New linear bromopyrrole-imidazolidine alkaloids from the Formosan sponge Agelas nakamurai

Chemical investigation of the natural products from Formosan sponge Agelas nakamurai led to the isolation of two undescribed bromopyrrole-imidazolidine alkaloids, nakamudines A and B. The structures of the compounds were determined by extensive spectroscopic analyses, including 2D NMR correlations, while their relative configurations were resolved via NOESY correlation analysis. The alkaloids were assigned as rare linear bromopyrrole alkaloidal epimers possessing an 2,4-imidazolidinedione (hydantoin) moiety. The cytotoxicity and antibacterial activity of these alkaloids were assessed, however, they did not exhibit significant activity in the bioassays conducted.