Claisen rearrangement over the past nine decades.

Claisen-rearrangement-mediated ring contraction of macrocyclic lactones : A new approach to carbocycles and heterocycles

N-Alkylation of the β-amino acid derivative 16, derived from (L)-aspartic acid, by the allylic chloride 12b followed by deprotection and lactonization leads to the nine-membered azalactone 18. Enolate Claisen rearrangement of this leads stereospecifically, via a boat-like transition state (cf. 6), to the pyrrolidine acid 19; subsequent one-carbon homologation, oxidation and deprotection affords (–)-(α)-kainic acid 1.

Total synthesis of (–)-α-kainic acid

The diastereoselectivity of the unprecedented coupling reaction depends on the presence of substituents on the bridgehead positions of the substrates.

J. D. Jun. Munger

Papers

The Stereospecific Total Synthesis of (±)-cis-Chrysanthemic Acid via the Alicyclic Claisen Rearrangement