Further optimization of compound 1 to engage pi-pi interactions with Trp-88 and Phe-91 from a pyridine substituent can be envisioned (Figure ). Interestingly, the eutomer observed in the co-crystal structures exhibits the (R,R) configuration, not matching the stereochemistry of the original player designed compound with the (R,S) configuration, but does maintain the key pharmacophores (Figure ).