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GLUCURONIC ACIDS. 221
On account of this tendency to ring-formation the amino-acetalde-
hyde as well as the amino-aldehydes as a group, stand, according to Neu-
berg, in close relationship to many ring systems, such* as imidazole,
piperazine, pyrazine, pyridine and others, and also to the alkaloids.
The amino-sugars, like the amino-aldehydes, can also unite, form-
ing ring compounds, and this seems to be the case on the decomposi-
tion of free glucosamine in aqueous solution, which occurs with access
cf air (Lobry de Bruyn). As found by Stolte l
2,5-ditetraoxybutyl
pyrazine (= fructosazine) is hereby produced according to the following
equation:
NH2 N
/ y\
O.1H9C4.CH+CHO O4H9C4.C CH
+0= I ||
+3H2
CHO CH.C4H9O4 HC C.C4H9O4
/ V
NH2 N
Fructosazine
The 2,5-ditetraoxybutyl pyrazine, which Stolte obtained by Lobry
de Bruyn’s 2
method from fructose in methyl alcohol solution and
ammonia, and which he calls fructosazine, can be oxidized outside of the
body into 2,5-pyrazine dicarboxylic acid.
The same acid can be formed in the animal body (rabbits), although not
constantly, after introducing fructosazine. It also passes into the urine of
rabbits after intravenous injection of d-fructose and glycocoll (Spiro), a behavior
which Spiro claims indicates that carbohydrates in metabolism react with the
cleavage products of proteins. Stolte’s experiments to decide the question
whether in the animal body the glucosamine in its decomposition passes into
fructosazine did not at first yield conclusive results. His more recent investiga-
tions 3
show on the contrary that in rabbits 2-oxymethylpyrazine-5-carboxylic
acid is formed as an oxidation product, and this can be oxidized outside of the
body into pyrazine-2, 5-dicarboxyIic acid.
b. Glucuronic Acids.
The glucuronic acids occurring in the animal body either physiolog-
ically or pathologically, are conjugated acids which will be described in
detail in a subsequent chapter (XIV). We will here describe only the
d-glucuronic acid in connection with the carbohydrates.
CHO
d-Glucuronic acid (glycuronic acid), C6Hio07 = (CH.OH)4 , is a deriva-
COOH
tive of glucose, and has been synthetically prepared by E. Fischer and
1
Hofmeister’s Beitriige, 11.
2
Cited by Stolte, Hofmeister’s Beitrage, 11.
3
Spiro, Hofmeister’s Beitriige, 10, p. 283; Stolte, Biochem. Zeitschr., 12.
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