation of a diarylamine using our palladium(II)-catalyzed oxidative cyclization. Treatment of the intermediate 8-hydroxyCarbazoles 8 with prenal (7) and different additives led either to the pyrano[2,3-a]Carbazoles 6 or the [1,4]oxazepino[2,3,4-jk]Carbazoles 15. The pyran annulation was investigated to determine the influence of substitution pattern, additives, and reaction time on the selectivity.
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First Total Synthesis of the Cytotoxic Carbazole Alkaloid Excavatine‐A and Regioselective Annulation to Pyrano[2,3‐a]Carbazoles and [1,4]Oxazepino[2,3,4‐jk]Carbazoles
European Journal of Organic Chemistry, 2017Co-Authors: Christian Brütting, Arndt W. Schmidt, Olga Kataeva, Hans-joachim KnölkerAbstract:We describe the first total synthesis of the cytotoxic Carbazole Alkaloid excavatine-A (1). The Carbazole framework was constructed via double C-H bond activation of a diarylamine using our palladium(II)-catalyzed oxidative cyclization. Treatment of the intermediate 8-hydroxyCarbazoles 8 with prenal (7) and different additives led either to the pyrano[2,3-a]Carbazoles 6 or the [1,4]oxazepino[2,3,4-jk]Carbazoles 15. The pyran annulation was investigated to determine the influence of substitution pattern, additives, and reaction time on the selectivity.
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Synthesis of the Pyrano[3,2-a]Carbazole Alkaloids Koenine, Koenimbine, Koenigine, Koenigicine, and Structural Reassignment of Mukonicine
Synthesis, 2015Co-Authors: Christian Schuster, Arndt W. Schmidt, Anne Jager, Marika Rönnefahrt, Konstanze K. Julich-gruner, Hans-joachim KnölkerAbstract:Using the palladium(II)-catalyzed oxidative cyclization of a diarylamine and the annulation of a dimethylpyran ring by Lewis acid promoted reaction with prenal as key steps, the total syntheses of the 6-oxygenated pyrano[3,2-a]Carbazole Alkaloids koenine and koenimbine, and of the 6,7-dioxygenated pyrano[3,2-a]Carbazole Alkaloids koenigine and koenigicine (koenimbidine, koenidine) were achieved. Moreover, these studies led to an improved synthetic route to the 2,6-dioxygenated Carbazole Alkaloid glycozolidol. Mukonicine, originally published as 6,8-dimethoxypyrano[3,2-a]Carbazole, was found to be identical with koenigicine.
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Total synthesis of glycomaurrol and eustifoline-C by DIBAL-H promoted reductive ring opening of pyrano[2,3-c]Carbazoles ☆
Tetrahedron, 2015Co-Authors: Ronny Hesse, Arndt W. Schmidt, Hans-joachim KnölkerAbstract:Abstract The palladium-catalyzed construction of the Carbazole framework provides an efficient access to 3-hydroxy-6-methylCarbazole (glycozolinine) (5). Regioselective annulation of a pyran ring at glycozolinine (5) using either a C5- or a C10-building block leads to the pyrano[2,3-c]Carbazole Alkaloids glycomaurin (5,6-pyranoglycozoline, eustifoline-A) (2) and eustifoline-B (4), respectively. Reductive opening of the pyran ring with DIBAL-H in the presence of an additional Lewis acid transformed 2 into the 5-prenyl-substituted Carbazole Alkaloid glycomaurrol (1) and 4 into the 5-geranyl-substituted homologue eustifoline-C (3).
Christian Brütting - One of the best experts on this subject based on the ideXlab platform.
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first total synthesis of the cytotoxic Carbazole Alkaloid excavatine a and regioselective annulation to pyrano 2 3 a Carbazoles and 1 4 oxazepino 2 3 4 jk Carbazoles
European Journal of Organic Chemistry, 2017Co-Authors: Christian Brütting, Arndt W. Schmidt, Olga Kataeva, Hans-joachim KnölkerAbstract:We describe the first total synthesis of the cytotoxic Carbazole Alkaloid excavatine-A (1). The Carbazole framework was constructed via double C-H bond activation of a diarylamine using our palladium(II)-catalyzed oxidative cyclization. Treatment of the intermediate 8-hydroxyCarbazoles 8 with prenal (7) and different additives led either to the pyrano[2,3-a]Carbazoles 6 or the [1,4]oxazepino[2,3,4-jk]Carbazoles 15. The pyran annulation was investigated to determine the influence of substitution pattern, additives, and reaction time on the selectivity.
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First Total Synthesis of the Cytotoxic Carbazole Alkaloid Excavatine‐A and Regioselective Annulation to Pyrano[2,3‐a]Carbazoles and [1,4]Oxazepino[2,3,4‐jk]Carbazoles
European Journal of Organic Chemistry, 2017Co-Authors: Christian Brütting, Arndt W. Schmidt, Olga Kataeva, Hans-joachim KnölkerAbstract:We describe the first total synthesis of the cytotoxic Carbazole Alkaloid excavatine-A (1). The Carbazole framework was constructed via double C-H bond activation of a diarylamine using our palladium(II)-catalyzed oxidative cyclization. Treatment of the intermediate 8-hydroxyCarbazoles 8 with prenal (7) and different additives led either to the pyrano[2,3-a]Carbazoles 6 or the [1,4]oxazepino[2,3,4-jk]Carbazoles 15. The pyran annulation was investigated to determine the influence of substitution pattern, additives, and reaction time on the selectivity.
Samir Bhattacharya - One of the best experts on this subject based on the ideXlab platform.
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a Carbazole Alkaloid deactivates mtor through the suppression of rictor and that induces apoptosis in lung cancer cells
Molecular and Cellular Biochemistry, 2015Co-Authors: Priyajit Chatterjee, Soma Seal, Sandip Mukherjee, Rakesh Kundu, Mantu Bhuyan, Nabin C Barua, Pranab Kumar Baruah, Santi Sinha P Babu, Samir BhattacharyaAbstract:Non-small cell lung cancer (NSCLC) is known to be a difficult cancer to treat because of its poor prognosis, limited option for surgery, and resistance to chemo or radiotherapy. In this study, we have demonstrated that suppression of rictor expression in A549 and H1299 NSCLC cells by mahanine, a Carbazole Alkaloid, disrupted constitutive activation of mTOR and Akt. Mahanine suppression of rictor gene expression and consequent attenuation of its protein expression affected the inhibition of mTOR (Ser-2481) and Akt (Ser-473) phosphorylation. Since mahanine treatment revealed this new insight of rictor-mTOR relationship, we examined an association between mTOR activation with rictor expression. Interestingly, in rictor knockdown (KD) NSCLC cells, mTOR activation was significantly impaired. Transfection of rictor over-expression vector into the NSCLC cells reversed this situation. In fact, both rictor KD and mahanine treated cells showed considerably depleted phospho-mTOR level. These results indicate that rictor is required to maintain constitutive activation of mTOR in lung cancer cells. When mTOR kinase activity in rictor KD cells was examined with Akt as substrate, a significant reduction of Akt phosphorylation indicated impairment of mTOR kinase potentiality. Disruption of mTOR and Akt activation caused drastic mortality of NSCLC cancer cells through apoptosis. Hence, our study reveals a new dimension in mTOR-rictor relationship, where rictor stands to be a suitable therapeutic target for lung cancer.
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mahanine restores rassf1a expression by down regulating dnmt1 and dnmt3b in prostate cancer cells
Molecular Cancer, 2013Co-Authors: Soumik Agarwal, Nabin C Barua, Samir Bhattacharya, Karishma S Amin, Shankar Jagadeesh, Gokul Baishay, P G Rao, Partha P BanerjeeAbstract:Background Hypermethylation of the promoter of the tumor suppressor gene RASSF1A silences its expression and has been found to be associated with advanced grade prostatic tumors. The DNA methyltransferase (DNMT) family of enzymes are known to be involved in the epigenetic silencing of gene expression, including RASSF1A, and are often overexpressed in prostate cancer. The present study demonstrates how mahanine, a plant-derived Carbazole Alkaloid, restores RASSF1A expression by down-regulating specific members of the DNMT family of proteins in prostate cancer cells.