Heteroaromatic alkaloids, nakijinamines, from a sponge Suberites sp.

Abstract The structures of seven new secondary metabolites isolated from an Okinawan marine sponge Suberites sp., nakijinamines A ( 1 ), B ( 2 ), and F–I ( 3 – 6 ) and 6-bromoconicamin ( 7 ), have been elucidated on the basis of spectroscopic analysis, chemical conversion, and conformational analysis. These analyses disclosed that 1 – 6 were heteroaromatic alkaloids having the hybrid structures of an aaptamine-type alkaloid and an indole alkaloid, while 7 was a bromoindole alkaloid. Nakijinamine I ( 6 ) is the first example of an aaptamine-type alkaloid possessing a 1,4-dioxane ring. Antimicrobial activities of 1 – 7 were evaluated.