20 W. G. OVEREND AND M. STACEY 



Hydrolysis of aqueous solutions of yeast nucleic acid can be accomplished 

 by the agency of enzymic preparations from sweet almonds, lucerne seeds 

 or germinated peas.^^ Good yields of guanosine and adenosine are obtained, 

 and acidic hydrolysis of the former nucleoside yields D-ribose.^^- »« Details 

 for the isolation of D-ribose from yeast nucleic acid have been patented by 

 Laufer and Charney;^^ the method aims essentially at facilitating the 

 separation of nucleosides from a hydrolysate of the nucleic acid. 



Addition of cuprous ions results in precipitation of the purine nucleosides 

 as cuprous salts. Acidic hydrolysis of the salts results in the formation of 

 D-ribose and the insoluble cuprous salts of adenine and guanine. Alter- 

 natively, the nucleic acid is hydrolyzed to a mixture of nucleotides which 

 are converted into their cuprous salts by addition of copper sulfate and 

 sodium bisulfite. The pyrimidine nucleotides remain in solution, but the 

 purine nucleotides are precipitated. After separation and washing these 

 purine nucleotides are subjected to hydrolysis with sulfuric acid. Insoluble 

 cuprous salts of adenine and guanine are removed from the hydrolysate by 

 filtration, leaving a solution containing D-ribose and sulfuric and phosphoric 

 acids. Addition to the solution of an alkaline earth hydroxide followed by 

 filtration gives a solution of practically pure D-ribose. »» Nowadays it is 

 more usual to separate nucleoside and nucleotide mixtures by ion-exchange 

 resin chromatography. ^^ [Cf. Cohn, Chapter 6.] 



2. Identification and Estimation 

 A tentative identification of ribose may be achieved from the usual tests 

 for a reducing sugar and specific tests for pentoses. Determinations on 

 crystalline samples of the melting point, specific rotation and optical 

 crystallographic properties will serve to differentiate between the various 

 pentoses. Of the derivatives which -can be prepared for characterization, 

 substituted hydrazones have been preferred. At various times the p-bromo- 

 phenylhydrazone,i2. ,4. i5, 33. to, 76, 79. ioo-io3the benzylphenylhydrazone,!^. 74 

 the p-toluenesulf onylhydrazone^s • '"^ and to a lesser extent the diphenyl- 



» H. Bredereck and G. Rothe, Ber. 71, 408 (1938). 



»« H. Bredereck, M. Kothnig, and Eva Berger, Ber. 73, 956 (1940). 



" L. Laufer and J. Charney, U. S. Pat. 2,379,913 (July 10, 1945). 



98 L. Laufer and J. Charney, U. S. Pat. 2,379,914 (1945). 



99 W. E. Cohn, Science 109, 377 (1949); /. Am. Chem. Soc. 71, 2275 (1949); /. Am. 

 Chem. Soc. 72, 1471 (1950). 



looW. Alberda van Ekenstein and J. J. Blanksma, Chem. Weekblad 11, 182 (1914); 

 Brit. Abstr. 106 (i), 388 (1914). 



101 P. A. Levene and R. S. Tipson, J. Biol. Chem. 115, 731 (1936). 



102 C. W. Klingensmith and W. L. Evans, J. Am. Chem. Soc. 61, 3012 (1939). 

 "3 p. A. Levene and W. A. Jacobs, Ber. 42, 3247 (1909). 



104 B. Helferich and H. Schirp, Chem,. Ber. 86, 547 (1953). 



