Stereoisomerspecific

Stereoisomer-specific, or stereoisomer specificity, describes situations in which a property, action, or outcome depends on which specific stereoisomer of a compound is present. Stereoisomers share the same molecular formula and connectivity but differ in the three-dimensional arrangement of their atoms, most commonly as enantiomers (mirror images) or diastereomers (non-mirror-symmetric forms). In many biological and chemical contexts, only certain stereoisomers are responsible for a given effect.

In biology, stereospecific interactions are common because biological targets such as enzymes, receptors, and transport proteins are chiral. This leads to stereoselectivity or enantioselectivity, where one stereoisomer binds more effectively or has a different activity or metabolism than others. Stereospecific reactions in chemistry are those that inherently produce or require a particular stereoisomer, such as a reaction that yields predominantly one enantiomer or diastereomer due to the reaction mechanism.

A practical example is ibuprofen, where the S-enantiomer is the more active anti-inflammatory form, while the R-enantiomer is less active and can slowly convert to the S form in the body. In pharmaceutical development, stereoisomer specificity influences drug efficacy and safety, leading to emphasis on enantiomeric purity and the reporting of enantiomeric excess. Analytical methods, including chiral chromatography and optical rotation measurements, are used to assess and quantify stereoisomeric composition.

See also: chirality, enantioselectivity, diastereoselectivity, stereochemistry, enantiomer.