In 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 group on the anomeric carbon in the axial position of glucose, then the sugar is an alpha anomer. If, however, that hydroxyl is in the equatorial position, 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")

The anomeric effect helps 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-glucose has an optical rotation of +112 degrees and its anomer, β-D-glucose, has an optical rotation of +19 degrees.

See also

*Haworth projection

External links

* [ Chin. Chem. Soc., Vol. 46(3) 283 (1999)] "On the Assignment of Anomeric Configuration" (pdf)

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  • Anomer — A|no|mer [griech. áno̅ = oben; ↑ Isomer], das; s, e; auch A|no|me|re, das; n, n: bei Monosacchariden bes. Bez. für die beiden ↑ Epimeren, die bei Ring Kette Tautomerie infolge Umwandlung der offenkettigen Aldose bzw. Ketose in die cycl.… …   Universal-Lexikon

  • Anomer — Die beiden Anomere der Furanoseform der D Erythrose. Das anomere Zentrum ist hier das Kohlenstoffatom in der rechten Spitze des Moleküls …   Deutsch Wikipedia

  • anomer — noun Any diastereoisomer of a sugar or derivative differing in configuration only at C 1 of an aldose or C 2 of a ketose …   Wiktionary

  • anomer — One of two sugar molecules that are epimeric at the hemiacetal or hemiketal carbon atom (carbon 1 in aldoses, carbon 2 in most ketoses); e.g., α d glucose and β d glucose. SEE ALSO: sugars. Cf.:epimer. * * * an·o·mer an ə mər n a cyclic… …   Medical dictionary

  • anomer — n. one of two sugar molecules that pertain to epimers which differ in the manner they are configured about their respective carbonyl carbon atom …   English contemporary dictionary

  • anomer — an·o·mer …   English syllables

  • anomer — …   Useful english dictionary

  • Mutarotation — is the change in the optical rotation that occurs by epimerization (that is the change in the equilibrium between two epimers, when the corresponding stereocenters interconvert). Cyclic sugars show mutarotation as α and β anomeric forms… …   Wikipedia

  • Carbohydrate — Carbohydrates (from hydrates of carbon ) or saccharides (Greek σάκχαρον meaning sugar ) are the most abundant of the four major classes of biomolecules, which also include proteins, lipids and nucleic acids. They fill numerous roles in living… …   Wikipedia

  • Anomeric effect — In organic chemistry, the anomeric effect or Edward Lemieux effect is a stereoelectronic effect that describes the tendency of heteroatomic substituents adjacent to a heteroatom within a cyclohexane ring to prefer the axial orientation instead of …   Wikipedia

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