When two diastereoisomers (isomers that are not mirror images of each other) differ at only one chiral centre they are referred to as epimers. For example, when two monosaccharide carbohydrates have a different conformation of the H and OH on one of their asymmetric carbons (other than carbon 5) they are epimers. The sugars D- β-Glucose and D- β-Mannose are epimers at carbon 2 (they have different conformations at carbon 2) but the rest of their carbons are in the same conformation . Likewise, the sugars D-Glucose and D-Galactose are epimers of each other at C4 (carbon 4).
- ↑ Stryer. L, Tymoczko. J, Berg. J. (2012) Biochemistry, 7th Edition, W.H. Freeman and Company, USA, p.331 -332