Selective Deconstructive Lactamization of the Indolo[2,3‐a]quinolizine Skeleton for the Total Synthesis of (+) and (−)‐Cuscutamine

The general approach for accessing to a tetracyclic hexahydro‐3H‐indolizino[8,7‐b]indol‐3‐one alkaloids is that what involves the construction of the γ‐lactam ring from a tricyclic precursor. Here in this report, we disclose a new synthetic strategy that permits the direct deconstruction of the tetracyclic indolo[2,3‐a]quinolizine motif into the tetracyclic hexahydroindolizin‐3‐one scaffold of the naturally occurring (+)‐cuscutamine without the use of either transition or precious metals. Additionally, the current total synthesis of both enantiomers provides structural clarification of the natural occurring alkaloid.