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

Abstract

AbstractThe 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.