Benzimidazole glycosides

Benzimidazole Derivatives.—In recent years benzimidazole glycosides have become of interest in the chemistry of anti-pernicious anemia factors. This interest prompted Petrow and his colleagues226 to prepare benzimidazole glycosides with 2-desoxysugars as the carbohydrate component. 

The presence of the benzimidazole system in a natural product is most striking in the case of vitamin Bi2 (cyanocobalamin). It was isolated from liver extracts and from the fungus Streptomyces griseus. It is an antipemicious anaemia factor. Elucidation of its complex structure was achieved by X-ray analysis (Crawfoot-Hodgkin 1957). 5,6-Dimethylbenzimidazole is bonded via the atom N-I to D-ribose as an A -glycoside N-3 is linked to a cobalt ion which is situated in the centre of a corrin system (see p 489). 

Table 5 contains ribonucleotides with the common amino and carbonyl structures, with extra substituents, and with totally unsubstituted bases like purine or benzimidazole. Apparent values and velocities do not vary more than about tenfold in the presence of specific effector deoxyribonucleotides. Guanine and cytosine nucleotides have usually fastest and compounds with fewer base substituents show decreased reaction rates. Loss of substrate activity is only observed in syn-oriented nucleotides where the nucleobase is rotated about the glycosidic bond like in 8-bromo-ADP or -ATP. Molecular conformation-enzyme activity relationships have been discussed in detail ... 

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