(Tétrahydro-1,2,3,6 pyridinyl-4)-3 1H-indoles: synthèse, propriétés sérotoninergique et anti-dopaminergiques

Synthesis and biological evaluation of novel 3-(5-substituted-1H-indol-3-yl)pyrrolidine-2,5-dione derivatives with a dual affinity for serotonin 5-HT1A receptor and SERT

The serotonin 1A (5-HT1A) receptors and serotonin transporter (SERT) are important biological targets in the treatment of diseases of the central nervous system, especially for depression. In this study, new 3-(1H-indol-3-yl)pyrrolidine-2,5-dione derivatives linked with the 3-(1,2,3,6-tetrahydropyridin-4-yl)-1H-indole moiety were synthesised and evaluated for their affinity for 5-HT1A receptor and serotonin reuptake inhibition. Selected compounds were then tested for their affinity for D2, 5-HT2A, 5-HT6 and 5-HT7 receptors, and also in in vitro metabolic stability assays in human microsomes. Finally, in vivo assays allowed us to evaluate the agonist-antagonist properties of pre- and postsynaptic 5-HT1A receptors. 3-(1-(4-(3-(5-methoxy-1H-indol-3-yl)-2,5-dioxopyrrolidin-1-yl)butyl)-1,2,3,6-tetrahydropyridin-4-yl)-1H-indole-5-carbonitrile (4f) emerged as the most promising compound from the series, due to its favourable receptor binding profile (Ki(5-HT1A) = 10.0 nM; Ki(SERT) = 2.8 nM), good microsomal stability and 5-HT1A receptor agonistic activity.

Identification of Bioactive Small Molecule Inhibitors of Separase

Separase, a cysteine protease of the CD clan, triggers chromosome segregation during mitosis by cleaving the cohesin ring entrapping the two sister chromatids. Deregulated separase activity is associated with aneuploidy, a hallmark of most human cancers. In fact, separase is highly overexpressed in many solid cancers, making it an attractive chemotherapeutic target. To identify small molecules capable of inhibiting separase in its complex cellular environment, we established a highly sensitive assay to quantify separase activity in cells and screened a 51 009-member library for separase inhibitors. In vitro assays confirmed that the identified compounds efficiently inhibited separase, while not affecting caspase-1, another CD-clan protease structurally related to separase. Importantly, HeLa cells with compromised separase activity displayed severe chromosome segregation defects upon compound treatment, confirming that the identified inhibitors are bioactive in tumor tissue culture cells. Structure-activity relationship studies succeeded in the optimization of the most promising inhibitor. Overall, this study demonstrates the feasibility of identifying separase-specific inhibitors, which serve as promising lead compounds for the development of clinically relevant separase inhibiting drugs.

Synthesis and biological evaluation of novel pyrrolidine-2,5-dione derivatives as potential antidepressant agents. Part 1

A series of 3-(1H-indol-3-yl)pyrrolidine-2,5-dione derivatives was synthesized and their biological activity was evaluated. The chemical structures of the newly prepared compounds were confirmed by (1)H NMR, (13)C NMR and ESI-HRMS spectra data. All tested compounds proved to be potent 5-HT1A receptor and serotonin transporter protein (SERT) ligands. Among them, compounds 15, 18, 19 and 30 showed significant affinity for 5-HT1A and SERT. Computer docking simulations carried out for compounds 15, 31 and 32 to models of 5-HT1A receptor and SERT confirm the results of biological tests. Due to high affinity for the 5-HT1A receptor and moderate affinity for SERT, compounds 31, 32, 35, and 37 were evaluated for their affinity for D2L, 5-HT6, 5-HT7 and 5-HT2A receptors. In vivo tests, in turn, resulted in determining the functional activity of compounds 15, 18, 19 and 30 to the 5-HT1A receptor. The results of these tests indicate that all of the ligands possess properties characteristic of 5-HT1A receptor agonists.

Systematic in vivo screening of a series of 1-propyl-4-arylpiperidines against dopaminergic and serotonergic properties in rat brain: a scaffold-jumping approach

A series of 1-propyl-4-arylpiperidines were synthesized and their effects on the dopaminergic and serotonergic systems tested in vivo and in vitro. Scaffold jumping among five- and six-membered bicyclic aryl rings attached to the piperidine ring had a marked impact on these effects. Potent and selective dopamine D(2) receptor antagonists were generated from 3-indoles, 3-benzoisoxazoles, 3-benzimidazol-2-one, and 3-benzothiophenes. In contrast, 3-benzofuran was a potent and selective inhibitor of monoamine oxidase (MAO) A. The effects of the synthesized compounds on 3,4-dihydroxyphenylacetic acid (DOPAC) levels correlated very well with their affinity for dopamine D(2) receptors and MAO A. In the 4-arylpiperidine series, the most promising compound for development was the 6-chloro-3-(1-propyl-4-piperidyl)-1H-benzimidazol-2-one (19), which displayed typical dopamine D(2) receptor antagonist properties in vivo but produced only a partial reduction on spontaneous locomotor activity. This indicates that the compound may have a lower propensity to induce parkinsonism in patients.

Biotin tethered homotryptamine derivatives: high affinity probes of the human serotonin transporter (hSERT)

Quantum dot conjugates of compounds capable of inhibiting the serotonin transporter (SERT) could form the basis of fluorescent probes for live cell imaging of membrane bound SERT. Additionally, quantum dot-SERT antagonist conjugates may be amenable to fluorescence-based, high-throughput assays for this transporter. This Letter describes the synthesis of SERT-selective ligands amenable to conjugation to quantum dots via a biotin-streptavidin binding interaction. SERT selectivity and affinity were incorporated into the ligand via a tetrahydropyridine or cyclohexylamine derivative and the affinity of these compounds for SERT was measured by their ability to produce SERT-dependent currents in Xenopus laveis oocytes.

Novel 4-aryl-pyrido[1,2-c]pyrimidines with dual SSRI and 5-HT(1A) activity. part 3

A number of 4-aryl-5,6,7,8-tetrahydropyrido[1,2-c]pyrimidine with 3-(1,2,3,6-tetrahydro-pyridin-4-yl)-1H-indole or 2-methyl-3-(1,2,3,6-tetrahydro-pyridin-4-yl)-1H-indole residues were synthesized for further investigation of SAR in a group of pyrido[1,2-c]pyrimidine derivatives with dual 5-HT(1A)/SERT activity. Compounds 8a-8p were found to be potent ligands for both 5-HT(1A) and SERT with K(i) ranging from 28,3 to 642 nM and 42,4 nM-1,8 μM, respectively. Moreover compounds 8a, 8b, 8c, 8d, 8e and 8g were found to be selective agonists, while 8i as an antagonist of 5-HT(1A) presynaptic receptors in the inducible hypothermia test in mice.

3-(4-(6-Fluoroalkoxy-3,4-dihydroisoquinoline-2(1H)-yl)cyclohexyl)-1H-indole-5-carbonitriles for SERT imaging: chemical synthesis, evaluation in vitro and radiofluorination

Aminocyclohexyl indoles bind with high affinity and specificity toward the serotonin transporter (SERT). Based on this structural lead, we designed fluoroalkoxydihydroisoquinoline-cyclohexyl indole carbonitriles for future application as (18)F-labeled tracers for SERT imaging by PET. Six compounds, three pairs of cis- and trans-isomer derivatives, respectively, were synthesized and evaluated in vitro. The chemistry of the new compounds, their affinity and specificity data, the general route to the phenolic precursor for labeling, and the successful (18)F-fluoroalkylation of one pair of compounds are described herein.

Synthesis and characterization of a pegylated derivative of 3-(1,2,3,6-tetrahydro-pyridin-4yl)-1H-indole (IDT199): a high affinity SERT ligand for conjugation to quantum dots

Quantum dots consisting of a cadmium selenide core encapsulated in a shell of cadmium doped zinc sulfide have the potential to revolutionize fluorescent imaging of live cell cultures. In order to utilize these fluorescent probes it is necessary to functionalize them with biologically active ligands. In this paper we report the design and synthesis of a ligand that has a high affinity for the serotonin transporter (SERT) that may be conjugated to quantum dots.

Conformationally restricted homotryptamines 3. Indole tetrahydropyridines and cyclohexenylamines as selective serotonin reuptake inhibitors

A series of indole tetrahydropyridine and indole cyclohexenylamines was prepared, and their binding affinities at the human serotonin transporter (SERT) were determined. In particular, a nitrile substituent at the C5 position of the indole ring gave potent SERT activity. The stereochemistry of the N,N-dimethylamine substituent was determined for the most potent indole cyclohexenylamine, 6a. The enantiomers of 6a were energy minimized and compared to other conformationally restricted SSRIs. Compound 6a was found to give a dose-response similar to the SSRI fluoxetine in microdialysis studies in rats.

A Study of 5-Nitroindole Alkylation

A detailed study of the 5-nitroindole alkylation, the key step in the synthesis of Zafirlukast, is presented. A broad distribution of alkyl derivatives has been found. 2,3- And 1,3-dialkylindoles can be selectively obtained in a ZnBr2-catalyzed reaction. Structure of all the products was fully assigned.

2-Alkyl-3-(1,2,3,6-tetrahydropyridin-4-yl)-1H-indoles as novel 5-HT6 receptor agonists

A series of 2-alkyl-3-(1,2,3,6-tetrahydropyridin-4-yl)-1H-indoles were synthesized and evaluated for their 5-HT6 activity. The most potent agonist in this series was 5-chloro-2-methyl-3-(1,2,3,6-tetrahydropyridin-4-yl)-1H-indole with an IC50=7.4 nM in 3H-LSD binding and an EC50=1.0 nM in a functional assay measuring production of cyclic AMP.

Conformationally restricted homotryptamines. 2. Indole cyclopropylmethylamines as selective serotonin reuptake inhibitors

A series of indole cyclopropylmethylamines were found to be potent serotonin reuptake inhibitors. Nitrile substituents at the 5 and 7 positions of the indole ring gave high affinity for hSERT, and the preferred cyclopropane stereochemistry was determined to be (1S,2S)-trans. The cis-cyclopropanes had 20- to 30-fold less affinity than the trans, and the preferred cis stereochemistry was (1R,2S)-cis. Substitution of the indole N-1 position with methyl or ethyl groups gave a 10- to 30-fold decrease in affinity for hSERT, suggesting either a hydrogen-bonding interaction or limited steric tolerance in the region of the indole nitrogen. Compound (+)-12a demonstrated potent hSERT binding (Ki = 0.18 nM) in vitro and was more than 1000-fold less potent at hDAT, hNET, 5-HT1A, and 5-HT6. In vivo, (+)-12a produced robust, dose-dependent increases in extracellular serotonin in rat frontal cortex typical of a selective serotonin reuptake inhibitor. The maximal response produced by (+)-12a was similar to that of fluoxetine but at an approximately 10-fold lower dose.

Inhibitors of the serotonin transporter protein (SERT): the design and synthesis of biotinylated derivatives of 3-(1,2,3,6-tetrahydro-pyridin-4-yl)-1H-indoles. High-affinity serotonergic ligands for conjugation with quantum dots

There is a growing demand for compounds with specificity for the serotonin transporter protein (SERT) that can be conjugated to cadmium selenide/zinc sulfide core shell nanocrystals. This letter describes the design and synthesis of two different biotinylated SERT antagonists that can be attached to streptavidin-coated cadmium selenide/zinc sulfide core shell nanocrystals.

Medicinal Chemistry Driven Approaches Toward Novel and Selective Serotonin 5-HT6Receptor Ligands

Based on a medicinal chemistry guided hypothetical pharmacophore model, novel series of indolyl sulfonamides have been designed and prepared as selective and high-affinity serotonin 5-HT(6) receptor ligands. Furthermore, based on a screening approach of a discovery library, a series of benzoxazinepiperidinyl sulfonamides were identified as selective 5-HT(6) ligands. Many of the compounds described in this paper possess excellent affinities, displaying pK(i) values greater than 8 (some even >9) and high selectivities against a wide range (>50) of other CNS relevant receptors. First, structure-affinity relationships of these ligands are discussed. In terms of functionality, high-affinity antagonists, as well as agonists and even partial agonists, were prepared. Compounds 19c and 19g represent the highest-affinity 5-HT(6) agonists ever reported in the literature. These valuable tool compounds should allow for the detailed study of the role of the 5-HT(6) receptor in relevant animal models of disorders such as cognition deficits, depression, anxiety, or obesity.

Binding affinity and biological activity of oxygen and sulfur isosteres at melatonin receptors as a function of their hydrogen bonding capability

Analogues of melatonin (1) and of N-acetyl 5-ethoxytryptamine (3) in which the oxygen atoms are replaced by sulfur have been prepared and tested against human and amphibian melatonin receptors. All sulfur analogues show a decreased binding affinity at human MT1 and MT2 receptors and a reduced potency as melatonin agonists on the Xenopus melanophore assay. The 5-methoxy oxygen of melatonin is significantly more important for receptor binding than the amide oxygen. N-Acetyl 5-ethoxytryptamine shows a decrease in both binding affinity and potency in comparison with melatonin. In this series, replacing either the ethoxy or amide oxygen by sulfur has a similar but smaller effect on both binding affinity and potency. Using K(B)(H) values from Abraham's equations we have assessed the possibility of estimating EC50 values for sulfur isosteres from the EC50 values of their oxygen analogues.

SLV310, a novel, potential antipsychotic, combining potent dopamine D2 receptor antagonism with serotonin reuptake inhibition

In this paper, SLV310 is presented as a novel, potential antipsychotic displaying the interesting combination of potent dopamine D(2) receptor antagonism and serotonin reuptake receptor inhibition in one molecule. As such, SLV310 could be useful in treating a broad range of symptoms in schizophrenia. This paper describes the structure-activity relationship in a series of compounds leading to SLV310 (6b, 2-[4-[4-(5-fluoro-1H-indol-3-yl)-3,6-dihydro-2H-pyridin-1-yl]-butyl]-phthalimide) together with pharmacological data showing the unique profile of this compound.

Studies towards the next generation of antidepressants. Part 1: Indolylcyclohexylamines as potent serotonin reuptake inhibitors

A series of indolylcyclohexylamines possessing potent and selective serotonin reuptake inhibition is reported. The most interesting compounds proved to have subnanomolar 5-HT transporter activity, and exhibited moderate 5-HT(1A) affinity.

Novel 3-(4-piperidinylthio)-1H-indoles as potent nonopioid orally active central analgesics

A series of 3-(4-piperidinylthio)-1H-indoles was synthesized and evaluated in mice in the phenylbenzoquinone(PBQ)-induced writhing and hot plate tests. Most of these compounds are good analgesics with activities comparable to that of morphine. Among them compound 1i (UP 237-61), which has a strong serotonin binding profile, has an interesting antinociceptive activity which is not reversed by naloxone.

5-HT reuptake inhibitors with 5-HT(1B/1D) antagonistic activity: a new approach toward efficient antidepressants

As part of our research program toward new, potential antidepressants, a series of unsymmetrical ureas has been prepared and evaluated as 5-HT reuptake inhibitors with 5-HT(1B/1D) antagonistic activities. The design of these compounds was based on coupling of various indole derivatives, previously shown to inhibit 5-HT reuptake, to three different aniline moieties, which are part of known 5-HT(1B/1D) ligands. Binding experiments in rat frontal cortex using [(125)I]iodocyanopindolol, in calf striatum using [(3)H]5-HT, and in rat hippocampus using [(3)H]8-OH-DPAT as radioligands, respectively, revealed significantly higher affinity at the 5-HT(1B) receptor as compared to the affinities for the 5-HT(1A) and 5-HT(1D) receptors for a number of compounds, among them 4-(5-fluoro-1H-indol-3-yl)piperidine-1-carboxylic acid [4-methoxy-3-(4-methylpiperazin-1-yl)phenyl]amide (5), the corresponding 4-fluoro-1H-indol-3-yl analogue 21a, and the corresponding 6-fluoro-1H-indol-3-yl analogue 21b. Conformational restriction of the aniline moiety in 5 only slightly enhanced the 5-HT(1B) affinity, whereas introduction of an aniline moiety with higher conformational flexibility resulted in a less potent 5-HT(1B) receptor ligand as compared to 5. The functional 5-HT(1B/1D) antagonistic activity was investigated using the rabbit saphenous vein model as well as the [(3)H]5-HT release from guinea pig cortical slices. All new compounds tested in the rabbit saphenous vein model were shown to antagonize the sumatriptan-evoked contractile responses with pA(2) values ranging from 7.3 to 8.7. These observations were consistent with the results of the cortical slice model, in which the ureas were found to block the sumatriptan-induced inhibition of potassium-evoked [(3)H]5-HT release. The 5-HT reuptake inhibition of the ureas determined in rat brain synaptosomes was found to be either increased or decreased as compared to the uncoupled indole derivatives indicating that the reuptake inhibition shown by the ureas is not only due to the indole part but also affected by the aniline moiety of the molecule. Among this series of compounds described the ureas 5, 21a, and 21b seem to be the most interesting candidates showing both 5-HT reuptake inhibition and 5-HT(1B/1D) antagonism in vitro. This dual pharmacological profile should in theory lead to a pronounced enhancement in serotonergic neurotransmission and consequently to a more efficient treatment of depression.

Characterization of [3H]CP-96,501 as a selective radioligand for the serotonin 5-HT1B receptor: binding studies in rat brain membranes

3-(1,2,5,6-Tetrahydro-4-pyridyl)-5-n-propoxyindole (CP-96,501) was found to be more selective ligand at the serotonin 5-HT1B receptor than the commonly used 5-HT1B agonist, 3-(1,2,5,6-tetrahydro-4-pyridyl)-5-methoxyindole (RU 24969). In rat brain membranes, the tritiated derivative, [3H]CP-96,501, was found to bind with a high affinity (KD, 0.21 nM) to a single binding site (nH, 1.0). The receptor density of this site (Bmax, 72 fmol/mg of protein) matched that of the 5-HT1B receptor determined with [3H]5-HT. Competition curves of 16 serotonergic compounds in [3H]CP-96,501 binding also indicated a single binding site. The rank order of their binding affinities with this new radioligand showed a high degree of correlation with their affinities at the 5-HT1B receptor determined with [3H]5-HT or [125I]iodocyanopindolol. Serotonergic compounds displayed competitive inhibition of [3H]CP-96,501 binding. In the presence of 5'-guanylylimidodiphosphate [Gpp(NH)p], [3H]CP-96,501 to displace [125I]iodocyanopindolol binding was also decreased. These findings are consistent with the agonist nature of CP-96,501. The results of this study suggest that [3H]CP-96,501 is a useful agonist radioligand for the 5-HT1B receptor.

Optically active benzamides as predictive tools for mapping the dopamine D2 receptor

Substituent variations on the pyrrolidinyl nitrogen of sulpiride, a selective D2 dopamine antagonist, showed that in vitro and in vivo activities are concentrated in the (S) optical series for N-alkyl analogs and in the (R) series for N-benzyl analogs. To account for these unusual structure-activity relationships, a pharmacophoric model was built from the crystallographic structure of (-)piquindone and extended to 14 other D2 antagonists. This model considers the lone pair orientation of the basic nitrogen rather than its spatial location. Two distinct active conformations for benzamides were defined, corresponding to the (S) and (R) series. An extended pharmacophore is then proposed involving four main anchoring areas: (i) an aromatic site Ar1, (ii) a tertiary nitrogen with its lone pair orthogonal to the Ar1 plane, (iii) a dipole delta 1 coplanar to the Ar1 ring and (iv) three sites for the N-substituent, including a small hydrophobic pocket and two different aromatic binding sites Ar2 and Ar3. To probe the predictive value of this model, structures were designed and several compounds were synthesized and tested as inhibitors of [125I]iodo-sulpiride binding to rat striatal membranes and as antagonists of apomorphine-induced stereotyped behavior in mice.