Regio‐ and Stereoselective Homologation of 1,2‐Bis(Boronic Esters): Stereocontrolled Synthesis of 1,3‐Diols and Sch 725674

Abstract

1,2‐Bis(boronic esters), derived from the enantioselective diboration of terminal alkenes, can be selectively homologated at the primary boronic ester by using enantioenriched primary/secondary lithiated carbamates or benzoates to give 1,3‐bis(boronic esters), which can be subsequently oxidized to the corresponding secondary‐secondary and secondary‐tertiary 1,3‐diols with full stereocontrol. The transformation was applied to a concise total synthesis of the 14‐membered macrolactone, Sch 725674. The nine‐step synthetic route also features a novel desymmetrizing enantioselective diboration of a divinyl carbinol derivative and high‐yielding late‐stage cross‐metathesis and Yamaguchi macrolactonization reactions.