Synthesis of C-β-D-glucopyranosyl derivatives of some fused azoles for the inhibition of glycogen phosphorylase

Annulated C-beta-D-glucopyranosyl heterocycles were synthesized and tested as inhibitors of glycogen phosphorylase. 2-(beta-D-Glucopyranosyl)-1H-imidazo[4,5-b] pyridine was formed by ring-closure of O-perbenzoylated C-beta-D-glucopyranosyl formic acid with 2,3-diaminopyridine in the presence of triphenylphosphite. Cyclisations of bromomethyl 2,3,4,6-tetra-O-benzoyl-beta-D-glucopyranosyl ketone with a set of 2-aminoheterocycles resulted in constitutionally reversed C-beta-D-glucopyranosyl imidazoles fused by pyridine, pyrimidine, thiazole, 1,3,4-thiadiazole, benzothiazole and benzimidazole. O-Debenzoylation of the above compounds was effected by standard transesterification to get the test compounds. The 1H-imidazo[4,5-b] pyridine proved to be a low micromolar inhibitor (K-i = 21.1 mu M) of rabbit muscle glycogen phosphorylase b, while the other heterocycles displayed weak or no inhibition against the same enzyme.