416 



VITAMIN Bi2 



responding 2-ethoxymethylene-o-phenylenediamine tetraacetyl-D-glucoside . 

 Conversion to the benzimidazole was accomplished by hot dilute hydro- 

 chloric acid.^^ 



Hydrolysis of the acetyl groups was accomplished by heating the tetra- 

 acetate in 6 iV hydrochloric acid at 100° for 3 hours. 



An alternative method for the preparation of a benzimidazole glycoside 

 involved the reaction of the silver salt of the benzimidazole with the aceto- 

 bromosugar as follows: 



C— CH2OAC 

 H 



0- 



OAc H 



H I I 



c— c c- 



H OAc H 



N 



OAc 



I 

 C — 



-C— CH2OAC 

 H 



/^/ 



\/ N 



This latter method was used for the confirmation of the structure of the 

 benzimidazole glucosides. 



The /3-D-glycopyranosides of benzimidazole, 5-methyl-, 4,5-dimethyl-, 

 and 5 , 6-dimethylbenzimidazole were prepared by these methods. ^^ 



A series of benzimidazole pentosides was prepared by the orthoformate 

 condensation.^" The following compounds were prepared: benzimidazole- 

 l;S-D-xylopyranoside ; 5-methylbenzimidazole-l|S-D-xylopyranoside ; benzim- 

 idazole- la-L-arabopyranoside; benzimidazole-la-D-arabopyranoside; 5(or 

 6)-methylbenzimidazole-lQ:-L-arabopyranoside ; 5 , 6-dimethylbenzimidaz- 

 ole-la-L-arabopyranoside ; 5 , 6-dimethylbenzimidazole-l-L-rhamnopyrano- 

 side. 



1. Radioactive Modifications 



Isotope-labeled vitamin B12 has been prepared to facilitate the deter- 

 mination or assay of vitamin B12, and also to study its metabolism. Cobalt 

 60-labeled vitamin Bi2 has been prepared*^ by adding the cobalt GO as the 



" C. Rosenblum and D. T. Woodbury, Science 113, 215 (1951); L. Chaiet, C. Rosen- 

 blum, and D. T. Woodbury, ibid. Ill, 601 (1950). 



