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 pyridimum chlorochromate (PCC) oxidation. The penultimate intermediates were racemic eburnamine (2) and racemic isoeburnamine (3).