Marine tunicates have proven to be a rich source of intriguing structures and interesting biological activities.2 In our continuing survey of bioactive compounds from Okinawan marine organisms,3 we have reported a novel β-carboline, named eudistomidin A (1), with powerful calmodulin antagonistic activity from the Okinawan tunicate Eudistoma glaucus4. © 1990, American Chemical Society. All rights reserved.