Main observation and conclusionrnA detailed chemical study on the Hainan soft coral Sinularia crass has resulted in the isolation and characterization of eleven cas-bane-type diterpenoids,named sinucrassins A-K (1-11),along with six known related ones (12-17).Their structures were eluci-dated by extensive spectroscopic analyses and comparison with the reported data.The absolute configurations of new compounds were determined by the X-ray diffraction analysis and computer-assisted structural elucidation including 13C NMR data calculation and time-dependent density functional theory/electronic circular dichroism calculation.