40 THE CHEMICAL CONSTITUTION OF THE PROTEINS 



The condensation of benzaldehyde and hippuric acid, and the 

 formation of phenylalanine by the action of ammonia had been pre- 

 viously carried out by Plochl in 1 884, but he was unable to explain the 

 various 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, as follows : 



COOC 2 H 5 

 C 6 H 5 CH 2 C1 | 

 > CH . CH 2 C 6 H 5 



COOC 2 H 5 



Benzylmalonic ester 



KOH 



NH, 



).CH 9 C r H f 



COOH 



ester Benzylbromacetic acid or 



phenyl-o-bromopropionic acid 



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

 Phenyl-a-aminopropionic acid 



By this means large amounts of phenylalanine can be prepared, 

 and 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 COOCoH. 



Br 



B 

 CH 2 



OOC 2 H 5 



CO 



| 

 C 



HBr + 



X\ 



C0 



C 6 H 4 



COOC 2 H 5 

 Bromomalonic ester 



CH . 



| 



Na 

 C 6 H, -- > 



COOC 2 H 6 



| /Na 



\ X C 

 X 



C 6 H 5 .CHoCl 



COOC 2 H 5 



Sodium phthalimido- 

 malonic ester 



N\ 

 \ 



. C 6 H 5 



C0 NaOH 



C 6 H 4 --- 



Phthalimidomalonic ester 



COONa 



CH 2 . C 6 H B 



HC1 



COOC 2 H 5 

 Benzylphthalimido- 

 malonic ester 



\NH.CO .C,.H 4 COONa 

 COONa 



Sodium phthalimidobenzyl- 

 malonate 



C 6 H 4 (COOH) 2 + CO 2 



Phthalic acid 



