Unusual Cladiellin-type Diterpenoids from the South China Sea Soft Coral Cladiella krempfi: Structures and Struc-ture-Activity Relationship with EGFR

Two new cladiellin-type diterpenoids (1 and 2), and four known related compounds 3-6, were isolated from the South China Sea soft coral Cladiella krempfi. Compound 2 is the third example of cladiellins of an unusual peroxy group at C-6 position in C. krempfi. The structures and absolute configurations of the new compounds were established by extensive spectroscopic analysis, X-ray diffraction, and/or chemical correlation. In bioassay, all the compounds were evaluated for the cytotoxicity and the EGFR inhibitory activity. Molecular docking experiment was conducted to study the structure-activity relationship of cladiellin-type diterpenoids on EGFR inhibitory activity.