Simple Total Syntheses of Marine Alkaloids, Batzelline C, Isobatzelline C, Damirone A, and Makaluvamine A

Abstract

Batzelline C and isobatzelline C were synthesized in eight (or nine) steps from indole-3-carboxaldehyde. Syntheses of damirone A and makaluvamine A are also reported.Marine alkaloids having 1.3,4.5-tetrahydropyrrolo[4,3,2-delquinolieas a common skeleton are of great interest owing to their potent biological a~tivities?.~ such as cytotoxicand topoisomerase II inhibition.lsobatzelline C3 (protonated form of 1 ) and batzelline c4 (2) are members of those alkaloids and their total syntheses have already been a ~h i e v e d .~ However, they are still laborious and require long steps.We have intended to attain total syntheses of natural products as simple as possiblesa by creating suitable r e a c t i ~n s .~-~N o w , we wish to report simple syntheses of 1 :I) 6 : 19.0, 36