x THE PROTEIDS 429 



CH 3 . N CO HN CO CH 3 . N CO 



II II II 



OC C NH OC C N.CH OC C N.CH, 



V.TT \ 



^CH 



CH 3 . N C N CH 3 . N C N CH 3 . N C N 



Theophyllin or Theocin Theobronrine Caffeine 



(2,6-dioxy-l , 3-dimethyl- (2,6-dioxy-3,7-dimethyl- (2,6-dioxy-l,3,7-trimethyl- 



purin). purin). purin). 



The synthesis of guanin and similar compounds has been studied 

 specially by Behrend and Rosen l (uric acid), Stolle and Hofmann 2 

 (diamino - guanidin), Traube, 3 Pellizzari and Cantoni 4 (diamino- 

 guanidin). 



The four purin -derivatives hypoxanthin, xanthin, adenin, and 

 guanin occur in the body only in the nucleic acids and their 

 dissociation -products, and hence are called 'nuclein- bases,' 'alloxur- 

 bases,' or ' xanthin-bases.' The manner in which the purins are linked 

 to the nucleic acids has been investigated by Burian, 5 who points 

 out that purin, being composed of pyrimidin and imido-azol (see p. 

 428), gives for this reason both the alloxan reaction of pyrimidin and 

 the silver reaction of imido-azol. Imido-azol with diazobenzene-sul- 

 phonic acid 



,N=N, 



S0 3 



forms diazo-benzene-imido-azol 



HC N. 



N:N-C 6 H 5 



HC N' 



Diazo-benzene-imido-azol. 



Analogously with other azotising mixtures, yellow or red, stable sub- 

 stances are formed which, on the addition of ammoniacal silver nitrate, 

 give red, generally gelatinous precipitates, and these, like the silver 

 compounds of imido-azol and of the purin bodies, are almost insoluble 

 in an excess of ammonia. 



The same reaction is obtained with a, /3, and /z substitution products 

 of imido-azol (see formula on p. 428), but it does not occur (1) if 

 place n ( = No. 7 of the purin group) is already occupied by a substi- 



1 Behrend and Rosen, Liebig's Annalen, 161. 235 (1872). 



2 E. Stolle and K. Hofmann, JBer. d. deutsch. ckem. Ges. 37. 4524 (1904). 



3 Wilhelm Traube, iMd. 37. 4544 (1904). 



4 G. Pellizzari and C. Cantoni, 38. 283 (1905). 



5 R. Burian, Ber. d. deutsch. chem. Ges. 37- 696 (1904). 



