The histrionicotoxins are a family of alkaloids, originally isolated from the skin extracts of the amphibian Dendrobatidae histrionicus, that display non-competitive inhibition of the nicotinic acetylcholine receptor. The biological activity of these compounds, combined with a protected natural source, has given rise to considerable interest from a synthetic chemistry standpoint.
This manuscript describes the synthesis of 6,6,5-isoxazolidine scaffolds of the histrionicotoxin spirocycles, from bis-α,β-unsaturated nitrile intermediates of well defined stereochemistry, using both conventional batch-type and continuous flow techniques.
A library of both racemic and enantiomeric examples of perhydrohistrionicotoxin and its conformationally restricted precursors has been synthesised. Additionally, analogues of perhydrohistrionicotoxin, one example bearing an epimeric centre and other species furnished with pendant side chains of increased length have been synthesised.