Among other natural products with indirubin-like kinase
inhibitory activities are the meridianins (e.g., meridianin A;
94; Scheme 17), a group of halogenated indole derivatives
that are closely related to the base structures of the psammopemmins
(e.g., psammopemmin A; 95; Scheme 17) and
discodermindole (96; Scheme 17). The psammopemmins and
discodermindol were isolated from sponges, whereas the
meridianins were isolated from the ascidian Aplidium meridianum