Glycosylamines 2-amino-2-deoxy

Enzyme and source 5-Amino-S-deoxy- hexopyranose 1,5-Dideoxy- 1,5-iminohexitol Glycosylamine References... 

Synthesis of ds-fused OZT starting from 2-amino-2-deoxy-D-glucose and D-mannose hydrochlorides in conditions similar to those applied for glycosylamines was recently published (Scheme 6).36 In contrast with data previously reported for tram-fused thiocarbamate,32 the isomeric isothiocyanates were not detected. 

The initiating reaction between aldoses and amines, or amino acids, appears to involve a reversible formation of an N-substituted aldosyl-amine (75) see Scheme 14. Without an acidic catalyst, hexoses form the aldosylamine condensation-product in 80-90% yield. An acidic catalyst raises the reaction rate and yet, too much acid rapidly promotes the formation of 1-amino-l-deoxy-2-ketoses. Amino acids act in an autocat-alytic manner, and the condensation proceeds even in the absence of additional acid. A considerable number of glycosylamines have been prepared by heating the saccharides and an amine in anhydrous ethanol in the presence of an acidic catalyst. N.m.r. spectroscopy has been used to show that primary amines condense with D-ribose to give D-ribopyrano-sylamines. ... 

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... 

Compared with the /V-substituted glycosylamines, the l-amino-l-deoxy-2-ketoses are more stable to moist acid atmospheres, but are still heat-labile and decompose rapidly in mild alkali. They exert greater reducing power, although less than reduc-tones. They brown more easily with amino acids. Acid hydrolysis gives much compared with little HMF, but no hexose is recovered, in keeping with the reaction s being irreversible (however, see below). 

Like the iV-substituted glycosylamines, the JV-substituted 1-amino-l-deoxy-2-ketoses are colorless when the parent amine is colorless. 1-Deoxy-1-p-toluidino-D-fructose is tasteless, but derivatives of the more strongly basic amines are bitter. 

The open-chain forms of glycosylamines (see Section 1.2.3) are Schiff bases and are labilised towards deprotonation of an adjacent carbon in much the same way as the open-chain forms of the sugars themselves. Reprotonation of the first-formed enamine on the carbon bearing the nitrogen atom will give an a-aminocarbonyl compound. The formation of a l-deoxy-l-amino-2-ketoses... 

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). 

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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