Stereoisomers differing in configuration or arrangement of —OH group on a single asymmetric carbon are known as epimers. For example, mannose and glucose are epimers (Figure 2.2). The position of the —OH group differs only in the C-2 position. Similarly, galactose and glucose are epimers. The position of the —OH group differs only in the C-4 position.

Note: Mannose and galactose are not epimers of each other as they differ in the position of the —OH group at two positions.