3.9 Alkaloid Derived Auxiliaries: Cinchona Alkaloids and Derivatives

Cinchona alkaloids have been used as the source of chirality in a wide range of reactions. As ligands for metals, they can be used in asymmetric oxidations, such as dihydroxylation or aminohydroxylation of an alkene, or asymmetric reductions, especially of α -keto esters. The alkaloids can be modified at a number of centers, and this has allowed their use as organocatalysts in a wide range of transformations to provide high degrees of asymmetric induction. Examples of such reactions are alkylations of ketones, Michael reactions, epoxidations, and anhydride openings.