io THE CHEMICAL CONSTITUTION OF THE PROTEINS 



This compound was also prepared from benzoyl-triglycyl-glycine azide 

 and glycine ester. 



The further lengthening of the chain by means of the azide of 

 benzoyl-tetraglycyl-glycine could not be accomplished since this com- 

 pound could not be prepared, but the next member of the series, 

 benzoyl-pentaglycyl-glycine ester, 



C 6 H 5 . CO . (NH . CH 2 . CO) 5 . N . CH 2 . COOC 2 H 5 , 



was prepared from benzoyl-triglycyl-glycine azide and glycyl-glycine 

 ester. This was identical with the original 7-acid of 1883, of which 

 Curtius and Benrath had determined the constitution. 



By condensing the biuret base, which in the meanwhile had been 

 proved to be triglycyl-glycine ester with hippurazide, Curtius and Levy 

 obtained again the former benzoyl-tetraglycyl-glycine, and by condens- 

 ing it with hippuryl-glycine azide they obtained benzoyl-pentaglycyl- 

 glycine ester, and thus by a less circuitous method attained to the same 

 compound as they had prepared from hippurazide. Further lengthening 

 of the glycyl chain has not as yet been carried out by this method, but 

 the method has been adapted by Curtius and Lambotte to the forma- 

 tion of alanine chains, namely : 



Hippuryl-alanine, C 6 H B . CO . NH . CH 2 . CO NH . CH(CH,) . COOH from hippurazide 



and o-alanine. 

 Hippuryl-alanyl-alanine, C 6 H 5 . CO . NH . CH 2 . CO -- NH . CH(CH 3 ) . CO -- NH . 



CH(CH 3 ) . COOH from hippuryl-alanine azide and o-alanine. 

 Hippuryl-alanyl-alanyl-alanine, C 6 H 5 . CO . NH . CH . CO NH . CH(CH 3 ) . CO 



NH . CH . (CH 3 ) . CO NH . CH(CH 3 ) . COOH 'from hippuryl-alanyl-alanine azide 



and a-alanine. 



These all contain the glycine residue as well as the alanine residue in 

 their molecule ; in order to eliminate the glycine residue and obtain 

 compounds without the glycine radical, Curtius and van der Linden 

 prepared the following compound : 



Benzoyl-alanyl-alanine, C 6 H 5 . CO . NH . CH(CH-) . CO NH . CH(CH,) . COOH from 

 benzoyl-alanine azide, which was prepared from benzoyl-alanine, as obtained by 

 Fischer's method, and alanine. 



Benzoyl-alanine azide was also combined with glycine, and this 

 radical introduced at the end of the chain ; thus they prepared 



Benzoyl-alanyl-glycine, C 6 H 5 . CO . NH . CH(CH 3 ) . CO NH . CH 2 . COOH from benzoyl- 

 alanine azide and glycine. 



Benzoyl-alanyl-glycyl-glycine, C 6 H 8 . CO . NH . CH(CH 3 ) . CO NH . CH 2 . CO - 

 NH . CH 2 . COOH from benzoyl-alanyl-glycine azide and glycine, or benzoyl-alanine 

 azide and glycyl-glycine. 



The behaviour of hippurazide with the dibasic aspartic acid was 

 investigated by Th. and H. Curtius in order to build up chains con- 

 taining this amino acid. By the action of hippurazide upon aspartic 

 acid in alkaline solution they obtained hippuryl-aspartic acid : 



