Synthesis and receptor binding studies of 3-substituted piperazine derivatives

In order to find novel receptor ligands various substituents were introduced into the side chain in position 3 of the piperazine 5. During nucleophilic substitution of the hydroxy group of 5 aziridinium ions were formed, resulting in rearranged 1,4-diazepanes and piperazines as side products. 1,2-anellated piperazines 15, 18 and 19 were prepared by hydrogenation of the α,β-unsaturated ester 13 and by condensation of the primary amine 16b with formaldehyde, respectively. Receptor binding studies with radioligands revealed that the phenylacetamide 17b interacts with moderate affinity (Ki = 181 nM) and considerable selectivity with σ1 receptors.

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