Enantiospecific

Enantiospecific refers to a chemical transformation in which the stereochemical outcome is determined by the absolute configuration of a chiral substrate. In an enantiospecific reaction, each enantiomer of the starting material furnishes a distinct enantiomer of the product, with little or no formation of the other product. Consequently, using the R- or S-enantiomer of the substrate yields opposite product enantiomers.

This concept is distinct from enantioselectivity. Enantioselectivity describes reactions that preferentially form one enantiomer over the other from a racemic or prochiral substrate, often yielding an enantiomeric excess. Enantiospecificity requires an enantiopure substrate and describes faithful transfer of chirality to the product, often via retention or inversion of configuration at stereocenters.

Examples include SN2 substitutions on chiral centers, which typically proceed with inversion and are therefore enantiospecific, as well as several enzymatic transformations that transplant the substrate’s chirality into a single product enantiomer.

Note on usage: Some authors use stereospecific synonymously with enantiospecific, but enantiospecific emphasizes enantiomeric outcomes from defined chiral substrates. The extent of enantiospecificity is usually quantified by the enantiomeric excess of the product.