Lénantiosélectivité

Lénantiosélectivité is a term used in chemistry to describe the preferential formation of one enantiomer over another during a chemical reaction. This phenomenon is a specific type of stereoselectivity that plays a crucial role in asymmetric synthesis and chiral chemistry.

The concept is particularly important in pharmaceutical chemistry, where different enantiomers of a compound can exhibit significantly different biological activities. While one enantiomer may possess the desired therapeutic effect, its mirror image might be inactive or even harmful. Lénantiosélectivité allows chemists to synthesize the desired enantiomer preferentially, avoiding the need for costly and time-consuming separation processes.

This selectivity is typically achieved through the use of chiral catalysts, chiral auxiliaries, or chiral starting materials. Common methods include asymmetric hydrogenation, asymmetric epoxidation, and enantioselective aldol reactions. The degree of lénantiosélectivité is often quantified using the enantiomeric excess (ee) value, which measures the percentage excess of one enantiomer over the other.

The term derives from the Greek words "enantio" meaning opposite, and "selectivity" referring to the preference for one outcome over another. Understanding and controlling lénantiosélectivité has become essential in modern drug development, as regulatory agencies increasingly require pharmaceutical companies to demonstrate the safety and efficacy of individual enantiomers rather than racemic mixtures.

Industrial applications of lénantiosélectivité extend beyond pharmaceuticals to include the production of agrochemicals, fragrances, and fine chemicals where chiral purity is essential for optimal performance and safety.