Cassane diterpenes with oxygen bridge from the seeds of Caesalpinia sappan. 
The seeds of the medicinal plant Caesalpinia sappan yielded fourteen cassane-type diterpenes, including six new rearranged ones named as caesalppans A-F (1-6).  Their structures were elucidated by spectroscopic analysis and comparison with literature data.  The isolated new compounds 1-6 possess lactone-type cassane diterpenoid skeleton with an oxygen bridge between C-19 and C-20, and were tested cytotoxic activity against four cancer cell lines using the MTT method.