PURINE BASES. 181 



and LEVENE and JACOBS J have prepared two nucleosides from this acid, guanosin 

 and adenosin, which have an analogous structure to inosin, namely, consist of 

 pentose combined with the corresponding purine base, as indicated by the 

 name. All three nucleosides, inosin, guanosin and adenosin are levorotatory. 

 The plant nucleic acids are closely related to the thymonucleic acids, but differ 

 from them by the fact that in the thymonucleic acids the pyrimidine groups 

 are represented by uracil, cytosine, and thymine, and in the triticonucleic acid 

 by cytoume and uracil. This last acid, which is dextrorotatory, yields on hydrol- 

 ysis "druanine, adenine, cytosine and uracil. (WHEELER and JOHNSON, OSBORNE 

 andMEYL. 2 ) As this last can be formed from the cytosine it is possible that only 

 thnprst three bases exist preformed in the acid. An acid with adenine, guanine 

 anoRwo molecules cytosine also corresponds to the formula where the relationship 

 of P to N jl 4 to 16. LEVENE has been able to prepare from the tubercle bacilli 

 nucleic aolfis whose nature has not been closely studied. 



PlasnMiic acid is an acid which was prepared by ASCOLI and KOSSEL 3 by 

 the actiwi of alkali upon yeast. It contains iron, and is soluble in very dilute 

 hydrochloVic acid (1 p. m.). It is still a question whether it is a mixture or a 

 chemical individual. 



In regard to the preparation of yeast and triticonucleic acid we must refer to 

 the works of ALTMANN, KOSSEL, OSBORNE and HARRIS. 4 



2. Purine Bases. 



The cleavage products obtained from the nucleic acids, the nuclein 

 bases, which are also called alloxuric bases by KOSSEL and KRUGER, are 

 members of the larger group of purines, to which also belongs the uric 

 acid which is a substance occurring in the animal body. The constitu- 

 tion of these bodies has been explained by E. FISCHER, 5 and he has 

 prepared many of the bodies synthetically. They can all be derived from 

 the synthetically prepared purine, 5114^, which has the formula given 

 below and which may be considered as a combination of a pyrimidine 

 ring with an imidazole ring. 



N=CH N=CH 



|| || HC NH 



HC C NH V HC CH CH 



!J_ 



H 



N 



Purine Pyriraidirie Imidazole 



The different purine bodies are derived therefrom by the substitution of the 

 various hydrogen atoms by hydroxyl, amide, or alkyl groups. In order to signify 

 the different positions of substitution FISCHER has proposed to number the nine 

 members of the purine nucleus in the following way: 



1N=C6 



2C 5C N7 



>C8. 



3N C N9 

 4 



1 Ber. d. d. chem. Gesellsch., 42, 2477 and 2703. 2 See foot-note 1, page 174. 



3 Ascoli, Zeitschr. f. physiol., Chem. 28. 4 See foot-note 3, p. 176. 



5 See E. Fischer, Untersuchungen in der Puringruppe (1882-1906) Berlin, 1907. 



