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  Total Synthesis of Dictyodendrin B

Fürstner, A., Domostoj, M. M., & Scheiper, B. (2005). Total Synthesis of Dictyodendrin B. Journal of the American Chemical Society, 127(33), 11620-11621. doi:10.1021/ja0541175.

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ja0541175si20050722_122055.pdf (Supplementary material), 3MB
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Fürstner, Alois1, Author              
Domostoj, Mathias M.1, Author              
Scheiper, Bodo1, Author              
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1Research Department Fürstner, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445584              

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 Abstract: A concise total synthesis of dictyodendrin B (1) is reported, a scarce marine alkaloid endowed with promising telomerase inhibitory activity. Key steps of the chosen route are a reductive cyclization of ketoamide 11 to indole 12 mediated by low-valent titanium (from TiCl3 and KC8) followed by a photochemical 6π-electrocyclization, which was performed in the presence of Pd/C and nitrobenzene to effect concomitant dehydrogenation/aromatization of the product initially formed. Regioselective bromination of the resulting pyrrolocarbazole 13 followed by lithium/bromine exchange and quenching of the resulting organolithium species with p-methoxybenzaldehyde installed the side chain at C2. Oxidation of the benzylic alcohol 15 thus obtained to ketone 17 was best achieved with catalytic amounts of tetra-n-propylammonium perruthenate (TPAP) and N-methylmorpholine-N-oxide (NMO) in dilute CH2Cl2 solution to avoid the formation of undue amounts of the unsymmetrical dimer 16. Ketone 17 was elaborated into the natural product by selective cleavage of the isopropyl ether with BCl3, introduction of the sulfate moiety with the aid of trichloroethyl chlorosulfuric acid ester, deprotection of all lateral methyl ether groups, and final reductive cleavage of the trichloroethyl ester moiety. The spectroscopic data of synthetic dictyodendrin B thus formed matched those of an authentic sample in all regards. Moreover, it was shown that global deprotection of the peripheral −OH groups in pyrrolo[2,3-c]carbazole 13 is accompanied by spontaneous air-oxidation to form the quinone core of dictyodendrin C.

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Language(s): eng - English
 Dates: 2005-06-222005-07-292005-08-24
 Publication Status: Published in print
 Pages: 2
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1021/ja0541175
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Title: Journal of the American Chemical Society
  Other : J. Am. Chem. Soc.
  Abbreviation : JACS
Source Genre: Journal
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Publ. Info: Washington, DC : American Chemical Society
Pages: - Volume / Issue: 127 (33) Sequence Number: - Start / End Page: 11620 - 11621 Identifier: ISSN: 0002-7863
CoNE: https://pure.mpg.de/cone/journals/resource/954925376870