Total Synthesis of (-)-Xylogranatopyridine B via a Palladium-Catalyzed Oxidative Stannylation of Enones.

ABSTRACT

We report a total synthesis of the pyridine-containing limonoid alkaloid (-)-xylogranatopyridine B in 11 steps from commercially available dihydrocarvone. The central pyridine ring was assembled by a late-stage fragment coupling approach employing a modified Liebeskind pyridine synthesis. One fragment was prepared by an allyl-palladium catalyzed oxidative enone ß-stannylation, in which the key bimetallic ß-stannyl palladium enolate intermediate undergoes a ß-hydride elimination. This methodology also allowed introduction of alkyl and silyl groups to the ß-position of enones.