Natural products (NPs) inspire the design and synthesis of novel biologically relevant chemical matter,f or instance through biology-oriented synthesis (BIOS). However, BIOS is limited by the partial coverageo fN P-like chemical space by the guiding NPs.The design and synthesis of "pseudo NPs" overcomes these limitations by combining NP-inspired strategies with fragment-based compound design through de novo combination of NP-derived fragments to unprecedented compound classes not accessible through biosynthesis. We describe the development and biological evaluation of pyrano-furo-pyridone (PFP) pseudo NPs,w hichc ombine pyridone-and dihydropyran NP fragments in three isomeric arrangements.C heminformatic analysis indicates that the PFPs reside in an area of NP-like chemical space not covered by existing NPs but rather by drugs and related compounds. Phenotypic profiling in atarget-agnostic "cell painting" assay revealed that PFPs induce formation of reactive oxygen species and are structurally novel inhibitors of mitochondrial complex I.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.