CHEMISTRY OF RIBOSE AND DEOXYRIBOSE 57 



case condensation of the crude product with theophylUne silver gave a 

 very small quantity of 3',4'-di-0-acetyl-2'-deoxy-D-ribopyranosyltheo- 

 phylline (D).^''^ 



Diacetyl-D-arabinal was treated with hydrogen chloride in benzene and 

 theophylline silver added to the crude product. Two forms (3 and 23 %) of 

 3' ,4'-di-0-acetyl-2'-deoxy-D-ribopyranosyltheophylline were obtained. 

 [The isomer formed in the smaller amount, was identical with the product 

 (D)]. Deacetylation afforded two forms of 2'-deoxy-D-ribopyranosyltheo- 

 phylline, which were considered to be a- and /3-anomers. To avoid instabili- 

 ties inherent in the deoxysugar, Lythgoe and his colleagues-^- attempted 

 to defer its formation until the final stage of the synthesis by making 2' ,3'- 

 anhydro-5'-0-trityl-7-i9-D-ribofuranosyltheophylline and then converting 

 it to the deoxysugar derivative by the procedures available for the con- 

 version of sugar epoxide rings to deoxysugars, but a negligible amount of 

 the 2'-deoxyribose derivative was obtained. Some chemical properties of 

 the naturally occurring deoxyribonucleosides have been examined. Towards 

 acidic hydrolysis, cytosine deoxyriboside exhibited the greatest stability .^°^ 

 As with the ribose nucleosides, it was found that purine deoxyribosides 

 rotate the plane of polarized light in a Jevo direction, whereas pyrimidine 

 nucleosides are dextroYota.tory }^^ 



Reaction between 5,6-dimethylbenzimidazole silver and 3,4-di-O-acetyl- 

 2-deoxy-D-ribopyranosyl chloride in xylene solution at 100° gave 5,6- 

 dimethylbenzimidazole- 1 - (3 ',4 '-di-O-acetyl-2 '-deoxy-D-ribopy ran oside) , hy- 

 drolysis of which furnished 5,6-dimethylbenzimidazole-l-(2'-deoxy-D- 

 ribopyranoside).'*^ In like manner, benzimidazole-l-(2'-deoxy-D-riboside) 

 was prepared. 



As is the case with 0-glycosides, the A^-glycoside derivatives of 2-deoxy- 

 sugars are hydrolyzed by acid much more rapidly than the normal pentose 

 or hexose analogues. This has been demonstrated for .V-phenyl-D-ribosyl- 

 amine and -2-deoxy-D-ribosylamine.'^° Cohn and his colleagues"" state 

 that adenine-9-(2'-deoxy-D-ribofuranoside-5'-phosphate), when in 0.01 A^ 

 hydrochloric acid at room temperature, liberated adenine at a rate of 2 % 

 per hour, whereas adenine-9-(i3-D-ribofuranoside-5'-phosphate) was unaf- 

 fected by this treatment. 5,6-Dimethylbenzimidazole glycosides are much 

 more stable than arylamine-A^-glycosides, but again the 2-deoxysugar de- 

 rivatives are more labile than the normal sugar derivatives. For example, 

 5,6-dimethylbenzimidazole-l-(2'-deoxy-D-ribopyranoside) is hydrolyzed by 

 heating in a sealed tube with 6 A^ hydrochloric acid for 12 hours at 100*^, 

 whereas the corresponding 5,6-dimethylbenzimidazole-l-(D-ribopyrano- 

 side) luidergoes no hydrolysis.' ^^ 



'"5 F. Bielschowsky and Marianne Siefken-Angermann, Z. physiol. Chem. 207, 210 

 (1932). 



