136 THE CHEMICAL CONSTITUTION OF THE PROTEINS 



mentioned four products resulted. As under anaerobic conditions a 

 large yield of skatoleacetic acid was obtained, and as skatole was the 

 principal product when it was fused with potash, Hopkins and Cole 

 regarded their substance as skatoleaminoacetic acid rather than the 

 isomeric indoleaminopropionic acid. 



The constitution of indole and skatole had been proved by synthe- 

 sis, but that of the other two compounds had not been determined, 

 and Nencki's formulae for them were accepted. Investigations by 

 Ellinger and Gentzen in 1903, who found that in the large intestine 

 indole was formed in large amounts from tryptophane, but skatole 

 only in small amounts, and that skatole only gave traces of indole 

 under the same conditions led Ellinger to doubt the accuracy of 

 Nencki's formulae for skatoleacetic and skatolecarboxylic acids, more 

 especially as Wislicenus and Arnold's skatolecarboxylic acid, which 

 was synthesised from propionyl formic acid phenylhydrazone had the 

 formula 



C.CHg 



NH 



and was not identical with the putrefaction product, which might equally 

 well possess the constitution of 



C.CHj.COOH 



NH 



The synthesis of this compound by Ellinger from /9-aldehydo- 

 propionic acid, prepared from aconic acid as follows : 



COOH COOH 



+ H 2 - CO, 

 C CH, . > C CH 2 



CH CH 2 CH 2 CH 2 



CH CO CH COOH CH COOH CHO COOH 



\/ \ \ 



O OH OH 



by condensation with phenylhydrazine, and the subsequent treatment 

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

 acid, 



CH2.CH 2 .COOCH 3 C.CH 2 .COOCH 3 



c 6 H 5 CH -> C.H/VH 





