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Abstract: Imidazo[4,5-b]pyridines are amongst the oldest known heteroaromatic derivatives. Their structural similarity with purine basis has however aroused the curiosity of biologists and resulted in the developments of innovative bioactive compounds. This review thus firstly describes the main synthetic ways currently used to produce imidazo[4,5-b]pyridine derivatives, and secondly gives examples of their potential, especially focusing on protein inhibition abilities, thus opening the way to applications as anti-- cancer or antimicrobial agents.

Novel 6-bromo-imidazo[4,5-b]pyridine derivatives (2-4, 5a-13a, and 6b, 8b-13b) have been synthesized based on a developed systematic approach involving the condensation of 5-Bromo-2,3-diaminopyridine with a suitable aromatic aldehyde in the presence of molecular iodine in water, followed by alkylation reactions using different alkyl dibromide agents. The synthesized compounds were characterized by the NMR spectroscopy technique. The structures of 8a, 9a, 12a, and 11b were confirmed using monocrystalline X-ray crystallography. Theoretical calculations have been carried out using DFT and TD-DFT methods at the B3LYP/6-31G++(d,p) level of theory. Intermolecular contacts between units of 8a, 9a, 12a, and 11b were determined through the Hirshfeld surface analysis. The molecular docking study has been performed to determine the binding affinity of 8a, 9a, 12a, and 11b into the binding site of S. aureus tyrosyl-tRNA synthetase as a target enzyme, and the results revealed that 9a is the most potent compound among the selected compounds with a binding affinity of −8.74 Kcal/mol. Communicated by Ramaswamy H. Sarma

In the title molecule, C20H24Br2N4, the imidazopyridine moiety is not planar as indicated by the dihedral angle of 2.0 (2)° between the constituent rings; the 4-dimethylaminophenyl ring is inclined to the mean plane of the imidazole ring by 27.4 (1)°. In the crystal, two sets of C—H...π(ring) interactions form stacks of molecules extending parallel to the a-axis direction. Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from H...H (42.2%), H...C/C...H (23.1%) and H...Br/Br...H (22.3%) interactions. The optimized structure calculated using density functional theory (DFT) at the B3LYP/ 6–311 G(d,p) level is compared with the experimentally determined structure in the solid state. The calculated HOMO–LUMO energy gap is 2.3591 eV.

The 5-bromo­pentyl chain is oriented so that the bromine atom is ca 4.4 Å from one of the methyl C atoms of the di­methyl­amino group. In the crystal, two sets of inversion-related C—H⋯π(ring) inter­actions form stacks of mol­ecules extending along the a-axis direction., In the title mol­ecule, C20H24Br2N4, the imidazo­pyridine moiety is not planar as indicated by the dihedral angle of 2.0 (2)° between the constituent rings; the 4-di­methyl­amino­phenyl ring is inclined to the mean plane of the imidazole ring by 27.4 (1)°. In the crystal, two sets of C—H⋯π(ring) inter­actions form stacks of mol­ecules extending parallel to the a-axis direction. Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from H⋯H (42.2%), H⋯C/C⋯H (23.1%) and H⋯Br/Br⋯H (22.3%) inter­actions. The optimized structure calculated using density functional theory (DFT) at the B3LYP/ 6–311 G(d,p) level is compared with the experimentally determined structure in the solid state. The calculated HOMO–LUMO energy gap is 2.3591 eV.

Oxidation of various 1-thioglycopyrano- and furanosides with H 2 O 2 /Ac 2 O/SiO 2 was performed in CH 2 Cl 2 /aprotic perfluorinated solvent mixtures (100:0 to 1:19, v/v). Reactions appeared much faster at a solvent ratio of 1:1 without significant over-oxidation to sulfones and modification of diastereoselectivity. Nevertheless, the nature of both the glycosyl moiety and the protecting group influenced the ( S S ):( R S ) product ratio.

The title compound, C13H9N3O3, crystallizes with two identical but differently oriented molecules in the asymmetric unit, the dihedral angle between the fused-ring systems of the two molecules being 64.39 (7)°. The two prop-2-ynyl chains are located on opposite sides of the molecule and are nearly perpendicular to the fused ring plane, as indicated by the C—N—C—C torsion angles in the range 106.0 (3)–113.4 (3)°. In the crystal, the two molecules are linked through C—H...O hydrogen bonds into dimers, which are subsequently linked by further C—H...O interactions, building a three-dimensional network.

Oxidation of various 1-thioglycopyrano- and furanosides with H 2 O 2 /Ac 2 O/SiO 2 was performed in CH 2 Cl 2 /aprotic perfluorinated solvent mixtures (100:0 to 1:19, v/v). Reactions appeared much faster at a solvent ratio of 1:1 without significant over-oxidation to sulfones and modification of diastereoselectivity. Nevertheless, the nature of both the glycosyl moiety and the protecting group influenced the ( S S ):( R S ) product ratio.

A variety of cyclic and acyclic allylic alcohols undergo efficient chemo-, regio- and/or stereoselective epoxidations in neutral aqueous solutions of amphiphilic carbohydrates (sucrose, L-arabinose, methyl or ethyl beta-D-fructopyranoside) by using dilute hydrogen peroxide in the presence of molybdic or tungstic salts.