404 VITAMIN Bi2 



that components a and /3 (slower moving) were 1 -substituted 5,6-dimethyl- 

 benzimidazoles.^^ • ^^ 



2 . 1 -q:-d-Ribofuranosido-5 , 6-dimethylbenzimidazole 

 The presence of the 1 , 2-diamino-4 , 5-dimethylbenzene moiety (IV) in 



CH3r\N< 



CH 



N< 



W 



vitamin B12 and also in riboflavin could hardly escape attention. Further- 

 more, by analogy it was logical to suspect the presence of an N-pentose 

 unit in combination with the 5, 6-dimethylbenzimidazole. More careful in- 

 vestigation of the mild acid hydrolysis of vitamin B12 yielded l-a-D-ribo- 

 furanosido-5 , 6-dimethylbenzimidazole (V) as a basic product with an ab- 

 sorption spectrum of the benzimidazole type. In addition, it gave a positive 

 carbohydrate color test.^^ A crystalline picrate of the degradation product 

 consumed 0.92 mole of periodate per mole, demonstrating a 1-pentofurano- 

 sido-5 , 6-dimethylbenzimidazole structure. The molecular formula of the 

 product also agreed with this composition. The conditions which were used 

 for the hydrolytic cleavage of the glycosidic linkage caused extensive de- 



CH3 



— o 



OH OH 



\/^^^ C— C— C— C— CH2OH 



/ H H H 

 H 



V 



composition of the pentose. The structure of the product was proved by 

 synthesis. 2-Nitro-4 , 5-dimethylaniline (VI) and 5-trityl-D-ribofuranose 

 (VII) reacted to give 2-nitro-4,5-dimethyl-N-(5'-trity]-D-ribofuranosido)- 

 aniline (VIII). Hydrogenation and condensation with ethyl formimino 

 ether hydrochloride yielded l-a:-D-ribofuranosido-5, 6-dimethylbenzimida- 

 zole (V), which was isolated as the picrate. Comparison of the picrates of 

 the natural and synthetic products confirmed their identity. For conven- 

 ience, compound V was given the designation a-ribazole.^^ The correspond- 

 ing isomer, /3-ribazole (IX), was also prepared. 



»2 G. R. Beaven, E. R. Holiday, E. A. Johnson, B. Ellis, P. Mamalis, V. Petrow, 



and B. Sturgeon, J. Pharm. Pharmacol. 1, 957 (1949). 

 '3 N. G. Brink, F. W. Holly, C. H. Sliunk, E. W. Peel, J. J. Cahill, and K. Folkers, 



J. Am. Chem. Soc. 72, 1866 (1950). 



I 



