68 THE CHEMICAL CONSTITUTION OF THE PROTEINS 



The synthesis of this compound by Ellinger from /3-aldehydo- 

 propionic acid, prepared from aconic acid as follows : 



COOH 



I +H 2 

 C CH 2 . > 



II I 

 CH CO 



\/ 



o 



COOH 



C-CH 2 



II I 



CH COOH 



- CO, 



CH CH 2 



II I 



CH COOH 



OH 



CHO COOH 



by condensation with phenylhydrazine, and the subsequent treatment 

 of the ester of the hydrazone which was formed with alcoholic sulphuric 

 acid. 



CH 2 . CH 2 . COOCH 3 

 C 6 H 5 CH 



\s. 



N 2 H 



C.CH 2 .COOCH 3 

 :CH 



NH 



showed that it was identical with Salkowski's acid, and that it was 

 indoleacetic acid and not skatolecarboxylic acid. 



Four formulas were therefore possible for tryptophane : 



C . CH 2 . CH(NH 2 )COOH C . CH(NH 2 )CH 2 COOH 



I. C 6 H 4 



CH 



\/ 



NH 



C . CH(COOH)CH 2 NH 2 



II. C 6 H 4 CH 



\/ 



NH 



III. C 6 H 4 CH 



C . C(NH 2 ) (CH 3 ) . COOH 



\/ 



NH 



IV. C 6 H 4 



\/ 

 NH 



CH 



and as Ellinger had found that tryptophane when given to dogs and 

 rabbits was converted into kynurenic acid, formula III. was regarded 

 as the most probable for tryptophane, because it most easily explained 

 this change : 



CH . COOH 



H 



HC 



