Total synthesis of the proposed structure of didemnaketal B has been accomplished. The C7-C21 spiroacetal domain was synthesized by exploiting our Suzuki-Miyaura coupling/spiroacetalization strategy. The C1-C7 acyclic domain was constructed via an Evans syn-aldol reaction and a vinylogous Mukaiyama aldol reaction. Finally, the C22-C28 side chain was introduced by means of a Nozaki-Hiyama-Kishi reaction. Comparison of the NMR spectroscopic data of our synthetic material with those of the authentic sample revealed that the proposed structure requires stereochemical reassignment.