Analysis of Benzenoid Substitution Patterns in Small Molecule Active Pharmaceutical Ingredients

Previous analyses have revealed that benzenoid rings are prevalent scaffolds in active pharmaceutical ingredients (APIs). Here, we analyze the substitution patterns of benzenoid rings in small molecule APIs approved by the FDA through 2019 and show that only a few substitution patterns (1-, 1,2-, 1,4-, and 1,2,4-) prevail, and the distribution has remained relatively constant over time. We postulate the connection between available synthetic methods and the occurrence of a few benzenoid substitution patterns by providing an overview of synthetic methods that elaborate existing substitution patterns and those that create new substitution patterns, including those of the former that are favored by medicinal chemists. Finally, we calculated medicinal chemistry properties of benzenoid containing APIs that are often used by practitioners as design elements, including druglikeness, shape, complexity, and similarity/diversity and discuss these properties in the context of synthesis.