CHEMISTRY OF NUCLEOSIDES AND NUCLEOTIDES 



139 



o- 





N. 



OH OH 

 I I 

 ■-CH-CH-CH-CH-CHrOH 



OH 



N 



I 



Guanosine 



OH OH 

 I I 

 CH-CH-CH-CH-CHrOH 





NH, 



II 



Adenosine 







OH OH 

 I I 

 ^CH-CH-CH-CH-CH^-OH 



O- 



OH OH 

 I [ 

 -CH-CHCH-CH-CH,OH 



N: 



OH 



NH, 



III 



Uridine 



IV 



Cytidine 



The two purine nucleosides present in deoxyribonucleic acid are adenine 

 deoxyriboside (V) and guanine deoxy riboside (VI). These are both 9-d- 

 (2'-deoxy)ribofuranosides in which the configuration of the glycoside link- 

 age is not known. 



OH 

 I 

 CH-CH:-CH-CH-CH,-OH 



I 



NH. 



o 



. N^ 



OH 

 I 

 L-CH-CHrCH-CH-CH. OH 



H,N|^ 



OH 



VI 



Adenine deoxyriboside 



Guanine deoxyriboside 



The major pyrimidine nucleoside components of deoxyribonucleic acid 

 are cytosine deoxyriboside (VII) and thymidine (thymine deoxja'iboside) 

 (VIII). These are both 3-D-(2'-deoxy)ribofuranosides of undetermined con- 

 figuration at the glycosidic linkage. Some samples of deoxyribonucleic acid 

 contain small amounts of the pyrimidine nucleosides, 5-methylcytosine 

 deoxyriboside (IX) and uracil deoxyriboside (X), but it is possible that the 

 latter is an artifact arising by bacterial deamination of the cytosine nucleo- 

 side.^ 



3 C. A. Dekker and A. R. Todd, Nature 166, 557 (1950). 



