Diastereoisomerisation

Diastereoisomerisation is a chemical process where a molecule undergoes a change in its stereochemistry to form a different diastereomer. Diastereomers are stereoisomers that are not mirror images of each other. This means they have different configurations at one or more, but not all, of their chiral centers. Unlike enantiomers, which are always formed in pairs through a single inversion of a chiral center, diastereoisomers can be interconverted under specific conditions, often involving heat or specific chemical reagents.

The process of diastereoisomerisation is distinct from epimerisation, which specifically refers to the interconversion of epimers, a subclass of diastereomers that differ in configuration at only one chiral center. Diastereoisomerisation is a broader term encompassing any change that leads to a different diastereomeric form. This transformation can occur through various mechanisms, including bond rotation around single bonds in certain acyclic molecules or ring opening and closing in cyclic systems. For molecules with multiple chiral centers, a change at one center can lead to a new diastereomeric relationship with existing stereoisomers.

Understanding diastereoisomerisation is crucial in organic chemistry, particularly in synthesis and reaction mechanisms. It can influence the physical and chemical properties of a compound, such as its solubility, melting point, and reactivity. In biological systems, the formation of different diastereomers can have significant implications for drug efficacy and interactions with biological targets. While often an unwanted side reaction in synthesis, controlled diastereoisomerisation can sometimes be exploited to selectively produce desired stereoisomers.