The Synthesis and Absolute Configuration of Enantiomeric Pure (R)- and (S)-3-(piperidin-3-yl)-1H-Indole Derivatives.

This article describes the synthesis of new chiral 3-(piperidin-3-yl)-1H-indole derivatives (R)-10a-c and (S)-11a-c from the corresponding diastereomers: (3R, 2R) and (3S, 2R)-2-[3-(1H-indol-3-yl)-1-piperidyl]-2-phenyl-acetamides (3R, 2R)-4a, (3R, 2R)-6b, (3R, 2R)-8c and (3S, 2R)-5a, (3S, 2R)-7b, (3S, 2R)-9c. Diastereomers were obtained by N-alkylation of derivatives of racemic 3-(piperidin-3-yl)-1H-indoles 1a-c using (S)-2-(4-toluenesulfonyloxy)-phenylacetic amide (S)-II. The same method was applied to obtain (3R, 2S)-methyl-2-[3-(1H-indole-3-yl)-1-piperidyl]-2-phenylacetate (3R, 2S)-2a and (3S, 2S)-methyl-2-[3-(1H-indole-3-yl)-1-piperidyl]-2-phenylacetate (3S, 2S)-3a diastereomers by treating amine 1a with (R)-2-(4-toluenesulfonyloxy)-phenylacetic acid methylester (R)-I. Systematic studies via single crystal X-ray crystallography were used to determine the molecular structure of the racemates 1a-c and the absolute configuration of the enantiomers. The solid racemates 1b and 1c were "true racemates" crystallizing in a centrosymmetric space group, while 1a formed a racemic conglomerate of homoenantiomeric crystals. The absolute configuration was determined for the enantiomeric pairs (R)-10a/(S)-11a, (R)-10b/(S)-11b, and (R)-12c/(S)-13c, as well as for (3S,2S)-3a. Spectra of 1H, 13CNMR, HPLC, and HRMS for diastereomers and enantiomers were consistent with the determined structures.

Synthesis of Novel Pyrido[1,2-c]pyrimidine Derivatives with 6-Fluoro-3-(4-piperidynyl)-1,2-benzisoxazole Moiety as Potential SSRI and 5-HT1A Receptor Ligands.

Two series of novel 4-aryl-2H-pyrido[1,2-c]pyrimidine (6a-i) and 4-aryl-5,6,7,8-tetrahydropyrido[1,2-c]pyrimidine (7a-i) derivatives were synthesized. The chemical structures of the new compounds were confirmed by 1H and 13C NMR spectroscopy and ESI-HRMS spectrometry. The affinities of all compounds for the 5-HT1A receptor and serotonin transporter protein (SERT) were determined by in vitro radioligand binding assays. The test compounds demonstrated very high binding affinities for the 5-HT1A receptor of all derivatives in the series (6a-i and 7a-i) and generally low binding affinities for the SERT protein, with the exception of compounds 6a and 7g. Extended affinity tests for the receptors D2, 5-HT2A, 5-HT6 and 5-HT7 were conducted with regard to selected compounds (6a, 7g, 6d and 7i). All four compounds demonstrated very high affinities for the D2 and 5-HT2A receptors. Compounds 6a and 7g also had high affinities for 5-HT7, while 6d and 7i held moderate affinities for this receptor. Compounds 6a and 7g were also tested in vivo to identify their functional activity profiles with regard to the 5-HT1A receptor, with 6a demonstrating the activity profile of a presynaptic agonist. Metabolic stability tests were also conducted for 6a and 6d.

Synthesis of new 5,6,7,8-tetrahydropyrido[1,2-c]pyrimidine derivatives with rigidized tryptamine moiety as potential SSRI and 5-HT1A receptor ligands.

Extended studies in the 4-aryl-pyrido[1,2-c]pyrimidine group resulted in 27 new compounds (10.1-10.27), 5,6,7,8-tetrahydropyrido[1,2-c]pyrimidine derivatives. In vitro tests (RBA) were carried out for 10.1-10.27 compounds in order to determine their affinity to 5-HT1A receptor and SERT protein. 10.1-10.3, 10.6, 10.7, 10.16 and 10.27 compounds had high binding ability to both molecular targets (5-HT1A Ki = 8-87 nM; SERT Ki = 8-52 nM). For these compounds (10.1-10.3, 10.6, 10.7, 10.16, 10.27) further in vitro, in vivo and metabolic stability tests were performed. In vitro studies in the extended receptor profile (D2, 5-HT2A, 5-HT6 and 5-HT7) showed their selectivity towards 5-HT1A receptor and SERT protein. In vivo tests revealed that compounds 10.7 and 10.16 had the properties of presynaptic antagonists of the 5-HT1A receptor. The redesign of the 2H-pyrido[1,2-c]pyrimidine residue present in the terminal part towards 5,6,7,8-tetrahydropyrido[1,2-c]pyrimidine resulted in the improved metabolic stability and enhanced affinity to both molecular targets (5-HT1A-R and SERT) compared to the precursors.

Synthesis of novel pyrido[1,2-c]pyrimidine derivatives with rigidized tryptamine moiety as potential SSRI and 5-HT1A receptor ligands.

The study enabled obtaining a number of new derivatives of 4-aryl-pyrido[1,2-c]pyrimidine 9.1-9.27 having conformationally restricted tryptamine moiety. In vitro studies (RBA) have shown that derivatives 9.1, 9.2, 9.4, 9.7, 9.9, 9.14 and 9.27 exhibit high affinity to molecular targets 5-HT1A receptor and SERT protein. In general, compounds with an unsubstituted or a para-substituted benzene ring of the pyrido[1,2-c]pyrimidine residue in the terminal part were characterized by higher binding ability, which can be justified by the greater flexibility of the structure. For the selected compounds 9.1, 9.7, 9.9 and 9.27, further in vitro, in vivo and metabolic stability tests were performed. The in vitro studies in the extended receptor profile (D2, 5-HT2A, 5-HT6 and 5-HT7) indicated their selectivity toward the 5-HT1A receptor and SERT protein. The in vivo studies (8-OH-DPAT-induced hypothermia in mice, FST) revealed that the compound 9.1 has the properties of presynaptic agonist of the 5-HT1A receptor, and compound 9.7 demonstrated the properties of a presynaptic antagonist of the 5-HT1A receptor. Metabolic stability studies, in turn, showed that compounds 9.1, 9.7 and 9.9, having an unsubstituted indole residue, were more resistant to biotransformation reactions of the first pass phase than was compound 9.27 containing a 5-methoxy-substituted indole residue. The obtained results allowed further optimization of the structure.

Selenized polysaccharides - Biosynthesis and structural analysis.

The main objective of our research was to analyze the structure of the Se-containing polysaccharides and to examine how the selenium is bound to the polysaccharide molecule. During investigation of the biosynthesis of new immunomodulators, we isolated a selenium (Se)-containing polysaccharide-protein fraction containing proteoglycans of molecular weights of 3.9 × 106 Da and 2.6 × 105 Da, composed of glucose or mannose, nearly 8% of protein and 190 µg Se/g dry weight. X-ray absorption spectroscopy (XAS) data analysis in the near edge region (XANES) confirmed that selenium in the Se-polysaccharides structure is present at the -II oxidation state and that Se is organically bound. The simulation analysis in the EXAFS (extended X-ray absorption fine structure) region suggested that selenium is most likely bound by a glycosidic-link in a ß-1,3 or α-1,4-glycosidic bond or substituted for oxygen in a pyranosidic ring. Calculations performed with Gaussian 03 software predicted deformations in the polysaccharide structure caused by the incorporation of the selenium atom including change in bond lengths and torsion angles and, as a result, disappearance of hydrogen bonds in the vicinity of the selenium atoms.

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

A series of novel 4-aryl-pyrido[1,2-c]pyrimidine derivatives containing a 1-(2-quinoline)piperazine moiety was synthesized. The chemical structure of new compounds was confirmed by FT-IR, (1)H NMR, (13)C NMR and HRMS spectra as well as elemental analysis. Affinity of the novel pyrido[1,2-c]pyrimidine derivatives for 5-HT1A, 5-HT2A receptors and serotonin transporter (SERT) was evaluated in an in vitro radioligand binding assay. Tested compounds showed moderate to high affinity for 5-HT1AR and SERT and low affinity for 5-HT2AR. Selected ligands were subjected to in vivo tests, such as induced hypothermia and the forced swimming test in mice, which determined presynaptic agonistic activity of the ligands 8d, 8e, 9d and 9e and presynaptic antagonistic activity of the ligands 8a, 8b, 9a, 9b. Additionally, metabolic stability evaluation was performed for selected ligands, proving that a para-substitution in the 4-aryl-pyrido[1,2-c]pyrimidine moiety leads to an increase in stability, whereas a substitution in the ortho-position lowers the stability.

Novel 4-aryl-pyrido[1,2-c]pyrimidines with dual SSRI and 5-HT1A activity. Part 4.

This project describes the synthesis, pharmacological and pharmacodynamic tests on two series of novel derivatives of 2H-pyrido[1,2-c]pyrimidine with potential binary binding to 5-HT1A receptors and SSRI + serotonin transporters. The influence of piperidinyl-indole (8.1-8.7) and tetrahydropyridinyl-indole (8.8-8.32) residues and indole 5-position substituents (R3 = Br, Cl, F) present in the pharmacophore element of ligands on their binding to both molecular targets was tested. A considerable impact of piperidinyl-indole residue on binding to both targets was confirmed and compounds with a high binding affinity were identified: Ki 5-HT1A = 12.4 nM; Ki SERT = 15.6 nM 8.1; Ki 5-HT1A = 5.6 nM; Ki SERT = 20.7 nM 8.7, while the presence of a tetrahydropyridinyl-indole residue was found to reduce the affinity of ligands to 5-HT1AR. The presence of chlorine (R3) in this series resulted in a notable reduction in binding to both targets (5-HT1A and SERT). Selected compounds had their metabolic stability in a first-pass test (human liver microsomes, NADPH) determined in vitro, and R1 and R2 substituents present on the terminal residue of pyrido[1,2-c]pyrimidine were recognized as having an impact on stability.

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.

Synthesis and anticonvulsant activity of novel 2,6-diketopiperazine derivatives. Part 2: Perhydropyrido[1,2-a]pyrazines.

A new series of chiral pyrido[1,2-a]pyrazine derivatives was synthesised and evaluated in in vivo animal models of epilepsy. A significant influence of the stereochemistry of the pyrido[1,2-a]pyrazine framework on the pharmacological activity was observed. Compounds with (4R,9aS) absolute configuration proved inactive, whereas other stereoisomers exhibited markedly dissimilar spectra of anti-seizure efficacy in the maximal electroshock seizure (MES), subcutaneous Metrazol seizure (scMET) and Pilocarpine-induced status prevention (PISP) tests. Importantly, the investigated agents revealed high potency in the 6Hz model, with the ED(50) values comparable to the reference drug Levetiracetam. Derivatives (4S,9aR)-6 and (4R,9aR)-6 emerged as promising new lead structures, the former having a broad spectrum of anticonvulsant activity and the latter showing high potency in 6Hz and PISP models.

Synthesis and anticonvulsant activity of novel 2,6-diketopiperazine derivatives. Part 1: perhydropyrrole[1,2-a]pyrazines.

A number of novel pyrrole[1,2-a]pyrazine derivatives were synthesized and evaluated in in vivo animal models of epilepsy. Among them, several compounds displayed promising seizure protection in the maximal electroshock seizure (MES), subcutaneous metrazol seizure (scMET), 6 Hz and pilocarpine-induced status prevention (PISP) tests, with ED(50) values comparable to the reference anticonvulsant drugs (AEDs). A critical influence of the stereochemistry and conformational preferences of the pyrrole[1,2-a]pyrazine core on in vivo pharmacological activity was observed. The mechanism of the anticonvulsant action of the agents synthesized is most probably not via inhibition of the voltage-dependent sodium (Na(+)) currents.

Synthesis and biological investigation of potential atypical antipsychotics with a tropane core. Part 1.

The synthesis, structure, in vitro and in vivo pharmacological activities of 3ß-acylamine derivatives of tropane (4a-n, 5a-g, 6a,b, 8a-c) are described. Among the investigated compounds, several displayed very high (in nM) affinity for the monoamine receptors 5-HT(1A), 5-HT(2A,) and D(2). The most interesting agent 6b revealed very high affinity for the 5-HT(2A) and D(2) receptors and high affinity for the 5-HT(1A) receptor. The in vivo head twitch model was used to demonstrate antagonism of the 5-HT(2A) receptor subtype by this compound. In another test, 6b caused hypothermia in mice, which was not attenuated by WAY 100635. In the climbing test, the compound did not significantly modify climbing behaviour following apomorphine administration. Moreover, 6b significantly reduced locomotor activity in mice. Molecular docking studies using a homology model of the 5-HT(1A) receptor revealed a significant role of the N-8 atom of the tropane core in stabilising the ligand-receptor complex due to strong hydrogen bonding with Asp116 located in the TMH 3 helix. Analogically, in a homology model of the 5-HT(2A) receptor, the N-8 atom formed a hydrogen bond with Gly369. In another homology model of the D(2) receptor, strong hydrogen bonding of the amide moiety in the 3ß position of the tropane nucleus with Asp85 was observed. Compound 6b displayed a favourable Meltzer index (1.21) which is a feature of atypical antipsychotic agents.

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.

Novel 4-aryl-pyrido[1,2-c]pyrimidines with dual SSRI and 5-HT1A activity: part 2.

Derivatives of 4-aryl-5,6,7,8-tetrahydro-pyrido[1,2-c]pyrimidine were synthesized. These compounds contain the 3-(4-piperidyl)-1H-indole residue or its 5-methoxy or 2-methyl derivative. In vitro binding tests were performed to determine the affinity of the compounds for the 5-HT(1A) receptor and serotonin transporter (SERT) proteins in the rat brain cortex. In vivo studies, particularly the inducible hypothermia test and forced swimming test, were conducted to determine agonistic/antagonistic activity with pre- and postsynaptic 5-HT(1A) receptors. Molecular modeling techniques were used to determine the binding modes of the selected compounds at the 5-HT(1A) receptor and SERT. The SAR analysis showed that the presence of the 3-(4-piperidyl)-1H-indole group or its 5-methoxy derivative, as well as a para substitution with -OCH(3) or -F in the aryl ring of 4-aryl-5,6,7,8-tetrahydro-pyrido[1,2-c]pyrimidine, results in an increased affinity for both the 5-HT(1A) receptors and SERT. In contrast, the presence of the 2-methyl-3-(4-piperidyl)-1H-indole group resulted in a considerable decrease in binding affinity.

Novel 4-aryl-pyrido[1,2-c]pyrimidines with dual SSRI and 5-HT1A activity, part 1.

A series of new derivatives of 4-aryl-pyrido[1,2-c]pyrimidine containing the 3-(4-piperidyl)-1H-indole residue or its 5-methoxy derivative were synthesized. They were characterized (i) in vitro by binding to 5-HT(1A) receptors and 5-HT transporter proteins in rat brain cortex membranes and (ii) in vivo in the mouse by induced hypothermia and forced swimming models for antagonist/agonist activity against the 5-HT(1A) autoreceptors and postsynaptic 5-HT(1A) receptors, respectively. Structure activity relationship evaluation indicated that the presence of the 3-(4-piperidyl)-1H-indole residue and ortho- or para-substituents with -F or -CH(3) groups in the aryl ring as well as an unsubstituted aryl in the 4-aryl-pyrido[1,2-c]pyrimidine moiety promoted low K(i) values for both receptors. In contrast, the presence of a 5-methoxy-3-(4-piperidyl)-1H-indole residue as well as -Cl or -OCH(3) substituents at the para position markedly reduced the receptor affinity.

Synthesis of 1-{4-[4-(adamant-1-yl)phenoxymethyl]-2-(4-bromophenyl)- 1,3-dioxolan-2-ylmethyl}imidazole with expected antifungal and antibacterial activity.

A multistep synthesis of a new analogue of ketoconazole, which was expected to show antifungal and antibacterial activity, has been described.

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.

Synthesis of new hexahydro- and octahydropyrido[1,2-c]pyrimidine derivatives with an arylpiperazine moiety as ligands for 5-HT1A and 5-HT2A receptors. Part 4.

New 4-aryl-2H-pyrido[1,2-c]pyrimidine-1,3-dione derivatives of arylpiperazine (6-18) were prepared and evaluated in vitro for their affinity for 5-HT1A, 5-HT2A, and alpha1 receptors. The influence of ortho substitution in the phenyl ring, substitution at position 4 of the pyrido[1,2-c]pyrimidine system, and its unsaturation degree were explored. The tested compounds showed high affinity for the 5-HT1A receptor (Ki = 1.3-79.2 nM) and moderate to low affinity for the 5-HT2A (Ki = 51.7-1405 nM) and alpha1 receptors (Ki = 19.7-382.3 nM). Compounds 8 and 10 showed the highest 5-HT1A receptor affinity (Ki = 1.3 and 2.2 nM, respectively) and were 37- and 35.9-fold, respectively, more selective in relation to alpha1 adrenoreceptors.

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

The preparation of new 4-aryl-hexahydropyridol 1,2-c]pyrimidine derivatives III-XXVI with an arylpiperazinylbutyl moiety in N-2 position has been described. Multi-stage synthesis techniques were used to obtain 4-arylhexahydro-1H,3H-pyrido[1,2-c]pyrimidine-1,3-dione Ia-f derivatives, being the starting compounds for further modification. N-alkylation of the imide group in compounds Ia-f followed, using 1,4-dibromobutane to yield bromobutyl derivatives IIa-f. The final products III-XXVI were obtained by condensation of aryl- or heteroaryl- piperazine with the bromobutyl derivatives IIa-f. Compounds XII, XIV, XIX, XX, XXIV-XXVI will be submitted to a pharmacological investigation for their affinity towards 5-HT1A, 5-HT2A and alpha1 adrenergic receptor, using radioligand binding assay.

Synthesis and conformation analysis of 3-substituted derivatives of 1H,3H-pyrido[2,3-d] pyrimidin-4-one of expected depressive nervous system. Part III.

Four series of new 1-aryl (heteroaryl) piperazinylacetyl derivatives of 1H,3H-pyrido[2,3-d] pyrimidin-4-one VIIa-o were synthesised. Substrates for the synthesis of VIa-d were obtained from the respective 3H-pyrido[2.3-d]pyrimidines IVa-d in the reaction with NaBH4. Compounds VIa-d were prepared by chloroacetylation. The obtained 1-chloroacetyl derivatives in the reaction with respective aryl (heteroaryl) piperazine formed 1-aminoacetyl derivatives of 2-phenyl-1 H.3H-pyrido[2.3-d]pyrimidin-4-one compounds VII1a-n. The structure ol compounds was analysed by 1H, 13C NMR spectroscopy.

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.