96 THE CHEMICAL CONSTITUTION OF THE PROTEINS 



N CO . CH 2 . C 6 H B NH . CO . CH 4 . C 8 H 5 



NH.CO.CH 2 .C 6 H 5 

 C 6 H 5 . CH 2 . CH COOH 

 thus showing the identity of the two substances. 



The condensation of benzaldehyde and hippuric acid, and the for- 

 mation of phenylalanine by the action of ammonia had been previously 

 carried out by Plochl in 1884, but he was unable to explain the vari- 

 ous stages which took place. 



E. Fischer has synthesised phenylalanine by the action of ammonia 

 upon the corresponding halogen fatty acid, which he prepares from 

 malonic ester and benzylchloride. There are six stages in the complete 

 process, which are as follow : 



COOC 2 H 6 COOC 2 H 6 COOC 2 H 5 



Na C 6 H 5 CH 2 C1 | KOH 



CH 5 > CHNa > CH. 



phenyl-o-bromopropionic acid 

 C 6 H 5 . CH 2 . CH(NH 2 )COOH 

 Phenyl-o-aminopropionic acid 



By this means large amounts of phenylalanine can be prepared ; 

 they have been employed in studying the derivatives of phenylalanine 

 and in the synthesis of polypeptides. 



Another synthesis of phenylalanine from malonic ester, in which 

 Gabriel's phthalimide reaction is also made use of, is described by 

 Sorensen, namely, 



COOC 2 H 5 COOC 2 H 5 COOC 2 H 6 



Br | / C0 \ / C0 \ Na 

 CH 2 > CHBr + KN< )C 6 H 4 > CH . N< )C 6 H 4 > 



\CO/ XXK 



COOC 2 H 5 COOC 2 H 5 COOC 2 H 5 



Bromomalonic ester Phthalimidomalonic ester 



COOC 2 H 6 COOC 2 H 5 COONa 



| /Na | /CH 2 .C 6 H 5 I X3H 2 .C 6 H 5 



C\ / C0 \ C 6 H 5 .CH 2 C1 C^ / C0 \ NaOH C/ HC 



i>N\ >C 6 H 4 > \N< )C 6 H 4 > | \NH . CO . C 6 H 4 COONa 



\CO/ X CO X COONa 



OOC 2 H 5 COOC 2 H 5 



Sodium phthalimido- Benzylphthalimido- Sodium phthalimidobenzyl- 



malonic ester malonic ester malonate 



