ON THE SYNTHESIS OF ALBUMINS 133 



Leucyl-glycyl-glycin : 



CH 3 < 



:CH . CH 2 . CH(NH,) . CO . NHCH 2 CO . NHCH,CO . OH. 



Phenyl-carbamino-leucyl-glycyl-glycin : 



C G H 5 . NH . CO . NH . CH(C 4 H 9 ) . CO . NHCH 2 CO . NHCH 2 CO . OH. 

 Leucyl-glycyl-glycin-ethyl-ester-hydrochlorate : C 12 H 23 4 N 2 HC1. 



The polypeptids derived from mono-amino-acids have a structure 

 which can be directly deduced from the synthesis, while their stereo- 

 chemistry is somewhat more difficult. All amino-acids derived from 

 albumins, with the exception of glycocoll, possess an asymmetrical 

 C-atom. In polypeptids there are present as many asymmetric C-atoms 

 as are present in amino-acids (except in glycocoll) linked together as an- 

 hydrides, and the number of independent optic isomers is expressed by 

 van't Hoff's formula 2 n . Thus a dipeptid having the general formula, 

 NH 2 .CHR.CO.NH.CHR.COOH, has two asymmetric C-atoms 



marked with a star, and therefore four active forms, dd, II, dl, and Id, 

 must exist, of which each two may form a racemic compound. If, on 

 the other hand, active components are used for building up poly- 

 peptids, such as active amino-acids and active halogen -containing 

 acid radicals, there are formed optically active polypeptids, and if one 

 of the components is racemic, then one may expect also two isomers. 

 Thus the natural, active tyrosin, in combination with inactive a-brom- 

 iso-caproic-acid, may exist in the two steric combinations dl and II. 



VARIOUS POLYPEPTIDS (II.) 



The following polypeptids of glycocoll, of inactive alanin, leucin, 

 and of active Z-tyrosin have been prepared by combination with 

 chlorides of chlor-acetyl, brompropionyl and inactive a-brom-iso- 

 capronyl. 



1. Dipeptids. Glycyl-glycin, alanyl -alanin, and leucyl- leucin, 

 obtained by a splitting up of diazipiperazinc, contain two like amino- 

 acids. The only known mixed diacipiperazine isglycin-alanin-anhydride : 



CO 

 ' \ 



HN 



CH.CH 



v , 

 CO 



