Atroposelective Total Synthesis of Axially Chiral Biaryl Natural Products

The optical purity of biaryls occurring in nature can vary largely. All biaryls covered in this review are characterized by a rotationally hindered axis, giving rise to the phenomenon of atropisomerism. The first method, the atropodiastereoselective biaryl coupling with internal asymmetric induction, is well suited if the target biaryl itself bears additional stereogenic centers in the proximity of the axis. This concept has mainly been applied to the total synthesis of bridged natural biaryls. Biphenyls constitute the simplest class of naturally occurring biaryls. Their structural variety ranges from constitutionally symmetric derivatives with few substituents to cross-coupled biaryl systems often further equipped with a complex substitution pattern. Binaphthopyrones constitute a small class of metabolites mainly occurring in fungi.