||Enediynes are a new class of antitumor antibiotics isolated from the fermentation broths of various microorganisms. These antitumor antibiotics possess a 9-/10-membered ring enediyne core which, after bioreductive activation, undergoes a cycloaromatization reaction (the Bergman cyclization) to generate the reactive radical intermediate. The latter species cause DNA strand cleavage via hydrogen atom abstraction from the deoxyribose moiety of DNA. Besides the natural products, synthetic enediynes also exhibit very promising DNA cleavage and cytotoxicity against cancer cell lines. In this presentation, our progress in development of stereo- and regiocontrolled allylic rearrangement of 1,5-diynes into cis-enediynes will be discussed.