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Total Synthesis of Illisimonin A
Total Synthesis and Structure Revision of (–)-Illisimonin A, a Neuroprotective Sesquiterpenoid from the Fruits of Illicium simonsii .
J. Am. Chem. Soc. 2019;
18 October 2019 (online)
Key wordsillisimonin A - semi–pinacol rearrangement - intramolecular Diels−Alder reaction - C–H oxidation
Burns and Rychnovsky report on the first total synthesis of illisimonin A, a sesquiterpenoid isolated from the fruits of Illicium simonsii. The combination of an intramolecular Diels–Alder reaction with a semi-pinacol rearrangement enables the rapid access of the target molecule’s core structure. Using a resolution strategy, the authors are also able to produce enantioenriched (–)-ilisimonin A.
Enone B is generated from simple starting materials. A 1,3-dioxa-2-silacyclohexenetemplated Diels–Alder reaction yields the congested intermediate D. Functional group interconversion leading to epoxide F pave the route for the crucial semi-pinacol rearrangement. Ultimately, functional group interconversions and a final directed C–H oxidation give rise to the natural product.