Rapid preparation of triazolyl substituted NH-heterocyclic kinase inhibitors via one-pot Sonogashira coupling-TMS-deprotection-CuAAC sequence.

The one-pot, three-component Sonogashira coupling-TMS-deprotection-CuAAC ("click") sequence is the key reaction for the rapid synthesis of triazolyl substituted N-Boc protected NH-heterocycles, such as indole, indazole, 4-, 5-, 6-, and 7-azaindoles, 4,7-diazaindole, 7-deazapurines, pyrrole, pyrazole, and imidazole. Subsequently, the protective group was readily removed to give the corresponding triazolyl derivatives of these tremendously important NH-heterocycles. All compounds have been tested in a broad panel of kinase assays. Several compounds, 8f, 8h, 8k, and 8l, have been shown to inhibit the kinase PDK1, a target with high oncology relevance, and thus they are promising lead structures for the development of more active derivatives. The X-ray structure analysis of compound 8f in complex with PDK1 has revealed the detailed binding mode of the molecule in the kinase.

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.

Dual 5-HT1A agonists and 5-HT re-uptake inhibitors by combination of indole-butyl-amine and chromenonyl-piperazine structural elements in a single molecular entity.

The dual serotonin (5-HT) re-uptake inhibitor and 5-HT(1A) receptor agonist vilazodone was found to increase central serotonin levels in rat brain. In the course of structural modifications of vilazodone 3-[4-[4-(2-oxo-2H-1-benzopyran-6-yl)-1-piperazinyl]-butyl]-1H-indole-5-carbonitrile 8i and its fluorine analogue 6-[4-[4-(5-fluor-3-indolyl)-butyl]-1-piperazinyl]-2H-1-benzopyran-2-one have been identified. These unsubstituted chromenones are equally potent at the 5-HT(1A) receptor and 5-HT transporter. The implementation of nitrogen functionalities in position 3 of the chromenones resulted in compounds acting as agonists at the 5-HT(1A) receptor and as 5-HT re-uptake inhibitors like vilazodone. Ex vivo 5-HT re-uptake inhibition and in vitro 5-HT agonism were determined in the PCA- and GTPgammaS-assay, respectively. The potential of these chromenones to increase central 5-HT levels was measured in microdialysis studies and especially the derivatives 3-[4-[4-(3-amino-2-oxo-2H-chromen-6-yl)-piperazin-1-yl]-butyl]-1H-indole-5-carbonitrile 8f, ethyl (6-[4-[4-(5-cyano-1H-indol-3-yl)-butyl]-piperazin-1-yl]-2-oxo-2H-chromen-3-yl)-carbamate 8h and N-(6-[4-[4-(5-cyano-1H-indol-3-yl)-butyl]-piperazin-1-yl]-2-oxo-2H-chromen-3-yl)-acetamide 8k give rise to rapid development of increased serotonin levels in rat brain cortex, lasting longer than 3h.

Indolebutylamines as selective 5-HT(1A) agonists.

A series of new 1-[4-(indol-3-yl)butyl]-4-arylpiperazines was prepared to identify highly selective and potent 5-HT(1A) agonists as potential pharmacological tools in studies of mood disorders. The combination of structural elements (indole-alkyl-amine and aryl-piperazine) known to introduce 5-HT(1A) receptor affinity and the proper selection of substituents (R on the indole moiety and R' on the aryl moiety) led to compounds with high receptor specificity and affinity. In particular, the introduction of the methyl ether or the unsubstituted carboxamide as substituents in position 5 of the indole (R) guaranteed serotonergic 5-HT(1A) affinity compared to the unsubstituted analogue. Para-substituted arylpiperazines (R') decreased dopaminergic D(2) binding and increased selectivity for the 5-HT(1A) receptor. Agonistic 5-HT(1A) receptor activity was confirmed in vivo in the ultrasonic vocalization test, and the results suggest that the introduction of the carboxamide residue leads to better bioavailability than the corresponding methyl ether. 3-[4-[4-(4-Carbamoylphenyl)piperazin-1-yl]butyl]-1H-indole-5-carboxamide 54 was identified as a highly selective 5-HT(1A) receptor agonist [GTPgammaS, ED(50) = 4.7 nM] with nanomolar 5-HT(1A) affinity [IC(50) = 0.9 nM] and selectivity [D(2), IC(50) > 850 nM]. 3-[4-[4-(4-Methoxyphenyl)piperazin-1-yl]butyl]-1H-indole-5-carboxamide 45 is one of the most potent and selective 5-HT(1A) agonists known [5-HT(1A), IC(50) = 0.09 nM; D(2), IC(50) = 140 nM].

Synthesis and structure--activity relationship in a class of indolebutylpiperazines as dual 5-HT(1A) receptor agonists and serotonin reuptake inhibitors.

Systematic structural modifications of indolealkylphenylpiperazines led to improved selectivity and affinity within this class of 5-HT(1A) receptor agonists. Introduction of electron-withdrawing groups in position 5 on the indole raises serotonin transporter affinity, and the cyano group proved to be the best substituent here. 5-Fluoro and 5-cyano substituted indoles show comparable results in in vitro and in vivo tests, and bioisosterism between these substituents was supported by calculation of the molecular electrostatic potentials and dipole moments. Compounds showing promising in vitro data were further examined in ex vivo (p-chloroamphetamine assay) and in vivo (ultrasonic vocalization) tests. Optimization of the arylpiperazine moiety indicated that the 5-benzofuranyl-2-carboxamide was best suited to increase 5-HT transporter and 5-HT(1A) receptor affinity and to suppress D(2) receptor binding. 5-[4-[4-(5-Cyano-3-indolyl)butyl]-1-piperazinyl]benzofuran-2-carboxamide 29 (vilazodone, EMD 68843) was identified as a highly selective 5-HT(1A) receptor agonist [GTPgammaS, ED(50) = 1.1 nM] with subnanomolar 5-HT(1A) affinity [IC(50) = 0.2 nM] and as a subnanomolar 5-HT reuptake inhibitor [RUI = 0.5 nM] showing a great selectivity to other GPCRs (e.g., D(2), IC(50) = 666 nM).