4-Aminotetrahydroquinazoline N-oxides form a prominent chemotype of orthoflavivirus reproduction inhibitors, attractive for the search of lead compounds for development as direct-action antiviral agents. Here we explored the relationship between the structure and antiviral activity within an extended series of adamantyl-containing 4-aminotetrahydroquinazolines, synthesized via SNAr reactions of 4-chlorotetrahydroquinazolines with adamantyl-containing amines. Most of the obtained compounds inhibited the reproduction of tick-borne encephalitis, yellow fever, and West Nile viruses in phenotypic assays with micromolar EC50s. The most favorable substituents at 4-amino group were 2-adamant-(1/2)-ylethyls, while the position 2 of heterocyclic core served as a toxicity switch, 2-chlorotetrahydroquinazolines being much less toxic than other analogues. Time-of-addition experiments for hit compounds against West Nile virus revealed a possibility for multi-factorial mechanism of action in the 4-aminotetrahydroquinazoline series.

This study presents a novel regioselective synthesis of 3-electron-withdrawing-group-(EWG)-substituted 5-sulfonyl- and 5-sulfinylisoxazoles from 3-EWG-5-nitroisoxazoles via nucleophilic aromatic substitution with thiophenols followed by oxidation with m-chloroperbenzoic acid (mCPBA). The scope of the reactions was explored, demonstrating high yields across a variety of functional groups and substituents. Optimized conditions enabled selective oxidation of thioaryl groups to sulfonyl or sulfinyl derivatives. Biological evaluation revealed that several compounds, especially 3-nitro-5-sulfonyl- and 5-sulfinylisoxazoles, exhibit potent antimicrobial activity against Gram-positive bacteria, fungi, and notably low MICs comparable to those of standard drugs. The mechanism of action studies indicate that these compounds induce the bacterial SOS response without inhibiting DNA synthesis-related enzymes such as DNA polymerase I, DNA gyrase, or topoisomerases I and IV, suggesting activation via bacterial reductases. These findings highlight the potential of these isoxazole derivatives as promising antimicrobial agents and provide new insights into their mechanism of action.

Nucleophilic ring-opening of bis(oxiranes), containing several reactive centers, can be used to elaborate straightforward atom-economy and stereoselective approaches to polyfunctionalized compounds. In the present work, ring-opening of cis- and trans-diastereomers of a spirocyclic bis(oxirane), containing a cyclooctane core (namely, 1,8-dioxadispiro[2.3.2.3]dodecane), upon treatment with various amines, was studied. Trans-isomer afforded aminoalcohols with 9-oxabicyclo[3.3.1]nonane moiety, formed via domino-process, including opening of an oxirane ring followed by intramolecular cyclization. Ring-opening of cis-isomer gave aminosubstituted cis-cyclooctane-1,5-diols, derived from independent reaction of two oxirane moieties. Activation of oxirane rings by the addition of LiClO4, acting as a Lewis acid, allowed the involvement of a number of primary and secondary aliphatic amines as well as aniline derivatives in the reaction. Scope and limitations of the reaction were studied and a series of aminoalcohols with a 9-oxabicyclo[3.3.1]nonane core and symmetric diaminodiols with a cyclooctane core were obtained.

The structures of isoxazole-containing cyclovinylogues of the intracellular fructose transporter protein GLUT5 inhibitor, N-(4-methylsulfonyl-2-nitrophenyl)benzo[d][1,3]dioxol-5- amine (MSNBA) were designed. The target substituted 3,4,5-isoxazoles were synthesized using a method for converting isoxazole-containing enamines to nitriles by their treatment with tert-butyl nitrite in the presence of boron trifluoride etherate. Primary bioassay demonstrated the ability of the target compounds to inhibit the proliferation of chronic myelogenous leukemia cells K562 in medium containing fructose or glucose.

Two series of novel 4-nitro-5-styrylisoxazoles (11 compounds) containing various macrocyclic substituents at positions 3 and 5 of the isoxazole cycle were obtained. Isoxazoles with macrocyclic signal unit in the styryl moiety demonstrated sensor properties in organic solvents to a number of metal cations (Mg(II), Ca(II), Zn(II), La(III), Al(III), Pb(II)). Aggregation-induced emission for the obtained dyes was found in the mixture of DMSO/H2O. In the presence of serum albumin, aggregates of macrocyclic styrylisoxazoles in an aqueous medium dissociated into monomers and formed complex with macromolecule. The compounds demonstrated cytoplasmic distribution in cells in two different forms as aggregates with ‘red’ fluorescence and dyes complexes with cellular proteins with ‘green’ fluorescence, which is promising for studying metabolic processes in the cell.

An efficient approach to previously unknown 5-cyano-4-nitroisoxazoles has been developed using nitrosation of 4-nitroisoxazole-based enamines with tert-butyl nitrite (TBN) followed by a BF3- or TFAA-mediated unusual C═C bond cleavage reaction. This two-step one-pot process is applicable to a broad range of substrates and provides the desired products in mild reaction conditions in moderate to high yields. The dichotomy of reactivity in the SNAr reaction of the resulting 5-cyano-4-nitroisoxazoles has been demonstrated by the cyano-group substitution with N-nucleophiles and the nitro-group substitution with thiophenols and rationalized with DFT-calculations.

A facile metal-free approach to 5-(1,2,3-triazol-1-yl)isoxazoles bearing a variety of functional groups in both heterocyles has been developed. A cyclization of 3-EWG-5-azidoisoxazoles with compounds possessing active methylene group proceeds smoothly under mild conditions in the presence of triethylamine or Cs2CO3 in alcohols or DMF affording fused hybrid triazole-isoxazole compounds in high yields up to 98%. Some mechanistic aspects of the cyclization reaction are discussed.

Pulmonary edema and acute respiratory failure, developing due to the vascular endothelium dysfunction, are common side effects of anticancer therapy. This study is the first approach to create an in vitro model system to estimate vascular response at the drug development/improvement stage and to determine whether it is possible to select an antitumor drug dose effectively suppressing malignant cells without a pathological effect on the endothelial cells function. In this study (1) the doses of several clinically used antitumor drugs suppressing the common tumor cell proliferation were determined experimentally; (2) the endothelial cell viability after exposure to selected doses of these drugs was assessed in vitro; (3) changes in the endothelial monolayer condition, as well as cultured endothelial cell reactions and intracellular disorders accompanying the effects of selected drugs doses were studied in vitro using the intravital observations and super-resolution microscopy methods. This approach allowed to select antitumor drug concentrations inhibiting cell proliferation in selected tumor lines, but having no critical effect on the viability of endothelial cells and their cytoskeletal structures. As the result, an in vitro model system for studying the side effects of medications on vascular permeability was created.

Steroid dimers of natural and synthetic origin possess an unusual and complex molecular architecture that may lead to the realization of peculiar effects in biological systems, in particular in different cancer cell lines. In the present work, diastereoselective ring-opening of mono- and polyoxiranes, containing a cyclooctane core, by azide-anion was performed to yield a series of azidoalcohols with different types of symmetry. The products were involved in copper-catalyzed azyde-alkyne cycloaddition (CuAAC) reaction with ethinylestradiol and ethinyltestosterone, and the resulting steroids and steroid dimers with triazole linkers were screened for their antiproliferative activity via (3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl tetrazolium bromide) assay. All the compounds revealed cytotoxicity toward several cancer cell lines. The effect of the most potent compound, containing two estradiol moieties, on the microtubules (MT) dynamics was investigated by immunofluorescent microscopy. The disruption of the majority of interphase cell cytoplasmic MT and mitotic event disturbances in the presence of the studied compound were observed. The latter effect caused the appearance of numerous multinucleated cells.

ABSTRACT A large series of previously unknown isoxazole containing difluoroboron β‐diketonate has been designed and synthesized from the available starting compounds. The photophysical properties of obtained compounds were studied, and the effects of the substituents in aromatic and isoxazole cycles of the BF 2 complexes on the fluorescence were investigated. The effect of solvatochromism were demonstrated. Cytotoxic activity against MCF‐7 (breast carcinoma), HCT‐116 (colon carcinoma), A549 (pulmonary carcinoma) and WI38 (fibroblasts from lung tissue) cell lines was tested and moderate toxicity in the concentration range of 10–100 μM was found for several compounds.

Nucleophilic ring-opening of 1,6,10,14-tetraoxatetraspiro[2.1.25.1.29.1.213.13]hexadecane, a cyclooctane structure spiro-fused with four oxirane fragments, under the action of sodium azide was studied. Depending on the relative configuration of stereocenters in the starting compound, the reaction proceeded as an intramolecular transannular cyclization with the formation of a 9-oxabicyclo[3.3.1]nonane skeleton or as an independent nucleophilic opening of the oxirane rings, leading to tetraazido tetraols of the cyclooctane series.

Positive allosteric modulators (PAMs) of AMPA receptors represent attractive candidates for the development of drugs for the treatment of cognitive and neurodegenerative disorders. Dimeric molecules have been reported to have an especially potent modulating effect, due to the U-shaped form of the AMPA receptor’s allosteric binding site. In the present work, novel bis(pyrimidines) were studied as AMPA receptor modulators. A convenient and flexible preparative approach to bis(pyrimidines) containing a hydroquinone linker was elaborated, and a series of derivatives with varied substituents was obtained. The compounds were examined in the patch clamp experiments for their influence on the kainate-induced currents, and 10 of them were found to have potentiating properties. The best potency was found for 2-methyl-4-(4-((2-methyl-5,6,7,8-tetrahydroquinazolin-4-yl)oxy)phenoxy)-6,7,8,9-tetrahydro-5H-cyclohepta[d]pyrimidine, which potentiated the kainate-induced currents by up to 77% in all tested concentrations (10−12–10−6 M). The results were rationalized via the modeling of modulator complexes with the dimeric ligand binding domain of the GluA2 AMPA receptor, using molecular docking and molecular dynamics simulation. The prediction of ADMET, physicochemical, and PAINS properties of the studied bis(pyrimidines) confirmed that PAMs of this type may act as the potential lead compounds for the development of neuroprotective drugs.

Nucleophilic ring-opening of 1,6,10,14-tetraoxatetraspiro[2.1.2(5).1.2(9).1.2(13).1(3)] hexadecane, a cyclooctane structure spiro-fused with four oxirane fragments, under the action of sodium azide was studied. Depending on the relative configuration of stereocenters in the starting compound, the reaction proceeded as an intramolecular transannular cyclization with the formation of a 9-oxabicyclo[3.3.1]nonane skeleton or as an independent nucleophilic opening of the oxirane rings, leading to tetraazido tetraols of the cyclooctane series.

This review considers the main approaches to the preparation of covalent organic perchlorates (COPs) and their chemical properties. COPs can be synthesized by the reactions of chlorine(VII) oxide with alcohols, alcoholates, and epoxides, the interaction of perchlorate anion with epoxides and alkenes, occurring upon activation of substrates by various electrophiles, and the oxidative nucleophilic substitution of alkyl halides. The reactivity of COPs is determined by the high nucleofugity of the perchlorate fragment, which makes them extremely active reagents in nucleophilic and electrophilic aromatic substitution reactions. A new direction in the study of the chemical properties of COPs is their interaction with nitriles, which is a modified version of the Ritter reaction.

1,2,3-Triazoles bearing additional functional groups have found applications as the ligands in catalysis of a broad scope of reactions, synthesis of transition metals complexes for various practicable purposes, and design of metal-based drugs. Triazolyl ligands accelerating CuAAC reactions, such as TBTA and TTTA, are nowadays commonly used in organic synthesis, and the search for novel ligands with a less complicated structure represents an important task. In the present work a series of hydroxyalkyltriazoles, containing a cyclooctane core, were synthesized via cycloaddition of readily available individual diastereomers of azidoalcohols or diazidodiols with phenylacetylene. The obtained hydroxyalkyltriazoles were probed as ligands for CuAAC reactions of benzyl azide with acetylenes, and 1-[(4-phenyl-1H-1,2,3-triazol-1-yl)methyl]cyclooctanol was demonstrated to act as an effective ligand for these processes. The complex salt of the abovementioned triazole and CuCl2 was readily obtained. According to X-ray diffraction analysis data, the complex contained two molecules of triazole, in which only N1-atoms of the triazole ring acted as coordination centers. Such a molecular structure correlates well with the efficiency of 1-[(4-phenyl-1H-1,2,3-triazol-1-yl)methyl]cyclooctanol as a ligand in CuAAC reactions: it is able to coordinate copper ions and, at the same time, it forms a sufficiently labile complex to not withdraw copper ions from the catalytic cycle.

Tick-borne encephalitis virus (TBEV), yellow fever virus (YFV), and West Nile virus (WNV) are flaviviruses causing emerging arthropod-borne infections of a great public health concern. Clinically approved drugs are not available to complement or replace the existing vaccines, which do not provide sufficient coverage. Thus, the discovery and characterization of new antiflaviviral chemotypes would advance studies in this field. In this study, a series of tetrahydroquinazoline N-oxides was synthesized, and the antiviral activity of the compounds was assessed against TBEV, YFV, and WNV using the plaque reduction assay along with the cytotoxicity to the corresponding cell lines (porcine embryo kidney and Vero). Most of the studied compounds were active against TBEV (EC50  2 to 33 μM) and WNV (EC50  0.15 to 34 μM) and a few also demonstrated inhibitory activity against YFV (EC50  0.18 to 41 μM). To investigate the potential mechanism of action of the synthesized compounds, time-of-addition (TOA) experiments and virus yield reduction assays were performed for TBEV. The TOA studies suggested that the antiviral activity of the compounds should affect the early stages of the viral replication cycle after cell entry. Compounds with tetrahydroquinazoline N-oxide scaffold show a broad spectrum of activity against flaviviruses and represent a promising chemotype for antiviral drug discovery.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Spirocyclic compounds containing heterocyclic moieties represent promising 3D scaffolds for modern drug design. In the search for novel anti-flaviviral agents, we have obtained a series of 3-[N,N-bis(sulfonyl)amino]isoxazolines containing spiro-annulated cyclooctane rings and assessed their antiviral activity against tick-borne encephalitis (TBEV), yellow fever (YFV), and West Nile (WNV) viruses. The structural analogs of spirocyclic compounds with a single sulfonyl group or 1,2-annulated cyclooctane ring were also investigated. Almost all the studied 3-[N,N-bis(sulfonyl)amino]isoxazolines revealed antiviral activity against TBEV and WNV. The most active against TBEV was spiro-isoxazoline derivative containing p-nitrophenyl groups in the sulfonyl part (EC50 2.0 ± 0.5 μM), while the highest potency against WNV was found for the compounds with lipophilic substituents in sulfonyl moiety, naphtyl being the most favorable one (EC50 1.3 ± 0.5 μM). In summary, two novel scaffolds of anti-flaviviral agents based on N,N-bis(sulfonyl)amino]isoxazoline were proposed, and the compounds of this type demonstrated activity against TBEV and WNV.