Asymmetric Diels—Alder Reactions of Chiral Cyclopropylidene Imide Dienophiles: Preparation of gem-Dimethyl- and Spirocyclopropane Norbornyl Carboxylic Acids.

A highly efficient strategy has been developed for the rapid asymmetric synthesis of gem-dimethyl and spirocyclopropyl norbornyl carboxylic acids. The key transformation involved the unprecedented asymmetric Diels-Alder reaction of highly reactive β,β-cyclopropyl-α,β-unstaturated N-acyloxazolidinones with cyclopentadiene affording the adducts in high yield and de. [ABSTRACT FROM AUTHOR]