Analysis of structure-activity data from a large corpus of medicinal chemistry literature identified a set of ring replacements that have a significant chance of improved biological activity. A database of these replacements for 245 common heterocyclic rings is provided. Based on the analysis of the whole data set, 80 diverse substituted rings are suggested for use in an early stage of hit optimization and in the design of focused libraries with the goal to explore structure-activity relationships and quickly improve the biological activity of the explored series. An easy to use Ring Replacement Recommender web tool, allowing medicinal chemists to interactively explore the recommended ring substitutions, is available at https://bit.ly/ringreplacement.

Bioisosteric replacement; Building blocks; Cheminformatics; Heterocyclic rings; Hit to lead optimization; Library design; Substituents