Synthesis of (±)-combretastatin D-1 and combretastatin D-2

Article abstract of DOI:10.1021/jo00097a052

(±)-Combretastatin D-1 was synthesized in 16 steps by way of its congener, combretastatin D-2. In the key step, the strained 15-membered lactone ring was formed using high-dilution Mitsunobu conditions in 89% yield. Saturated seco acid 4 was a much better substrate for the cyclization reaction than the unsaturated seco acid 3.