During application of reaction rules, structures deemed to be chemically unstable were sometimes produced which are unlikely to appear in real chemistry. The exponential growth in the number of species produced with each generation also quickly made the computation resource heavy. To ameliorate these issues, each computed product was examined for sterically problematic or "bad" substructures, and a molecular weight (MW) cutoff filter was applied (herein 200 amu). Any species containing a bad substructure or exceeding the prescribed MW limit created during reaction generation was discarded from the network. This helped to both clean bad products and limit the size of the product space input to the next generation, making further generation computation more tractable The forbidden "bad" structures were selected based on literature precedent (e.g., ), as well as those included in MolGen 5.0 85 , see SI File 2), e.g., three-and four-membered rings were excluded as they are typically unstable due to their large ring strain . Some chemically implausible substructures (e.g., structures with double bonds at bridgehead carbons, which violate Bredt's rule were also specifically forbidden. This filtering reduces the computational load for succeeding generations, and since each product must be computed before it is checked, limiting mass growth helps avoid "combinatorial explosions", which allows computation of more iterations than would otherwise be possible.