in ON THE SYNTHESIS OF ALBUMINS 127 



From alanin anhydride was obtained alanyl-alanin : 



/CH . (CH 3 ) NH /CH(CH 3 ) NH 2 



= 0^ >C = = C/ 



X NH CH . (CH 3 ) / N NH CH(CH 3 ) CO . OH 



Alanin anhydride > alanyl-alanin. 



By acting in an analogous manner on leucinimide l with fuming 

 hydrobromic acid, leucyl-leycin was prepared : 



C 4 H 9 C 4 H 9 



/CH NH X /CH NH 2 



o = c/ >c=o o = c/ 



X NH CH 7 X NH CH CO . OH 



C 4 H 9 C 4 H 9 



Leucin-imide > leucyl-leucin. 



The three substances just mentioned, namely : 



Glycyl-glycin NH 2 . CH 2 . CO NH CH 2 CO. OH 

 Alanyl-alanin NH 2 . CH(CH 8 ) . CO NH CH(CH 3 ) CO . OH 

 Leucyl-leucin NH 2 . CH(C 4 H 9 ) . CO NH CH(C 4 H 9 )CO.OH, 



Fischer has called ' dipeptids.' All three were obtained, as is explained 

 above, by the opening-up of a diaci-piperazin-ring. 



It is also pointed out in this paper that the instability of esters is 

 cured by the introduction of radicals into the ammo-group, for phenyl- 

 cyanate-glycyl-glycin 



C 6 H 5 . NH . CO . NHCH 2 CO . NHCH 2 CO . OH and 



carbethoxyl-glycyl-glycin-ester 



C 2 H 5 . OC NHCH 2 CO . NHCH 2 CO . OC 2 H 5 , 

 are very stable bodies. 2 



The desire of building up simple anhydrides of amino-acids was 

 awakened in Fischer by his discovery amongst the products of partially 

 dissociated silk fibroin, 3 of a body which was composed of glycocoll + 

 alanin, and he therefore set about finding means for protecting the 

 easily displaceable NH 2 -radical of amino acids. 



1 First prepared by Bopp, Ann. d. Chem. 69. 28 (1849). 



2 To make carbethoxyl-glycyl-glycin-ester dissolve rapidly, by shaking, 5 grammes of 

 gycyl-glyciu-ester in 20 grammes of water ; cool in ice- water ; add 4 '25 grammes ( = 1 

 mol.) of chlorocarboxylic-ethyl-ester, Cl CO . OC 2 H 5 , then add in three portions, shaking 

 vigorously, 2 '3 grammes of sodium carbonate dissolved in 20 ccm. of warm water, and 

 then cooled. The amount of sodium carbonate is just sufficient to bind all the halogen 

 of the chlorocarboxylic-ethyl-ester. The carbethoxy-glycyl-glycin-ester is precipitated 

 as a thick crystalline deposit; wash it with a little water; dissolve in 11 parts of hot 

 ester and precipitate with petroleum ether. 



3 Emil Fischer, Chemiker Zeitung, No. 80 (1902). 



