Design, Synthesis, Antiviral Evaluation, and Molecular Dynamics Simulation Studies of New Spirocyclic Thiopyrimidinones as Anti HCoV-229E.

The current pandemic threat presented by viral pathogens like SARS-CoV-2 (COVID-19) suggests that virus emergence and dissemination are not geographically confined. As a result, the quest for antiviral agents has become critical to control this pandemic. In the current study, we provide a novel family of spirocyclic thiopyrimidinone derivatives whose cytotoxicity and antiviral efficacy were investigated against human coronavirus 229E (HCoV-229E) as a model for the Coronaviridae family. We utilized MTT and cytopathic effect (CPE) inhibitory tests on green monkey kidney (vero-E6) cell lines. The new molecules showed varied degrees of antiviral activity against the vero-E6 cell lines with minimal cytotoxicity. With a high level of a selective index (SI=14.8), compound 9 showed outstanding inhibitory ability and could effectively suppress the human coronavirus 229E. Molecular dynamics simulation (MD) studies were performed to measure the interaction and stability of the protein-ligand complex in motion. The MD results for the most active compound 9 explored remarkable interactions with the binding pockets of the main protease (Mpro) of SARS-CoV-2 enzyme confirming the results gained from in vitro experiments. ADMET properties were also predicted for all the tested compounds. All these results demonstrated that the novel spirocyclic thiopyrimidinone derivatives would have the potential to be safe, low-cost chemical compounds that might be used as a novel therapeutic option for Coronaviridae viruses like COVID-19.

Synthetic Access to All Four Stereoisomers of Oxetin.

A short synthesis of all four stereoisomers of 3-amino-2-oxetanecarboxylic acid (oxetin) is described. The oxetane core is built using a Paternò-Büchi photochemical [2 + 2] cycloaddition; from the key intermediates, complementary resolution protocols provide access to enantiomerically pure oxetin and epi-oxetin on gram-scale.

Cooperative 5- and 10-membered ring interactions in the 10-helix folding of oxetin homo-oligomers.

Homo-oligomers of the natural product oxetin (cis-3-amino-2-oxetanecarboxylic acid) were prepared and their conformational behaviour studied in solution and solid state and by molecular modelling. The predominant secondary structure was a 10-helix, propiciously stabilized by a network of 5-membered ring H-bonds implicating ring oxygens and neighboring amide hydrogen atoms.