The lactone concept: An efficient pathway to axially chiral natural products and useful reagents

A highly efficient concept For the stereoselective synthesis of axially chi ral biaryl target molecules is presented: the atroposelective ring cleavage of configurationally unstable lactone-bridged biaryls. The method has almo st no restrictions concerning the substitution pattern, works even for subs trates with high steric hindrance at the ortho-position(s) of the axis, and allows the optional, atropo-divergent preparation of each atropisomer from the same biaryl lactone precursor and a recycling of the undesired minor p roduct in the sense of a chiral economy. A broad series of successful appli cations in natural product and ligand syntheses underlines the high value o f the method.