THE CHEMICAL CONSTITUTION OF THE UNITS 129 



In the presence of ammonia and formaldehyde, also a product from 

 the sugar, methylimidazole is formed as follows : 

 CH 3 .CO H 2 NH CH S C NH 



C 



HO H 2 NH 



CH 



H 



\CH 

 CH N 



3 H 2 



This condensation with formaldehyde as well as with methyl glyoxal 

 is confirmed by the formation of dimethylimidazole when ammonia 

 acts upon glucose and acetaldehyde. 



CH, . CO H 2 NH 

 CHO H 2 NH 



CH 



|| \ 

 O CH 3 



CH C NH 



. CH 3 



CH-N 



From imidazole by condensation with glycocoll and simultaneous oxida- 

 tion histidine may possibly be formed thus : 



CH NH 

 VCH 



C N 



I 



CH NH 

 \ 



^ 



C N 



CH 2 



CH 



+ H 2 

 CH.NHj 

 COOH 



CH, 



H 



+ 

 H 



CH . NH 2 

 COOH 



and by condensation with urea xanthine may arise : 

 NH 2 3 CH 3 NH CO 



CO + C NH CO C NH . + 3HO a 



NH 2 O CH N 



\CH 



NH C N 



\CH 



PT. I. 



