CHEMISTRY OF NUCLEOSIDES AND NUCLEOTIDES 



155 



1 > — " X^ ~ 



MeOjC N MeO^C N 



H.N-OC n' 

 H,N-OC ^ 



KOBr 



R. 



YLQf 



N: 



OH 



Xanthosine 



„> 



R = 2'3'5'-Triacetyl-D-ribofuranosyl 

 Ri = D-ribofuranosyl 



h. Pyrimidine Nucleosides 



Pyrimidine nucleosides have been synthesized from aeetohalogeno-sugars 

 and suitably substituted pyrimidines. When the pyrimidine employed bears 

 substituents, such as hydroxyl, which are capable of prototropic change, the 

 glycosyl residue becomes attached thereto and heterocyclic iV-glycosides 

 cannot be produced in this manner.^"' ^'-' " However, A^-glycosides are 

 obtained by the action of aeetohalogeno-sugars on 2 ,6-dialkoxypyrimidines, 

 in which tautomerization possibilities are excluded. This is an extension of 

 the reaction observed between alkyl halides and 2,6-dialkoxypyrimidines 

 whereby 3-alkyl-6-alkoxy-2-ketopyrimidines are formed. 



Thus, interaction of acetobromoglucose and 2,6-diethoxypyrimidine gives 

 an acetylglucoside which on hydrolysis with hydrogen chloride in methanol 

 yields 3-D-glucosyluracil. Alternatively, b}^ treatment of the acetylated 

 glucoside with ammonia, 3-D-glucosylcytosine is formed.*^' ** Several struc- 

 tural analogues have been prepared by this method.*'- ^° Starting from 

 acetobromoribofuranose and 2,6-diethoxypyrimidine the natural nucleo- 



" G. E. Hilbert and T. B. Johnson, J. /l?n. Chern. Soc. 52, 4489 (1930). 

 «8 G. E. Hilbert and E. F. Jansen, J. Am. Chem. Soc. 58, 60 (1936). 

 «9 G. E. Hilbert, /. Biol. Chem. 117, 331 (1937). 

 90 G. E. Hilbert and C. E. Rist, J. Biol. Chem. 117, 371 (1937). 



