Synthesis of a marine polyether toxin, okadaic acid [1]1 1 Full Paper corresponding to the communications, M. Isobe, Y. Ichikawa and T. Goto, Tetrahedron Lett., 26, 5199 (1985); M. Isobe, Y. Ichikawa, D-L. Bai and T. Goto, Tetrahedron Lett., 26, 5203 (1985). - strategy and synthesis of segment a

Article abstract of DOI:10.1016/S0040-4020(01)86915-5

The title compound was divided into three retrosynthetic segments A, B and C, by disconnecting two C-C bonds at C- 14 15 and C- 27 28. Segment A for okadaic acid synthesis comprises the carbon skeleton from C-1 through C-14, which was further disconnected at the bonds between C-8 and C-9 into two fragments A₁ and A₂. Each fragment was synthesized in the optically active form from D-glucose derivatives. Key steps are the oxymercuration and anti-selective heteroconjugate addition to elaborate the asymmetric carbons on acyclic parts of these fragments. The coupling was facilitated between the acetylenic carbanion and the lactone carbonyl of the respective fragments. The segment A was synthesized in 36 steps.