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220 THE CAKBOHYDRATES.
treated with alkali, with a hydrochloric-acid solution of dimethylaminobenzalde-
hyde, when a beautiful red color is obtained.
Glucosamine is best prepared from decalcified lobster-shells by treat-
ing with hot concentrated hydrochloric acid. 1
In regard to its prepara-
tion from protein substances we must refer to the works cited on page
84, footnote 5.
Albamine (diglucosamine), (CeHnC^N^+H^O, is the name given by S. Fran-
kel - to a body which he isolated from the products of the hydrolysis of ovalbumin
with baryta, as well as in its digestion. Albamine is amorphous, dextrogyrate,
and reduces after boiling with acids. As hydrolytic cleavage product it yields
^-glucosamine.
Galactosamine is claimed to have been found by Schulz and Ditthorn in
a glycoprotein of the spawn of the frog. This claim is not generally accepted,
v. Ekexstein and Blanksma 3
obtained galactose on the hydrolysis of the slimy
envelope of frog eggs.
According to Offer,4
pentosamine occurs in the liver of the horse. Accord-
ing to Offer, the pentose derivative, which he calls dipentosamine (CsHyOs.NH^o-l-
H2 and a second, perhaps a diacetyl-pentosamine 2(CH3 CO)CioHi8N207 (?),
also occur in the liver. The first gives pentose reactions and reduces Fehling’s
solution after boiling with acid. The only amino-sugar positively detected in
the animal organs is glucosamine.
The amino-sugars, as intermediary bodies between the carbohydrates
and oxyamino-acids, are of great physiological interest, and this interest
has become still more important since Netjberg was first able to pre-
pare the corresponding amino-aldehyde from glycocoll and then also
from other amino-acids. From the ethyl ester of glycocoll in acid solu-
tion Neuberg 5
obtained the amino-acetaldehyde. NH2.CH2.CHO, by
treatment with sodium amalgam. This aldehyde is very unstable and
has a tendency to condensation with ring formation, and Neuberg
obtained therefrom by oxidation with corrosive sublimate and caustic
soda, pyrazine according to the equation:
NH2
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