The biomimetic synthesis of SNF4435C and SNF4435D, and the total synthesis of the polyene metabolites aureothin, N-acetyl-aureothamine and spectinabilin

Full details of the biomimetic conversion of polyene metabolite spectinabilin () into the isomeric natural products SNF4435C () and SNF4435D () by a cascade of E/Z-isomerizations and electrocyclizations are reported. Additionally, short total syntheses of the related natural products (±)-aureothin (), (±)-N-acetyl-aureothamine () and (±)-spectinabilin () are presented. The key steps in the synthesis of , and are the construction of the tetrahydrofuran motif using a palladium-catalyzed cycloaddition and the ruthenium-catalyzed cross metathesis of alkene to form the common intermediate, boronic ester , which was further transformed using a trans-selective Suzuki coupling with a dibromide and a stereospecific Negishi-type methylation.