Interestingly, compound 2 contained a hemiketal at C-11 in fragment A (derived from OH-10 and carbonyl at C-11). Generally,the presence of hydroxyl at C-10 and carbonyl at C-11 were common in rearranged 9 (10/20)-abeoabietane type diterpenoids. However, no abietane or icetexane type diterpenoid with a hemiketal at C-11 was found up to now. This was the first dimer with a hemiketal at C-11.