THE SYNTHESIS OF THE PROTEINS 15 



The further work, published in 1906, of Curtius and his pupils is 

 concerned with the action of nitrous acid upon the polyglycine com- 

 pounds : diazoacetyl glycine ester N 2 : CH . CO NH . CH 2 . COOC 2 H 5 

 was formed by the action of nitrous acid upon glycyl-glycine ester hydro- 

 chloride and diazoacetyl glycyl-glycine ester N 2 : CH . CO NH . 

 CH 2 . CO NH . CH 2 . COOC 2 H 5 by its action upon diglycyl-glycine 

 ester hydrochloride. 



By the action of ammonia on the first body diazoacetyl glycine 

 amide, 



N, : CH . CO NH . CH 2 . CO . NH 2 , 



was formed, and on the latter diazoacetyl glycyl-glycine amide, 

 N 2 :CH.CO NH.CH 2 .CO NH.CH 2 .CO NH 2 . 



These are yellow substances, but when excess of ammonium hydroxide 

 or liquid ammonia is added to the esters colourless substances are 

 obtained ; they were at first regarded as azomethane derivatives, but 

 have since been shown to be the ammonium salts, e.g., of isodiazoacetyl 

 glycine amide, 



N^ 



| ^C . CO . NH . CH 2 . CO . NH 2 . 

 NH 4 .N/ 



