A one-pot synthesis of a hybrid triterpenoid-steroid molecule, hollongdione (22,23,24,25,26,27-hexanordammar-3,20-dion), was achieved in a yield of 89%, based on the selective dehydration of dipterocarpol following ozonolysis. The structure of hollongdione was confirmed by X-ray analysis for the first time. Dammar-20(22),24(25)-dien inhibited the growth of Mycobacterium tuberculosis (strain H37Rv) in vitro with a MIC of 50 μg/mL.