Sustainability from agricultural waste: chiral ligands from oligomeric proanthocyanidins via acid-mediated depolymerization

Oligomeric proanthocyanidins (OPCs, Ar′ = 3,4-(HO) 2 (C 6 H 3 ) are abundant natural products found in agricultural and forestry waste such as pine bark, grape seeds, and the peels of mangosteen. We have demonstrated that the OPCs can be converted into small molecule chiral ligands by using proper nucleophiles for acid depolymerization of the OPCs. The chiral ligands may have potential for sustainable asymmetric catalysis.