Characterization and structural analysis of the potent antiparasitic and antiviral agent tizoxanide

Synthesis, antiviral activity, preliminary pharmacokinetics and structural parameters of thiazolide amine salts

Background: The thiazolides, typified by nitazoxanide, are an important class of anti-infective agents. A significant problem with nitazoxanide and its active circulating metabolite tizoxanide is their poor solubility. Results: We report the preparation and evaluation of a series of amine salts of tizoxanide and the corresponding 5-Cl thiazolide. These salts demonstrated improved aqueous solubility and absorption, as shown by physicochemical and in vivo measurements. They combine antiviral activity against influenza A virus with excellent cell safety indices. We also report the x-ray crystal structural data of the ethanolamine salt. Conclusion: The ethanol salt of thiazolide retains the activity of the parent together with an improved cell safety index, making it a good candidate for further evaluation.

Accurate location of hydrogen atoms in hydrogen bonds of tizoxanide from the combination of experimental and theoretical models

To obtain detailed information about the position of hydrogen atoms in hydrogen bonds, HBs, of crystalline organic molecular compounds is not an easy task. In this work we propose a combination of ssNMR experimental data with theoretical procedures to get such information. Furthermore, the combination of experimental and theoretical models provides us with well-defined grounds to analyse the strength of π-stacking interactions between layers of hydrogen bonded molecules. Two different theoretical models were considered, both approaches being quite different. The first one is a solid-state model, so that the periodicity of a crystalline system underlies calculations of the electronic energy, the electronic density and NMR parameters. The other one is a molecular model in which molecules are taken as isolated monomers, dimers and tetramers. These two models were applied to the tizoxanide, TIZ, molecular crystal though it can widely be applied to any other molecular crystal. By the application of the quantum molecular model it was possible to learn about the way the intermolecular HBs affect the position of hydrogen atoms that belong to HBs in TIZ. This molecule has two intermolecular HBs that stabilize the structure of a basic dimer, but it also has an intramolecular HB in each monomer whose position should be optimized together with the other ones. We found that by doing this it is possible to obtain reliable results of calculations of NMR spectroscopic parameters. Working with the solid-state model we found that any local variation of the TIZ crystalline structure is correlated with the variation of the values of the NMR parameters of each nucleus. The excellent agreement between experimental and calculated chemical shifts leads to the conclusion that the N10-H10 bond distance should be (1.00 ± 0.02) Å.

Metal-mediated reactions towards the synthesis of a novel deaminolysed bisurea, dicarbamolyamine

A new selective cobalt acetate tetrahydrate or cerium nitrate hexahydrate mediated cleavage of the C–N bond of a benzoyl isothiocyanate derivative to give (carbamoylamino)methanethioamide is presented. The cleavage of the C–N could not be achieved in the absence of thione. The novel silver-mediated conversion of a thione to the carbonyl was achieved on 1-((benzamido)formyl)urea and replicated on (carbamoylamino)methanethioamide to give the deaminolyzed bisurea (dicarbamolyamine). The compounds were characterized by IR, NMR, microanalysis and GC–MS. The single crystal X–ray diffraction studies of the crystal structures of compounds I, II, III and V is discussed.

Crystal structure of 2-nitro-N-(5-nitro-1,3-thia-zol-2-yl)benzamide

In the title compound, C₁₀H₆N₄O₅S, the mean plane of the non-H atoms of the central amide fragment C—N—C(=O)—C [r.m.s. deviation = 0.0294 Å] forms dihedral angles of 12.48 (7) and 46.66 (9)° with the planes of the thia­zole and benzene rings, respectively. In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds, forming chains along [001]. In addition, weak C—H⋯O hydrogen bonds link these chains, forming a two-dimensional network, containing R⁴₄(28) ring motifs parallel to (100).