Title:
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Synthesis of Huperzine A and analogues
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Huperzine A is a natural product, originally isolated from the Chinese club moss
Huperzia serrata, which is currently undergoing clinical trials in the U.S. and has
already been approved in China for the treatment of Alzheimer's disease (AD). This
sesquiterpene alkaloid of the Lycopodium family is an eXGellent selective and reversible
inhibitor of acetylcholinesterase (AChE), which is an established target in the palliative
treatment of AD.
Huperzine A has been the target of several syntheses and a number of analogues have
also been prepared. However, all of the synthetic approaches to date have been
essentially linear and thus not ideal for analogue preparation. This thesis describes the
completed development of the first formal convergent synthesis of (±)-huperzine A,
starting from commercially available cyclohex-2-enone and aminopicoline. A key step
in the synthesis is an intramolecular Heck cyclisation, which gives the core tricycle of
the natural product Optimisation of the intramolecular Heck reaction allowed for it to
be carried out on a multi-gram scale and in 72% yield.
Once completed, th~ converg~nt synthesis could now be used in the preparation ofnovel
huperzine A analogues, which would be tested for AChE inhibitory activity and also for
broad range CNS activity. Initial analogue work described in this thesis has proved
promising, with a nitrogen atom having been successfully incorporated into the tricyclic
core at two different positions via Beckmann rearrangements.
This thesis also describes the resolution of a key intermedi~te in the newly-developed
racemic synthesis, thus allowing for the synthesis of enantiomerically-pure huperzine A
or related analogues.
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