Phenylpiperazine derivatives with strong affinity for 5HT1A, D2A and D3 receptors

Recent advances in dopamine D2 receptor ligands in the treatment of neuropsychiatric disorders

Dopamine is a biologically active amine synthesized in the central and peripheral nervous system. This biogenic monoamine acts by activating five types of dopamine receptors (D_1-5 Rs), which belong to the G protein-coupled receptor family. Antagonists and partial agonists of D₂ Rs are used to treat schizophrenia, Parkinson's disease, depression, and anxiety. The typical pharmacophore with high D₂ R affinity comprises four main areas, namely aromatic moiety, cyclic amine, central linker and aromatic/heteroaromatic lipophilic fragment. From the literature reviewed herein, we can conclude that 4-(2,3-dichlorophenyl), 4-(2-methoxyphenyl)-, 4-(benzo[b]thiophen-4-yl)-1-substituted piperazine, and 4-(6-fluorobenzo[d]isoxazol-3-yl)piperidine moieties are critical for high D₂ R affinity. Four to six atoms chains are optimal for D₂ R affinity with 4-butoxyl as the most pronounced one. The bicyclic aromatic/heteroaromatic systems are most frequently occurring as lipophilic appendages to retain high D₂ R affinity. In this review, we provide a thorough overview of the therapeutic potential of D₂ R modulators in the treatment of the aforementioned disorders. In addition, this review summarizes current knowledge about these diseases, with a focus on the dopaminergic pathway underlying these pathologies. Major attention is paid to the structure, function, and pharmacology of novel D₂ R ligands, which have been developed in the last decade (2010-2021), and belong to the 1,4-disubstituted aromatic cyclic amine group. Due to the abundance of data, allosteric D₂ R ligands and D₂ R modulators from patents are not discussed in this review.

Coumarin-piperazine derivatives as biologically active compounds

A number of psychiatric disorders, including anxiety, schizophrenia, Parkinson's disease, depression and others CNS diseases are known to induce defects in the function of neural pathways sustained by the neurotransmitters, like dopamine and serotonin. N-arylpiperazine moiety is important for CNS-activity, particularly for serotonergic and dopaminergic activity. In the scientific literature there are many examples of coumarin-piperazine derivatives, particularly with arylpiperazines linked to a coumarin system via an alkyl liner, which can modulate serotonin, dopamine and adrenergic receptors. Numerous studies have revealed that the inclusion of a piperazine moiety could occasionally provide unexpected improvements in the bioactivity of various biologically active compounds. The piperazine analogs have been shown to have a potent antimicrobial activity and they can also act as BACE-1 inhibitors. On the other hand, arylpiperazines linked to coumarin derivatives have been shown to have antiproliferative activity against leukemia, lung, colon, breast, and prostate tumors. Recently, it has been reported that coumarin-piperazine derivatives exhibit a Fneuroprotective effect by their antioxidant and anti-inflammatory activities and they also show activity as acetylcholinesterase inhibitors and antifilarial activity. In this work we provide a summary of the latest advances in coumarin-related chemistry relevant for biological activity.

Highly Selective Dopamine D3 Receptor Antagonists with Arylated Diazaspiro Alkane Cores

A series of potent and selective D3 receptor (D3R) analogues with diazaspiro alkane cores were synthesized. Radioligand binding of compounds 11, 14, 15a, and 15c revealed favorable D3R affinity (Ki = 12-25.6 nM) and were highly selective for D3R vs D3R (ranging from 264- to 905-fold). Variation of these novel ligand architectures can be achieved using our previously reported 10-20 min benchtop C-N cross-coupling methodology, affording a broad range of arylated diazaspiro precursors.

Development of selective agents targeting serotonin 5HT1A receptors with subnanomolar activities based on a coumarin core

A series of 18 new 5-[3-(4-aryl-1-piperazinyl)propoxy]coumarin derivatives from the corresponding bromoalkyl derivatives have been designed and synthesized by us using a microwave-assisted protocol. Radioligand binding assays of this series of compounds as well as a previously synthesized series of 17 structurally-similar compounds showed that six systems have very high affinities to the 5-HT1A receptor (0.3-1.0 nM) and good selectivity against the 5-HT2A receptor. Molecular docking, structural studies and structure-activity relationship studies were used to gain more insight into the atomistic details of ligand binding and rationalize the obtained results.

Synthesis of a new series of aryl/heteroarylpiperazinyl derivatives of 8-acetyl-7-hydroxy-4-methylcoumarin with low nanomolar 5-HT1A affinities

We synthesized a series of aryl/heteroarylpiperazinyl derivatives of 8-acetyl-7-hydroxy-4-methylcoumarin and evaluated their antidepressant-like activity. We used a fast, microwave-assisted synthesis protocol and ¹H, ¹³C NMR and HRMS spectrometry to confirm the structure of all compounds. We also used radioligand binding assays to determine the affinities towards 5-HT_1A and 5-HT_2A receptors and performed molecular docking studies to rationalize obtained results. Among the evaluated compounds seven displayed high affinity to the 5-HT_1A (3a-1.3 nM, 5a-1.6 nM, 10a-1.6 nM, 11a-1.0 nM, 3b-1.0 nM, 5b-0.8 nM and 11b-1.5 nM) as well as significant 5-HT_1A antagonist profiles. The equilibrium dissociation constant values of tested compounds shown differential intrinsic activity (3a-190 nM, 3b-28 nM, 5a-48 nM, 5b-23 nM, 10b-180 nM, 11a-99 nM, 11b-38 nM) of antagonist mode. Molecular docking studies using a homology model of 5-HT_1A revealed that ligand 5b is stabilized mainly by hydrogen bonds to Ser190.

Antifungal activity of umbelliferone derivatives: Synthesis and structure-activity relationships

Umbelliferone was an important allelochemical with a wide spectrum bioactivity. In our previous study, C7 hydroxy in the backbone of umbelliferone was identified to be responsible for its phytotoxicity and the targeted modification of the above site could lead to the phytotoxicity loss. In view of this, a series of hydroxycoumarins and C7 O-substituted umbelliferone derivatives were efficiently synthesized to evaluate their antifungal activity against four phytopathogenic fungi. Most of them, as we predicted, exhibited improved fungicidal activity. The phytotoxicity of effective compounds was also assayed by Lactuca sativa to investigate their side effects on plant growth. Compounds 9 and 17 were identified to show strong antifungal activity with low phytotoxicity. A brief investigation on structure-activity relationships revealed that the modification at the C7 hydroxy of umbelliferone could be a promising way to enhance the antifungal activity with decreasing the phytotoxicity.

Implication of coumarins towards central nervous system disorders

Coumarins are widely distributed, plant-derived, 2H-1-benzopyran-2-one derivatives which have attracted intense interest in recent years as a result of their diverse and potent pharmacological properties. Particularly, their effects on the central nervous system (CNS) have been established. The present review discusses the most important pharmacological effects of natural and synthetic coumarins on the CNS, including their interactions with benzodiazepine receptors, their dopaminergic and serotonergic affinity, and their ability to inhibit cholinesterases and monoamine oxidases. The structure-activity relationships pertaining to these effects are also discussed. This review posits that natural or synthetic coumarins have the potential for development in the therapy of psychiatric and neurodegenerative disorders, including Alzheimer's and Parkinson's diseases, schizophrenia, anxiety, epilepsy, and depression.

New arylpiperazines with flexible versus partly constrained linker as serotonin 5-HT(1A)/5-HT(7) receptor ligands

A series of new long-chain arylpiperazine (LCAP) derivatives with flexible and partly constrained alkyl linker were synthesized and investigated in vitro as potential serotonin 5-HT(1A) and 5-HT(7) receptor ligands. The compounds were prepared by a two-step procedure using naphthalimide and 2H-1,3-benzoxazine-2,4(3H)-dione as imides, and 1-(2-methoxyphenyl)piperazine (o-OMe-PhP) and 1,2,3,4-tetrahydroisoquinoline (THIQ) as amine pharmacophores. Modifications of the spacer structure included introduction of flexible penta- and hexamethylene chains as well as partly constrained m- and p-xylyl moieties. In general, the new compounds were more active at the 5-HT(1A) than at the 5-HT(7) receptor, and the o-OMe-PhP derivatives displayed higher affinities than their respective THIQ analogs. The spacer modifications had little effect on the observed in vitro activities. Within the o-OMe-PhP series, except for a small binding reduction for ligands containing the m-xylyl moiety, there was no substantial change in the compounds' potency at both receptors, while for the THIQ derivatives a clear structure-activity relationship was visible only for the interaction of the compounds with the 5-HT(7) receptor, which strongly favored flexible analogs.

Synthesis and anti-bacterial screening of ethyl 6-oxo-3-phenyl-1,6-dihydropyrano[3,2-e]indole-2-carboxylate and 7-phenyl-5H-pyrano [3′,2′:4,5]indolo[1,2-a]quinoxaline-6,10-dione

Ethyl 6-oxo-3-phenyl-1,6-dihydropyrano[3,2- e]indole-2-carboxylate 3a-c were synthesised from ethyl 2-[(2-oxo-2 H-1-benzopyran-6-yl)-hydrazono]-3-phenylpropanoate 2a-c. Compounds 2a-c was in turn prepared by reacting diasotised solution of 6-aminocoumarin and ethyl-2-benzylacetoacetate. N-nitroarylation of ethyl 6-oxo-3-phenyl-1,6-dihydropyrano[3,2- e]indole-2-carboxylate 3a-c was carried out with 2-chloronitrobenzene to give ethyl 1-(2-nitrophenyl)-6-oxo-3-phenyl-1,6-dihydropyrano[3,2- e]indole-2-carboxylate 4a-c, which on catalytic reductive cyclisation with H2/Ni affords 7-phenyl-5 H-pyrano[3′,2′:4,5]indolo[1,2- a]quinoxaline-6,10-dione 5a-c. The structures of all these compounds have been established on the basis of analytical and spectral data. All the compounds show significant antibacterial activity.

DNA-directed alkylating agents: synthesis, antitumor activity and DNA affinity of bis-N,N′-trisubstituted 1,2,4-triazolo-piperazines

A series of 1,4-bis-(1,5-dialkyl-1H-1,2,4-triazol-ylmethyl)piperazines and N-methyl-piperazine analogs were prepared spontaneously from the cycloaddition of various reactive cumulenes with the piperazino-1,4-(bis-ethanenitrile) and 1-cyanomethyl-4-methyl-piperazine, respectively. The new compounds were evaluated for their DNA affinity and antitumor activity.

A novel series of hybrid compounds derived by combining 2-aminotetralin and piperazine fragments: binding activity at D2 and D3 receptors

A series of 7-hydroxy-2-[N-alkyl-(N-(4-phenylpiperazine)-alkyl)amino]tetralins was developed based on a novel hybrid approach that combined 2-aminotetralin and arylpiperazine pharmacophoric moieties. Our preliminary study revealed that a four-methylene butyl linker produced very potent compounds for both the D2 and D3 receptors. Further structure-activity studies led to a novel template showing 50- to 100-fold selectivity for the D3 receptor.

Coumarins from the aerial part of Halocnemum strobilaceum

Four known coumarins, coumarin (1), 7-hydroxy-3-methylcoumarin (2), oreoselone (3) and heraclenin (4), were isolated from aerial part of Halocnemum strobilaceum. Their structures were determined by 1 and 2-D NMR techniques.

High potent and selective arylpiperazine derivatives as ligands for the 5-HT1A receptor

This paper reports the synthesis and affinities on the 5-HT1A versus the alpha1A receptors of new arylpiperazinylalkylthiothienopyrimidine and thiadiazole derivatives 16-24. Arylpiperazines 16-23 show affinities values in the nanomolar range for the 5-HT1A receptor. The compound 16 is highly potent (Ki 0.26 nM, selectivity 28), the derivatives 20 and 21 are less potent, but highly selective (Ki 9.40 and 5.06 nM, selectivity 207 and 73, respectively).