Total synthesis of (±)-20S-hydroxy-1,2-dehydro-pseudoaspidospermidine via a C-H activation/transannular cyclization
Christian Leitner1, Tanja Gaich
1University of Konstanz, Department of Chemistry, Konstanz, Germany. Tanja.gaich@uni-konstanz.de.
Abstract:
A total synthesis to the pseudoaspidospermidine family via a C-H activation/transannular cyclization strategy has been accomplished. The applicability of this approach is showcased in the concise synthesis (ten steps) of (±)-20S-hydroxy-1,2-dehydro-pseudoaspidospermidine (4) starting from literature known compound 11. Via a joint synthetic sequence we were also able to address the related iboga alkaloid (±)-isovelbanamine (7) in nine steps. Key features of this synthesis are a transannular cyclization to generate the pseudoaspidospermidine skeleton (C-H activation) and a Witkop photocyclization reaction providing a 9-membered lactam. It is also worth mentioning that the joint synthetic sequence can be carried out on a multigram scale.
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