Quaternary protoberberine alkaloids and quaternary benzophenanthridine alkaloids are two biosynthetically related natural product families of biological importance. Although significant advances have been achieved in the synthetic chemistry of these alkaloids, a unified approach to these tetracyclic pyridinium-contained alkaloids remains elusive until our recent report. Herein, we report a concise, modular, divergent approach to two of them, pseudoberberine and nitidine, based on our newly developed strategy in five and seven steps. The key transformations include an Ag-promoted annulation, an isoquinoline-directed C-H vinylation, and switchable aza-6 pi- or all-carbon-6 pi-electrocyclization. (C) 2021 Elsevier Ltd. All rights reserved.