Convergent Stereoselective Synthesis of the C16-C37 Subunit of Sorangicin A.

A convergent stereoselective route to the C16-C37 fragment of sorangicin A is disclosed using an α-chloro sulfide for C-C bond formation. The key intermediate, an α,β-unsaturated ketone, is revealed by a [2,3] sigmatropic rearrangement of a propargylic sulfoxide. Three disparate approaches are detailed to create the C25 carbinol stereocenter. The cis-2,6-disubstitution of the THP ring is secured by ionic hydrogenation. A cross-metathesis reaction and Julia-Kocienski olefination furnish the C16-C37 fragment of sorangicin A.