sugar chemistry, an anomer is a special type of epimer. It is a stereoisomer( diastereomer, more exactly) of a saccharide(in the cyclic form) that differs only in its configuration at the hemiacetal(or hemiketal) carbon, also called the anomeric carbon. If the structure is analogous to one with the hydroxyl groupon the anomeric carbon in the axial position of glucose, then the sugar is an alpha anomer. If, however, that hydroxyl is in the equatorialposition, then the sugar is a beta anomer. For example, α-D-glucopyranose and β-D-glucopyranose, the two cyclic forms of glucose, are anomers.For -L- the α and β are contrarywise. ("see" Glycosidic bond"for details")
anomeric effecthelps stabilize the α-anomer. The term for interconversion between the two anomers is mutarotation.
The two different anomers are two distinct chemical structures, and thus have different physical and chemical properties, notably
optical rotation. For example, α-D- glucosehas an optical rotation of +112 degrees and its anomer, β-D-glucose, has an optical rotation of +19 degrees.
* [http://www.sinica.edu.tw/~ccswww/zj-BI-1999-P.283.pdf Chin. Chem. Soc., Vol. 46(3) 283 (1999)] "On the Assignment of Anomeric Configuration" (pdf)
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