Haterumaimides F−I, Four New Cytotoxic Diterpene Alkaloids from an Ascidian Lissoclinum Species

Four new monochlorinated diterpene alkaloids, haterumaimides F−I (<BO>1</BO>−<BO>4</BO>), and two known ones, dichlorolissoclimide and chlorolissoclimide, were isolated from an ascidian Lissoclinum sp. Their structures with absolute stereochemistries were elucidated by chemical and spectral analyses. Haterumaimides F−I (<BO>1</BO>−<BO>4</BO>) inhibited the first cleavage of fertilized sea urchin eggs and exhibited potent to weak cytotoxicities against P388 cells.