THE CHEMICAL CONSTITUTION OF THE UNITS 89 



inactive leucine, when compared with the leucine prepared from 

 isovaleraldehyde, hydrogen cyanide and ammonia, was found to be 

 identical with it, and further, both compounds gave d-leucine, when 

 acted upon by the mould Penicillium glaucum, and the same leucic 

 acid, when treated with nitrous acid. Leucine is therefore a-aminoiso- 

 butylacetic acid, 



CH 3 \. 



\CH . CH a . CH(NH 2 )COOH. 



CIV 



Among the syntheses of a-amino acids carried out by his own method 

 by E. Erlenmeyer, jun., that of leucine was described in 1901 by 

 Erlenmeyer and Kunlin. It was prepared from a-benzoylamido-/3- 

 isopropylacrylic acid, 



CH 3 \ 



\CH-CH = C COOH 

 rw ' 



NH-co-c 6 H 5 



which resulted when isobutylaldehyde and hippuric acid were condensed 

 together in the presence of acetic anhydride and the condensation 

 product, 



C x ^C . CH, 

 CH, X J 



was treated with alkali. 



By heating a-benzoylamido-/3-isopropylacrylic acid in sealed tubes 

 at 150-170 C., with excess of ammonia, hydrolysis occurred with the 

 formation of leucine, isovalerianic acid and benzoic acid : 



CH 3 \ CH S \ 



J>CH CH 2 CH COOH \CH . CH 2 . COOH 



CH/ I^ H2 CH/ 



Leucine Isovalerianic acid 



Bouveault and Locquin have also synthesised leucine by the 

 reduction of a-oximinoisobutylacetic acid, which was prepared in a 

 similar way to the isomeric compound from which they obtained iso- 

 leucine. 



The most convenient method of preparing leucine by synthesis is 

 that given by Fischer and Schmitz in 1906 by the action of ammonia 

 upon the corresponding halogen derivative of isocaproic acid, which 

 they prepared by brominating the alkylmalonic ester and heating, 

 whereby it was converted into the bromo-fatty acid. The several 

 reactions are represented by the following scheme : 



