Synthesis and structure-activity relationships of a new model of arylpiperazines. 4. 1-[omega-(4-Arylpiperazin-1-yl)alkyl]-3-(diphenylmethylene) - 2, 5-pyrrolidinediones and -3-(9H-fluoren-9-ylidene)-2, 5-pyrrolidinediones: study of the steric requirements of the terminal amide fragment on 5-HT1A affinity/selectivity

Experimental and Theoretical Study of Phosphine-Catalyzed Reaction Modes in the Reaction of α-Substituted Allenes with Aryl Imines

A new phosphine-catalyzed reaction of α-substituted allenes with aryl imines, in stark contrast to classic cycloaddition reactions, has been developed. This reaction delivers valuable highly functionalized itaconimides with excellent stereoselectivities by a new «un-cyclizing» reaction mode involving β'-carbon of α-substituted allenes. Moreover, the present «un-cyclizing» reaction can also be carried out in a one-pot fashion and scaled up to the gram scale by using aryl aldehydes, without the need to isolate the aryl imines. Mechanistic studies and control experiments reveal the crucial role of H2 CO3 for the present reaction mode. In addition, density functional theory (DFT) calculations were performed to understand the possible mechanism.

Synthetic approaches to potent heterocyclic inhibitors of tuberculosis: A decade review

Tuberculosis (TB) continues to be a significant global health concern with about 1.5 million deaths annually. Despite efforts to develop more efficient vaccines, reliable diagnostics, and chemotherapeutics, tuberculosis has become a concern to world health due to HIV, the rapid growth of bacteria that are resistant to treatment, and the recently introduced COVID-19 pandemic. As is well known, advances in synthetic organic chemistry have historically enabled the production of important life-saving medications that have had a tremendous impact on patients’ lives and health all over the world. Small-molecule research as a novel chemical entity for a specific disease target offers in-depth knowledge and potential therapeutic targets. In this viewpoint, we concentrated on the synthesis of a number of heterocycles reported in the previous decade and the screening of their inhibitory action against diverse strains of Mycobacterium tuberculosis. These findings offer specific details on the structure-based activity of several heterocyclic scaffolds backed by their in vitro tests as a promising class of antitubercular medicines, which will be further useful to build effective treatments to prevent this terrible illness.

Palladium-Catalyzed Domino Aminocarbonylation of Alkynols: Direct and Selective Synthesis of Itaconimides

The first direct and selective synthesis of substituted itaconimdes by palladium-catalyzed aminocarbonylation of alkynols is reported. Key to the success of this transformation is the use of a novel catalyst system involving ligand L11 and appropriate reaction conditions. In the protocol here presented, easily available propargylic alcohols react with N-nucleophiles including aryl- and alkylamines as well as aryl hydrazines to provide a broad variety of interesting heterocycles with high catalyst activity and excellent selectivity. The synthetic utility of the protocol is demonstrated in the synthesis of natural product 11 with aminocarbonylation as the key step. Mechanistic studies and control experiments reveal the crucial role of the hydroxyl group in the substrate for the control of selectivity.

Synthesis, in vitro and in vivo pharmacological evaluation of serotoninergic ligands containing an isonicotinic nucleus

Isonicotinamide derivatives, linked to an arylpiperazine moiety, were prepared and their affinity to 5-HT1A, 5-HT2A and 5-HT2C receptors were evaluated. The combination of structural elements (heterocyclic nucleus, alkyl chain and 4-substituted piperazine) known to play critical roles in affinity for serotoninergic receptors and the proper selection of substituents led to compounds with high specificity and affinity towards serotoninergic receptors. In binding studies, several molecules showed high affinity in nanomolar and subnanomolar range at 5-HT1A, 5-HT2A and 5-HT2C receptors and moderate or no affinity for other relevant receptors (D1, D2, α1 and α2). N-(3-(4-(bis(4-fluorophenyl)methyl)piperazin-1-yl)propyl)isonicotinamide (4s) with Ki = 0.130 nM, was the most active and selective derivative for the 5-HT1A receptor compared to other serotoninergic, dopaminergic and adrenergic receptors. Compound 4o, instead, showed 5-HT2A affinity values in subnamolar range. Moreover, the compounds having better affinity and selectivity binding profile towards 5-HT1A and 5-HT2A receptors were selected in order to be tested by in vitro and in vivo assays to determine their functional activity.

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.

Discovery of LASSBio-772, a 1,3-benzodioxole N-phenylpiperazine derivative with potent alpha 1A/D-adrenergic receptor blocking properties

We described herein the discovery of 1-(2-(benzo[d] [1,3]dioxol-6-yl)ethyl)-4-(2-methoxyphenyl) piperazine (LASSBio-772), as a novel potent and selective alpha 1A/1D adrenoceptor (AR) antagonist selected after screening of functionalized N-phenylpiperazine derivatives in phenylephrine-induced vasoconstriction of rabbit aorta rings. The affinity of LASSBio-772 for alpha 1A and alpha 1B AR subtypes was determined through displacement of [(3)H]prazosin binding. We obtained Ki values of 0.14 nM for the alpha 1A-AR, similar to that displayed by tamsulosin (K(i) = 0.13 nM) and 5.55 nM for the alpha 1B-AR, representing a 40-fold higher affinity for alpha 1A-AR. LASSBio-772 also presented high affinity (K(B) = 0.025 nM) for the alpha 1D-AR subtype in the functional rat aorta assay, showing to be equipotent to tamsulosin (K(B) = 0.017 nM).

Discovery of a novel 5-HT(3) antagonist/5-HT(1A) agonist 3-amino-5,6,7,8-tetrahydro-2-{4-[4-(quinolin-2-yl)piperazin-1-yl]butyl}quinazolin-4(3H)-one (TZB-30878) as an orally bioavailable agent for irritable bowel syndrome

We have prepared a series of quinazolinone derivatives linked with piperazinylquinoline for the treatment of irritable bowel syndrome (IBS). Using pharmacophore analysis, we designed and synthesized compounds which bind to both serotonin receptor subtype 1A (5-HT(1A)) and subtype 3 (5-HT(3)). Quinazolinone derivatives with a sulfur atom in the linker showed high affinity in in vitro assays, but low in vivo activity. Focusing on the linker to improve the pharmacokinetic profile, the sulfur atom in the linker was replaced with a methylene group. Further optimization led to the discovery of compound 17m (TZB-30878) ( J. Pharmacol. Exp. Ther. 2007 , 322 , 1315 - 1323 , Patent WO2005082887 (A1), 2005 ), a novel 5-HT(1A) agonist/5-HT(3) antagonist in the 3-aminoquinazolinone series. In in vivo functional assays, 17m dose dependently inhibited the Bezold-Jarisch reflex and induced 5-HT(1A)-mediated behaviors, and in an IBS animal model, 17m significantly inhibited stress-induced defecation. Pretreatment by WAY-100635 (5-HT(1A) antagonist) significantly attenuated but did not abolish the inhibitory effects of 17m. These results suggested that 17m exerted inhibitory effects via both 5-HT(1A) agonistic and 5-HT(3) antagonistic activities and that 17m would be useful as a therapeutic agent for IBS.

Quantitative structure-affinity relationship of 5-HT1A receptor ligands by the classification tree method

The influence of molecular structure of 346 ligands on their affinity for 5-HT1A receptors was investigated. It was shown that the effectiveness of the proposed novel approach for interpretation of decision tree models compared favourably with the PLS method. In the context of the proposed approach, molecular fragments and their values of the relative influence on the affinity for 5-HT1A receptors were defined.

Synthesis of a new scaffold: the 7H,8H-pyrimido[1,6-b]pyridazin-6,8-dione nucleus

This paper describes a modified method of preparation of a number of alpha-aryl-alpha-(pyridazin-3-yl)-acetonitriles via the C-arylation reaction of the corresponding carbanionsof phenylacetonitriles using 3-chloropyridazine derivatives. KOH and DMSO were used inthe deprotonation process, which made the reaction very simple and safe to perform.Nitriles were obtained in the hydrolysis reaction to the corresponding alpha-aryl-alpha-(pyridazin-3-yl)-acetamide derivatives, which were next subjected to cyclization to afford the finalproducts. A number of new derivatives of 7H,8H-pyrimido[1,6-b]pyridazin-6,8-dione weresynthesized in the cyclocondensation reaction of respective alpha-aryl-alpha-(pyridazin-3-yl)-acetamides with diethyl carbonate in the presence of EtONa. The structure andcomposition of the new compounds were confirmed by IR, (1)H- and (13)C- NMR analysesand by elemental C, H and N analysis.

The influence of modifications in imide fragment structure on 5-HT1A and 5-HT7 receptor affinity and in vivo pharmacological properties of some new 1-(m-trifluoromethylphenyl)piperazines

New, flexible (7, 9, 11 and 13) and rigid (8, 10, 12 and 14) imides with a 1-(m-trifluorophenyl)piperazine fragment and a tetramethylene or a 1e,4e-cyclohexylene spacer, respectively, showed very high affinity (K(i)=0.3-34 nM) and agonistic in vivo activity for 5-HT(1A) receptors. Flexible new compounds and the previously described 5 also bound to 5-HT(7) receptors (K(i)=21-134 nM). Selected glutarimide derivatives, that is, the most potent postsynaptic 5-HT(1A) receptor agonist rigid compound 8 and its flexible analogue 7, as well as the previously described full agonist-rigid compound 6 and the partial agonist-its flexible counterpart 5 exhibited moderate affinity for alpha(1)-adrenoceptors (K(i)=85 - 268 nM), but were practically devoid of any affinity for dopamine D(2) sites. Those glutarimides demonstrated anxiolytic- (5 and 7) and antidepressant-like (5, 6 and 8) activity in the four-plate and the swim tests in mice, respectively; at the same time, however, they inhibited the locomotor activity of mice. The antidepressant-like effect of 8 was significantly stronger than that induced by imipramine used as a reference antidepressant.

CoMFA methodology in structure-activity analysis of hexahydro- and octahydropyrido[1,2-c]pyrimidine derivatives based on affinity towards 5-HT1A, 5-HT2A and alpha1-adrenergic receptors

Structural features of the pyrido[1,2-c]pyrimidine derivatives with arylpiperazine moiety and their affinities towards 5-HT1A, 5-HT2A and alpha1-adrenergic receptors were analyzed using the CoMFA procedure. On the basis of 3D-QSAR models for the 5-HT2A and alpha1-adrenergic receptors, four compounds with expected better affinity/selectivity were proposed and synthesized. The affinities obtained confirm experimentally the usefulness of CoMFA models. Our results suggest that active conformations adopted by the studied molecules when interacting with the receptors are neutral instead of the protonated ones.

1,2,4-Benzothiadiazine derivatives as alpha1 and 5-HT1A receptor ligands

A series of new 1,2,4-benzothiadiazine derivatives with an arylpiperazine mojety linked at position 3 of the heterocyclic ring were synthesized and assessed for their pharmacological profiles at alpha(1)-adrenoceptor subtypes (alpha(1A), alpha(1B) and alpha(1D)) by functional experiments and by in vitro binding studies at human cloned 5-HT(1A) receptor. Compound 1 was identified as a novel alpha(1D) antagonist (pK(b)alpha(1D)=7.59; alpha(1D)/alpha(1A)>389; alpha(1D)/alpha(1B)=135) with high selectivity over 5-HT(1A) receptor (5-HT(1A)/alpha(1D)<0.01), while compound 6, a 3,4-dihydro-derivative, was characterized as a novel 5-HT(1A) receptor ligand, highly selective over alpha(1D)-adrenoceptor subtype (pK(i)5-HT(1A)=8.04; 5-HT(1A)/alpha(1D)=1096). Further pharmacological studies demonstrated that 6 is a partial agonist at 5-HT(1A) receptor (E(max)=23, pD(2)=6.92).

Benzimidazole derivatives. Part 5: design and synthesis of new benzimidazole-arylpiperazine derivatives acting as mixed 5-HT1A/5-HT3 ligands

A series of new mixed benzimidazole-arylpiperazine derivatives were designed by incorporating in general structure III the pharmacophoric elements of 5-HT(1A) and 5-HT(3) receptors. Compounds 1-11 were synthesized and evaluated for binding affinity at both serotoninergic receptors, all of them exhibiting high 5-HT(3)R affinity (K(i)=10-62nM), and derivatives with an o-alkoxy group in the arylpiperazine ring showing nanomolar affinity for the 5-HT(1A)R (K(i)=18-150nM). Additionally, all the synthesized compounds were selective over alpha(1)-adrenergic and dopamine D(2) receptors (K(i)>1000-10,000nM). Compound 3 was selected for further pharmacological characterization due to its interesting binding profile as mixed 5-HT(1A)/5-HT(3) ligand with high affinity for both receptors (5-HT(1A): K(i)=18.0nM, 5-HT(3): K(i)=27.2nM). In vitro and in vivo findings suggest that this compound acts as a partial agonist at 5-HT(1A)Rs and as a 5-HT(3)R antagonist. This novel mixed 5-HT(1A)/5-HT(3) ligand was also effective in preventing the cognitive deficits induced by muscarinic receptor blockade in a passive avoidance learning test, suggesting a potential interest in the treatment of cognitive dysfunction.

1-Aryl-4-(4-succinimidobutyl)piperazines and their conformationally constrained analogues: synthesis, binding to serotonin (5-HT1A, 5-HT2A, 5-HT7), α1-adrenergic, and dopaminergic D2 receptors, and in vivo 5-HT1A functional characteristics

Starting with the structure of potent 5-HT(1A) ligands, that is, MM77 [1-(2-methoxyphenyl)-4-(4-succinimidobutyl)piperazine, 4] and its constrained version 5 (MP349), previously obtained in our laboratory, a series of their direct analogues with differently substituted aromatic ring (R=H, m-Cl, m-CF(3), m-OCH(3), p-OCH(3)) were synthesized. The flexible and the corresponding 1e,4e-disubstituted cyclohexane derivatives were designed in order to investigate the influence of rigidification on 5-HT(1A) affinity, selectivity for 5-HT(2A), 5-HT(7), D(1), and D(2) binding sites and functional profile at pre- and postsynaptic 5-HT(1A) receptors. The new compounds 19-25 were found to be highly active 5-HT(1A) receptor ligands (K(i)=4-44 nM) whereas their affinity for other receptors was: either significantly decreased after rigidification (5-HT(7)), or controlled by substituents in the aromatic ring (alpha(1)), or influenced by both those structural modifications (5-HT(2A)), or very low (D(2), K(i)=5.3-31 microM). Since a distinct disfavor towards rigid compounds was observed for 5-HT(7) receptors only, it seems that the bioactive conformation of chain derivatives at those sites should differ from the extended one. Several in vivo models were used to asses functional activity of 19-25 at pre- (hypothermia in mice) and postsynaptic 5-HT(1A) receptors (lower lip retraction in rats and serotonin syndrome in reserpinized rats). Unlike the parent antagonists 4 and 5, all the new derivatives tested were classified as partial agonists with different potency, however, similar effects were observed within pairs (flexible and rigid) of the analogues. The obtained results indicated that substitution in the aromatic ring, but not spacer rigidification, controls the 5-HT(1A) functional activity of the investigated compounds. Moreover, an o-methoxy substituent in the structure of 5 seems to be necessary for its full antagonistic properties. Of all the new compounds studied, trans-4-(4-succinimidocyclohexyl)-1-(3-trifluoromethylphenyl)piperazine 24 was the most potent 5-HT(1A) receptor ligand in vitro (K(i)=4 nM) and in vivo, with at least 100-fold selectivity for the other receptors tested.

The impact of spacer structure on 5-HT7 and 5-HT1A receptor affinity in the group of long-chain arylpiperazine ligands

New cis-, trans-2-butene and 1,2-bismethylbenzene analogues of MM77 and NAN-190 (1-[4-[4-(2-methoxyphenyl)-piperazin-1-yl]-butyl]-pyrrolidine-2,5-dione and isoindole-1,3-dione, respectively) were synthesized. The differences in their in vitro affinity for serotonin 5-HT(7) and 5-HT(1A) receptors were explained using a conformational analysis. A bioactive conformation of those compounds for the 5-HT(7) receptor, different from that established for 5-HT(1A), was proposed.

Synthesis and structure–activity relationships of a new model of arylpiperazines. Part 7: Study of the influence of lipophilic factors at the terminal amide fragment on 5-HT1A affinity/selectivity

The influence of lipophilic factors at the amide fragment of a new series of (+/-)-7a-alkyl-2-[4-(4-arylpiperazin-1-yl)butyl]-1,3-dioxoperhydropyrrolo[1,2-c]imidazoles 2 and of (+/-)-7a-alkyl-2-[(4-arylpiperazin-1-yl)methyl]-1,3-dioxoperhydropyrrolo[1,2-c]imidazoles 3 has been studied. Variations of logP have been carried out by introducing different hydrocarbonated substituents (R(1)) at the position 7a of the bicyclohydantoin, namely the non-pharmacophoric part. All the new compounds exhibit high potency for the 5-HT(1A) receptor; however, affinities for the alpha(1) receptor are high for compounds 2a-l while compounds 3a-f are selective over this adrenergic receptor. On the other hand, differences in logP do not notably affect the K(i) values for the above receptors.

Design and synthesis of new benzimidazole-arylpiperazine derivatives acting as mixed 5-HT1A/5-HT3 ligands

A series of new benzimidazole-arylpiperazine derivatives III were designed, synthesized and evaluated for binding affinity at serotoninergic 5-HT(1A) and 5-HT(3) receptors. Compound IIIc was identified as a novel mixed 5-HT(1A)/5-HT(3) ligand with high affinity for both serotonin receptors and excellent selectivity over alpha(1)-adrenergic and dopamine D(2) receptors. This compound was characterized as a partial agonist at 5-HT(1A)Rs and a 5-HT(3)R antagonist, and was effective in preventing the cognitive deficits induced by muscarinic receptor blockade in a passive avoidance learning test.

Design and synthesis of S-(-)-2-[[4-(napht-1-yl)piperazin-1-yl]methyl]-1,4-dioxoperhydropyrrolo[1,2-a]pyrazine (CSP-2503) using computational simulation. A 5-HT1A receptor agonist

Based on a computational model for 5-HT(1A)R-ligand interaction and QSAR studies, we have designed and synthesized a new series of arylpiperazines 2-8 which exhibit high 5-HT(1A)R affinity and selectivity over alpha(1)-adrenergic receptors. Among them, compound CSP-2503 (4) has been pharmacologically characterized as a 5-HT(1A)R agonist at somatodendritic and postsynaptic sites, endowed with anxiolytic properties.

Synthesis of new hexahydro- and octahydropyrido[1,2-c]pyrimidine derivatives with an arylpiperazine moiety as ligands for 5-HT1A and 5-HT2A receptors

Synthesis applied to prepare compounds 5-15 and 17-22 discussed in this paper has been presented in Scheme 1. Multi-stage preparation techniques were used to obtain 4-aryl-hexahydro 1-4 and (R,R) and (S,S) 4-aryl-octahydropyrido[1,2-c]pyrimidine-1,3-dione (16) derivatives, being the starting compounds for further modification. N-Alkylation of the imide group in compounds 1-4 and 16 followed, using 1,4-dibromobutane to yield monobromobutyl derivatives 5-8 and 17. Subsequent condensation of those compounds with appropriate 1-aryl or 1-heteroarylpiperazine led to the final hexahydro- 9-15 and octahydro- 18-22 pyrido[1,2-c]pyrimidine-1,3-dione derivatives. The final products were subjected to screening test to elucidate the affinity to 5-HT1A and 5-HT2A receptors.

[1,2,4]Triazole derivatives as 5-HT(1A) serotonin receptor ligands

A series of new 4-amino-3-[3-[4-(2-methoxy or nitro phenyl)-1-piperazinyl] propyl]thio]-5-(substitutedphenyl)[1,2,4]triazoles 11a-t was synthesized in order to obtain compounds with high affinity and selectivity for 5-HT(1A) receptor over the alpha(1)-adrenoceptor. A series of isomeric 4-amino-2-[3-[4-(2-methoxy or nitro phenyl)-1-piperazinyl]propyl]-5-(substitutedphenyl)-2,4-dihydro-3H[1,2,4]triazole-3-thiones 12a-r was also isolated and characterized. New compounds were tested to evaluate their affinity for 5-HT(1A) receptor and alpha(1)-adrenoceptor in radioligand binding experiments. As a general trend, triazoles 11a-t showed a preferential affinity for the 5-HT(1A) receptor whereas isomeric 2,4-dihydro-3H[1,2,4]triazole-3-thiones 12a-r preferentially bind to the alpha(1)-adrenoceptor site. Several molecules showed affinities in the nanomolar range and 4-amino-3-[3-[4-(2-methoxyphenyl)-1-piperazinyl]propyl]thio]-5-(4-propyloxy-phenyl)[1,2,4]triazole (11o) was the most selective derivative for the 5-HT(1A) receptor (K(i) alpha(1)/K(i) 5-HT(1A)=55). The decrease in 5-HT(1A) receptor selectivity in 3-[3-[4-(2-methoxyphenyl)-1-piperazinyl]propyl]thio]-5-(substitutedphenyl)[1,2,4] triazole 14a-b, lacking in the amino group in 4-position of the triazole ring, in comparison with their analogues in the series 11a-t, suggest that the amino function represents a critical structural feature in determining 5-HT(1A) receptor selectivity in this class of compounds.

Benzolactam derivatives and their affinity for alpha 1- and alpha 2-adrenoreceptors

A series of benzolactam derivatives has been evaluated for their affinity for alpha 1 and alpha 2-adrenoreceptors. The influence of terminal amine and amide fragments on the affinity and selectivity has been investigated. It has been found that derivatives containing 1,2,3,4-tetrahydroisoquinoline (THIQ) as the basic component can form potent alpha 1 and/or alpha 2 ligands, and that their alpha 1/alpha 2 selectivity depends on the benzolactam fragment.

Synthesis of new (benzimidazolyl)piperazines with affinity for the 5-HT1A receptor via Pd(0) amination of bromobenzimidazoles

The synthesis of a new family of (benzimidazolyl)piperazines has been developed through Pd(0) mediated amination of 4- and 6-bromobenzimidazole derivatives. Preliminary studies showed that some of these compounds are potent 5-HT1A receptor ligands.

Design and synthesis of 2-[4-[4-(m-(ethylsulfonamido)-phenyl) piperazin-1-yl]butyl]-1,3-dioxoperhydropyrrolo[1,2-c]imidazole (EF-7412) using neural networks. A selective derivative with mixed 5-HT1A/D2 antagonist properties

A test series of 32 phenylpiperazines III with affinity for 5-HT1A and alpha1 receptors was subjected to QSAR analysis using artificial neural networks (ANNs), in order to get insight into the structural requirements that are responsible for 5-HT1A/alpha1 selectivity. Good models and predictive power were obtained for 5-HT1A and alpha1 receptors. A comparison of these models gives information for the design of the new ligand EF-7412 (5-HT1A:Ki(nM)= 27; alpha1: Ki(nM) > 1000). This derivative displayed affinity for dopamine D2 receptor (Ki = 22 nM) and is selective for all other receptor examined (5-HT2A, 5-HT3, 5-HT4 and Bz). EF-7412 acts an antagonist in vivo in pre- and postsynaptic 5-HT1A receptor sites and as an antagonist in dopamine D2 receptor.