THE NUCLEINIC BASES. 79 



] r 7-dimethyl-2,6-dioxypurin, and caffein l,3,7-trimethyl-2,6-dioxy- 

 purin. Theophyllin and theobromin are isomeric with paraxanthin, 

 and structurally' l ? 3-dimethyl-2,6-dioxypuriii and 3,7-dimethyl-2,6- 

 dioxypurin, respectively. Epiguanin is similarly derived from 

 guanin by the replacement of the hydrogen atom at 7 with methyl, 

 .and is hence 7-methyl-guanin. 



HN CO CH 3 .N CO 



CO C N.CH 3X CO C N.CH 3X 



I ^CH ^CH 



Hetcroxanthin = C 6 H 6 N 4 O 2 . Paraxanthin = C 7 H 8 N 4 3 . 



CO 



C N.CH 3X 



I >CH 



CH 3 .N C N- 



Caffein = C 8 H 10 N 4 O 2 . 



CH 3 .N CO HN CO 



CO C NH V CO C N.CH 3X 



>CH >CH 



CH 3 .N C N r CH 3 .N C N^ 



Theophyllin = C 7 H 8 N 4 O 2 . Theobromin = C 7 H 8 N 4 O 2 . 



HN CO 



HN = C C N.CH 3 s 



I I! 



HN C 



Epiguanin = C 6 H 7 N 5 O. 



Oarnin is apparently closely related to hypoxanthin, as on treatment 

 with bromine it yields methyl bromide, carbon dioxide, and the brom- 

 liydrate of hypoxanthin, according to the equation : 



C 7 H 8 N 4 O 3 + 2Br == C 5 H 4 N 4 O.HBr -f CH 3 Br + CO 2 . 



Its structural formula is thus possibly the following : 



CH 3 .N CO 



I I 



CHOH C NH v 



i ii X CH 



' HN CO = CO N ^^ 



Episarcin is but little known. Its formula is given as C 4 H 6 N 3 O, 

 but it is possible that this is not correct. The substance has un- 

 doubtedly many properties in common with epiguanin, and future 

 researches indeed may possibly show that the two are identical. 



These various nucleinic bases, which Gautier also designates as 

 the xanthin leueomains, have the character of feeble alkaloids, and 

 combine with hydrochloric acid and platinum chloride to form 

 crystalline salts, which are dissociated only very slowly or not at all 

 by water. When fused with alkalies they lose the greater portion 

 of their nitrogen in the form of cyanogen, and, as a matter of fact, 



