PROTEINS 107 



by the microorganism, the other to a much smaller degree, or 

 not at all. 



The optically active acids then may be built up into peptids 

 at will. Three methods are in use to effect this synthesis. 



1. Ester method. 



Glycocoll ester is converted into a ring compound 



C 2 H 5 C CH 2 NH 2 1 



+ -> 2C 2 H 5 OH + 



H 2 N CH 2 COOC 2 H 5 



CH 2 NH 



CO CO 



NH - - CH 2 



Under the action of alkali this ring compound is split open, 

 forming a dipeptid 



NH 2 CH 2 CO NH CH 2 COOH 



Of course the amino acids used may be varied, and thus differ- 

 ent dipeptids obtained. The method serves only to build up 

 dipeptids, however, and if two different amino acids are used 

 it has certain other disadvantages. 



2. Synthesis by means of acid chlorides. 



If glycocoll is treated with chloracetyl-chloride the following 

 reaction takes place: 



C1CH 2 CO Cl + NH 2 CH 2 COOH - HC1 + 

 Cl CH 2 CO NH. CH 2 COOH 



By the action of ammonia, the chlorine atom may be replaced 

 by NH 2 , and a dipeptid results. 



NH 2 CH 2 CO NH. CH 2 COOH. 



This may be treated with chloracetyl chloride again, and in a 

 manner perfectly analagous to the first reaction, a tri-peptid 

 or higher peptid built up. Here again various amino acids, and 

 various halogen derivatives may be used. The limitation of this 



