1,4,9,9-tetramethyloctahydro-4,7-(epoxymethano)azulen-5(1H)-one, a natural product as a potential inhibitor of COVID-19: Extraction, crystal structure, and virtual screening approach

In the present work, we describe the extraction of a natural product namely 1,4,9,9-tetramethyloctahydro-4,7-(epoxymethano)azulen-5(1H)-one, and its structure was confirmed by single crystal X-ray diffraction analysis. The conformations of the 5-, 6-, and 7-membered rings in the title compound, C15H24O2, have been probed by a Cremer-Pople puckering analysis. C—H···O hydrogen bonds generate chains in the crystal that stretch along the c-axis direction. The Hirshfeld surface analysis method was used to stabilize the crystal packing of the natural compound. Accompanied by experimental studies, quantum chemical calculations were also performed to compare the structural elucidation and the results of these geometrical parameters exhibited excellent agreement. The compound was also docked with several drug targets of the SARS-CoV-2 virus and found to show the best binding with the main protease enzyme, having a binding energy of -12.31 kcal/mol and interacting with His41 and Cys145 residues. The dynamic stability deciphered the complex to be stable with an average RMSD of 3.8 Å. The compound dynamics with the enzyme showed the compound conformation to be highly stable. The intermolecular binding free energy determined the compound-main protease enzyme to show high interaction energy of < 40 kcal/mol. Together, these studies demonstrate the compound to be a lead structure against SARS-CoV-2.

1,4,9,9-tetramethyloctahydro-4,7-(epoxymethano)azulen-5(1H)-one, a natural product as a potential inhibitor of COVID-19: Extraction, crystal structure, and virtual screening approach.

In the present work, we describe the extraction of a natural product namely 1,4,9,9-tetramethyloctahydro-4,7-(epoxymethano)azulen-5(1H)-one, and its structure was confirmed by single crystal X-ray diffraction analysis. The conformations of the 5-, 6-, and 7-membered rings in the title compound, C15H24O2, have been probed by a Cremer-Pople puckering analysis. C-H···O hydrogen bonds generate chains in the crystal that stretch along the c-axis direction. The Hirshfeld surface analysis method was used to stabilize the crystal packing of the natural compound. Accompanied by experimental studies, quantum chemical calculations were also performed to compare the structural elucidation and the results of these geometrical parameters exhibited excellent agreement. The compound was also docked with several drug targets of the SARS-CoV-2 virus and found to show the best binding with the main protease enzyme, having a binding energy of -12.31 kcal/mol and interacting with His41 and Cys145 residues. The dynamic stability deciphered the complex to be stable with an average RMSD of 3.8 Å. The compound dynamics with the enzyme showed the compound conformation to be highly stable. The intermolecular binding free energy determined the compound-main protease enzyme to show high interaction energy of < 40 kcal/mol. Together, these studies demonstrate the compound to be a lead structure against SARS-CoV-2.

Synthesis, X-ray crystal structure, Hirshfeld surface analysis and computational investigation into the potential inhibitory action of novel 6-(p-tolyl)-2-((p-tolyl)thio)methyl-7H-[1.2.4]triazolo[5,1-b][1,3,4]thiadiazine inhibits the main protease of COVID-19.

In recent times, the novel coronavirus disease (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has now become a worldwide pandemic. With over 71 million confirmed cases, even though the effectiveness and side effects of the specific drugs and vaccines approved for this disease are still limited. Scientists and researchers from all across the world are working to find a vaccine and a cure for COVID-19 by using large-scale drug discovery and analysis. Heterocyclic compounds are regarded to be valuable sources for the discovery of new antiviral medications against SARS-CoV-2 because virus occurrences are still on the rise, and infectivity and mortality may also rise shortly. In this regard, we have synthesized a new triazolothiadiazine derivative. The structure was characterized by NMR spectra and confirmed by X-ray diffraction analysis. The structural geometry coordinates of the title compound are well reproduced by DFT calculations. NBO and NPA analyses have been performed to determine the interaction energies between bonding and antibonding orbital, and natural atomic charges of heavy atoms. Molecular docking suggests that the compounds may have good affinity for SAR-CoV-2 main protease, RNA-dependent RNA polymerase and nucleocapsid enzymes, particularly the main protease enzyme (binding energy of -11.9 kcal mol-1). The predicted docked pose of the compound is dynamically stable and reports a major van der Waals contribution (-62.00 kcal mol-1) to overall net energy.Communicated by Ramaswamy H. Sarma.

Potential SARS-CoV-2 RdRp inhibitors of cytidine derivatives: Molecular docking, molecular dynamic simulations, ADMET, and POM analyses for the identification of pharmacophore sites.

The RNA-dependent RNA polymerase (RdRp) of SARS-CoV-2 is one of the optimum targets for antiviral drug design and development. The hydroxyl groups of cytidine structures were modified with different aliphatic and aromatic groups to obtain 5´-O-acyl and 2´,3´-di-O-acyl derivatives, and then, these derivatives were employed in molecular modeling, antiviral prediction, molecular docking, molecular dynamics, pharmacological and POM studies. Density functional theory (DFT) at the B3LYP/6-31G++ level analyzed biochemical behavior and molecular electrostatic potential (MESP) of the modified cytidine derivatives. The antiviral parameters of the mutated derivatives revealed promising drug properties compared with those of standard antiviral drugs. Molecular docking has determined binding affinities and interactions between the cytidine derivatives and SARS-CoV-2 RdRp. The modified derivatives strongly interacted with prime Pro620 and Lys621 residues. The binding conformation and interactions stability were investigated by 200 ns of molecular dynamics simulations and predicted the compounds to firmly dock inside the RdRp binding pocket. Interestingly, the binding residues of the derivatives were revealed in high equilibrium showing an enhanced binding affinity for the molecules. Intermolecular interactions are dominated by both Van der Waals and electrostatic energies. Finally, the pharmacokinetic characterization of the optimized inhibitors confirmed the safety of derivatives due to their improved kinetic properties. The selected cytidine derivatives can be suggested as potential inhibitors against SARS-CoV-2. The POM Theory supports the hypothesis above by confirming the existence of an antiviral (Oδ--O'δ-) pharmacophore site of Hits.

One-pot synthesis, X-ray crystal structure, and identification of potential molecules against COVID-19 main protease through structure-guided modeling and simulation approach.

Although antimicrobial resistance before the Covid-19 pandemic is a top priority for global public health, research is already ongoing on novel organic compounds with antimicrobial and antiviral properties in changing medical environments in connection with Covid 19. Thanks to the Biginelli reaction, which allows the synthesis of pyrimidine compounds, blockers of calcium channels, antibodies, antiviral, antimicrobial, anti-inflammatory, or antioxidant therapeutic compounds were investigated. In this paper, we aim to present Biginelli's synthesis, its therapeutic properties, and the structural-functional relationship in the test compounds that allows the synthesis of antimicrobial compounds. Both the DFT and TD-DFT computations of spectral data, molecular orbitals (HOMO, LUMO) analysis, and electrostatic potential (MEP) surfaces are carried out as an add-on to synthetic research. Hirshfeld surface analysis was also used to segregate the different intermolecular hydrogen bonds involved in the molecular packing strength. Natural Bond Orbital (NBO) investigation endorses the existence of intermolecular interactions mediated by lone pair, bonding, and anti-bonding orbitals. The dipole moment, linear polarizability, and first hyperpolarizabilities have been explored as molecular parameters. All findings based on DFT exhibit the best consistency with experimental findings, implying that synthesized molecules are highly stable. To better understand the binding mechanism of the SARS-CoV-2 Mpro, we performed molecular docking, molecular dynamics (MD) simulations, and binding free energy calculations.

Synthesis, crystal structure, and a molecular modeling approach to identify effective antiviral hydrazide derivative against the main protease of SARS-CoV-2.

In the fall of 2019, a new type of coronavirus took place in Wuhan city, China, and rapidly spread across the world and urges the scientific community to develop antiviral therapeutic agents. In our effort we have synthesized a new hydrazide derivative, (E)-N'-(1-(4-bromophenyl)ethylidene)-2-(6-methoxynaphthalen-2-yl)propanehydrazide for this purpose because of its potential inhibitory proprieties. The asymmetric unit of the title molecule consists of two independent molecules differing noticeably in conformation. In the crystal, the independent molecules are linked by N-H···O and C-H···O hydrogen bonds and C-H···π(ring) interactions into helical chains extending along the b-axis direction. The chains are further joined by additional C-H···π(ring) interactions into the full 3-D structure. To obtain a structure-activity relationship, the DFT-NBO analysis is performed to study the intrinsic electronic properties of the title compound. Molecular modeling studies were also conducted to examine the binding affinity of the compound for the SARS-CoV-2 main protease enzyme and to determine intermolecular binding interactions. The compound revealed a stable binding mode at the enzyme active pocket with a binding energy value of -8.1 kcal/mol. Further, stable dynamics were revealed for the enzyme-compound complex and reported highly favorable binding energies. The net MMGBSA binding energy of the complex is -37.41 kcal/mol while the net MMPBSA binding energy is -40.5 kcal/mol. Overall, the compound disclosed the strongest bond of ing the main protease enzyme and might be a good lead for further structural optimization.

Synthesis and Identification of Novel Potential Molecules Against COVID-19 Main Protease Through Structure-Guided Virtual Screening Approach.

The novel coronavirus disease that arises in the end of 2019 (COVID-19) in Wuhan, China, has rapidly spread over the globe and was considered as a world pandemic. Currently, various antiviral therapies or vaccines are available, and many researches are ongoing for further treatments. Targeting the coronavirus' main protease (key enzyme: 3CLpro) is growing in importance in anti-SARS-CoV-2 drug discovery process. The present study aims at predicting the antiviral activity of two novel compounds using in silico approaches that might become potential leads against SARS-CoV-2. The 3D structures of the new compounds are elucidated by single-crystal X-ray techniques. The interactions between different units of 4 and 5 were emphasized by analyzing their corresponding Hirshfeld surfaces and ESP plots. NBO and FMO analyses were investigated as well. Molecular docking combined with molecular dynamics simulations (MDs) was performed to investigate the binding modes and molecular interactions of 4 and 5 with the amino acids of coronavirus main protease (6LU7) protein. The best docking scores were obtained for both ligands through the major binding interactions via hydrogen/hydrophobic bonds with the key amino acids in the active site: HIS41, CYS145, MET49, MET165, HIS172, and GLU166 amino acids. A MD simulation study was also performed for 100 ns to validate the stability behavior of the main protease 3CLpro-ligand complexes. The MD simulation study successfully confirmed the stability of the ligands in the binding site as potent anti-SARS-CoV-2 (COVID-19) inhibitors. Additionally, MMPBSA energy of both docked complexes was determined as a validation assay of docking and MD simulations to validate compound conformation and interaction stability with 3CLpro. The synthesized compounds might be helpful in the fight against COVID-19 prior to biological activity confirmation in vitro and in vivo.