CHEMISTRY OF RIBOSE AND DEOXYRIBOSE 63 



the presence and absence of borate, by the differences in susceptibihty of 

 their methyl pyranosides to periodate oxidation, and by the differences 

 in their decomposition rates in alkah. The decreasing order of stabiUty to 

 alkaU (0.01 N XaOH at 22°) is ribose-2-phosphate— which is scarcely at- 

 tacked — ribose-3-phosphate, and ribose-5-phosphate- — which is the most 

 labile. Methods were described for the interconversion of the various salts 

 of these phosphates. Comparison of the properties of the salts of the pure 

 ribose-2- and -3-phosphates prepared by Cohn et aU^^ with those described 

 by Levene and Harris'" • -'^ • ''^ for preparations of ribose phosphates in- 

 dicates that the latter workers were handling mixtures composed of about 

 20 parts of ribose-2 -phosphate and 80 parts of ribose-3 phosphate. In the 

 light of present knowledge it is clear that the experimental conditions em- 

 ployed by Levene and Harris could not have resulted in retention of iso- 

 meric integrity, but would be expected to result in the formation of mix- 

 tures. Consequently, the samples prepared by Cohn and his colleagues are 

 the first pure preparations of ribose-2- and -3-phosphate. When ribose-2- or 

 -3-phosphate is heated for 2 hours with Dowex 50 (H+) resin or for 45 

 minutes with 0.1 iV sulfuric acid it forms ribose-4-phosphate.^^* The 

 yields ranged from 8 to 10% of theory, and not enough material was 

 isolated to permit characterization of a solid salt of the compound. 

 Khym ct alP^ prepared ribose-5-phosphate by treating adenosine-5'-phos- 

 phate with Dowex 50 (H+) resin at 100° for 4 minutes. Thereafter the 

 solution was cooled and more than 96 % of the adenine and adenosine com- 

 pounds were removed by filtration. The ribose phosphate {ca. 95 % yield) 

 was isolated in crystalline form as the barium salt. A fraction contain- 

 ing 70-80% of D-ribose-5-phosphate is obtained when xylose and ad- 

 enosine triphosphate are incubated with pentose phosphate isomerase 

 (from extracts of Lactobacillus -peniosus) }^^ A new simplified procedure for 

 the isolation of deoxyribose-1 -phosphate has been developed: it involves 

 the phosphorolysis of thymidine in the presence of dicyclohexylammonium 

 hydrogen phosphate, followed by a fractionation step with n-butanol- 

 diethyl ether, which yields crystalline dicyclohexylammonium deoxyribose- 

 1-phosphate after a single filtration.^^^ Reaction between thymine and 

 deoxyribose-1 -phosphate in the presence of mammalian thymidine phos- 

 phorylase gives thymidine which can be isolated in crystalline form.^^^ 



The preparation and properties of 2,3,4-tri-0-benzoyl-i3-D-ribose have 

 been described,^" and new benzoyl derivatives of D-ribofuranose and 

 aldehydo-i>-v\hos,e have been outlined. ^^^ A preliminary X-ray study is 



"6 J. O. Lampen, J. Biol. Chem. 204, 999 (1953). 



336 M. Friedkin and DeWayne Roberts, J. Biol. Chem. 207, 257 (1954). 



337 H. G. Fletcher, Jr., and R. J. Ness, /. .4m. Chem. Soc. 76, 760 (1954). 



338 R. K. Ness, H. W. Diehl, and H. G. Fletcher, Jr., J. Am. Chem. Soc. 76, 763 (1954). 



