26 THE CHEMICAL CONSTITUTION OF THE PROTEINS 



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

 have since been shown to be the ammonium salts, eg. t of isodiazoacetyl 

 glycine amide, 



N ^v 



I ^C.CO.NH.CH-.CO.NH,. 

 NH 4 .N/ 



The later work of Curtius and his pupils is upon the action of 

 hydrazine on these compounds : diazoacetic ester did not give the ex- 

 pected hydrazide, but lost ammonia and yielded the hydrazide of 

 triazo-acetic acid. Diazoacetyl glycine ester gave the hydrazide, 

 which was converted on further action into the diammonium salt of 

 5-oxytriazole-i -acetic hydrazide. The next homologue in the series 

 behaved like diazoacetyl glycine ester. Hydrochloric acid gas con- 

 verted diazoacetylglycine hydrazide into chloracetyl-glycine hydrazide 

 hydrochloride ; chloracetyl-glycine-azide resulted on treatment with 

 nitrous acid. 



These compounds have given us an insight into complex glycine, 

 alanine and aspartic acid derivatives. Since E. Fischer has prepared 

 by his methods (see under polypeptides) compounds containing these 

 amino acids without the presence of the benzoyl group which is strange 

 to the protein molecule, no great interest has been attached to them, 

 but at present the aspartic acid compounds, if we disregard Schiffs 

 polyaspartic acid, which probably has another constitution than that 

 represented, are the most complex substances known containing this 

 important constituent of the protein molecule. 



The transformations of the derivatives increase our interest in 

 these compounds prepared by Curtius and his pupils, and give an 

 impulse to their further study, especially as formaldehyde is such an 

 important compound in the synthesis of sugars by plants, and as the 

 diamino acids and diamines occur as products of decomposition of pro- 

 teins by enzymes and bacteria, although according to our present know- 

 ledge they are not formed in nature in this manner. 



