Thioxanthene-derived analogs as σ1 receptor ligands

An investigation of the structure–affinity relationships for the binding of thioxanthene-related structures indicates that an intact thioxanthene ring is not required for binding at σ1 receptors, and that with the appropriate structural modifications, affinity can be enhanced to the subnanomolar level. Certain of the analogs displayed >180-fold selectivity for σ1 versus σ2 receptors.