Divulging the regioselectivity of epoxides in the ring-opening reaction, and potential himachalene derivatives predicted to target the antibacterial activities and SARS-CoV-2 spike protein with docking study

•α-Himachalene could be a potential drug for SARS-CoV-2.•Bromine atoms located at the epoxy group in compound 8 increased the drug binding affinity.•The attack of the epoxide 1 and 2 by hydride ion H−presented a high regioselectivity. The ring-opening reaction of epoxides 1b and 1c utilizing LiAlH4, have been studied within the Molecular Electron Density Theory (MEDT) at the B3LYP/6–31(d) computational level. The regioisomeric reaction paths including the two oxiranes cycles of epoxides 1b and 1c have been explored. DFT calculations show that the attack of the hydride ion H− is favorable on the carbon C3 for the epoxide 1b, while this action is realized on carbon C2 for the epoxide 1c in the highest conformity with the experimental outcomes. Furthermore, we have operated a docking calculation to examine the antibacterial activities of the products 1a-1f, further more we have performed a docking calculation to scrutinize the products 1–9 against SARS-CoV-2. Indeed, the docking results showed that α-himachalene (2) possess a higher affinity to the main protease.