Stereoselective Synthesis of the C1-C22 Carbon Framework of (-)-Amphidinolide K.

Two stereoselective routes to the C7-C22 subunit of amphidinolide K are disclosed. Jacobsen's hydrolytic kinetic resolution and Sharpless' asymmetric dihydroxylation reactions have been employed for the construction of the tetrahydrofuran ring. The C10-C11, C16-C17, C9-O, and C18-O bonds have been created using α-chloro sulfide intermediates and [2,3] sigmatropic rearrangement. Marshall's propargylation protocol is utilized to create the C4 stereogenic center, and regioselective hydrozirconation/iodine quench afforded an alkenyl iodide which is employed in the NHK coupling with the C7-C22 subunit. Oxonia-Cope rearrangement resulted in the creation of the C18 carbinol stereogenic center and chain elongation.