A highly stereoselective and stereodivergent synthesis of two possible diastereomers of (-)-gummiferol was achieved, wherein the stepwise epoxidation and Cadiot-Chodkiewicz reaction were utilized for the construction of the diepoxide moiety and triacetylene part, respectively. Detailed comparison of their (1)H and (13)C NMR data and specific rotation with those of the natural product unambiguously elucidated the absolute stereostructure of gummiferol. In addition, the cytotoxic activity of the synthesized gummiferol, its stereoisomers, and its truncated analogues was evaluated, which clearly indicates that (1) the absolute configuration of the diepoxide moiety has little influence on the cytotoxic activity against human cancer cells and (2) the triacetylene unit is the crucial structural element required for exerting the cytotoxic activity.