Key Difference – Anomers vs Epimers
Anomers and epimers are both diastereomers. Epimer is a stereoisomer that differs in configuration at only one stereogenic center. An anomer is a cyclic saccharide and also an epimer that differs in the configuration, specifically at the hemiacetal or acetal carbon. This carbon is called the anomeric carbon. However, anomers are a special class of epimers. This is the key difference between anomers and epimers.
What are Anomers?
An anomer is a cyclic saccharide and also an epimer, where the difference in the configuration specifically occurs at the hemiacetal or acetal carbon. This carbon is called the anomeric carbon and it is derived from the carbonyl carbon (aldehyde or ketone functional group) of the open-chain form of the carbohydrate molecule. Anomerization is the process of conversion of one anomer to the other. The two anomers are distinguished by naming them alpha (α) or beta (β).
What are Epimers?
Epimers are found in carbohydrate stereochemistry. They are a pair of stereoisomers which differ only in the configuration at one stereogenic center. All the other stero-centers in these molecules are similar to each other. Some epimers are very useful in various industrial applications such as in producing drugs. Since epimers contain more than one chiral center, they are diastereomers. Out of all those chiral centers, they differ from each other in the absolute configuration at only one chiral center.
What is the difference between Anomers and Epimers?
Definition
Anomers: Anomers are a special set of epimers that differ in configuration only at the anomeric carbon. This happens when a molecule such as glucose converts into a cyclic form.
Epimers: Epimers are a pair of stereoisomers found in stereochemistry. They are two isomers which differ in configuration at only one chiral center. If the molecule contains any other stereocenters, they are all same in both isomers.
Examples
Anomers:
- α-D-Fructofuranose and β-D-fructofuranose
Epimers:
- Doxorubicin and epirubicin
- D-erythrose and D-threose
Definitions:
Stereogenic center:
A stereocenter or stereogenic center is also known as a chiral center. These molecules are characterized by having mirror image forms, where they are not superposable upon one another.
Diastereomers:
Diastereomers or diastereoisomers are one category of a stereoisomer. This happens when two or more stereoisomers of a compound have different configurations at one or more (but not all) of the equivalent (related) stereocenters. But, they are not mirror images of each other.
References:
Image Courtesy:
“Doxorubicin–epirubicin comparison” By Fvasconcellos 21:12, 15 October 2007 (UTC) – Own work (Public Domain) via Commons Wikimedia
“Erythrose Threose” By Roland Mattern – Roland1952 (Public Domain) via Commons Wikimedia
“D-Fructose Haworth” By Fvasconcellos 21:12, 15 October 2007 (UTC) – Own work (Public Domain) via Commons Wikimedia