Cocaine isosterism

Similarly, Carroll et al. (176)reported that the 1,2,4-oxadiazoles (e.g., 37) that are bio-isosteres of ester groups, are potent cocaine analogs. Compound (37) had low nanomolar affinity for the dopamine uptake transporter with greater than 100-fold selectivity for the dopamine transporter over the norepinephrine and serotonin transporters. 

Requirement for the Intact Tropane Ring System. We have seen earlier that there is no absolute requirement for the basic nitrogen in the tropane structure, and that even a polar oxygen isostere replacement is not needed for cocaine congeners to possess potent... 

---