THE CHEMICAL CONSTITUTION OF THE UNITS 137 



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

 indoleacetic acid and not skatolecarboxylic acid. 



Four formulae were therefore possible for tryptophane : 



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



I. C 6 H 4 CH 



\/ 

 NH 



C . CH(COOK)CH,NHj 



II. C 6 H 4 CH 



\X 

 NH 



C . 



(CH 3 ) . COOH 



III. C 6 H 4 CH 



\/ 



NH 



IV. C 6 H 4 CH 



\X 

 NH 



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 : 



NH- 



HC 



CH 



CH . COOH 



HC 



Kynurenic acid. 



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 B COOC 2 H 5 



/OCA I 



-CH. 



,OCaH B 



CHNa 



CH-j . CH 2 . CH< 



C 



Lv ** V-/JLA ^/ JL A/J * \^A^2 V-'A J\ 



X OC 2 H 5 | X OC 2 H B 



NaCl 



-hCl.CHa.CHjj. 



X OC 2 H 5 | 

 :OOC 2 H 5 COOC 2 H 5 



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

 into 7-aldehydobutyric acid with loss of alcohol and carbon dioxide : 



COOC 2 H 5 * H 



/OC 2 H B I 



CH . CH 2 . CH a . CH<^ + sH^O = CH . CH 2 . CHj . CHO + 4C 8 H S OH + CO, 



X OC 2 H B 

 COOC 2 H B COOH 



The hydrazone of this compound when treated with alcoholic sulphuric 

 acid gave the ester of indolepropionic acid : 



