THE CHEMICAL CONSTITUTION OF ITS UNITS 69 



Ellinger's further work did not confirm this supposition. By con- 

 densing /3-chloropropionacetal with sodium malonic ester he obtained 

 propionacetal malonic ester, 



COOC 2 H 5 COOC 2 H 5 



/OC 2 H 5 | 



CHNa + Cl . CH 2 . CH 2 . CH^ = CH . CH 2 . CH 2 . CH< + NaCl 



| X OC 2 H 5 | X OC 2 H 6 



COOC 2 H 5 COOC 2 H 5 



which, when heated in a sealed tube with water to 190, was converted 

 into ry-aldehydobutyric acid with loss of alcohol and carbon dioxide : 



COOC 2 H 5 H 



/OC 2 H 6 I 



CH . CH 2 . CH 2 . CH<( + 3 H 2 = CH . CH 2 . CH 2 . CHO + 4 C 2 H 5 OH + CO 2 



I X OC 2 H 5 



COOC 2 H 5 COOH 



The hydrazone of this compound when treated with alcoholic sulphuric 

 acid gave the ester of indolepropionic acid : 



CH 2 .CH 2 .CH 2 .COOH CH 2 . CH 2 . CH 2 COOH C . CH, . CH 2 COOH 



I I /\ 



CHO -> CH _ C 6 H 4 CH 



W / \/ 



\/ NH 



N 2 H 



The indolepropionic acid obtained by hydrolysis was identical with 

 Nencki's skatoleacetic acid, and tryptophane was therefore either 



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



NH NH 



and kynurenic acid must be formed by some other reaction. 



Hopkins and Cole had obtained by the oxidation of tryptophane with 

 ferric chloride a body of the composition of C 9 H 7 NO ; this body has 

 been shown by Ellinger to be /3-indole-aldehyde, firstly by oxidising 

 it to /3-indole-carboxylic acid, 



C . CHO C . COOH 



NH NH 



a compound synthesised by Ciamician and Zatti, and secondly by 

 synthesis from indole and alcoholic chloroform. From this compound by 

 the method employed by Erlenmeyer in the synthesis of phenylalanine, 

 Ellinger and Flamand synthesised tryptophane in 1907. 



By condensing /3-indolealdehyde with hippuric acid the azlactone is 

 obtained, 



