Synthesis and DNase I Inhibitory Properties of New Squaramides

Three new monosquaramides (3a-c) were synthesized, characterized by IR, NMR and X-ray, and evaluated for inhibitory activity against deoxyribonuclease I (DNase I) and xanthine oxidase (XO) in vitro. The target compounds inhibited DNase I with IC₅₀ values below 100 μM, being at the same time more potent DNase I inhibitors than crystal violet, used as a positive control. 3-Ethoxy-4-((1-(pyridin-3-yl)propan-2-yl)amino)cyclobut-3-ene-1,2-dione (3c) stood out as the most potent compound, exhibiting a slightly better IC₅₀ value (48.04 ± 7.98 μM) compared to the other two compounds. In order to analyze potential binding sites for the studied compounds with DNase I, a molecular docking study was performed. Compounds 3a-c are among the most potent small organic DNase I inhibitors tested to date.

Fast Quantum Approach for Evaluating the Energy of Non-Covalent Interactions in Molecular Crystals: The Case Study of Intermolecular H-Bonds in Crystalline Peroxosolvates

Energy/enthalpy of intermolecular hydrogen bonds (H-bonds) in crystals have been calculated in many papers. Most of the theoretical works used non-periodic models. Their applicability for describing intermolecular H-bonds in solids is not obvious since the crystal environment can strongly change H-bond geometry and energy in comparison with non-periodic models. Periodic DFT computations provide a reasonable description of a number of relevant properties of molecular crystals. However, these methods are quite cumbersome and time-consuming compared to non-periodic calculations. Here, we present a fast quantum approach for estimating the energy/enthalpy of intermolecular H-bonds in crystals. It has been tested on a family of crystalline peroxosolvates in which the H∙∙∙O bond set fills evenly (i.e., without significant gaps) the range of H∙∙∙O distances from ~1.5 to ~2.1 Å typical for strong, moderate, and weak H-bonds. Four of these two-component crystals (peroxosolvates of macrocyclic ethers and creatine) were obtained and structurally characterized for the first time. A critical comparison of the approaches for estimating the energy of intermolecular H-bonds in organic crystals is carried out, and various sources of errors are clarified.

Experimental and theoretical investigation of conformational states and noncovalent interactions in crystalline sulfonamides with a methoxyphenyl moiety

The conformational and noncovalent interaction properties of sulfonamides with a methoxyphenyl moiety were examined by both experimental and theoretical methods.

H-Bonded anion–anion complex trapped in a squaramido-based receptor

We report the experimental observation (X-ray characterization) of an anion–anion complex (anion = hydrogen fumarate) stabilized by H-bonds that is trapped in a secondary squaramide receptor.

Polymorphism in secondary squaramides: on the importance of π-interactions involving the four membered ring

We report the crystal structures of four new squaric acid derivatives, i.e. three polymorphs of 3,4-bis((2-(dimethylamino)ethyl)amino)cyclobut-3-ene-1,2-dione (1a–c) and a cocrystal with resorcinol. A DFT study has been also carried out to investigate the supramolecular assemblies.