Synthesis of Eburnamine,Isoeburnamine, and Eburnamonine via a Spirocyclic Intermediate

Racemic eburnamonine ( 1 ) was synthesized via 6 , an intermediate possessing local symmetry. Cleavage of the cyclopentene subunit led to pentacyclic aldehydes 8a / 8b which on subsequent borohydride and Wolff–Kishner reductions gave 12 . The final steps included a RuCl₃‐catalyzed periodate oxidation and pyridinium chlorochromate (PCC) oxidation. The penultimate intermediates were racemic eburnamine ( 2 ) and racemic isoeburnamine ( 3 ).