20 THE CHEMICAL CONSTITUTION OF THE PROTEINS 

 which, when treated with nitrous acid, gave benzoylazoimide, 



/N 

 C.H, . CO. HN . NH, + HNO, = 2 H,O + C 9 H 6 . CO N/ ||j 



By combining benzoylazoimide with glycine, he synthesised hippuric 

 acid, 



/N 

 C 6 H 6 . CO N/ |N + H 8 N . CH, . COOH = C B H 6 . CO NH . CH, . COOH + N S H, 



and by carrying out the same series of reactions with hippuric acid, the 

 compound hippurazide or hippurylazoimide was made, which could be 

 employed in synthesis in the place of the unknown hippuryl chloride ; 

 thus from hippuric ester by the following series of reactions hippuryl- 

 glycine was obtained identical with the compound previously obtained 

 in 1883 by the action of benzoyl chloride upon the silver salt of 

 glycine : 



. CO . NH . CH, . COOC,H B + H,N . NH, = C 8 H 8 . CO . NH . CH, . CO . HN . NH, + HOC,H 6 

 Hippuric ester Hydrazine Hippuryl-hydrazine 



C 8 H 6 . CO . NH . CH, . CO . HN . NH, + HNO, = C 8 H 5 . CO . NH . CH, . CO N/ ||| 

 Hippuryl-hydrazine Hippurazide 



C 9 H 8 . CO . NH . CH, . CO N/ ||| + H,N . CH, . COOH = 



Hippurazide Glycine 



C 8 H 5 . CO . NH . CH 2 . CO NH . CH, . COOH + N,H 



Hippuryl-glycine 



This method of combining together amino acids was further ex- 

 tended by Curtius and Wiistenfeld in 1902 by preparing the ester, the 

 hydrazide and azide of this compound and again combining it with 

 glycine, when benzoyl-diglycyl-glycine was obtained : 



C 9 H 5 . CO . NH . CH, . CO NH . CH a . COOH -> 



C 6 H, . CO . NH . CH, . CO NH . CH, . COOC,H 8 - 



C,H, . CO . NH . CH, . CO NH . CH, . CO HN . NH, -* 



/ N 

 C 6 H B . CO . NH . CH, . CO NH . CH, . CO N/ |N - 



C 6 H, . CO . NH . CH, . CO NH . CH, . CO NH . CH, . COOH 

 From this compound benzoyl-triglycyl-glycine was prepared by the 

 same series of reactions, and benzoyl-tetraglycyl-glycine by continuing 

 the process. 



Further experiments upon the formation of glycyl chains with 

 hippurazide were carried out by Curtius and Levy ; by combining 

 hippurazide with glycyl-glycine ester, prepared by the method of Fischer 

 and Fourneau (see below), benzoyl-diglycyl-glycine ester, identical with 

 the compound prepared by Curtius and Wiistenfeld, was obtained. The 



