Glycosylamines. rearrangement

Upon heating in the presence of traces of acid, iV-glycosylamines rearrange to arylamino derivatives of ketoses. For example, glucosylamine 3.41 gives the amino fructose 3.47. In fact, this reaction takes place with the most varied glycosylamines, derived from aliphatic amines, amino acids, etc., with a few varia-... 

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... 

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

Results of the many investigations into the mechanism of the Maillard reaction support one of two main theories. The first assumes the formation of glycosylamines which undergo the Amadori (or, for ketoses, the Heyns) rearrangement. The 1-amino-1-deoxyketose derivative (or 2-amino-2-de-... 

In the Maillard sequence, the initial reaction between a carbonyl group and a trivalent nitrogen atom is perhaps the most thoroughly investigated and best understood. As early as 1963, Reynolds (14) published a review with 140 references limited largely to the studies of reactions of aldoses with amines, the determination of the structures and properties of the first products of reaction (a glycosylamine), and the rearrangement of the latter to a more stable ketoseamine. 

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... 

As for the amine moiety, the rearrangement has been demonstrated (although not unequivocally in all cases) for mono-A -substituted glycosyl-amines derived from aromatic amines and aralkyl- and alkyl-amines and for di-A-substituted glycosylamines containing dialkyl, alkyl-aryl, aralkyl, isocyclic, and heterocyclic alkyl radicals. The rearrangement has been reported for A-glucosyl derivatives of amino acids, but not as yet... 

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. ... 

The rearrangement products derived from aromatic and non-aromatic heterocyclic amines crystallize readily from the lower alcohols. Unlike those of many of the A-substituted glycosylamines, the crystals are not solvated. On the other hand, the ketose derivatives of aralkyl- and alkyl-amines, such as 2-phenylethylamine, ethanolamine, diethanolamine, glycine ethyl ester, and phenylalanine (see Table II), are hydrated or alcoholated, or both, and are difficult to isolate in pure crystalline form. The crystals which have been isolated were hygroscopic. Alcohols, aqueous alcohols, and water are the most commonly used solvents for crystallization. Acetone, ether, or benzene have been added to the alcoholic media in order to increase the yield of crystalline compound. The use of solvents that contain peroxides promotes decomposition of the crystals during storage. ... 

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. 

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