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The standard assay for the determination of σ1 receptor affinities of novel compounds is a competitive binding assay using [3H]-(+)-pentazocine as radioligand and membrane preparations from guinea pig brain. Herein, a novel competitive binding assay was developed employing the hematopoietic cell line of human multiple myeloma (RPMI 8226), which expresses a large amount of the human σ1 receptor. Membrane fragments of RPMI 8226 cells were prepared and characterized. A Western blot analysis confirmed the high density of σ1 receptors in this cell line. Assay conditions were carefully optimized leading to an incubation period of 120 min, an incubation temperature of 37°C, and receptor material for each well was prepared from 300,000 cells. It was shown that a large excess (10 μM) of (+)-pentazocine, haloperidol, and di-o-tolylguanidine provided the same results during determination of the nonspecific binding. Saturation experiments with the radioligand [3H]-(+)-pentazocine led to a K d -value of 36±0.3 nM and a B max -value of 477±7 fmol/mg protein. These data resulted in approximately 122,000 σ1 binding sites per cell. The assay was validated by using six known σ1 ligands and eight σ1 ligands prepared in our lab. The K i -values determined with RPMI 8226-derived receptor material are in good accordance with the K i -values obtained with guinea pig brain membrane preparations. Compared with guinea pig brain preparations, the RPMI 8226-derived receptor material represents a better standardized receptor material with a high density of human σ1 receptors. [ABSTRACT FROM AUTHOR]

It has been reported that bioisosteric replacement of an 1,2,4-oxadiazole ring by an 1,3,4-oxadiazole ring leads to higher polarity, reduced metabolic degradation by human liver microsomes and reduced interaction with hERG channels. In a seven to eight step synthesis 1,3,4-oxadiazles 9a-c were synthesized as bioisosteric analogs of high-affinity but rather lipophilic CB 2 ligands 1a-c containing an 1,2,4-oxadiazole ring. The 1,3,4-oxadiazole derivatives 9a and 9b show 10- and 50-fold reduced CB 2 affinity compared to the 1,2,4-oxadiazole derivatives 1a and 1b , respectively. However, the 1,3,4-oxadiazole 9a has high CB 2 affinity ( K i = 25 nM) and high selectivity over the CB 1 receptor.

The title compounds, C22H29NO2 (3) and C22H29NO2 (4) [systematic names: (1S*,2R*)-7-meth-oxy-2-methyl-3-(4-phenyl-but-yl)-2,3,4,5-tetra-hydro-1H-3-benzazepin-1-ol and (1R*,2R*)-7-meth-oxy-2-methyl-3-(4-phenyl-but-yl)-2,3,4,5-tetra-hydro-1H-3-benzazepin-1-ol, are diastereomers with the relative configuration of the adjacent hydroxyl and methyl groups at the seven-membered azepine ring being trans in (3) and cis in (4). In the crystals the orientation of these groups is -anti-periplanar (3) and +syn-clinal (4). In both cases, the crystals studied proved to be of a racemic mixture, with relative configurations (R*,S*)-3 and (R*,R*)-4. In both compounds, the seven-membered azepine ring has a chair-like conformation, and the 4-phenyl-butyl side chain adopts a extended conformation in (R*,S*)-3, but a twisted conformation in (R*,R*)-4. In the crystal of (S*,R*)-3, mol-ecules are linked via C-H⋯O hydrogen bonds, forming slabs parallel to the ac plane. In the crystal of (R*,R*)-4, mol-ecules are linked via O-H⋯N hydrogen bonds, forming chains propagating along the c-axis direction. The chains are linked by C-H⋯O hydrogen bonds, forming slabs parallel to the ac plane.

In the title compound, C25H27NO4S, which crystallized as a racemate, the relative configuration of the adjacent OH and CH3 groups on the azepine ring is trans. The seven-membered azepin ring has a chair-like conformation. The planar aromatic rings of the benzyl and tosyl-ate moiety are inclined to the planar 3-benzazepine ring by 78.39 (15) and 77.03 (14)°, respectively, and to each another by 13.82 (15)°. In the crystal, mol-ecules are linked via O-H⋯O and C-H⋯O hydrogen bonds, forming double-stranded chains along the a-axis direction. The chains are linked via C-H⋯π inter-actions, forming a three-dimensional architecture.

A large set of tetrahydro-2-benzazepines with an α-hydroxy or α-(aryl)alkoxy substituted benzyl moiety in the 5-position was prepared according to the recently reported C6C1 + C3N synthetic strategy. The Heck reaction of 2-iodobenzaldehyde acetal 4 and the subsequent Stetter reaction led to the ketone 7, which was reduced diastereoselectively to form the like-configured alcohol 8. The diastereomeric unlike-configured alcohol 9 was obtained by a Mitsunobu inversion of 8. Alkylation and reductive cyclization of the diastereomeric alcohols 8 and 9 provided like- and unlike-configured 2-benzazepines 13 and 23, which allowed the introduction of various substituents at the N-atom. Analysis of the relationship between the structure and the σ1 affinity revealed that large substituents such as the butyl, benzyl or 4-phenylbutyl moiety at the benzazepine N-atom resulted in high affinity ligands. A p-methoxybenzyl ether is less tolerated by the σ1 receptor than a methyl ether or an alcohol. The unlike-configured alcohols 25d and 27d show slightly higher σ1 affinity than their like-configured diastereomers 15d and 17d. With respect to the σ1 affinity, σ1/σ2 selectivity and lipophilic ligand efficiency, like- and unlike-configured alcohols 15d and 25d represent the most promising σ1 ligands of this series. Interactions of the novel 2-benzazepines with various binding sites of the NMDA receptor were not observed.

In order to increase the polarity of the potent CB2 ligand 1a, the homologous hydroxyalkyl carbazoles 2a-c were prepared and pharmacologically evaluated. An important step in the synthesis is the hydroxyalkylation of carbazole with cyclic sulfates providing the 2-hydroxyethyl and 3-hydroxypropyl derivatives 5a and 5b in a one-step reaction. The final propionamides 2a-c were prepared using the recently reported coupling reagent COMU®. The X-ray crystal structure of 2c displays an almost coplanar arrangement of the 3-phenyl-1,2,4-oxadiazole biaryl system. The increased polarity of 2a is associated with an almost 100-fold reduced CB2 affinity. The 3-hydroxypropyl derivative 2b represents the best compromise between lipophilicity and CB2 affinity (Ki  = 33 nM)., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)