CHEMISTRY OF NUCLEOSIDES AND NUCLEOTIDES 



163 



phosphate residue is located at the 2' ,3'- or 5'-position on the sugar chain.^ 

 The ribose phosphate produced by acid hydrolysis must be ribose-5-phos- 

 phate since it is oxidized with nitric acid to a ribonic acid phosphate and 

 not a n6o-trihydroxyglutaric acid phosphate. » 



OH OH 



OH OH OH 



H0CH-CH.CH-CH.CH.0P03H. -^ HO.C CH-CH- CH-CHrOPOaH, 



D-Ribose-5-phosphate D-Ribonic acid-5-phosphate 



The structure of ribonic acid-5-phosphate is confirmed by its slow con- 

 version into a 7-lactore.i^^' 155 Also, the sugar phosphate itself is converted 

 into a methylribofuranoside-5-phosphate rather than a mixture of furano- 

 side and pyranoside^^^ and is reduced to optically active ribitol-5-phosphate. 

 Full proof for the structure of ribose-5-phosphate is given by its synthesis 

 from methyl 2, 3-isopropylideneribofuranoside. Phosphorylation with phos- 

 phoryl chloride, then acid hydrolysis, gives the S-phosphate.^" Better yields 

 are obtained by phosphorylation with dibenzyl phosphorochloridate, then 

 hydrogenolysis and acid hydrolysis.'^* 



-0- 



OH OH 

 •-CH-CH-CH-CH-CH^-OPCH, 



nJC> 



OH ^^ 



XXI 

 Muscle inosinic acid 



h. Adenosine-5' -phosphate (muscle adenylic acid) (XXII) 



As its name implies, this nucleotide was first isolated from muscle.'^" 

 but it is now known to occur as a structural unit of ribonucleic acid and of 

 several coenzymes. Since it can be deaminated to inosine-5'-phosphate by 

 an enzyme present in muscle tissue,!^^ it must bear the same relationship 

 to that nucleotide as does adenosine to inosine, i.e., it must be adenosine-5'- 

 phosphate. Furthermore, the two nucleotides liberate phosphoric acid at 



>53 p. A. Levene and W. A. Jacobs, Ber. 42, 335 (1909). 



i5< P. A. Levene and H. S. Simms, J. Biol. Chem. 65, 31 (1925). 



165 P A Levene and T. Mori, J. Biol. Chem. 81, 215 (1929). 



156 p A. Levene, S. A. Harris, and E. T. Stiller, J. Biol. Chem. 105, 153 (1934). 



157 P. A. Levene'and E. T. Stiller, J. Biol. Chem. 104, 299 (1934). 



158 A. M. Michelson and A. R. Todd, J. Chem. Soc. 1949, 2476. 



159 G. Schmidt, Z. physiol. Chem. 179, 243 (1928). 



