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212 THE CARBOHYDRATES.
The first artificial preparation of a sugar was made by Butlerow. On
treating trioxymethylene, a polymer of formaldehyde, with lime-water he obtained
a faintly sweetish syrup called methylenitan. Loew l
later obtained a mixture
of serveral sugars, from which he isolated a fermentable sugar, called methose,
by condensation of formaldehyde in the presence of bases. The most important
and comprehensive syntheses of sugar have been performed by E. Fischer 2
The starting-point of these syntheses is a-acrose, which occurs as a condensa-
tion product of formaldehyde. The name a-acrose has been given to this body
because it is obtained from acrolein bromide by the action of bases (Fischer).
It is also obtained admixed with fi-acrose on the oxidation of glycerin with
bromine in the presence of sodium carbonate and treating the resulting mixture
with alkali. On the oxidation with bromine a mixture of glyceric aldehyde,
CH2 OH.CH(OH).CHO, and dioxyacetone, CH2 (OH).CO.CH2 OH, is obtained.
These two bodies may be considered as true sugars, namely, glyceroses or trioses.
It seems as if a condensation to hexoses takes place on treatment with alkalies.
a-acrose may be isolated from the above mixture and obtained pure by first
converting it into osazone and then retransforming this into the sugar, a-acrose
seems to be identical with r-fructose. With yeast one-half, the levogyrate
rf-fructose ferments, while the dextrogyrate Z-fructose remains. The r- and
Z-fructose may be prepared in this way.
On the reduction of a-acrose we obtain a-acrite, which is identical with r-
mannite. On oxidation of r-mannite we obtain r-mannose, from which only
Z-mannose remains on fermentation. On further oxidation of r-mannose it
yields r-mannonic acid. The two active mannonic acids may be separated from
each other by the fractional crystallization of their strychnine or morphine salts.
The two corresponding mannoses may be obtained from these two acids, d- and
Z-mannonic acids, by reduction.
rf-fructose can be obtained from cZ-mannose with the osazone as an inter-
mediary step and it remains now to speak of .the formation of glucoses. The
d- and Z-mannonic acids are partly converted into d- and Z-gluconic acids on heat-
ing with quinoline, and d- or Z-glucose is obtained on the reduction of these acids;
Z-glucose is best prepared from Z-arabinose by means of the cyanhydrin reaction,
using Z-gluconic acid as the intermediate step. The combination of Z- and d-
gluconic acids, forming r-gluconic acid, yields r-glucose on reduction.
The artificial preparation of sugars by means of the condensation of formalde-
hyde has received special interest because, according to Baeyer’s assimilation
hypothesis, in plants formaldehyde is first formed by the reduction of carbon
dioxide, and the sugars are produced by the condensation of this formaldelvyde.
Bokorny 3
has shown, by special experiments on algse Spirogyra, that formalde-
hyde sodium sulphite was split by the living algse cells. The formaldehyde set
free is immediately condensed to carbohydrate and precipitated as starch.4
Among the hexoses known at the present time only glucose, fructose,
and galactose are really of physiological-chemical interest; therefore of
the other hexoses only mannose will be incidentally mentioned.
rf-Glucose (grape sugar) also called dextrose and diabetic sugar
—
occurs abundantly in the grape, and also, often accompanied with fructose
1
Butlerow, Ann. d. Chem. u. Pharm., 102; Compt. rend., 53; O. Loew, Journ. f.
prakt. Chem. (N. F.), 33, and Ber. d. deutsch. chem. Gesellsch., 20, 21, 22.
2
Ber. d. d. chem. Gesellsch., 21, and 1. c, p. 197.
3
Biolog. Centralbl. 12, pp. 321 and 481.
* In regard to the syntheses of sugar see also W. Lob and Pulvermacher Bioch.
Zeitschr, 23, 10 (1909), 26, 231 (1910).
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