Effect of Aromatic System Expansion on Crystal Structures of 1,2,5-Thia- and 1,2,5-Selenadiazoles and Their Quaternary Salts: Synthesis, Structure, and Spectroscopic Properties.

Rational manipulation of secondary bonding interactions is a crucial factor in the construction of new chalcogenadiazole-based materials. This article reports detailed experimental studies on phenanthro[9,10-c][1,2,5]chalcogenadiazolium and 2,1,3-benzochalcogenadiazolium salts and their precursors. The compounds were synthesized, characterized employing NMR and UV-Vis spectroscopy. TD-DFT calculations were also performed. The influence of the size of the aromatic system on the molecular motifs formed by the compounds in the solid state has been studied by means of single-crystal X-ray diffraction. In case of the salts, the nature of an anion was also taken into consideration. The results show that cyclic [E···N]2 supramolecular synthon connects neighboring molecules of phenanthro[9,10-c][1,2,5]chalcogenadiazoles, with a relatively large aromatic system, in dimers regardless of the chalcogen atom in the molecule. Both N-methyl-2,1,3-benzothiadiazolium and N-methylphenanthro[9,10-c][1,2,5]chalcogenadiazolium cations have a strong affinity for triflate and iodide anions, therefore the formation of S···N or Se···N secondary bonding interactions is observed only in two out of the eight quaternary salts. Less coordinating anions must be used to enable the building blocks studied to form cyclic [E···N]2 synthons. Moreover, for two of the triflate salts, which are isostructural, a new supramolecular motif has been observed.

In vivo evaluation of the CB1 allosteric modulator LDK1258 reveals CB1-receptor independent behavioral effects.

In the present study, we examined whether LDK1258, which produces strong CB1 receptor allosteric effects in in vitro assays, would elicit in vivo effects consistent with allosteric activity. In initial studies, LDK1258 reduced food consumption and elicited delayed antinociceptive effects in the chronic constrictive injury of the sciatic nerve (CCI) model of neuropathic pain, which unexpectedly emerged 4 h post-injection. UPLC-MS/MS analysis quantified significant levels of LDK1258 in both blood and brain tissue at 30 min post-administration that remained stable up to 4 h. The observation that LDK1258 also produced respective antinociceptive and anorectic effects in rimonabant-treated wild type mice and CB1 (-/-) mice suggests an off-target mechanism of action. Likewise, LDK1258 produced a partial array of common cannabimimetic effects in the tetrad assay, which were not CB1 receptor mediated. Additionally, LDK1258 did not substitute for the CB1 receptor orthosteric agonists CP55,940 or anandamide in the drug discrimination paradigm. In other in vivo assays sensitive to CB1 receptor allosteric modulators, LDK1258 failed to shift the dose-response curves of either CP55,940 or anandamide in producing thermal antinociception, catalepsy, or hypothermia, and did not alter the generalization curve of either drug in the drug discrimination assay. Thus, this battery of tests yielded results demonstrating that LDK1258 produces antinociceptive effects in the CCI model of neuropathic pain, anorectic effects, and other in vivo pharmacological effects in a manner inconsistent with CB1 receptor allosterism. More generally, this study offers a straightforward screening assay to determine whether newly synthesized CB1 receptor allosteric modulators translate to the whole animal.

(4-(Bis(4-fluorophenyl)methyl)piperazin-1-yl)(cyclohexyl)methanone hydrochloride (LDK1229): a new cannabinoid CB1 receptor inverse agonist from the class of benzhydryl piperazine analogs.

Some inverse agonists of cannabinoid receptor type 1 (CB1) have been demonstrated to be anorectic antiobesity drug candidates. However, the first generation of CB1 inverse agonists, represented by rimonabant (SR141716A), otenabant, and taranabant, are centrally active, with a high level of psychiatric side effects. Hence, the discovery of CB1 inverse agonists with a chemical scaffold distinct from these holds promise for developing peripherally active CB1 inverse agonists with fewer side effects. We generated a new CB1 inverse agonist, (4-(bis(4-fluorophenyl)methyl)piperazin-1-yl)(cyclohexyl)methanone hydrochloride (LDK1229), from the class of benzhydryl piperazine analogs. This compound binds to CB1 more selectively than cannabinoid receptor type 2, with a Ki value of 220 nM. Comparable CB1 binding was also observed by analogs 1-[bis(4-fluorophenyl)methyl]-4-cinnamylpiperazine dihydrochloride (LDK1203) and 1-[bis(4-fluorophenyl)methyl]-4-tosylpiperazine hydrochloride (LDK1222), which differed by the substitution on the piperazine ring where the piperazine of LDK1203 and LDK1222 are substituted by an alkyl group and a tosyl group, respectively. LDK1229 exhibits efficacy comparable with SR141716A in antagonizing the basal G protein coupling activity of CB1, as indicated by a reduction in guanosine 5'-O-(3-thio)triphosphate binding. Consistent with inverse agonist behavior, increased cell surface localization of CB1 upon treatment with LDK1229 was also observed. Although docking and mutational analysis showed that LDK1229 forms similar interactions with the receptor as SR141716A does, the benzhydryl piperazine scaffold is structurally distinct from the first-generation CB1 inverse agonists. It offers new opportunities for developing novel CB1 inverse agonists through the optimization of molecular properties, such as the polar surface area and hydrophilicity, to reduce the central activity observed with SR141716A.

Optimization of chemical functionalities of indole-2-carboxamides to improve allosteric parameters for the cannabinoid receptor 1 (CB1).

5-Chloro-3-ethyl-N-(4-(piperidin-1-yl)phenethyl)-1H-indole-2-carboxamide (1; ORG27569) is a prototypical allosteric modulator for the cannabinoid type 1 receptor (CB1). Here, we reveal key structural requirements of indole-2-carboxamides for allosteric modulation of CB1: a critical chain length at the C3-position, an electron withdrawing group at the C5-position, the length of the linker between the amide bond and the phenyl ring B, and the amino substituent on the phenyl ring B. These significantly impact the binding affinity (KB) and the binding cooperativity (α). A potent CB1 allosteric modulator 5-chloro-N-(4-(dimethylamino)phenethyl)-3-propyl-1H-indole-2-carboxamide (12d) was identified. It exhibited a KB of 259.3 nM with a strikingly high binding α of 24.5. We also identified 5-chloro-N-(4-(dimethylamino)phenethyl)-3-hexyl-1H-indole-2-carboxamide (12f) with a KB of 89.1 nM, which is among the lowest KB values obtained for any allosteric modulator of CB1. These positive allosteric modulators of orthosteric agonist binding nonetheless antagonized the agonist-induced G-protein coupling to the CB1 receptor, yet induced ß-arrestin mediated ERK1/2 phosphorylation.

Helicity discrimination in N,N'-dibenzoyl-1,2,3,4,7,8,9,10-octahydro-1,10-phenanthrolines and their thiono- and selenocarbonyl analogues by inclusion complexation with chiral diols.

X-ray crystallographic analysis of the title compounds revealed that they assume a folded helical conformation of an approximate C2 symmetry in the solid state. Dithioamide 5b, diselenoamide 5c and monoselenoamide 5d were resolved to enantiomers by inclusion crystallization with optically active diols (TADDOLs). The absolute configuration of the guest molecules in the complexes 5b·6a, 5c·6a and 5d·6a was assigned as P. The optical activity of the resolved compounds is manifested by their CD spectra showing relatively strong Cotton effects in the region of thionoamide and selenoamide n­π* transition. The optically active thiono- and selenoamides are configurationally labile compounds and gradually racemize in solution but they are stable in the form of the inclusion complexes. The first-order kinetics of the racemization in solution allowed us to assign the racemization barriers by the spectropolarimetric measurements.

(R,R)-1-Acetyl-1'-(2,4,6-trinitro-phen-yl)-2,2'-bipyrrolidine.

The structure of the title mol-ecule, C16H19N5O7, is mainly determined by the steric effect of a bulky 2,4,6-trinitro-phenyl group attached to the N atom of a pyrrolidine ring. Both pyrrolidine rings adopt an envelope conformation, with one of the methylene C atoms as the flap in each case, and the N-C-C-N torsion angle along the bond connecting the two pyrrolidine rings is -174.9 (2)°. The benzene ring of the 2,3,5-trinitro-phenyl substituent is deformed and the r.m.s. deviation of its six atoms from the best plane is 0.026 Å. The N atoms of the two nitro groups in the ortho positions deviate from the best plane of the benzene ring by -0.033 (5) and 0.385 (5) Å. These groups, as well as the pyrrolidine ring, are twisted relative to the aromatic ring in the same direction, their best planes forming dihedral angles of 30.2 (2), 64.8 (1) and 46.6 (2)°, respectively, with the ring. An intra-molecular C-H⋯O hydrogen bond occurs. In the crystal, there is a short [O⋯C = 3.019 (4) Å] contact between a nitro O atom and a C atom of the benzene ring bearing the nitro group and a C-H⋯O inter-action between a methyl H atom and another nitro O atom.

Helicity discrimination in diaryl dichalcogenides generated by inclusion complexation with chiral hosts.

Inclusion complexation of diaryl dichalcogenides with either cholic acid or chiral diols results in their helicity discrimination and an induction of optical activity that can be detected by solid-state CD measurements.

Enantiomeric resolution of N,N'-dimethyldithiodianthranilide through diastereomeric silver(I) complex. Circular dichroism spectra, racemization barrier, and molecular self-assembly.

Planar chiral N,N'-dimethyldithiodianthranilide (2b) was resolved to enantiomers through a diasteromeric complex with easily accessible silver(I) (1S)-camphorosulfonate (3). The (-)-2b enantiomer was assigned the R absolute configuration from the X-ray crystal structure of the silver complex. The compound is configurationally stable and its racemization occurs through boat-to-boat ring inversion (DeltaG(double dagger) = 36.5 +/- 0.2 kcal mol(-1) at 438 K). The analysis of the CD spectrum of the title compound showed that the n-pi* Cotton effect sign is determined by the helicity of the skewed thiobenzamide chromophore. The molecules of 2b are unable to achieve efficient crystal packing by themselves and easily form inclusion complexes with toluene or pentafluorophenol.

The novel cannabinoid CB1 receptor neutral antagonist AM4113 suppresses food intake and food-reinforced behavior but does not induce signs of nausea in rats.

Drugs that interfere with cannabinoid CB1 transmission suppress various food-motivated behaviors, and it has been suggested that such drugs could be useful as appetite suppressants. Biochemical studies indicate that most of these drugs assessed thus far have been CB1 inverse agonists, and although they have been shown to suppress food intake, they also appear to induce nausea and malaise. The present studies were undertaken to characterize the behavioral effects of AM4113, which is a CB1 neutral antagonist, and to examine whether this drug can reduce food-reinforced behaviors and feeding on diets with varying macronutrient compositions. Biochemical data demonstrated that AM4113 binds to CB1 receptors, but does not show inverse agonist properties (ie no effects on cyclic-AMP production). In tests of spontaneous locomotion and analgesia, AM4113 reversed the effects of the CB1 agonist AM411. AM4113 suppressed food-reinforced operant responding with rats responding on fixed ratio (FR) 1 and 5 schedules of reinforcement in a dose-dependent manner, and also suppressed feeding on high-fat, high-carbohydrate, and lab chow diets. However, in the same dose range that suppressed feeding, AM4113 did not induce conditioned gaping, which is a sign of nausea and food-related malaise in rats. These results suggest that AM4113 may decrease appetite by blocking endogenous cannabinoid tone, and that this drug may be less associated with nausea than CB1 inverse agonists.

A neutral CB1 receptor antagonist reduces weight gain in rat.

Cannabinoid (CB)1 receptor inverse agonists inhibit food intake in animals and humans but also potentiate emesis. It is not clear whether these effects result from inverse agonist properties or from the blockade of endogenous cannabinoid signaling. Here, we examine the effect of a neutral CB1 antagonist, AM4113, on food intake, weight gain, and emesis. Neutral antagonist and binding properties were confirmed in HEK-293 cells transfected with human CB1 or CB2 receptors. AM4113 had no effect on forskolin-stimulated cAMP production at concentrations up to 630 nM. The Ki value of AM4113 (0.80 +/- 0.44 nM) in competitive binding assays with the CB1/2 agonist [3H]CP55,940 was 100-fold more selective for CB1 over CB2 receptors. We determined that AM4113 antagonized CB1 receptors in brain by blocking hypothermia induced by CP55,940. AM4113 (0-20 mg/kg) significantly reduced food intake and weight gain in rat. Compared with AM251, higher doses of AM4113 were needed to produce similar effects on food intake and body weight. Unlike AM251 (5 mg/kg), a highly anorectic dose of AM4113 (10 mg/kg) did not significantly potentiate vomiting induced by the emetic morphine-6-glucoronide. We show that a centrally active neutral CB1 receptor antagonist shares the appetite suppressant and weight loss effects of inverse agonists. If these compounds display similar properties in humans, they could be developed into a new class of antiobesity agents.

Planar chiral dianthranilide and dithiodianthranilide molecules: optical resolution, chiroptical spectra, and molecular self-assembly.

Planar chiral dianthranilide (1) was resolved to enantiomers with use of (-)-(1S,4R)-camphanoyl chloride as a chiral derivatizing agent. The (+)-1 enantiomer was assigned the S absolute configuration from the X-ray crystal structure of its N,N'-dicamphanoyl derivative. Optical resolution of dithionodianthranilide (2) was accomplished by inclusion crystallization with (R,R)-1,2-diaminocyclohexane, and the X-ray structure of the corresponding adduct revealed the (-)-2stereoisomer has the R configuration. A slow boat-to-boat ring inversion (DeltaG(++) = 24.1 +/- 0.1 kcal mol(-1)) causes racemization of (+)-1 in solution as manifested by a gradual decrease of the CD spectrum whereas, (-)-2 is configurationally stable at these conditions. The analysis of the CD spectra of the title compounds showed that the n-pi* Cotton effect signs are determined by the helicity of the skewed benzamide and thiobenzamide chromophores. The solid-state structures of the racemic and homochiral forms of 1 and 2 show different self-assembly patterns: the racemate (+/-)-1 prefers the cyclic R(2)(2)(8) hydrogen bond motif, whereas the crystalline DMSO solvates of (+/-)-1 and (+)-1 consist of 1D homochiral hydrogen-bonded assemblies generated by the C(6) motif. In the case of dithionolactams (+/-)-2 and (-)-2 two types of 1D networks were observed: in the racemate they are generated by the centrosymmetric R(2)(2)(8) and R(2)(2)(12) hydrogen bond motifs, whereas the molecules in the homochiral crystals are connected solely with use of the strongly nonplanar R(2)(2)(8) motif.

2,4,6-Trimethylbenzamide.

The crystal structure of the title compound, C(10)H(13)NO, displays an infinite one-dimensional network composed of primary amide molecules connected by N-H...O[double bond]C hydrogen bonds involving the anti NH amide H atoms, thus generating a C(4) motif. This network is additionally stabilized by a weak N-H...pi interaction between the syn-oriented amide H atom and the aromatic ring of a neighbouring molecule. The distance between the H atom and the ring centroid is 2.50 A. The amide group and the aryl moiety are nearly perpendicular, forming an intramolecular dihedral angle of 84.69 (6) degrees.