140 



J. BADDILEY 



OH 



LCH-CHj-CH-CH-CHj-OH 



OH 



'-CH-CHrCH-CH-CH,-OH 



OH 



•^CH-CHj-CH-CH-CH^-OH 



NH, 



OH 



l-CH-CHj-CH-CH-CHa-OH 

 I 



N 



OH 



IX 



5-Methylcytosine deoxyriboside 



X 



Uracil deoxyriboside 



2. Structure of Nucleosides 

 a. The Nature of the Bases 



Adenosine was discovered by Levene and Jacobs^ as a component of ribo- 

 nucleic acid. They showed that it yielded adenine (6-aminopurine) on acid 

 hydrolysis. The structure and synthesis of adenine and other purine and 

 pyrimidine bases from nucleic acids are discussed in Chapter 3. Guanine 

 (2-amino-6-hydroxypurine) was identified as the purine component of 

 guanosine by Schulze.^ The pyrimidine nucleosides uridine and cytidine 

 yield the pyrimidines uracil (2 , 4-dihydroxypyrimidine) and cytosine (4- 

 amino-2-hydroxypyrimidine), respectively, on vigorous acid hydrolysis. 



The deoxyribosides of adenine, guanine, cytosine, and thymine yield the 

 respective purines and pyrimidines after acid hydrolysis.^- ^ 



6. Carbohydrate Components 



The carbohydrate component of ribonucleic acid, and hence of the cor- 

 responding nucleosides, was described by Hanmiarsten^ as a pentose, and 

 its identification as D-ribose followed later. Levene and Jacobs^ "^ obtained it 

 crystalline and reported that it was a new sugar resembling arabinose in 

 many of its properties but differing from both d- and L-arabinose in melting 



* P. A. Levene and E. S. London, J. Biol. Chem. 81, 711 (1929); 83, 793 (1929). 



« W. Klein, Z. physiol. Chem. 224, 244 (1934); 255, 82 (1938). 



« O. Hammarsten, Z. physiol. Chem. 19, 19 (1894). 



' P. A. Levene and W. A. Jacobs, Ber. 41, 2703 (1908). 



» P. A. Levene and W. A. Jacobs, Ber. 42, 1198 (1909). 



9 P. A. Levene and W. A. Jacobs, Ber. 44, 746 (1911). 



