Convergent Assembly of the Spiroacetal Subunit of Didemnaketal B

A highly convergent synthesis of the C9−C28 spiroacetal subunit of didemnaketal B has been accomplished. Assembly of the C9−C15 alkylborate and C16−C21 enol phosphate by means of Suzuki−Miyaura coupling and acid-catalyzed cyclization of the derived dihydroxy enol ether enabled a rapid and efficient construction of the spiroacetal subunit. The C22−C28 side chain was incorporated via Nozaki−Hiyama−Kishi coupling to complete the synthesis.