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Stereoselective Synthesis of the C1-C9 and C11-C25 Fragments of Amphidinolides C, C2, C3, and F.

An efficient synthesis of the C1-C9 and the C11-C25 fragments of amphidinolides C, C2, C3, and F from a common intermediate is reported. The construction of the C1-C9 fragment involves an intramolecular hetero-Michael cyclization to form the 3,5-disubstituted trans-tetrahydrofuran moiety. The approach to prepare the C11-C25 fragment utilizes a highly stereoselective aerobic cobalt-catalyzed alkenol cyclization and a chelated Mukaiyama aldol reaction to form the C13-C14 bond and to concomitantly install the C13 hydroxyl group.