414 



JOSEPH H. PRATT 



Guanin (C 5 H 5 N 5 O) = 2. Amino 6 

 oxypurin = 



CO 



NH 2 C NH 



N C 

 CH,N CO 



CO C 



/CH S 



>CH 



Caffein (C 8 H 10 N" 4 O 2 = 1.3.7 Tri- 



methyl 2.6 dioxypurin CH 3 N C N 



The close relation of uric acid to allantoin was recognized by Wbhler 

 and Liebig. This substance had been previously isolated from the am- 

 niotic fluid of the cow. They found it could be obtained by the oxidation 

 of uric acid. Although it does not contain the purin ring its relation to 

 uric acid is shown in the structural formula : 



H 2 N OH 



Allantoin 



OC 



HN" 



C 



C NH 



Liebig and Wb'hler also obtained alloxan and urea by the oxidation of 

 uric acid with nitric acid. It was later shown that suitable oxidizing 

 agents may convert uric acid into oxalic acid (Glaus). 



Uric acid when heated with concentrated hydrochloric acid in closed 

 tubes is broken down into glycocoll, carbon dioxid and ammonia (Strecker). 



C 6 H 4 N 4 3 + 5 H 2 O = CH 2 + 3 CO 2 -f 3 NH 3 



COOH 

 uric acid glycocoll 



Uric acid can then yield four important decomposition products- 

 glycocoll, urea, allantoin and oxalic acid. Allantoin is the only 

 one of these four substances that is definitely known to be formed in the 

 physiological destruction of uric acid, although Pincussohn(&) (1919) has 

 presented evidence that oxalic acid may be one of the final products in 

 the breakdown of purins. 



The synthesis of uric acid from urea and glycocoll has been produced 

 artificially (Horbaczewski), but it could not be imitated by feeding these 

 compounds. Medicus published the correct structural formula of uric acid 



