Issue 38, 2023

Diastereoselective synthesis and structure–affinity relationships of σ1 receptor ligands with spirocyclic scaffold

Abstract

Spirocyclic scaffolds play an increasing role in drug discovery as they define a rigid three-dimensional space to increase specific interactions with protein binding sites. Herein, a spirocyclic center was introduced into the lead compound 1 to rigidify its flexible benzylaminoethyl side chain. The key step of the synthesis was the reaction of different α,β-unsaturated amides 6 and 13–16 with methyl acrylate in the presence of TBDMSOTf. DFT calculations explain the mechanism of this transformation as concerted Diels–Alder reaction (functionals B3LYP and TPSS) or double (aza)-Michael addition (functionals PBE and wB97X-D). After separation of the diastereomeric spirocyclic products 8 and 17–20, LiAlH4 reduction provided the spirocyclic hydroxymethyl piperidines 21a,b–25a,b showing low nanomolar σ1 affinity (Ki < 100 nM). trans-Configured ligands (a-series) showed higher or equal σ1 affinity and higher selectivity over σ2 receptors and GluN2B-NMDA receptors than their cis-configured analogs (b-series). The additional hydroxymethyl moiety brings the log D7.4 value in a promising range. The high σ1 affinity (Ki = 3.6 nM) and the low lipophilicity result in the highest lipophilic ligand efficiency for the dispiro compound 23a (LLE = 6.0). The spirocyclic compounds reported herein and in particular the dispiro compound 23a demonstrate that ligands containing a large number of sp3 C-atoms possess favorable pharmacological (σ1 receptor affinity, receptor selectivity) and physicochemical properties (log D7.4 value) resulting in promising LLE.

Graphical abstract: Diastereoselective synthesis and structure–affinity relationships of σ1 receptor ligands with spirocyclic scaffold

Supplementary files

Article information

Article type
Paper
Submitted
24 Jul 2023
Accepted
04 Sep 2023
First published
04 Sep 2023

Org. Biomol. Chem., 2023,21, 7730-7752

Diastereoselective synthesis and structure–affinity relationships of σ1 receptor ligands with spirocyclic scaffold

T. Winge, D. Schepmann, J. Schmidt, C. Daniliuc, E. Würthwein and B. Wünsch, Org. Biomol. Chem., 2023, 21, 7730 DOI: 10.1039/D3OB01169K

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