Three new pyridoacridine type alkaloids from a singaporean ascidian.

Two new pyridoacridine alkaloids, kuanoniamines E and F, and a new ring-opened pyridoacridine alkaloid, subarine, were isolated from a Singaporean ascidian. Also isolated were known pyridoacridine alkaloids ascididemin and kuanoniamines A and D. The structures of the alkaloids were determined by spectroscopic methods.