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

Abstract

Annulated C-β-d-glucopyranosyl heterocycles were synthesized and tested as inhibitors of glycogen phosphorylase. 2-(β-d-Glucopyranosyl)-1H-imidazo[4,5-b]pyridine was formed by ring-closure of O-perbenzoylated C-β-d-glucopyranosyl formic acid with 2,3-diaminopyridine in the presence of triphenylphosphite. Cyclisations of bromomethyl 2,3,4,6-tetra-O-benzoyl-β-d-glucopyranosyl ketone with a set of 2-aminoheterocycles resulted in constitutionally reversed C-β-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 μM) of rabbit muscle glycogen phosphorylase b, while the other heterocycles displayed weak or no inhibition against the same enzyme.

Keywords: C-glycosyl heterocycle; Fused azole; Glycogen phosphorylase; Imidazole; Inhibitor.