Synthesis and binding assays of novel 3,3-dimethylpiperidine derivatives with various lipophilicities as σ₁ receptor ligands.

Starting from two carbocyclic analogs, a series of 3,3-dimethylpiperidine derivatives was prepared and tested in radioligand binding assays at σ(1) and σ(2) receptors, and at Δ(8)-Δ(7) sterol isomerase (SI) site. The novel compounds mostly bear heterocyclic rings or bicyclic nucleus of differing lipophilicities. Compounds 18a and 19a,b demonstrated the highest σ(1) affinity (K(i)=0.14-0.38 nM) with a good selectivity versus σ(2) binding. Among them, 18a had the lowest ClogD value (3.01) and only 19b was selective versus SI too. Generally, it was observed that more planar and hydrophilic heteronuclei conferred a decrease in affinity for both σ receptor subtypes.