Amadori rearrangement compounds

It is well known that the Maillard reaction in foods is initiated by the formation of colorless and tasteless intermediates, which preferentially are formed in low-moisture systems ( ,5.). In this way by reaction of glucose with amino acids fructose-amino acids are formed via Amadori rearrangement of the primary glucosyl-ami-no acids (1 ). Fructose-amino acids e.g. have been isolated from freeze-dried apricots and peaches ( 6,7,8j. Amadori compounds arising from aldoses and amino acids are formed during drying of foods of plant origin and can be easily detected by amino acid analysis (j>). 

Scheme 2.2 Amadori rearrangement leading to the Amadori compound, the N-substituted 1 -amino-2-deoxy-2-ketose...

Horvat, S., Roscic, M., Varga-Defterdarovic, L., Horvat, J. Intramolecular rearrangement of the monosaccharide esters of an opioid pentapeptide formation and identification of novel Amadori compounds related to fructose and tagatose. J. Chem. Soc., Perkin Trans. 1 1998, 909-914. 

In the first step an aldose sugar reacts with an amino compound to form the Schiff base 1 which undergoes further reactions and rearranges into an aminoketose 2, the so-called Amadori compound [23-25]. Fig. 3.19 shows the reaction scheme with glucose as the reducing sugar. Heyns and co-workers [26] found aminoaldoses as first intermediates in a similar mechanism when ketose sugars were used. 

The most extensive part of this Section collects the Amadori compounds of D-fructose, that is, the l-amino-l-deoxy-n-fructoses. These substances, derivatives of the amino sugar isoglucosamine, are known to be rearrangement products of D-glucosylamines. Many problems, reviewed by Hodge (see Ref. 251), regarding their structure and possible mode of formation have been solved during the past few years. 

The Amadori compounds can react further with a second sugar molecule, resulting in glycosy-lamine formation and subsequent conversion to di-D-ketosylamino acids ( diketose amino acids ) by an Amadori rearrangement ... 

N.m.r. spectroscopy has been used to study the equilibrium existing between the isomeric forms of D-fructose (143 R = OH) and of each of the Amadori-rearrangement products (143) in [ Hs]pyridine. There was generally 46% of -D-pyranose, 7% of a-o-pyranose, 30% of -o-furanose, 12% of a-D-furanose, and 5% of the keto-form at equilibrium, the position of which varied only slightly depending on the substituent at C-1. The vacuum thermolysis of 1-deoxy-l-L-prolino-D-fructose has been examined as part of an investigation aimed at establishing the importance of Amadori compounds as precursors of... 

---