The directed synthesis of axially chiral ligands, reagents, catalysts, and natural products through the ‘lactone methodology’

Axially chiral biaryls have become increasingly important during the past years—as structurally, biosynthetically, and pharmacologically remarkable natural products, but also as useful tools in asymmetric synthesis: as chiral reagents, ligands, and catalysts. Nevertheless, only few generally applicable synthetic protocols for the atropo-enantio- or -diastereoselective construction of biaryl bonds have been developed. The ‘lactone methodology’ as described in detail in the preceeding article, provides directed, atropo-divergent access to any of the two respective atropisomers starting from the identical immediate precursor, a (usually) configurationally unstable, since lactone-bridged biaryl. In this article the efficiency of the ‘lactone method’ in the total synthesis of natural products and in the preparation of axially chiral ligands is demonstrated for selected examples.