Stereoselective total synthesis of axially chiral natural products via biaryl lactones.

Axially chiral natural products are rewarding synthetic targets, due to their wide distribution, diverse structures, and promising bioactivities. The "lactone concept" provides an efficient strategy for the regio- and stereoselective construction of even bulky biaryls. Key steps are the intramolecular coupling of the ester-prefixed molecular portions to give (mostly configurationally unstable) biaryl lactones and their stereoselective ring cleavage (usually by dynamic kinetic resolution), leading to the one or-optionally-the other atropisomeric product from the same lactone. Stereoisomeric byproducts can be recycled by recyclization back to the lactone. The broad applicability of the method is demonstrated in the total synthesis of selected representatives from five very different classes of natural biaryl products.