Divergent Total Syntheses of (−)‐Daphnezomines A and B and (+)‐Dapholdhamine B

The daphnezomine A-type subfamily of Daphniphyllum alkaloids structurally features a unique aza-adamantane core skeleton and anticipates efficient strategies for completing their syntheses to thoroughly investigate their biological activities. Herein, divergent total syntheses of (−)-daphnezomines A and B and (+)-dapholdhamine B have been accomplished in 16~20 steps from a known epoxide via rapid construction of a common core intermediate. The present work features a Ti-mediated radical cyclization to establish the azabicyclo[3.3.1]nonane ring system, an intramolecular Heck reaction to install the bridgehead all-carbon quaternary stereocenter, a tandem deprotection/reduction/keto amine-carbinolamine tautomerization to furnish the aza-adamantane backbone, and an NIS-promoted 6-endo-trig aminocyclization to assemble the (+)-dapholdhamine B backbone.