Two cell differentiation inducing pyridoacridines from a marine sponge Biemna sp. and their chemical conversions

Abstract Two pyridoacridines, N -hydroxymethylisocystodamine ( 1 ) and neolabuanine A ( 2 ), together with the known ecionine A ( 3 ), ecionine B ( 4 ), isocystodamine ( 5 ), N -methylisocystodamine ( 6 ), 9-hydroxyisoascididemin ( 7 ), and biemnadin ( 8 ), were isolated from a marine sponge Biemna sp. Several of these compounds were shown to induce cell differentiation of K562 leukemia cells into erythrocytes. Following inspection of the NMR data, and comparison of these data with literature values, we demonstrated that neolabuanine A ( 2 ) had the structure previously reported as labuanine A ( 2 ), and that the compound initially reported under the name of labuanine A possessed the structure assigned to ecionine A ( 3 ). We found that both neolabuanine A ( 2 ) and ecionine A ( 3 ) were gradually converted to 9-hydroxyisoascididemin ( 7 ), indicating that 2 and 3 can be considered both as precursors of 7 .