Amadori rearrangement structure

Knowledge about the chemical structure of the antioxidative MRP is very limited. Only a few attempts have been made to characterize them. Evans, et al. (12) demonstrated that pure reductones produced by the reaction between hexoses and secondary amines were effective in inhibiting oxidation of vegetable oils. The importance of reductones formed from amino acids and reducing sugars is, however, still obscure. Eichner (6) suggested that reductone-like compounds, 1,2-enaminols, formed from Amadori rearrangement products could be responsible for the antioxidative effect of MRP. The mechanism was claimed to involve inactivation of lipid hydroperoxides. 

Tjan SB, van den Ouweland GAM. PMR investigation into the structure of some N-substituted 1-amino-1-deoxy-D-fructoses (Amadori rearrangement products). Tetrahedron 1974 30 2891-2897. 

When the structure of a compound is known, the current British-Ameri-can practice42 will be followed. No specific recommendation was made for naming Amadori rearrangement products, but, under Rule 8, the systematic name for the Amadori product of JV-i>-glucosyl-DL-leucine could be 1-(dl-l-carboxy-3-methylbutyl)amino-l-deoxy-D-fructose (I or II), and this name conflicts with the requirement that the carboxyl function takes precedence and that the name should end in acid. Consequently, this compound should be named as N- (n-ara zno-tetrahydroxy-2-oxohexyl)-DL-leucine. A shorter and equally unambiguous name would be l-(DL-leucino)-l-deoxy-D-fructose. (This is sometimes shortened to DL-leucino-deoxyfructose. Such compounds have also been called fructose-leucine, but this is not recommended since it may be confused with such expressions as the fructose-leucine system.11)... 

The intermediate endiol structures give rise to a facile sugar decomposition by which different aliphatic or cyclic mono- or dicarbonyl compounds are formed. For Amadori rearrangement products two reaction pathways are known the 1-deoxy or the 3-deoxyosone pathways. 

Figure 1. Different possible structures for an Amadori rearrangement product.

VIII. Proof of Structure of Amadori Rearrangement Products. 199... 

In 1937, the true structure of the rearranged product was reported by Kuhn and Weygand. Amadori s stable isomers were shown to be unbranched A-substituted l-amino-l-deoxy-2-ketoses. Therefore, in a strict sense, the reaction named by Kuhn and Weygand the Amadori rearrangement is the complete conversion of a Af-substituted aldosylamine to a iV-substituted l-amino-l-deoxy-2-ketose. On this basis, simple enolization of an aldosylamine or ketosylamine to the intermediate 1,2-enolic form common to both should not be construed as the Amadori rearrangement. Also, the recently demonstrated conversion of a ketosylamine to a 2-amino-2-deoxyaldose does not come under the definition in spite of an obvious similarity to the Amadori rearrangement. 

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. 

However, other paths are possible at this point (or after the first Amadori rearrangement step), the end result being the formation of a non-repetitive polymer with the following idealized structure [9],... 

Further work on chemical structure and reactivity might well include an examination of the possibility of occurrence of an Amadori rearrangement in the case of the glycosyl ureides. In addition, studies of the tautomerism of glycosyl ureides under various conditions of pH and of the neighboring-group effect would be of value in the interpretation of many of the seemingly unorthodox chemical reactions of these compounds. 

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. 

On the other hand, 6-esters of D-glucose and Tyr-terminal peptides rearrange in pyridine-acetic acid (but not in dry methanol, see Seetion n.l.b.vui later) into stable bicyclic D-fiuctosamine structures (26) (Scheme 10). The length and rigidity of the bridging peptide, however, defines its ability to form the Amadori rearrangement products and their tautomeric equilibria in solutions. ... 

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