Synthesis and evaluation of N-cycloberberine derivatives as a novel class of anti-SARS-CoV-2 pseudovirus agents

There is no specific drug against COVID-19, but berberine (BBR) has moderate anti-SARS-CoV-2 pseudovirus activity. Taking BBR as the lead, 18 novel N-cycloberberine derivatives were synthesized and evaluated for their anti-SARS-CoV-2 pseudovirus activities in vitro. Structure-activity relationship analysis revealed that introducing an appropriate heterocyclic group at position 9 might be beneficial for potency. Among the tested compounds, compound 3m showed the most potent activity against SARS-CoV-2, with EC₅₀ value of 1.61 μmol·L^-1 and SI value of 22.2, much better than that of BBR. Additional experiment indicated that 3m had inhibitory activity on multiple processes in viral invasion, including adsorption and membrane fusion, suggesting a multi-target synergistic mechanism of action. These results provide a novel family of lead compounds for the discovery of anti-SARS-CoV-2 candidates.