1. PNP_Status. Compounds were assigned to one of four categories according to their NP fragment combination graphs. The NP library fragments used for this purpose are Murcko scaffolds (the core structures containing all rings without substituents except for double bonds, n=1673) derived from a representative set of 2000 NP fragment clusters. Because of their ubiquitous appearances in NPs, the phenyl ring and glucose moieties were specifically excluded as fragments. The phenyl ring however does appear in some fragments, combined with other ring systems. The categories are: