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I80LEUCINE. 143
is boiled with sugar of lead and then ammonia be elded to the cooled
solution, shining crystalline leaves of leucine-lead oxide separate. Leucine
dissolves cupric hydroxide, but dors not reduce on boiling.
Leucine is readily soluble in alkalies and acids. It gives crystalline
compounds with mineral acids. If Leucine hydrochloride is boiled with
alcohol containing 3-4 ]><•! cenl BC1, long narrow crystalline prisms of
leucine-ethyl-ester hydrochloride, melting at 134° (’.. an- formed. The
picrate of the leucine ester melts at 128°. The phenylisocyanate of
’/-/-leucine melts at 165° and its anhydride at 12o° G. The o-naphthyl-
isocyanate leucine melts at 163.5°, the naphthalene-sulpho-Meucine
at 68° C.
Leucine is recognized under the microscope by the appearance of bail-
or knobs, by its action when heated (sublimation test), and by its
compounds, especially the hydrochloride and picrate of the ethyl ester
and the phenylisocyanate compound of the racemic leucine obtained
on heating with baryta water, the a-naphthylisocyanate compound and
the p-naphthalene-sulpho-leucine. According to the method suggested
by Lippich l
the leucine can be transformed into isobutylhydantoin,
having a melting-point of 205°, by boiling with an excess of urea and
baryta water. For the preparation and separation of leucine from the
other amino-acids of the leucine fraction special methods have been
suggested by F. Ehrlich and Wendel, Levene and v. Slyke.2
Leucinimide, CuH^N^ = "
9 ’
•, „ ’
TTT
’%
u ~ „ , was first obtained by Ritt-
HAU8EN in the hydrolytic cleavage products on boiling proteins with acids, and
subsequently by R. Cohx. Salaskix 3
obtained it in the peptic and tryptic
digestion oi haemoglobin. As an anhydride of leucine (2.5-diacipiperazine) it
is probably formed by a secondary change, from leucine.
It crystallizes in long needles and sublimes readily. The melting-point has
not been found constant in the different cases. The leucinimide (3.6-diisobutyl-
2.5-diacipiperazine) prepared synthetically by E. Fischer 4
from leucine-ethyl
ester melted at 271° C.
i-Isoleucine (/3-methyl-ethyl-a:-amino-propionic acid),
CH3C2H5
v
C6Hl3N°2
= CHNH2
COOH
1
Ber. d. d. chem. Gesellsch., 39.
- F. Ehrlich and Wendel, 1. o.; Levene and v. Slyke, Journ. of Biol. Chem.. 6.
3
Ritfhausen, Die Eiweisskorper der Getreidearten, etc., Bonn, 1872; R. Cohn,
Zeit?chr. f. physiol. Chem., 22 and 29; Salaskin, ibid., 32.
4
Ber. d. d. chem. Gepellsch., 34.
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