diarastereômeros

Diastereômeros are stereochemical isomers that are not related as mirror images. This definition distinguishes them from enantiomers, which are non-superimposable mirror images, and from meso compounds, which are optically inactive due to internal symmetry despite having stereogenic centers. Diastereomers arise when a molecule contains two or more stereogenic centers and at least one, but not all, of those centers differ in configuration.

The term comes from the Greek words “dia” (through) and “stereos” (solid), reflecting the different spatial arrangements that cannot be rotated into one another. Because diastereomers are not mirror images, their chemical and physical properties often differ significantly. Differences in melting and boiling points, solubilities, and biological activities are common, making separation of diastereomers by physical methods such as chromatography feasible.

Chemists frequently rely on diastereomeric relationships for asymmetric synthesis. By converting a mixture of diastereomers into a single diastereomeric derivative (a diastereomeric salt or complex), one can then separate the mixture and revert back to the desired enantiomer. This strategy underpins many resolutions and kinetic resolutions in organic synthesis.

Common examples of diastereomers include the two stereoisomers of tartaric acid that are not optical isomers, as well as epimers of sugars such as methyl-D-glucoside and methyl-D-galactoside, which differ only in the configuration at a single stereogenic center. In pharmaceuticals, the distinction between diastereomers can affect drug efficacy and safety, emphasizing the importance of stereochemical analysis in drug development.