Preparation of the substituted acetylene, which provides the starting material in the Diels-Alder reaction, below.

The first stage is a Diels-Alder reaction between N-carbomethoxypyrrole and phenylsulfonyl 6-chloro-3-pyridyl acetylene.

The double bonds were then reduced, first by sodium amalgum, followed by Platinum catalyst and hydrogen.

Finally, the N-carbomethoxy protecting group was removed to produce the products.

Silica gel chromatography was used to separate endo and exo isomers to produce a racemate of levo and dextro epibatidine.

Biosynthesis

This is still widely unexplored territory. today, Dr. John Daly is researching this area at the NIH.

It is believed that the frogs derive the alkaloids from their diet of insects in the rainforest. The absence of toxin production in captivity and in different environments offer evidence for this theory. The starting materials for for the alkaloids are thought to originate from the plants of the rainforest itself, so tracing back the food chain from frog to plant is an integral part of the research.

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