Morgan-Elson color reaction

Gottschalkii was able to characterize the split product formed by the action of influenza virus on ovomucin, and on the sialoprotein inhibitor from urine, by its ease of humin formation and its abihty to give the Morgan-Elson color reaction for N-acylated 2-amino-2-deoxyhexoses. Accordingly, he assigned the structure of a AT-substituted D-fructosamine to this product. Odin and Klenk, independently, both suggested that this split product is closely related to a nonulosaminic acid, and noted its ability to give a direct Ehrlich color reaction. Klenk and his coworkers were then able to establish unequivocally that the principal product ... 

JV-acetyl-D-glucosamine) (27) or, preferably, from the 3-0-substituted derivatives. It is an intermediate in the Morgan-Elson color reaction (see Section VII, la p. 202). 

Color reaction Positive Ninhydrin, Nitroprusside-reagent, Br2-H20, Lemieux, and Negative Tollens, Molish, Sakaguchi, Elson-Morgan, Ferric chloride. Ultraviolet End absorption. 

The Ehrlich reagent, developed originally for the colorimetric assay of pyrrole derivatives, was shown by Ehrlich to give a color with certain glycoproteins, with and without prior alkali treatment (3). The reagent consists of dimethylaminobenzaldehyde in strong hydrochloric acid. This assay later became the basis for the Morgan-Elson reaction for the deter-... 

The first observation on the reactions of glycosylamines with 3-dicarbonyl compounds is due to Elson and Morgan, who found that D-glucosylamine and 2,4-pentanedione, when heated in slightly alkaline solution, give a positive Ehrlich pyrrole test. They considered that 3-acetyl-2-methyl-4-(D-ara6wo-tetrahydroxybutyl)pyrrole (20) was formed and was responsible for the color reaction. 

The condensation of amino sugars with /3-keto esters in an alkaline medium results in considerable degradation of the (tetrahydroxybu-tyl)pyrrole produced, giving rise to small yields of 2-methylpyr-role,57,58 which seems to be the main chromophore in the Elson-Morgan reaction. Under these conditions, 3-amino-3-deoxyhexoses yield 2-methylpyrrole-4-carboxylic acid,59 which is, in part, responsible for the coloration produced with p-(dimethylamino)benzaldehyde. 

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