Previously, we reported the isolation of cassane-type diterpenes, sucutiniranes A-F, from the seeds of Bowdichia nitida. In this study, a series of sucutinirane derivatives was prepared, and their in vitro toxicity in the HL-60 cell line was evaluated. Then the action mechanism of a representative compound that induces cell death was investigated. Whereas C-6 or C-7 diol esters and ether decreased the activity against the HL-60 cell line, furan-oxidized derivatives 12 and 13 showed improvement or retention of the activity compared with those of the natural products sucutinirane A (11), E (1), and F (2). Treatment with sucutinirane derivative 13 elevated caspase 3/7 activity and also decreased expression of Bcl-2 family proteins, Mcl-1, and Bid. Derivative 13 generated reactive oxygen species in HL-60 cells, whose apoptotic effects were attenuated by the addition of an antioxidant, N-acetyl-l-cysteine. These results suggest that cassane butenolide 13 induces apoptosis in HL-60 via its oxidative effects.