Total Synthesis of Illisimonin A

Key words

illisimonin A - semi–pinacol rearrangement - intramolecular Diels−Alder reaction - C–H oxidation

Significance

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.

Comment

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.