Natural-product-derived fragments for fragment-based ligand discovery

Fragment-based ligand and drug discovery predominantly employs sp 2 -rich compounds covering well-explored regions of chemical space. Despite the ease with which such fragments can be coupled, this focus on flat compounds is widely cited as contributing to the attrition rate of the drug discovery process. In contrast, biologically validated natural products are rich in stereogenic centres and populate areas of chemical space not occupied by average synthetic molecules. Here, we have analysed more than 180,000 natural product structures to arrive at 2,000 clusters of natural-product-derived fragments with high structural diversity, which resemble natural scaffolds and are rich in sp 3 -configured centres. The structures of the cluster centres differ from previously explored fragment libraries, but for nearly half of the clusters representative members are commercially available. We validate their usefulness for the discovery of novel ligand and inhibitor types by means of protein X-ray crystallography and the identification of novel stabilizers of inactive conformations of p38α MAP kinase and of inhibitors of several phosphatases. Natural products populate areas of chemical space not occupied by average synthetic molecules. Here, an analysis of more than 180,000 natural product structures results in a library of 2,000 natural-product-derived fragments, which resemble the properties of the natural products themselves and give access to novel inhibitor chemotypes.