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Chemical reaction by which unequal amounts of two product isomers are formed. It is normally not possible to synthesize from materials that do not have optical activity (i.e., are not chiral) one stereoisomer of a chiral compound without the other, but use of a chiral auxiliary, such as an enzyme or other catalyst, a solvent, or an intermediate, can force the reaction to produce predominantly or only one isomer. Asymmetric syntheses are often called stereoselective; if one product forms exclusively, it is stereospecific.
This entry comes from Encyclopædia Britannica Concise. For the full entry on asymmetric synthesis, visit Britannica.com.