Concise Total Syntheses of Pyr­ido[4,3- b]carbazole Alkaloids Using Copper-Mediated 6π-Electrocyclization.

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]