Desymmetrization

Typical substrates are epoxides, diols, dienes, and cyclic carboxylic acid anhydrides. : In another example, a symmetrical cyclic imide is subjected to asymmetric deprotonation resulting in a chiral product with high enantioselectivity. Partial hydrogenation converts benzil (PhC(O)C(O)Ph) into chiral hydrobenzoin. The process can be implemented enantioselectively using transfer hydrogenation. : (Ph = The precursor benzil has C2v symmetry, and the product is C2 symmetric. Citric acid is also a symmetric molecule that can be desymmetrized by partial methylation. The alcoholysis of cyclic anhydrides can be conducted enantiosymmetrically using chiral amine catalysts. A related example is the hydrolysis of prochiral diesters catalyzed by chiral phosphoric acids. ==Formal symmetry considerations==

Desymmetrizations involve the loss of an improper axis of rotation (mirror plane, center of inversion, rotation-reflection axis). In other words, desymmetrisations convert prochiral precursors into chiral products. ==References==