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Anomerization of glycosides typically occurs under acidic conditions. Typically, anomerization occurs through protonation of the exocyclic acetal oxygen, ionization to form an oxocarbenium ion with release of an alcohol, and nucleophilic attack by an alcohol on the reverse face of the oxocarbenium
493:
and occurs readily in solution and is catalyzed by acid and base. This reversible process typically leads to an anomeric mixture in which eventually an equilibrium is reached between the two single anomers.
455:(on the same side) to the exocyclic oxygen attached to the anomeric reference atom (in the OH group) the anomer is Ī±. If the two oxygens are trans (on different sides) the anomer is Ī². Thus, the
636:
Because anomers are diastereomers of each other, they often differ in physical and chemical properties. One of the most important physical properties that is used to study anomers is the
584:
Anomers are different in structure, and thus have different stabilizing and destabilizing effects from each other. The major contributors to the stability of a certain anomer are:
564:
bond between C-1 (the carbon bound to two oxygens) and C-5 oxygen is cleaved (forming the open-chain compound) and reformed (forming the cyclic compound). When the
368:
is the process of conversion of one anomer to the other. As is typical for stereoisomeric compounds, different anomers have different physical properties,
758:
Varki, A.; Cummings, R. D.; Esko, J. D.; Freeze, H. H.; Stanley, P.; Bertozzi, C. R.; Hart, G. W.; Etzler, M. E.; Bertozzi, C. R.; Rabuka, D. (2009).
692:
436:
the anomeric reference atom is the stereocenter that is farthest from anomeric carbon in the ring (the configurational atom, defining the sugar as
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602:, which usually destabilize the anomer that has the anomeric group in an axial orientation on the ring. This effect is especially noticeable in
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of the two anomers is specific for the regarding sugar. For example, regardless of the configuration of the starting
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Every two anomers are designated alpha (Ī±) or beta (Ī²), according to the configurational relationship between the
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is the anomeric carbon C-1; in hemiketals, it is the carbon derived from the carbonyl of the ketone (e.g. C-2 in
592:, which stabilizes the anomer that has an electron withdrawing group (typically an oxygen or nitrogen atom) in
98:
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group is reformed, the OH group on C-5 may attack either of the two stereochemically distinct sides of the
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396:= Fischer projection with C-1 at the top of the anomeric centre. C-5 is the anomeric reference atom.
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between the anomeric group and other groups on the ring, leading to destabilization of the anomer.
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between the anomeric group and other groups on the ring, leading to stabilization of the anomer.
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Pair of stereoisomers that differ only at the carbon atom bearing an aldehyde or ketone group
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group on C-1. Which side it attacks on determines whether the Ī±- or Ī²-anomer is formed.
505:-glucose, a solution will gradually move towards being a mixture of approximately 64% Ī²-
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If in the cyclic
Fischer projection the exocyclic oxygen atom at the anomeric centre is
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orientation on the ring. This effect is abolished in polar solvents such as water.
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form, since in open-chain form, the anomeric carbon atom is planar and thus
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Anomerization is the process of conversion of one anomer to the other. For
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626:-glucopyranoside, the Ī²-anomer is the more stable anomer in water. For
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and other six-membered ring compounds. This is a major factor in water.
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form. However, in order for anomers to exist, the sugar must be in its
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of the anomeric carbon and the reference atom are the same (both
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Though the cyclic forms of sugars are usually heavily favoured,
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forms. In aldohexoses this equilibrium is established as the
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form as an intermediate product between Ī± and Ī² anomer
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may be too technical for most readers to understand
101:. Unsourced material may be challenged and removed.
556:in aqueous solution are in equilibrium with their
517:of the mixture changes; this phenomenon is called
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352:. More formally stated, then, an anomer is an
826:
723:"Chemistry - Queen Mary University of London"
682:(4th ed.). McGraw-Hill Higher Education.
677:
524:
64:Learn how and when to remove these messages
840:
833:
819:
633:, the Ī±-anomer is the more stable anomer.
513:-glucopyranose. As the ratio changes, the
448:-glucopyranose the reference atom is C-5.
324: 'part') is a pair of near-identical
328:or diastereomers that differ at only the
292:Learn how and when to remove this message
274:Learn how and when to remove this message
258:, without removing the technical details.
219:Learn how and when to remove this message
161:Learn how and when to remove this message
539:
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383:
766:. Cold Spring Harbor Laboratory Press.
14:
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760:"Structural Basis of Glycan Diversity"
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256:make it understandable to non-experts
467:) in the Ī± anomer and opposite (one
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99:adding citations to reliable sources
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29:
24:
698:Compendium of Chemical Terminology
487:, anomerization is referred to as
25:
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580:Physical properties and stability
332:, the carbon atom that bears the
45:This article has multiple issues.
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576:ion, followed by deprotonation.
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340:functional group in the sugar's
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86:needs additional citations for
53:or discuss these issues on the
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509:-glucopyranoside and 36% of Ī±-
320: 'up, above' and
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1:
664:
640:, which can be monitored by
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654:Monosaccharide nomenclature
647:
10:
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764:Essentials of Glycobiology
525:Mechanism of anomerization
420:, hence they are relative
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424:. The anomeric centre in
893:Cyclohexane conformation
600:1,3-diaxial interactions
360:carbon atom in a cyclic
191:may need to be rewritten
1386:Isomaltooligosaccharide
711:10.1351/goldbook.A00003
457:absolute configurations
418:anomeric reference atom
404:= Haworth projections.
392:of Ī±-D-glucopyranose.
1593:Carbohydrate chemistry
1380:Galactooligosaccharide
678:Francis Carey (2000).
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306:carbohydrate chemistry
1374:Fructooligosaccharide
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444:). For example, in Ī±-
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807:at Wikimedia Commons
358:hemiacetal/hemiketal
95:improve this article
703:Ī± (alpha), Ī² (beta)
544:Open-chain form of
475:) in the Ī² anomer.
408:= Mills projection.
741:2010-10-27 at the
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374:specific rotations
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638:specific rotation
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432:-fructose). In
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1199:Mannoheptulose
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631:-mannopyranose
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84:This article
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1392:Maltodextrin
1273:Isomaltulose
1064:Deoxy sugars
1000:Ketotetrose
903:Mutarotation
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380:Nomenclature
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308:, a pair of
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195:Please help
190:
188:lead section
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93:Please help
88:verification
85:
61:
54:
48:
47:Please help
44:
1550:Xanthan gum
1538:Amylopectin
1410:Beta-glucan
1321:Maltotriose
1136:Ketohexoses
1089:Aldohexoses
1069:Deoxyribose
1004:Erythrulose
962:Ketotriose
952:Aldotriose
642:polarimetry
554:hemiacetals
434:aldohexoses
426:hemiacetals
390:projections
151:August 2024
1587:Categories
1326:Melezitose
1268:Isomaltose
1263:Cellobiose
929:Aldodiose
665:References
566:hemiacetal
562:hemiacetal
558:open-chain
548:-galactose
534:Open-chain
388:Different
362:saccharide
342:open-chain
312:(from
121:newspapers
50:improve it
1480:Galactose
1435:Cellulose
1425:Sizofiran
1349:Stachyose
1331:Raffinose
1298:Trehalose
1283:Lactulose
1104:Galactose
1027:Arabinose
989:Erythrose
841:Types of
604:pyranoses
209:July 2014
56:talk page
1572:Category
1501:Glycogen
1484:Galactan
1462:Fructose
1447:Chitosan
1420:Lentinan
1369:Acarbose
1303:Turanose
1247:Multiple
1188:Heptoses
1176:Rhamnose
1171:Fuculose
1156:Tagatose
1141:Fructose
1057:Xylulose
1052:Ribulose
1016:Pentoses
978:Tetroses
881:Geometry
872:Pyranose
867:Furanose
782:20301274
739:Archived
648:See also
570:aldehyde
463:or both
416:and the
334:aldehyde
264:May 2011
110:"Anomer"
18:Anomeric
1543:Amylose
1491:Glucose
1466:Fructan
1456:Dextran
1452:Dextrin
1430:Zymosan
1293:Sucrose
1288:Maltose
1278:Lactose
1227:Nonoses
1222:Octoses
1215:Above 7
1151:Sorbose
1146:Psicose
1124:Mannose
1109:Glucose
1099:Altrose
1081:Hexoses
994:Threose
945:Trioses
850:General
745:
356:at the
350:achiral
310:anomers
250:Please
135:scholar
1533:Starch
1528:Pectin
1523:Mannan
1518:Lignin
1495:Glucan
1472:Inulin
1440:Chitin
1166:Fucose
1129:Talose
1114:Gulose
1094:Allose
1042:Xylose
1037:Ribose
1032:Lyxose
922:Dioses
898:Epimer
888:Anomer
862:Ketose
857:Aldose
805:Anomer
780:
770:
354:epimer
346:cyclic
338:ketone
137:
130:
123:
116:
108:
1388:(IMO)
1382:(GOS)
1376:(FOS)
1358:Other
1119:Idose
693:IUPAC
594:axial
499:ratio
322:Ī¼ĪĻĪæĻ
316:
314:Greek
142:JSTOR
128:books
778:PMID
768:ISBN
622:For
588:The
497:The
372:and
114:news
747:PDF
707:doi
705:".
453:cis
440:or
336:or
318:į¼Ī½Ļ
304:In
254:to
97:by
1589::
1493:/
1482:/
1464:/
1454:/
776:.
762:.
695:,
644:.
521:.
400:,
376:.
364:.
59:.
834:e
827:t
820:v
784:.
725:.
709::
629:D
624:D
546:D
511:D
507:D
503:D
473:S
469:R
465:S
461:R
446:D
442:L
438:D
430:D
406:4
402:3
398:2
394:1
295:)
289:(
277:)
271:(
266:)
262:(
248:.
222:)
216:(
211:)
207:(
203:.
193:.
164:)
158:(
153:)
149:(
139:Ā·
132:Ā·
125:Ā·
118:Ā·
91:.
66:)
62:(
20:)
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