Substituents of life: The most common substituent patterns present in natural products
Bioorganic & Medicinal Chemistry, 54,116562 (2022)
Download list of the most common substituents present in natural products npsubstituents.txt.

Database of 4 million medicinal chemistry relevant ring systems
Journal of Chemical Information and Modelling, accpeted (2024)
Download database of 3,931,782 ring systems in SMILES format