Epimer
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In chemistry, an epimer is a stereoisomer of another compound that has a different configuration at only one of several chiral carbon centers. Stereoisomers include enantiomers and diastereomers, both which contain a chiral carbon center (excluding geometric isomers, which is a class of diastereomers).
When an epimer becomes incorporated into a ring structure it is called an anomer.
For example, the sugars α-glucose and β-glucose are epimers. In α-glucose, the -OH group on the first (anomeric) carbon is in the direction opposite the methylene group. In β-glucose, the -OH group is oriented in the same direction as the methylene group [1].
