Stereocontrolled Synthesis of Adjacent Acyclic Quaternary‐Tertiary Motifs: Application to a Concise Total Synthesis of (−)‐Filiformin

Lithiation/borylation methodology has been developed for the synthesis of acyclic quaternary‐tertiary motifs with full control of relative and absolute stereochemistry, thus leading to all four possible isomers of a stereodiad. A novel intramolecular Zweifel‐type olefination enabled acyclic stereocontrol to be transformed into cyclic stereocontrol. These key steps have been applied to the shortest enantioselective synthesis of (?)‐filiformin to date (9 steps) with full stereocontrol.