CHEMISTRY OF RIBOSE AND DEOXYRIBOSE 31 



of preparation were employed. The conditions of interconversion of these two isomers 

 followed exactly those found to be satisfactory for interconverting the A'-phenj'l-D- 

 ribosylamines. Likewise two isomers of A^-o-nitrophenyl-D-ribosylamine were sj'n- 

 thesized. The absorption of ultraviolet light by both isomers of A'-p-tolyl-D-ribo- 

 sylamine in methanolic solution was measured during the time mutarotation changes 

 were occurring. There was no appreciable change in the absorption corresponding 

 to the change in optical rotation which occurred. The absorption curve closely re- 

 sembled those obtained with simple aromatic amines, the main difference being a 

 slight lateral shift of the maxima [e.g., A^-p-tolylribosylamine (formed in the absence 

 of water) has Xmax. 2450 (log « 4.47) and 2900 A. (log « 3.72) whereas the other isomer 

 shows Xmax. 2500 (log e 5.62) and 2940 A. (log e 4.25). Aniline is reported'^^ to have 

 Xmax. 2300 (log ( 3.90) and 2800 A. (log « 2.30)]. Details of other arylamine-A^-ribosides 

 are listed in the Appendix (Table VII).- Reference has already been made to the 

 ability of arjiamine-A^-ribopyranosides to form "complex salts" with the soluble 

 salts of alkali metals. 



Ribobenzimidazole [2- {p-riho- 1,2,3, 4-tetrahydroxybutyl)benzimida- 

 zole] has been used for the characterization of this pentose and as a means 

 of identifying the sugar component of yeast nucleic acid.'^"^^ These ex- 

 periments were described in Section III. (2). Recently interest in ribosyl- 

 benzimidazole derivatives has been stimulated by the finding that 5,6- 

 dimethylbenzimidazole-a-D-ribofuranoside (XXXI) is a component part 

 of the molecule of vitamin B12. Folkers and his colleagues^''' ^^ and workers 

 in other laboratories^^"^* succeeded in degrading vitamin B12 by acidic hy- 

 dryolsis to XXXI, the structure of which was confirmed by synthesis.^^ 

 2-Nitro-4,5-dimethylaniline (XXXII) was condensed with 5-o-trityl-D- 

 ribofuranose (XXXIII) to give 2-nitro-4,5-dimethyl-A^-(5'-trityl-D-ribo- 

 furanosido)aniline (XXXIV) or one of its tautomers. Successive hy- 

 drogenation and condensation of XXXIV with ethyl formimino ether 

 hydrochloride and acid hydrolysis yielded 5,6-dimethylbenzimidazole-Q:- 

 D-ribofuranoside (XXXI), isolated as the crystalline picrate. When XXXIV 

 was acetylated prior to conversion to the benzimidazole derivative, the final 

 product obtained after the above sequence of reactions and deacetylation 

 was an isomer of XXXI. Optical rotation data suggested that it was the 

 )3-isomer. For both isomers the furanose structure for the sugar moiety was 

 confirmed by periodate titration. For convenience the dextrorotatory 

 isomer (XXXI) was termed a-ribazole and the levorotatory isomer was 

 referred to as /3-ribazole. Natural and synthetic a-ribazole had rat animal 

 protein factor activity of about J^oo of that displayed by vitamin B12 .^^^ 

 At the level used j8-ribazole had about the same activity as the a-isomer. 

 Wacker and Weygand'" have studied /3-ribazole as an inhibitor of Lacto- 

 bacillus leichmannii 313. 



162 Yor references see Ann. Rpts. on Progr. Chem. (Chem. Soc. London) 42, 124 (1945). 

 1" Gladys Emerson, F. W. Holly, C. H. Shunk, N. G. Brink, and K. Folkers, J. Am. 



Chem. Soc. 73, 1069 (1951). 

 i«^ A. Wacker and F. Weygand, Z. Naturforsch. 6b, 130 (1951). 



