22 THE CHEMICAL CONSTITUTION OF THE PROTEINS 



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 : 

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



CH, . COOH 



The ester of this compound was converted into the hydrazide by means 

 of hydrazine, 



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



CHj.CO.HN. NH, 



from which hippuryl-aspartic acid azide was obtained by the action of 

 nitrous acid : 



C 6 H B . CO NH . CH, . CO NH . CH . CO . N, 



CH, . CO . N, 



This reacted in ethereal solution with aspartic ester yielding hippuryl- 

 asparagyl-aspartic ester from which the free acid, 



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



JCH, . COOH 

 H, . CO NH . CH . COOH 



CH, . COOH 

 was obtained by saponification with baryta. 



The hydrazide of this compound was then prepared from the ester 

 in the usual manner, and from this the azide, which did not, however, 

 possess the normal structure, but that of the hydrazi-azide, 



C 9 H, . CO NH . CH, . CO NH . CH . CO NH . CH . CO . N, 



CH, . CO . NH 

 CH,.CO.NH 



CH, . CO NH . CH . CO . N, 

 The condensation product of this compound with aspartic ester was not 

 isolated, but the complex hippuryl-disaspartyl-aspartic acid hydrazi- 

 hydrazide, its hydrazine derivative, 

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



CH,.CO.NH CH,.CO HN.NH, 

 CH,.CO.NH CH,.CO HN.NH, 



CH, . CO NH . CH . CO NH . CH . CO HN . NH, 

 was obtained when the condensation product was treated in alcoholic 

 solution with hydrazine hydrate. 



Just in the same way hi ppuryl-aspartyl-glycine ester, 



C,H, . CO . NH . CH, . CO NH . CH . CO NH . CH, . COOC.H. 



CH, . CO NH . CH, /COOCjH, 



