CHEMISTRY OF RIBOSE AND DEOXYRIBOSE 45 



prepare 2,3,5-tri-O-acetyl-D-ribose by hydrolysis of arylamine derivatives 

 have afforded only crude amorphous samples of the ester.^- ^°' ^^^ Recently, 

 Zinner^'^ has reported the preparation of all the tetra-0-acetates of D-ribose. 

 Methods for obtaining tetra-O-acetyl-D-ribonic acid have been investi- 

 gated by Tishler et al.'^*° Acetylation of the acid according to the procedure 

 of Robbins and Upson^*' resulted in the production of some tetra-O-acetyl- 

 D-ribonic acid in low yield (15%), admixed with tri-0-acetyl-D-ribonolac- 

 tone (10%) and an intractable oil. A method was developed which gave 

 the required acetate in high yield. Cadmium D-ribonate was treated at 10° 

 with acetic anhydride and hydrogen chloride and the crystalline ribonic 

 acid tetra-0-acetate was obtained in 85% of the theoretical yield. The 

 cation is important in this acetylation, as shown by the varying yields 

 of product obtained when other salts were used. When made to react with 



Cation Ba++ Ca++ K+ NH4+ Cd++ 



Yield of product (%)... 4 22 25 46 85 



phosphorus oxychloride in chloroform, tetra-0-acetyl-D-ribonamide was 

 converted to tetra-0-acetyl-D-ribononitrile.^*° 



Knowledge of the benzoates of D-ribose is due mainly to the researches 

 of Hudson, Fletcher and their co-workers. A crystalline tetra-0-benzoate 

 was obtained by benzoylation of the sugar in p3a-idine solution at low 

 temperature."^ This was considered to have the /3-configuration and was 

 demonstrated to have a pyranose structure by conversion into tri-0- 

 benzoyl-D-ribosyl bromide, which was condensed with the potassium salt of 

 2-thionaphthol to give 2'-naphthyl-l-thio-/3-D-riboside tri-0-benzoate. 

 DesuKurization with Raney nickel and subsequent debenzoylation af- 

 forded an anhydroribitol in high yield. This product resembled 1 , 5-an- 

 hydro-D-xylitoP^^ and 1 , 5-anhydro-D-arabitoP^^ in its solubility characteris- 

 tics. Neither the anhydro derivative nor its acetyl or benzoyl derivatives 

 exhibited optical activity. This would be expected if it had a meso structure, 

 as would be the case if the original tetra-0-benzoate had a pyranose(l ,5)- 

 lactol ring structure. Periodate oxidation on the anhydroribitol confirmed 

 this lactol ring structure. Hydrolysis of 2,3,4-tri-O-benzoyl-D-ribosyl 

 bromide with moist acetone in the presence of an acid-acceptor (Ag2C03) 

 yielded 2,3,4-tri-O-benzoyl-D-ribose.i^^' ^''^ The isomeric 2,3,5-tri-O-ben- 

 zoyl derivative has also been prepared in crystalline form.^^* Esters of 



"0 K. Ladenburg, M. Tishler, J. W. Wellman, and R. D. Babson, /. Am.. Chem. Soc. 



66, 1217 (1944). 

 "1 G. B. Robbins and F. W. Upson, /. Atn. Chem. Soc. 60, 1788 (1938). 

 «« H. G. Fletcher, Jr., and C. S. Hudson, J. Am. Chem. Soc. 69, 921 (1947). 

 "« H. G. Fletcher, Jr., and C-. S. Hudson, J. Am. Chem. Soc. 69, 1672 (1947). 

 *" R. K. Ness and H. G. Fletcher, Jr., J. Am. Chem. Soc. 75, 3289 (1953). 



