THE CHEMICAL CONSTITUTION OF ITS UNITS 39 



The mechanism of this reaction was explained by Erlenmeyer and 

 Kunlin in 1899. Just as benzoyl-a-amidocinnamic acid is converted by 

 alkali into phenylpyruvic acid and benzamide, so also does this reaction 

 take place with ammonia; the phenylpyruvic acid then reacts with 

 ammonia giving a body of the composition, 



C 6 H 5 C 6 H 5 



CH, CH 2 



I /OHHCK | 



C/ \ ft 



\ / C 



I X NH / | 

 COOH COOH 



which loses carbonic acid yielding, 



C 6 H 5 C 6 H 5 



CH 2 CH 2 



I xOHHOx | 

 C<Q ;>CH 



| x NH ' 

 COOH 



This substance contains the group, 



CHOH NH COH COOH 



I 



which, by rearrangement and by the loss of a molecule of water, becomes 



_CO NH CH COOH 



I 

 and it therefore changes into phenylacetyl-phenylalanine : 



C 6 H 5 C 6 H B 



CH 2 CH 2 



CH NH CO 



COOH 



By subsequent hydrolysis phenylalanine and phenylacetk acid result. 

 The proof of this reaction was given by the synthesis of phenylacetyl- 

 phenylalanine by condensing benzaldehyde with phenaceturic acid : 



. CH 2 C 6 H 5 / N CO . CH 2 C 6 H 5 



C 6 H 5 . CHO + CH = C 6 H 5 -CH = G( \ + 2 H 2 O 



X COOH X CO 



hydrolysing the resulting lactimide, just as in the case of benzoyl-a- 

 amidocinnamic acid, reducing it with sodium amalgam : 



N CO . CH 2 . C 6 H 5 NH . CO . CH 2 . C 6 H 5 



C 6 H 5 -CH=C/ | M CA CH = i 



x co 



NH.CO.CH 2 .C 6 H 5 

 C 6 H 5 . CH 2 . CH COOH 

 and showing the identity of the two substances. 



