428 



CHEMISTRY OF THE PROTEIDS 



CHAP. 



3. Purin-derivatives 



These have been known for a much longer time than have the 

 simple pyrimidin-derivatives. Kossel was the first to discover hypo- 

 xanthin l amongst the dissociation-products of nucleic acid, and later 

 found also xanthin, guanin, and adenin. 2 



Hypoxanthin, C 5 H 4 N 4 = oxy-purin. 

 Xanthin, C 5 H 4 N 4 2 = 2'6-dioxy-purin. 



Adenin, C 5 H 5 N 5 = 6-amino-purin. 



Guanin, C 5 H 5 N 5 = 2-amino-6-oxy-purin. 



Purin. the mother-substance of these ' xanthin-bases,' contains a 

 pyrimidin remainder : the meta-di-azin and the imido-azol radical. 



N=CH 



1 N== 6 CH 



HC CH HC 



I II II + 



N CH N 



Pyrimidin. Meta-di-azin + 



WHC- 



-NH 



[|8J 



5 C 7 NH 



\ 



8 CH 



C- 



-N=' 



Imido-azol 

 (glyoxalin). 



Purin. 



The following formulae are arranged by the author in this order : 

 purin -oxy-purins->amino-purin->amino - oxy -purin->oxy- methyl - 

 purins : , 



N=CH HN CO HN CO 



C NH 

 \ 



CH 



N C N 



Purin. 



HN CO 



HC C NH 



C N 



Hypoxanthin 

 (6 oxy-purin). 



OC C NH 

 II \ 



CH 



HN C N 



Xanthin 

 (2'6 oxy-purin). 



HN CO 



OC C NH 



/CO 

 HN C NH 



Uric acid 

 (2,6,8 trioxy-purin). 



HC C NH 



N C N 



Adenin 

 (6-amino-purin). 



NH 9 .C C NH 

 \ 



CH 



N C N 



Guanin 

 (2-amiuo, 6-oxy-purin). 



1 A. Kossel, ibid. 4. 290 (1880). 



2 A. Kossel, ibid. 7. 7 (1882) ; 10. 248 (1886) ; Arch.f. (Anat. u.} Physiol. 1893, 

 p. 157 ; Kossel and A. Neumann, Ber. d. deutsch. chem. Ges. 27. II. 2215 (1894). 



