Enantioselective Synthesis of a Key Intermediate toward Dragmacidin E via Base-Promoted Olefin Isomerization–Ir-Catalyzed Asymmetric Hydrogenation Sequence

Abstract

We report a practical approach for synthesizing a chiral building block en route to the asymmetric total synthesis of dragmacidin E. The strategy features a base-promoted olefin isomerization of 1 followed by an Ir-catalyzed asymmetric hydrogenation under ambient hydrogen pressure. Gram-scale hydrogenation of geminally di-substituted olefin 5 using 3 mol% of the chiral Ir catalyst (R,R)-2 afforded (+)-(R)-3 in 88% yield and 89% enantiomeric excess (ee).