Tautomerism in Quinoxalines Derived from the 1,4-Naphthoquinone Nucleus: Acid Mediated Synthesis, X-ray Molecular Structure of 5-Chlorobenzo[<i>f</i>]quinoxalin-6-ol and Density Functional Theory Calculations

Gómez, Jesús Gómez; Lage, Mateus R.; Carneiro, José Walkimar de M.; Resende, Jackson A. L. C.; Vargas, Maria D.

doi:10.5935/0103-5053.20130028

Cited by 8 publications

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“…The DFT functional B3LYP became quite popular because of its versatility and has been used in the theoretical study of several different systems since its release. However, B3LYP and other popular functionals are unsuitable for studying systems where noncovalent interactions play a key role. ,− On the other hand, new DFT-based functionals have been implemented with empirical corrections for dispersion energy duly to ensure greater accuracy in treating long-range interactions. This is the case of the DFT functional ωB97X-D, which is also robust for its use in the study of the thermochemistry of organic systems. ,− Therefore, a DFT study is performed herein employing the ωB97X-D functional and 6-31G(d) basis set for the calculations for the individual compounds (RIF and TRIS) and to study interactions in the heterodimer (RIF–TRIS) that constitutes the coamorphous material, contributing to the elucidation of its formation and physical stability.…”

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confidence: 99%

Preparation and Characterization of a Rifampicin Coamorphous Material with Tromethamine Coformer: An Experimental–Theoretical Study

Queiroz,

Barros,

de Sousa

et al. 2024

Mol. Pharmaceutics

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Rifampicin (RIF) is an antibiotic used to treat tuberculosis and leprosy. Even though RIF is a market-available drug, it has a low aqueous solubility, hindering its bioavailability. Among the strategies for bioavailability improvement of poorly soluble drugs, coamorphous systems have been revealed as an alternative in the increase of the aqueous solubility of drug systems and at the same time also increasing the amorphous state stability and dissolution rate when compared with the neat drug. In this work, a new coamorphous form from RIF and tromethamine (TRIS) was synthesized by slow evaporation. Structural, electronic, and thermodynamic properties and solvation effects, as well as drug−coformer intermolecular interactions, were studied through density functional theory (DFT) calculations. Powder X-ray diffraction (PXRD) data allowed us to verify the formation of a new coamorphous. In addition, the DFT study indicates a possible intermolecular interaction by hydrogen bonds between the available amino and carbonyl groups of RIF and the hydroxyl and amino groups of TRIS. The theoretical spectra obtained are in good agreement with the experimental data, suggesting the main interactions occurring in the formation of the coamorphous system. PXRD was used to study the physical stability of the coamorphous system under accelerated ICH conditions (40 °C and 75% RH), indicating that the material remained in an amorphous state up to 180 days. The thermogravimetry result of this material showed a good thermal stability up to 153 °C, and differential scanning calorimetry showed that the glass temperature (T g ) was at 70.0 °C. Solubility studies demonstrated an increase in the solubility of RIF by 5.5-fold when compared with its crystalline counterpart. Therefore, this new material presents critical parameters that can be considered in the development of new coamorphous formulations.

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