Privileged structures - dream or reality: preferential organization of azanaphthalene scaffold

The concept of privileged structures/substructures (PS) is the idea that certain structural features produce biological effects more often than others. The PS method can be seen as an offspring of fragonomics, which is based on recent experimental measurements of protein-ligand interactions. If PS prove to be true, then chemical motives that enrich biological activity can be used when designing new drugs. However, PS remain controversial because we cannot be sure whether the excess of active structures does not result from an abundance in chemical libraries. In this review, we will focus, in particular, on the preferential organization of azanaphthalene scaffolds (AN) in drugs and natural products (NP), which are preferred by Nature in evolution. We will show that knowledge discovery in molecular databases can reveal interesting time-trends profiles for important classes of potentially privileged scaffolds. The chemical library of AN is dominated by monoaza-compounds, among which quinoline appears to be the most frequently investigated scaffold; however; more sophisticated database mining seems to indicate different PS patterns within the AN scaffold family.