Polyoxygenated diterpenoids of the eunicellin-type from the Chinese soft coral Cladiella krempfi

A detailed chemical investigation of the Chinese soft coral Cladiella krempfi has yielded four new eunicellin-based diterpenoids along with five known compounds. The stereostructures of the new metabolites have been elucidated by extensive spectroscopic analysis, mainly based on 2D NMR spectroscopy, and by chemical transformations. A remarkable variation in the diterpene composition in dependence of the exact site of collection was observed. Some of the isolated diterpenoids were shown to exhibit antiproliferative activity against C6 glioma cells, multi-drug resistant tumor cell line.