The novel class of spirocyclic σ1 ligands 3 (6′, 7′-dihydro-1′ H-spiro [piperidine-4, 4′- pyrano [4, 3-c] pyrazoles]) was designed by the combination of the potent σ1 ligands 1 and 2 in one molecule. Thorough structure affinity relationships were derived by the variation of the substituents in position 1′, 1, and 6′. Whereas the small electron rich methylpyrazole heterocycle was less tolerated by the σ1 receptor protein, the introduction of a phenyl ...
