Diastereodivergent synthesis of the C8–C18 precursor and C1′–C11′ subunit of pamamycin 607 induced by a chiral sulfoxide group

A key step in obtaining the C8–C18 and C1′–C11′ fragments of pamamycin 607, which differ by the syn- and anti-configuration of one chiral center α to the tetrahydrofuran ring, was the chelation controlled E–Z-isomerization of the substituted vinyl tetrahydrofuran intermediate 3a which has so far been obtained only in the more stable E-configuration.