From The School of Biomedical Sciences Wiki
Epimers are when the configuration of sugars differ only at only a single asymmetric centre.
Epimers are a type of stereoisomer that only differs at one chiral carbon even though there may be more than one chiral carbon in the structure. The isomerism will occur because of a difference in the position of an OH group on a chiral carbon. 
- ↑ Berg J., Tymoczko J and Stryer L. (1988) Biochemistry, 3rd edition, New York: WH Freeman. Page 333
- ↑ Difference Between Anomers and Epimers, Pediaa, 2017, [Cited 20/10/17], Available at: www.pediaa.com/difference-between-anomers-and-epimers/#Epimers