130 CHEMISTRY OF THE PROTEIDS CHAP. 



ji 



consisting of the anhydrides of the two different aliphatic amino-acids, 

 namely, amino-acetic and amino-propionic acid : 



CH 



x 



o = c< 



X CH(CH 3 ) 



Methyl-diacipiperazin. 



Acting in the same way with chloracetyl-chloride on glycyl-gly- 

 cin-ester, C1CH 2 . CONHCH 2 CO . NHCH 2 CO . OC 2 H 5 , or chloracetyl- 

 glycyl-glycin-ester, was obtained. By carefully saponifying the latter 

 there resulted Cl . CH 2 CO . NHCH 2 CO . NHCH 2 CO . OH, or chlora- 

 cetyl-glycyl-glycin, which when treated with concentrated watery 

 ammonia did not give rise to a diacipiperazin, but to the simple tripeptid 

 or di-glycyl-glycin, NH 2 CH 2 CO NHCH 2 CO NHCH 2 . COOH. 



Amino-acid chains containing no acyl-radicals l Fischer has called 

 peptids ; and the method just described of obtaining peptids, is of the 

 highest importance, for it allows of the union of the most diverse 

 amino-acids, arid in the case of glycin even yields tetra-glycyl-glycin : 

 NH 2 CH 2 CO[NHCH 2 CO] 3 . NHCH 2 COOH. 



In his fourth paper Fischer further shows that, in addition to 

 introducing an acid-chloride radical into the amino-group, it is also 

 possible after having protected the amino-group by means of the acid- 

 halogen chloride, to introduce another Cl-atom into the carboxyl-group 

 of an amino-acid by means of phosphorus pentachloride, PC1 5 , 2 and 

 then to combine the chlorinated acid-chloride-amino-acid with other 

 ammo-esters. Thus, a-brom-isocapronylglycin-chloride + glycin-ester 

 yields a-bromisocapronyl-glycyl-glycin-ester. By saponification and 

 subsequent treatment with ammonia, this ester is converted into its 

 corresponding tetra-peptid. 



Other acyl-derivatives of amino-acids, for example, benzoyl-com- 

 pounds, react similarly. Thus C 6 H 5 CO . NH . CH 2 . COC1, or hippuryl 

 chloride, is obtained by shaking together finely divided hippuric acid 

 with acetyl-chloride and phosphorus-perita-chloride. 



Hippuryl-chloride reacts readily with the esters of the amino-acids 

 or with alkaline solutions of the latter (see later) giving rise, for example, 

 to benzoyl-glycyl-glycin. This latter after being converted into the 

 chlorinated compound by means of PC1 5 , will combine with glycin- 

 ester to form the benzoyl-di-glycin-ester. 



It is thus possible to obtain the same benzoyl - bodies which 



1 See footnote on p. 118. 



2 Phosphorus penta-chloride, PC1 5 , is generally used for substituting Cl for OH, It 

 also acts as a dehydrating agent, converting amides into nitrites, and it forms anhydrides 

 out of dibasic acids. 



