142 THE PROTEIN SUBSTANCES. 



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

 MANN) . The same is produced by the action of gaseous HC1 upon leucine 

 in alcohol ; and the free ethyl ester can be obtained from this by the 

 method suggested by E. FISCHER. 1 



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

 of d-Z-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 by the appearance of balls or knobs under the 

 microscope, by its action when heated (sublimation test), and by its com- 

 pounds, especially the hydrochloride and picrate of the ethyl ester and 

 the phenylisocyanate compound of the racemic leucine obtained on heat- 

 ing with baryta water, the a-naphthylisocyanate compound and the 

 /?-naphthalene-sulpho-leucine. According to the method suggested by 

 LIPPICH 2 the leucine can be transformed into isobutylhydantoin, having 

 a melting point of 205, by boiling with an excess of urea and baryta water. 

 In the detection of leucine, it must be first isolated, and the preparation 

 of the ethyl ester and distillation of the same are important in this regard. 

 In order to avoid the difficulties which occur in the preparation of pure 

 leucine, EHRLICH and WENDEL 3 have suggested a new method. 



P* TT r^fi ]V"fT f^O 

 Leucinimide, C 12 H 2 2N 2 O 2 = 4 9 ';v/ A / nTT , was first obtained by RITT- 



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

 subsequently by R. CORN. SALASKIN 4 obtained it in the peptic and tryptic 

 digestion of haemoglobin. As an anhydride of leucine (2.5-cliacipiperazine) 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 5 from leucine-ethyl 

 ester melted at 271 C. 



\/ 



PTT 



Isoleucine (methyl-ethyl-a-amino-propionic acid) C 6 H 13 NO 2 = . 



CHJNH 2 



COOH 



is an isomer of leucine discovered by F. EHRLICH, who first isolated it 

 from the mother-liquor after removing the sugar from beet-sugar 

 molasses. He also found it in the hydrolysis of several proteins, and 



1 Rohmann, Ber. d. d. chem. Gesellsch., 30; E. Fischer, ibid., 34. 



2 Ber. d. d. chem. Gesellsch., 39. 



3 Biochem. Zeitschr., 8. 



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

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



5 Ber. d. d. chem. Gesellsch., 34. 



