Olivacine-type alkaloids

The enaminedione may be heterocyclic and its intramolecular condensation via Michael addition of an indole moiety is possible, as shown in a new, easy and simple route to the olivacine-type alkaloid ring system by cyclocondensing a substituted indolylethyl-aminomethylenepiperidine-2,4-dione, followed by elimination of ethanea-mine moietyr89 (equation 214). 

Intramolecular Mannich type reaction of the conjugated iminium salt 426 should lead to ellipticine (228) via an intermediate 427. Alternatively, the conjugated iminium salt 426 could hydrolyze to afford the 2-vinylsubstituted indole 428, which, on cyclization through an intermediate 429, would lead to guatambuine (233). This alkaloid, on demethylation and dehydrogenation, should afford olivacine (238a) (375) (Scheme 3.11). 

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