Amino sugars, reaction with 8-dicarbonyl compounds

Strecker [34] discovered that the reaction between amino acids (glycine, alanine, leucine) and the tricarbonyl compound alloxan yields CO2 and aldehydes. The Strecker degradation of amino acids occurs also with dicarbonyl compounds [35] including those that are formed in the course of the Maillard reaction, in particular deoxyglycosones and some of the smaller sugar fragments like 7 and diacetyl. Fig. 3.22 shows the reaction pathway that involves the formation of an imine 8, followed by decarboxylation and liberation of the resulting aminoketo compound and the Strecker aldehyde from the intermediate 10. Odour-active Strecker aldehydes which... 

The reaction of 1-amino-l-deoxy-D-fructose with /3-dicarbonyl compounds in aqueous acetone at neutral pH has also been studied. The acetate of this amino sugar affords, with ethyl acetoacetate, ethyl 2-methyl-4-(D-om6wo-tetrahydroxybutyl)pyrrole-3-carboxylate (17). As in previous... 

The death on October 8, 2009 of Antonio Gomez Sanchez is noted with regret. He was one of the successors of the Seville carbohydrate school built up by Francisco Garcia Gonzalez, with whom he coauthored in Volume 20 a chapter on the reaction of amino sugars with 1,3-dicarbonyl compounds, a subject that was a major theme of Gomez Sanchez s research. 

Garc a GonzAlez, F., and G6mez Sanchez, A., Reactions of Amino Sugars with fteto-Dicarbonyl Compounds, 20, 303-355... 

Sialic (neuraminic) acids have structural features in common with compounds assumed to be intermediates in the formation of pyrroles from amino sugars and -dicarbonyl compounds, and some of their properties will be interpreted with this in mind. This article terminates with a discussion of the relationship between these reactions and some biological processes. 

The reaction of amino sugars with (8-dicarbonyl compounds in alkaline solution produces (tetrahydroxybutyl) pyrroles together with simpler pyrrole compounds lacking the tetrahydroxybutyl side-chain. 2-Amino-2-deoxy-D-glucose hydrochloride and ethyl acetoacetate, heated in aqueous solution at pH 9.7, give a mixture of ethyl 2-methyl-5-(D-ara )mo-tetra-hydroxybutyl)pyrrole-3-carboxylate (1) and ethyl 2-methylpyrrole-3-carboxylate. The yields of these compounds are in the approximate ratio... 

A -Acyl substitution of 2-amino-2-deoxyaldohexoses prevents their reaction with /3-dicarbonyl compounds from giving pyrrole derivatives. Instead, the products of the aldol reaction of the aldehydo form of the sugar with the active methylene group of the /3-dicarbonyl compound are formed. These substances have the structural features of higher-carbon, branched-chain carbohydrates. 

Consideration of the number of bonds affected in the reaction of amino sugars with 8-dicarbonyl compounds (Scheme A X = NH, )V-alkyl, A -aryl) allows the presumption that the mechanism is complex and that,... 

On comparing the reactions of 2-amino-2-deoxyaldoses and 1-amino-l-deoxyketoses with 8-dicarbonyl compounds, which yield pyrroles (Scheme A, X = NH, A -alkyl, or A -aryl), with the reactions of the nonnitrogenous aldoses and ketoses with the same compounds, which yield furan derivatives (Scheme A, X = 0), it may be noted that the changes of bonds are the same. It seems reasonable, therefore, to assume that both processes proceed through the same, or at least similar, mechanisms. From the experimental point of view, the main differences between these two reactions concern rates and catalysts. Aldoses and ketoses react very slowly in the absence of such acidic catalysts as zinc chloride and ferric chloride. The reactions of the amino sugars are much faster and are usually performed under neutral or slightly basic conditions. 

In the reactions of 2-amino-2-deoxy-D-glucose with some /3-dicarbonyl compounds (such as ethyl acetoacetate, 2,4-pentanedione, or pyruvic acid) in alkaline solution, pyrroles lacking the tetrahydroxybutyl chain are obtained. The loss of this group cannot occur with the already formed (tetrahydroxybutyl)pyrroles, because these compounds, as exemplified by 3-acetyl-2-methyl-5-(D-ora wo-tetrahydroxybutyl)pyrrole (2), remain unchanged at the pH (9-10) of the reaction. The fission of the sugar chain most probably occurs for one of the intermediates of the reaction, for instance (79), and it may be formulated as a concerted-elimination reaction catalyzed by the hydroxyl ion, as indicated in Scheme C. The... 

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. 

Amino-2-deoxyaldohexoses, 1-amino-l-deoxyketohexoses, and their V-alkyl and JV-aryl derivatives react with /3-dicarbonyl compounds, giving substituted (tetrahydroxybutyl)pyrroles. It is, most probably, a general reaction of 2-amino-2-deoxyaldoses and 1-amino-l-deoxyketoses which parallels the formation of (polyhydroxyalkyl)furans from nonnitrogenous monosaccharides. In the reactions with amino sugars in alkaline media, simpler pyrrole compounds lacking the tetrahydroxybutyl chain are also obtained. 

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