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Desymmetrization in stereochemistry is the modification of a molecule that results in the loss of one or more symmetry elements. A common application of this class of reactions involves the introduction of chirality.〔Willis, Michael C. "Enantioselective desymmetrization" Journal of the Chemical Society, Perkin Transactions 1: Organic and Bio-Organic Chemistry 1999, pp. 1765-1784. 〕 Formally, such conversions required 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.〔''Basic Terminology of Stereochemistry'', G.P. Moss Ed. Pure Appl. Chem., Vol. 68, No. 12, pp. 2193-2222, 1996.〕 ==Examples== Typical substrates are epoxides, diols, dienes, and carboxylic acid anhydrides.〔 One example is the conversion of cis-3,5-diacetoxycyclopentene to monoacetate. In this transformation, the plane of symmetry in the precursor is lost, and the product is asymmetric. The desymmetrisation itself is not usually considered useful. The ''enantioselective'' desymmetrisation however delivers a useful product. This particular conversion utilizes the enzyme cholinesterase.〔Donald R. Deardorff, Colin Q. Windham, and Chris L. Craney "Enantioselective Hydrolysis of cis-3,5-diacetoxycyclopentene: (1R,4S)-(+)-4-Hydroxy-2-cyclopentenyl Acetate" Organic Syntheses, Coll. Vol. 9, p.487 (1998); Vol. 73, p.25 (1996).〕 :300px In another example, a symmetrical cyclic imide is subjected to asymmetric deprotonation resulting in a chiral product with high enantioselectivity.〔Vincent Rodeschini, Nigel S. Simpkins, and Fengzhi Zhang "Chiral lithium amide base desymmetrization of a ring fused imide: formation of (3as,7as)-2-()-1,3-dioxo-octahydro-isoindole-3a-carboxylic acid methyl ester" Org. Synth. 2007, volume 84, 306. 〕 Transfer hydrogenation converts benzil (PhC(O)C(O)Ph) into one enantiomer of hydrobenzoin: :PhC(O)C(O)Ph + 2 H2 → PhCH(OH)CH(OH)Ph The precursor benzil has C2v symmetry, and the product is C2 symmetric. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「desymmetrization」の詳細全文を読む スポンサード リンク
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