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Relevant academic research and scientific papers

Structural investigations of a series of 1,6-aryl-7-hydroxy-2,3-dihydroimidazo[1,2-a]pyrimidin-5(1H)-ones with potential antinociceptive activity

The structural investigations of a series of new bioactive imidazo[1,2-a]pyrimidines 1-6 were undertaken using IR, 1H and 13C NMR spectroscopic analysis, X-ray crystal structure determinations and theoretical calculations. The compounds 1-6 were obtained by condensation of the respective 1-aryl-4,5-dihydro-1H-imidazol-2-amine hydrobromide and diethyl phenylmalonate in presence of sodium methoxide in methanol and for these compounds the equilibrium between possible O10-enol/O11-keto (a), O11-enol/O10-keto (b) and O10,O11-diketo (c) tautomeric forms were investigated in the gaseous phase, solution and crystalline state. Spectroscopic studies 1H, 13C NMR and IR allowed for the identification of the compounds 1-6 but they did not indicate explicitly their tautomeric forms present in solution and in the solid state. The X-ray analysis showed that the molecules of all investigated compounds exist as the O10-enol/O11-keto (a) tautomeric form in the crystalline state. The hydroxyl and carbonyl groups characteristic for existing tautomeric form are involved in a strong intra- and/or intermolecular O-H?O and O-H?N hydrogen bonds. The theoretical calculations at DFT/B3LYP/6-311++G(d,p) level showed that two tautomeric forms (a) and (c) can coexist both in gas phase and the solution with the population of them being in the relation (a) > (or ?) (c). The comparison of the experimentally recorded IR, 1H and 13C spectra with the corresponding spectra theoretically calculated for all possible tautomeric forms of 1-6 shows that the correlation of experimental and theoretical spectra can be used to a limited extent for the identification of tautomeric forms.

Synthesis, pharmacological activity and molecular modeling of 1-Aryl-7- Hydroxy-2,3-dihydroimidazo[1,2-A]pyrimidine-5(1H)-ones and their 6-substituted derivatives

Pain management is an important medical problem with social and economic consequences. Opioid receptors are among the most important molecular targets involved in antinociception. We have previously reported several series of antinociceptive compounds with the affinity to opioid receptors. In search for novel compounds acting on central nervous system with antinociceptive activity we synthesized a series of 1-aryl-7-hydroxy-2,3-dihydroimidazo[1,2- A]pyrimidine-5(1H)-ones and their 6-phenyl derivatives. The novel compounds were subjected to extensive pharmacological studies to assess their effect on motor coordination, body temperature, clonic seizures and tonic convulsions and their antinociceptive activity. In the writhing test the antinociceptive activity of some derivatives was reversed by naloxone, thus we can assume that their activity may be associated with opioid system. We also used molecular modeling to describe active conformations of the studied compounds and to build a pharmacophore model. As in the previously reported series of the compounds, the studied substances exerted antinociceptive activity probably associated with the opioid system without possessing a protonable nitrogen atom. Furthermore, we calculated structural, electronic and ADMET parameters (volume, surface area, polar surface area, ovality, dipole moment, HOMO and LUMO energies, polarizaibility, molar refractivity, lipophilicity, the charges on the heteroatoms, aqueous solubility, and blood-brain barrier permeation parameter) for novel compounds in order to address the observed structure-activity relationship.