Pd-Catalyzed Direct C–H Bond Functionalization of Spirocyclic σ<sub>1</sub> Ligands: Generation of a Pharmacophore Model and Analysis of the Reverse Binding Mode by Docking into a 3D Homology Model of the σ<sub>1</sub> Receptor
作者:Christina Meyer、Dirk Schepmann、Shuichi Yanagisawa、Junichiro Yamaguchi、Valentina Dal Col、Erik Laurini、Kenichiro Itami、Sabrina Pricl、Bernhard Wünsch
DOI:10.1021/jm300894h
日期:2012.9.27
To explore the hydrophobic binding region of the sigma(1) receptor protein, regioisomeric spirocyclic thiophenes 9-11 were developed as versatile building blocks. Regioselective alpha- and beta-arylation using the catalyst systems PdCl2/bipy/Ag2CO3 and PdCl2/P[OCH(CF3)(2)](3)/Ag2CO3 allowed the introduction of various aryl moieties at different positions in the last step of the synthesis. The increasing sigma(1) affinity in the order 4 < 5/6 < 7/8 indicates that the positions of the additional aryl moiety and the S atom in the spirocyclic thiophene systems control the sigma(1) affinity. The main features of the pharmacophore model developed for this class of sigma(1) ligands are a positive ionizable group, a H-bond acceptor group, two hydrophobic moieties, and one hydrophobic aromatic group. Docking of the ligands into a sigma(1) 3D homology model via molecular mechanics/Poisson-Boltzmann surface area calculations led to a very good correlation between the experimentally determined and estimated free energy of receptor binding. These calculations support the hypothesis of a reverse binding mode of ligands bearing the aryl moiety at the "top" (compounds 2, 3, 7, and 8) and "left" (compounds 4, 5, and 6) positions, respectively.