CHEMISTRY OF RIBOSE AND DEOXYRIBOSE 43 



methyl-D-ribose, identical with that obtained from adenosine and guanosine. 

 The structure of the synthetic material was rigidly established by the usual 

 methods of carbohydrate chemistry. Further confirmation of the structure 

 has since been provided by Barker. '^'' Benzylation of methyl 2,3-0-iso- 

 propylidene-D-ribofuranoside afforded the 5-benzyl ether, which on hydroly- 

 sis was converted to syrupy 5-0-benzyl-D-ribose.-^^ Originally it was 

 reported by Bredereck et al.^^ that direct tritylation of D-ribose in pyridine 

 solution yields crystalline 5-0-trityl-a-D-ribose, and Barker and Lock^^^ 

 demonstrated that acetylation without prior isolation of the trityl deriva- 

 tive tripled the yield of acetylated trityl ether. An improved alternative 

 preparation of S-O-trityl-cc-D-ribofuranose was reported by Zinner."^ In 

 a subsequent publication Bredereck and Greiner-^^ described methods for 

 the preparation of several trityl ethers (e.g., 1-, 5-, 1,3(2?)-, 1,5- and 

 1 ,3,5-) of D-ribose and of their acetyl and benzoyl derivatives. 



(2) Esters. The acetates and benzoates of D-ribose have been extensively 

 investigated. Acetylation in pyridine solution at low or ordinary tem- 

 peratures results in the formation of crystalline 1 ,2,3,4-tetra-0-acetyl-(S- 

 D-ribopyranose.^•■^• 110 '235 When acetic anhydride and sodium acetate were 

 used as acetylating agents at higher temperature the product was 1,2,3,5- 

 tetra-0-acetyl-D-ribofuranose.'^' Zinner'^^ investigated the acetylation with 

 acetic anhydride of ribose in pyridine solution at various temperatures and 

 found that increase in the reaction temperature is accompanied by more 

 formation of the furanose isomer, so that at 100° the proportions of the 

 furanose and pyranose forms are approximately equal. The first synthesis 

 of crystalline D-ribofuranose tetraacetate was accomplished successfully 

 by Howard ef a/.'^^ by reductive detritylation of 1 ,2,3-tri-0-acetyl-5-0- 

 trityl-D-ribo furanose (XLI) and subsequent acetylation. The tetraacetate is 



OAc 



/ 

 H— C 



H— C— OAc 



H— C— OAc 



I 

 H— C— O 



CH20CPh3 

 XLI 



"2 G. W. Kenner, C. W. Taylor, and A. R. Todd, J. Chem. Soc. 1949, 1620. 



2" G. R. Barker and M. V. Lock, J. Chem. Soc. 1950, 23. 



"^ H. Bredereck and W. Greiner, Chem. Ber. 86, 717 (1953). 



"5 H. Zinner, Chem. Ber. 86, 817 (1953). 



