asymmetric catalysis by lewis acids rely on catalysts with chiral ligands coordinated to the metal center. over the years, a small number of chiral ligand scaffolds have stood out as having "privileged" catalytic properties suitable for a wide range of applications, often of unrelated mechanisms. current research efforts in asymmetric lewis acid catalysis mostly utilize or modify those ligands rather than create new scaffolds "de novo". the "privileged" scaffolds share a few common features, including chemical stability and relative ease of elaboration. the majority of the scaffolds are multidentate. most of them also have high scaffold rigidity within the ligand. several of them have fairly mature stereoinduction models available. some "privileged" scaffolds, as identified by jacobsen and zhou, are introduced below.