Synthesis of (-)-kainic acid using chiral lithium amides in an asymmetric dearomatizing cyclization

Chiral lithium amide bases are able to deprotonate N-benzyl-N-cumyl anisamides enantioselectively to yield enantiomerically enriched benzylic organolithiums. These spontaneously undergo dearomatising cyclisation to yield, in high enantiomeric excess enantiomerically enriched partially saturated isoindolones, which in some cases may be recrystallised to enantiomeric purity. These isoindolone derivatives are converted in nine steps, among them a surprisingly regioselective Baeyer-Villiger reaction, to (-)-kainic acid.