144 J. BADDILEY 



aminated to uridine without loss of the ribose residue it follows that the 

 glycosidic linkage does not involve the 6-substituent in these nucleosides. 

 Furthermore, position 5 may be dismissed from consideration since uridine 

 can be converted into 5-nitrouridine and 5-bromouridine without loss of the 

 carbohydrate residue. The formation of 4 , 5-diphenylhydrazinouridine 

 (XVI) by the action of bromine, then phenylhydrazine, on uridine indicates 

 the absence of substituents on positions 4 and 5.^^ This reaction is consid- 

 ered specific for 3-substituted uracil derivatives; consequently it seemed 

 likely that uridine and cytidine are 3-glycosides. 



The reaction between uridine and hydrazine to give pyrazolone also 

 indicates the absence of substituents at position 4.^^ Since uridine may 

 be converted into AT-methyluridine which, on hydrolysis, yields 1-methyl- 

 uracil (XVII), it follows that uridine and hence cytidine are 3-glycosides." 



Thymidine is probably a 3-glycoside since methylation and hydrolysis 

 of deoxyribonucleic acid results in the production of 1-methylthymine.^* 



e. The Ring Structure of the Carbohydrates 



The size of the sugar ring in the purine nucleosides has been determined 

 by methylation and oxidation. Acetylation of adenosine and subsequent 

 methylation then deacetylation yields a trimethyl-A''-methyladenosine and 

 this, on hydrolysis with dilute acid, gives V^-methyladenine and a tri- 

 methylribose.^^ The same trimethylribose may be isolated after similar 

 transformations on guanosine.^" Its structure is established by oxidation to 

 2,3,5-trimethyl-7-D-ribonolactone and then to meso-dimethoxysuccinic 

 acid. The trimethylribose itself was identified subsequently by comparison 

 with synthetic 2,3,5-trimethyl-D-ribofuranose.^^ 



" P. A. Levene, /. Biol. Chem. 63, 653 (1925). 



28 P. A. Levene and L. W. Bass, /. Biol. Chem. 71, 167 (1926). 



" P. A. Levene and R. S. Tipson, /. Biol. Chem. 104, 385 (1935). 



28 H. Bredereck, G. Muller, and E. Berger, Ber. 73, 1058 (1940). 



29 P. A. Levene and R. S. Tipson, J. Biol. Chem. 94, 809 (1932). 



30 P. A. Levene and R. S. Tipson, /. Biol. Chem. 97, 491 (1932). 



31 P. A. Levene and E. T. Stiller, J. Biol Chem. 102, 187 (1933). 



