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Graphical abstract Highlights • A series of novel 25-OCH 3 -PPD derivatives were synthesized. • Cytotoxic activities of the derivatives were evaluated on five human tumor cell lines. • Compounds 3a , 14a and 18a exhibited strong anti-tumor activities. • Having aromatic ester at the C3 position could enhance the antiproliferative activities. Abstract Previously we have reported that 25-OCH 3 -PPD could suppress the reproduction of cancer cells and cause apoptosis without obvious toxicity. Herein, we aimed to enhance its bioactivity by introducing aromatic groups to its dammarane-type skeleton. These synthesized derivatives were tested for their inhibitory activities against five cancer cell lines. Of them, compounds 3a , 14a and 18a had the strongest antiproliferative activities against tumor cells (IC 50 < 15 µM, 5-fold to 10-fold increases than 25-OCH 3 -PPD). Especially compound 14a displayed the most potent activity against DU145, MCF-7 and HepG2 cells (IC 50 = 6.7 ± 0.8, 4.3 ± 0.8 and 5.8 ± 0.6 µM, respectively). Structure-activity relationships demonstrated that having aromatic ester at the C3 position could improve the bioactivity. The data provided new insights into exploring novel antiproliferative lead compounds. [ABSTRACT FROM AUTHOR]