142 J. BADDILEY 



It formed a benzylphenylhydrazone, but not an osazone, and gave color 

 tests typical of the group of 2-deoxysugars. It differed from D-2-deoxyxylose, 

 but was indistinguishable from synthetic L-2-deoxyribose in all respects 

 except the sign of rotation. '"^ It was then, D-2-deoxyribose. Recently it has 

 been shown that cautious acid hydrolysis of deoxyribonucleic acid in the 

 presence of a-toluenethiol gives the benzyl mercaptal of D-2-deoxyribose 

 which may be isolated in crystalline form.'^ 



c. Nucleoside Conversions 



Some degree of generalization about structural features in nucleosides is 

 possible since, although all these features have not always been verified in 

 each nucleoside, the interconversions discussed below enable structural de- 

 ductions for one to be applied to others. 



Adenosine (II) is converted into inosine (9-D-ribofuranosylhypoxanthine) 

 (XII) by the action of nitrous acid.^^'^^ Inosine was isolated from natural 

 sources by Haiser and Wenzel in 1908, before its relationship to adenosine 

 and the nucleic acids w^as established.^^ Similarly, nitrous acid converts 

 guanosine (I) into xanthosine (9-D-ribofuranosylxanthine) (XIII).^^' 2"' -^ 



■0 



-0- 



OH OH OH OH 



II II 



^CH-CH-CHCH-CHo-OH l-CH-CH-CH-CH -CHj-OH 



OH OH ^^ 



xn XIII 



Inosine Xanthosine 



Adenine deoxyriboside is deaminated to hypoxanthine deoxyriboside by 

 an intestinal deaminase.^ This deaminase is usually present in the enzyme 

 concentrate used for the production of pyrimidine and purine deoxyribo- 

 sides from deoxyribonucleic acid ; consequently early methods for the isola- 

 tion of these nucleosides always yielded the hypoxanthine and not the 

 adenine derivative.^ The action of the deaminase may be inhibited by silver 

 ions. 



" P. A. Levene, L. A. Mikeska, and T. Mori, J. Biol. Chem. 85, 785 (1930). 



" P. W. Kent, Nature 166, 442 (1950). 



18 P. A. Levene and W. A. Jacobs, Ber. 43, 3150 (1910) . 



" P. A. Levene and R. S. Tipson, /. Biol Chem. Ill, 313 (1935). 



18 J. M. Gulland and E. R. Holiday, J. Chem. Sac. 1936, 765. 



19 F. Haiser and F. Wenzel, Monatsh. 29, 157 (1908). 



"o J. M. Gulland and T. F. Macrae, J. Chem. Soc. 1933, 662. 

 21 P. A. Levene, J. Biol. Chem. 55, 437 (1923). 



