A Direct and Stereocontrolled Route to Conjugated Enediynes

A unified synthetic route to 3-hex-en-1,5-diynes, a key building block found in many of the enediyne antitumor agents and designed materials, was developed. The method, which relies on a carbenoid coupling-elimination strategy is tolerant of a wide range of functionalities, and was applied to the synthesis of a variety of linear and cyclic enediynes. Reaction parameters can be adjusted to control stereoselectivity of the process, producing linear enediynes from 1:12 to >100:1 E:Z ratio, and in the case of cyclic enediynes, giving the exclusively Z C-9, C-10, or C-11 products. Key features of the process are the ready availability of precursors and the mildness and efficiency of the reaction. Application of the process in the design of materials precursors and preparation of enediyne antitumor agents are presented.