Figure 1. Structure of the lead compoud SM27 and the new identified hits, clustered according to structural features: mono-naphthalenes (SM.1 series) and bi-naphthalenes (SM.2 series).

For the most active SM.2 compounds, the main stereochemical requirements for binding and activity are colored: blue, urea bridge between the two napthalenes; orange, sulfonate-decorated additional naphtyl-azo group; purple, free amines on the two arylamine decorations in SM.2–18; red, substituents on the aryl-azo group.