3Alpha-acetyl-11-keto-alpha-boswellic acid (3alpha-acetoxy-11-oxo-olean-12-en-24-oic acid, 1) was synthesized by a radical-type reaction using bromine and 3alpha-acetyl-alpha-boswellic acid isolated from the oleo-gum-resin of Boswellia carterii. 1D and 2D NMR (COSY, HMBC, ROESY) at 500 MHz were used for shift assignments and structure verification. The compound investigated is present in a herbal preparation extracted from Boswellia serrata oleo-gum-resin, it inhibits the growth of chemotherapy-resistant human PC-3 prostate cancer cells in vitro and induces apoptosis as shown by activation of caspase 3 and the induction of DNA fragmentation. In addition, compound 1 is active IN VIVO as shown by inhibition of proliferation and induction of apoptosis in PC-3 prostate cancer cells xenotransplanted onto the chick chorioallantoic membrane.