CHEMISTRY OF NUCLEOSIDES AND NUCLEOTIDES 



149 



3-/3-D-glucopyranosyluracil and 3-/3-D-glucopyranosylcytosine, respectively. 

 The glucosides were prepared by the synthetic route described on page 155 

 and must be 3-/3-derivatives. 



N 







OH OH 



I I 



L-CH-CH-CH-CH-CH-CHrOH 

 I I 



N^ OH 



■O- 



N. 



CH-CHO OHC-CH-CHrCH 



I 



OH 



3-/3- D-Glucopyranosyluracil 



OH 



The /3-configuration of the natural nucleosides is also shown by the be- 

 havior of the 5'-tosyl derivatives of the basic members, adenosine and cyti- 

 dine. Both 2',3'-isopropylidene-5'-p-toluenesulfonyladenosine and the cor- 

 responding cytidine derivative isomerize with great ease to the respective 

 cyclonucleosides.^8 Steric requirements for these transformations are only 

 satisfied by /3-glycosides. 



— 



MeCMe 



/\ 



O O 



I I 



LcH-CH-CH-CH-CH,-OTs 





N 

 NH2 



TsO- 



X-ray analysis of several nucleosides has confirmed the structures al- 

 ready assigned on chemical evidence. In addition it appears that the gly- 

 cosidic linkage in adenosine lies in the same plane as the purine ring. The 

 purine ring is flat, in agreement with its aromatic properties, whereas the 

 sugar is slightly nonplanar. The sugar ring lies approximately perpendicular 

 to the purine ring in adenosine.*^ Certain other features have been noted. 

 Although the examination was incomplete, other nucleosides seem to con- 

 form to the same general pattern. [Cf. Jordan, Chapter 13.] 



3. Synthesis of Nucleosides 

 a. Purine Nucleosides 



A number of purine glycosides was synthesized by Emil Fischer and his 

 collaborators. These were mainly derivatives of theophylline, theobromine, 



« V. M. Clark, A. R. Todd, and J. Zussman, J. Chem. Soc. 1951, 2952. 

 " S. Furberg, Acta Chem. Scand. 4, 751 (1950). 



