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We developed a concise protocol for the synthesis of ellipticine quinone from the appropriate 3-iodoindole-2-carbaldehydes in four steps. The key step is the construction of carbazole-1,4-quinone through tandem Ring-Closing Metathesis (RCM) and dehydrogenation under oxygen atmosphere. Therefore, the ellipticine quinone analogs possessing substitution at the 8- and/or 9-positions were synthesized using this method. In total, 14 compounds were evaluated for antiproliferative activity against HCT-116 and HL-60 cell lines; 9-nitroellipticine quinone was found to have superior activity compared to calothrixin B. [ABSTRACT FROM AUTHOR]

Concise syntheses of 9-methoxyellipticine, 3,4-dihydroellipticine (µ-alkaloid D), 1,2,3,4-tetrahydroellipticine, 2-methyl-1,2,3,4-tetrahydroellipticine, olivacine, 3,4-dihydroolivacine, (±)-guatambuine, and (±)-janetine were developed starting from hexatriene intermediates readily obtained by Pd-catalyzed tandem cyclization/cross-coupling reaction of indolylborates. The route enables the facile construction of pyrido[4,3- b]carbazoles by Cu-catalyzed 6π-electrocyclization and subsequent transformation of the pyridocarbazole intermediates into pyrido[4,3- b]carbazole alkaloids. [ABSTRACT FROM AUTHOR]

In this study, we achieved the total synthesis of carbazole alkaloid mukoenine A through a seven-step sequence involving the construction of a carbazole framework using the electrocyclization of a 6π-electron system including an allene intermediate as the key step. Subsequently, the synthesis of pyrano[3,2- a ]carbazole alkaloid girinimbine was achieved by the construction of the pyran ring via selenoetherification of the o-allylic phenol moiety of mukoenine A. [Display omitted] • The total synthesis of mukoenine A has been accomplished via a seven-step sequence. • Girinimbine was synthesized by the construction of the pyran ring via mukoenine A. • The carbazole framework was constructed by the allene-mediated electrocyclization. [ABSTRACT FROM AUTHOR]

Abstract: A novel one-pot synthesis of carbazole-1,4-quinone by consecutive Pd-catalyzed cyclocarbonylation, desilylation, and oxidation reactions is described. We propose a possible mechanism of the cyclocarbonylation reaction between 3-iodo-2-propenylindole and CO (1 atm) in the presence of a tributyl(vinyl)tin and Pd-catalyst and the resulting acylpalladium species was directly coupled with a terminal alkene to produce the carbazole-1,4-quinone. To our knowledge, this is the first example of this type of reaction. A new formal total synthesis of a carbazole-1,4-quinone alkaloid, murrayaquinone A was established using this reaction. [Copyright &y& Elsevier]

Abstract: A tandem ring-closing metathesis and dehydrogenation reaction under oxygen atmosphere was newly developed to the synthesis of carbazole-1,4-quinones. This new tandem reaction was applied to the synthesis of murrayaquinone A in four steps. [Copyright &y& Elsevier]

In this study, the total syntheses of 1,3,4-trisubstituted carbazole alkaloid clausamine E was accomplished via an eight-step sequence using construction of the 1,4-dioxygenated carbazole framework based on the cyclocarbonylation between 3-iodo-2-(prop-2-enyl)indole and CO (1 atm) in the presence of tributyl(vinyl)tin and a Pd catalyst. Image 1 • The total synthesis of clausamine E has been accomplished via an eight-step sequence. • Synthesis of 1,4-dioxygenated carbazoles by Pd-catalyzed cyclocarbonylation. • This method could be used as a versatile method to synthesize substituted carbazoles. [ABSTRACT FROM AUTHOR]

3-Iodo-2-propenylindoles (I) are easily prepared from corresponding indole-2-carbaldehydes and vinyl Grignard reagents. [ABSTRACT FROM AUTHOR]

Cu-catalyzed 6π-electrocyclization of triene-substrates of type (I) provides a facile access to pyrido[4,3-b]carbazoles, which represent advanced intermediates for the construction of various ellipticine and olivacine alkaloids. [ABSTRACT FROM AUTHOR]