ISOLEUCINE. 143 



is boiled with sugar of lead and then ammonia be added to the cooled 

 solution, shining crystalline leaves of leucine-lead oxide separate. Leucine 

 dissolves cupric hydroxide, but does 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 per cent HC1, long narrow crystalline prisms of 

 leucine-ethyl-ester hydrochloride, melting at 134 C., are formed. The 

 picrate of the leucine ester melts at 128. The phenylisocyanate of 

 cW-leucine melts at 165 and its anhydride at 125 C. The a-naphthyl- 

 isocyanate leucine melts at 163.5, the naphthalene-sulpho-Z-leucine 

 at 68 C. 



Leucine is recognized under the microscope by the appearance of balls 

 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 /3-naphthalene-sulpho-leucine. According to the method suggested 

 by LIPPICH x 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, C 12 H 22 N 2 2 = ' V ' ^ > was first obtained by RITT- 



.04x19 



HAUSEN in the hydrolytic cleavage products on boiling proteins with acids, and 

 subsequently by R. COHN. SALASKIN 3 obtained it in the peptic and tryptic 

 digestion jf 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. 



2-Isoleucine (/3-methyl-ethyl-a-amino-propionic acid), 



CH 3 C 2 H 5 

 \/ 



COOH 



1 Ber. d. d. chem. Gesellsch., 39. 



2 F. Ehrlich and Wendel, 1. c.; Levene and v. Slyke, Journ. of Biol. Chem., 6. 



3 Ritthausen, Die Eiweisskorper der Getreidearten, etc., Bonn, 1872; R. Cohn, 

 Zeitschr. f. physiol. Chem., 22 and 29; Salaskin, ibid., 32. 



4 Ber. d. d. chem. Gesellsch., 34. 



