New pyridoacridine alkaloids from the purple morph of the ascidian Cystodytes dellechiajei

Two new pyridoacridine alkaloids, 13-didemethylaminocycloshermilamine D ( 1) and demethyldeoxyamphimedine ( 2), were isolated from the purple chromotype of the Western Mediterranean ascidian Cystodytes dellechiajei. This morph also contained the known shermilamine B ( 3), kuanoniamine D ( 4), N-deacetylshermilamine B ( 5), N-deacetylkuanoniamine D ( 6), styelsamines C ( 7), and D ( 8). The structures of new compounds were elucidated on the basis of spectroscopic data. A hypothetic biosynthetic pathway from the tetracyclic styelsamine D ( 8) was proposed for both compounds 1 and 2 and their antimicrobial potential was evaluated.