Vitamin B₁₂. XIX. Synthesis of the 1-D-Ribosides of 5,6-Dimethylbenzimidazole

The Chemistry of the Vitamin B12 Group.

“…Because the product from this oxidation and that from the oxidation (2 moles of periodate) of 5,6-dimethyl-l-0-D-glucopyranosylbenziminazole picrate were not the same, the «-configuration was postulated for the ribosylamine linkage. This conclusion was remarkable in view of the uniform ^-configuration of the natural purine and pyrimidine ribonucleosides, but the structure was confirmed as 5,6-dimethyI-l-«-n-ribofuranosylbenziminazole (VIII) by syntheses, one of which involved the preformed benziminazole (193), while others involved cyclization at a later stage (185) (Fig. 2).…”

Vitamin B12 and α-ribonucleosides

“…In 1952, Folkers and co-workers reported for the first time degradation products of B 12 by acid hydrolysis and they later compared the properties of the isolated product with synthetic α-ribozole (1-D-α-ribofuranosyl-5,6-dimethylbenzimidazole). 34 In order to prepare α-ribazole, 2-nitro-4,5-dimethyl-N-(5′-trityl-D-ribofuranosyl)aniline, 3, was used as a starting material. Hydrogenation of the nitroriboside in methanol on a palladium catalyst yielded the amine, 4, which was converted to the benzimidazole derivative, and subsequent removal of the trityl group afforded α-ribozole, 6 (Scheme 2).…”

Chemoselective Deprotection of α-Indole and Imidazole Ribonucleosides

“…Literature reports on the synthesis and deprotection of indole α-ribonucleosides are limited. Deprotection is a crucial step for these unstable α-ribonucleosides, [11][12][13][14][15][16][17][18] in order to retain the α-configuration and to achieve the synthesis of AdoCbl. Trityl (Tr), dimethoxytrityl (DMTr), and isopropylidene groups are commonly used for the protection of 5-hydroxyl and 2, 3-hydroxyl groups in both carbohydrate and nucleoside chemistry.…”