Quinolinic rearranged indole alkaloids

From corynantheal onwards the pathways diverge completely. The generation of the skeleton of the Cinchona bases requires not only a further reorganization of the terpenoid moiety but also a fundamental rearrangement of the indolic portion of the molecule to generate the quinoline residue. The currently favoured working hypothesis for this transformation is shown in Scheme 2 (13) — (14) — (15)— (16)—>(17) and (18). With the required skeleton in hand, only relatively trivial biochemical reactions are required to produce the known Cinchona alkaloids (21), (22), and (23). 

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