Staurosporine derivatives from the ascidian Eudistoma toealensis and its predatory flatworm Pseudoceros sp.

Two new indolocarbazole alkaloids, 3-hydroxy-3'-demethoxy-3'-hydroxystauros porine (5) and 11-hydroxy-4'-N-demethylstaurosporine (6), were isolated fro m the marine ascidian Eudistoma toealensis and its predator, the marine fla tworm Pseudoceros sp. In addition, five known derivatives were isolated in their protonated states, which caused the pyran-ring system to adopt a boat conformation. The structures were determined by 1D and 2D homonuclear and H-1-detected heteronuclear NMR spectroscopy and from comparisons with publi shed data. The heteronuclear correlations were necessary to establish relia ble data for the structure elucidation.