Glycosylamines Amadori rearrangement

Figure 44 Maillard reaction of lactose and fluoxetine HCI yielding major degradants glycosylamine, Amadori rearrangement product, and N-formyl fluoxetine.

The Maillard condensation is one of the most extensively studied reactions within the field of degradation chemistry, particularly in the area of food and nutritional science. Louis Mallard reported in 1912 that some amines react with reducing carbohydrates to produce brown pigments. The condensation typically yields a simple glycosylamine, which then readily undergoes the Amadori rearrangement to produce 1 -amino-1 -deoxy-2-ketoses [95]. Reducing carbohydrates... 

Rearrangement of the glycosylamine by an Amadori rearrangement type of reaction to yield an aldoseamine or ketoseamine. 

The Amadori rearrangement of the glycosylamines involves the presence of an acid catalyst and leads to the formation of ketose-amine or 1-amino-1-deoxyketose according... 

Occasionally, the Amadori rearrangement has been accomplished by heating the sugar and amine components, or the W-substituted glycosylamine, in alcohol without the addition of an acid catalyst. - However, acidic... 

Although there is no positive evidence in support of it, a plausible alternative to the above reaction sequence is enolization of the aldose before condensation with the amine. In such a sequence, the Y-substituted glycosylamine would not be a precursor of the aminodeoxyketose. This postulate merits investigation because, in spite of attempts to isolate Y, Y-dibenzyl-D-glucosylamine, this compound could not be found in the reaction product of D-glucose with dibenzylamine only D-glucose or the Amadori rearrangement product was isolated. ... 

Voto6ek and Wichterle " investigated the reaction of JV-substituted gly-cosylamines with hydrocyanic acid, but they did not start with the isolated glycosylamine. The sugar and amine were heated in alcohol, the hydrocyanic acid was added, and the mixture was allowed to cool. The structure of the crystalline nitrile isolated was not determined. Because the hydrogen cyanide could have added to the carbonyl group of the ketose after an Amadori rearrangement had occurred, the constitution of their products is open to question. 

On the basis of these results, Hakomori and coworkers53,54 proposed a l-deoxy-l-(N-peptidyl)-D-ketose structure for the linkage of the peptide and carbohydrate components of UGP I, II, and III this kind of structure is identical with that of the product of the Amadori rearrangement of glycosylamines. 

Substances of structures (105) and (106) may be intermediates in the Amadori rearrangement of glycosylamines (104) when this reaction is catalyzed by certain /3-dicarbonyl compounds. Hydrolysis of (106) would give the products of the rearrangement, the V-substituted 1-aniino-l-deoxy-D-fructoses (109). Hodgehas obtained some evidence for the existence of intermediate compounds in the Amadori rearrangement he formulated these as the branched-chain amino ketoses (78, X = iV-alkyl or V-aryl). 

Owing to the presence of active methylene compounds and ammonia, the conditions of these reactions are favorable for the occurrence of an Amadori rearrangement, and, on this basis, the structures proposed by Voto6ek and Valentin have been questioned.The products could be derived either from glycosylamines or from the 1-amino-l-deoxyketoses that result from their Amadori rearrangement. 

Amino acids may be involved in biochemical reactions of this type, through their conversion into glycosylamines by reaction with the monosaccharides. The glycosylamines may react directly with the /3-dicarbonyl compound, or after its Amadori rearrangement to the amino sugar. 

Whereas glycosylamines are polarographically inactive, some of their products formed by the Amadori rearrangement are polarographically reducible. It seems that only -amino ketones and derivatives of 1-amino-l-deoxy-D-fructose are reducible and can form tautomers with... 

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