Synthesis, Structure and Cytotoxicity Testing of Novel 7-(4,5-dihydro-1H-imidazol-2-yl)-2-aryl-6,7-dihydro-2H-imidazo[2,1-c][1,2,4]triazol-3(5H)-Imine Derivatives

The appropriate 1-arylhydrazinecarbonitriles 1a-c are subjected to the reaction with 2-chloro-4,5-dihydro-1H-imidazole (2), yielding 7-(4,5-dihydro-1H-imidazol-2-yl)-2-aryl-6,7-dihydro-2H-imidazo[2,1-c][1,2,4]triazol-3(5H)-imines 3a-c, which are subsequently converted into the corresponding amides 4a-e, 8a-c, sulfonamides 5a-n, 9, ureas 6a-I, and thioureas 7a-d. The structures of the newly prepared derivatives 3a-c, 4a-e, 5a-n, 6a-i, 7a-d, 8a-c, and 9 are confirmed by IR, NMR spectroscopic data, as well as single-crystal X-ray analyses of 5e and 8c. The in vitro cytotoxic potency of these compounds is determined on a panel of human cancer cell lines, and the relationships between structure and antitumor activity are discussed. The most active 4-chloro-N-(2-(4-chlorophenyl)-7-(4,5-dihydro-1H-imidazol-2-yl)-6,7-dihydro-2H-imidazo[2,1-c][1,2,4]triazol-3(5H)-ylidene)benzamide (4e) and N-(7-(4,5-dihydro-1H-imidazol-2-yl)-2-(p-tolyl)-6,7-dihydro-2H-imidazo[2,1-c][1,2,4]triazol-3(5H)-ylidene)-[1,1'-biphenyl]-4-sulfonamide (5l) inhibits the growth of the cervical cancer SISO and bladder cancer RT-112 cell lines with IC50 values in the range of 2.38-3.77 μM. Moreover, N-(7-(4,5-dihydro-1H-imidazol-2-yl)-2-phenyl-6,7-dihydro-2H-imidazo[2,1-c][1,2,4]triazol-3(5H)-ylidene)-4-phenoxybenzenesulfonamide (5m) has the best selectivity towards the SISO cell line and induces apoptosis in this cell line.

Synthesis and cytotoxic evaluation of benzoxazole/benzothiazole-2-imino-coumarin hybrids and their coumarin analogues as potential anticancer agents

Two series of 2-imino-coumarin based hybrids: 3-(benzoxazol-2-yl)-2H-chromen-2-imines 3-9 (series A-I) and 3-(benzothiazol-2-yl)-2H-chromen-2-imines 10-16 (series A-II), as well as their coumarin analogues: 3-(benzoxazol-2-yl)-2H-chromen-2-ones 17-21 (series B-I) and 3-(benzothiazol-2-yl)-2H-chromen-2-ones 22-28 (series B-II) were prepared as potential antitumor agents. The in vitro cytotoxic potency of the synthesized compounds was evaluated against five human cancer cell lines: DAN-G, A-427, LCLC-103H, RT-4 and SISO, and relationships between structure and anticancer activity are discussed. Among the compounds tested, 3-(benzo[d] oxazol-2-yl)-N,N-diethyl-2-imino-2H-chromen-7-amine (6, series A-I) and 3-(benzo[d]thiazol-2-yl)-6-fluoro-2H-chromen-2-one (26, series B-II) exhibited the most potent cytotoxic activity with IC₅₀ values ranging from <0.01 μM to 1.1 μM. In particular, compound 6 demonstrated remarkable cytotoxicity against the A-427 ovarian cancer, the lung cancer LCLC-103H, urinary bladder cancer RT-4 and cervical cancer SISO cell lines with IC₅₀ <0.01-0.30μM, inducing apoptosis in two representative cell lines.

Radiosynthesis and Preclinical Evaluation of an α2A-Adrenoceptor Tracer Candidate, 6-[18F]Fluoro-marsanidine

PURPOSE

The α₂-adrenoceptors mediate many effects of norepinephrine and epinephrine, and participate in the regulation of neuronal, endocrine, cardiovascular, vegetative, and metabolic functions. Of the three receptor subtypes, only α_2A and α_2C are found in the brain in significant amounts. Subtype-selective positron emission tomography (PET) imaging of α₂-adrenoceptors has been limited to the α_2C subtype. Here, we report the synthesis of 6-[¹⁸F]fluoro-marsanidine, a subtype-selective PET tracer candidate for α_2A-adrenoceptors, and its preclinical evaluation in rats and mice.

PROCEDURES

6-[¹⁸F]Fluoro-marsanidine was synthesized using electrophilic F-18 fluorination with [¹⁸F]Selectfluor bis(triflate). The tracer was evaluated in Sprague Dawley rats and in α_2A-knockout (KO) and wild-type (WT) mice for subtype selectivity. In vivo PET imaging and ex vivo brain autoradiography were performed to determine the tracer distribution in the brain. The specificity of the tracer for the target was determined by pretreatment with the subtype-non-selective α₂-agonist medetomidine. The peripheral biodistribution and extent of metabolism of 6-[¹⁸F]fluoro-marsanidine were also analyzed.

RESULTS

6-[¹⁸F]Fluoro-marsanidine was synthesized with [¹⁸F]Selectfluor bis(triflate) in a radiochemical yield of 6.4 ± 1.7 %. The molar activity was 3.1 to 26.6 GBq/μmol, and the radiochemical purity was > 99 %. In vivo studies in mice revealed lower uptake in the brains of α_2A-KO mice compared to WT mice. The results for selectivity were confirmed by ex vivo brain autoradiography. Blocking studies revealed reduced uptake in α_2A-adrenoceptor-rich brain regions in pretreated animals, demonstrating the specificity of the tracer. Metabolite analyses revealed very rapid metabolism of 6-[¹⁸F]fluoro-marsanidine with blood-brain barrier-permeable metabolites in both rats and mice.

CONCLUSION

6-[¹⁸F]Fluoro-marsanidine was synthesized and evaluated as a PET tracer candidate for brain α_2A-adrenoceptors. However, rapid metabolism, extensive presence of labeled metabolites in the brain, and high non-specific uptake in mouse and rat brain make 6-[¹⁸F]fluoro-marsanidine unsuitable for α_2A-adrenoceptor targeting in rodents in vivo.

Hybrid Molecules Composed of 2,4-Diamino-1,3,5-triazines and 2-Imino-Coumarins and Coumarins. Synthesis and Cytotoxic Properties

A series of 2-imino-2H-chromen-3-yl-1,3,5-triazine compounds 5⁻12, which are namely hybrids of 2,4-diamino-1,3,5-triazines and 2-imino-coumarins, was synthesized by reacting 2-(4,6-diamine-1,3,5-triazin-2-yl)acetonitriles 1⁻4 with 2-hydroxybenzaldehydes. After this, upon heating in aqueous DMF, 2-imino-2H-chromen-3-yl-1,3,5-triazines 10 and 12 were converted into the corresponding 2H-chromen-3-yl-1,3,5-triazines 13 and 14, which are essentially hybrids of 2,4-diamino-1,3,5-triazines and coumarins. The in vitro anticancer activity of the newly prepared compounds was evaluated against five human cancer cell lines: DAN-G, A-427, LCLC-103H, SISO and RT-4. The greatest cytotoxic activity displayed 4-[7-(diethylamino)-2-imino-2H-chromen-3-yl]-6-(4-phenylpiperazin-1-yl)-1,3,5-triazin-2-amine (11, IC₅₀ in the range of 1.51⁻2.60 μM).

Synthesis, Structure, Chemical Stability, and In Vitro Cytotoxic Properties of Novel Quinoline-3-Carbaldehyde Hydrazones Bearing a 1,2,4-Triazole or Benzotriazole Moiety

A small library of novel quinoline-3-carbaldehyde hydrazones (Series 1), acylhydrazones (Series 2), and arylsulfonylhydrazones (Series 3) bearing either a 1,2,4-triazole or benzotriazole ring at position 2 was prepared, characterized by elemental analyses and IR, NMR, and MS spectra, and then subjected to in vitro cytotoxicity studies on three human tumor cell lines: DAN-G, LCLC-103H, and SISO. In general, compounds 4, 6, and 8 substituted with a 1,2,4-triazole ring proved to be inactive, whereas the benzotriazole-containing quinolines 5, 7, and 9 elicited pronounced cancer cell growth inhibitory effects with IC50 values in the range of 1.23⁻7.39 µM. The most potent 2-(1H-benzotriazol-1-yl)-3-[2-(pyridin-2-yl)hydrazonomethyl]quinoline (5e) showed a cytostatic effect on the cancer cell lines, whereas N′-[(2-(1H-benzotriazol-1-yl)quinolin-3-yl)methylene]-benzohydrazide (7a) and N′-[(2-1H-benzotriazol-1-yl)quinolin-3-yl)methylene]-naphthalene-2-sulfonohydrazide (9h) exhibited selective activity against the pancreas cancer DAN-G and cervical cancer SISO cell lines. Based on the determined IC50 values, the compound 5e seems to be leading compound for further development as anticancer agent.

A new imidazoline-containing Bunte salt: synthesis, molecular and electronic structure

S-[(4,5-dihydro-1H-imidazol-2-yl)methyl]sulfothioate, a new imidazoline-containing Bunte salt 4 was prepared by reacting 2-chloromethylimidazoline 3 with sodium thiosulfate in aqueous solution at room temperature. The mechanism of the concerted SN2 reaction pathway was studied by means of quantum chemical calculations at the B3LYP/6-31G** level of theory. The molecular structure of compound 4 incorporating a formal amidine moiety was confirmed by single crystal X-ray diffraction analysis, while its electronic structure was studied using quantum chemical calculations at the MP2/6-311++G** level of theory.

Are Alpha-2D Adrenoceptor Subtypes Involved in Rat Mydriasis Evoked by New Imidazoline Derivatives: Marsanidine and 7-Methylmarsanidine?

The imidazoline compounds may produce mydriasis after systemic administration to some species (rats, cats, and mice). In mydriatic activity of imidazolines, α_2D-adrenoceptors subtype(s) seems to be involved. In this study, the pupil dilatory effect evoked by 2 newly synthesized imidazoline derivatives—α₂-adrenoceptor agonists: marsanidine and 7-methylmarsanidine—was compared. The compounds were tested alone as well as in the presence of α₂-adrenoceptor antagonists (nonselective, yohimbine, and selective toward the following α₂-adrenoceptor subtypes—α_2A-2-[(4,5-dihydro-1H-imidazol-2-yl)methyl]-2,3-dihydro-1-methyl-1H-isoindole maleate (BRL44408), α_2B-2-[2-(4-(2-methoxyphenyl)piperazin-1-yl)ethyl]-4,4-dimethyl-1,3-(2H,4H)-isoquinolindione dihydrochloride (ARC239), α_2C-JP1302, α_2D-2-(2,3-dihydro-2-methoxy-1,4-benzodioxin-2-yl)-4,5-dihydro-1H-imidazole hydrochloride [RX821002]). The agonists were studied in male Wistar rats and were administered intravenously in cumulative doses. The antagonistic compounds were given in a single dose before the experiment with marsanidine or 7-methylmarsanidine. Pupil diameter was measured with stereoscopic microscope equipped in green light filter. Marsanidine and 7-methylmarsanidine exerted marked mydriatic effects. BRL44408, JP1302, and ARC239 did not cause significant parallel shift to the right of the dose–effect curves obtained for both imidazolines. In case of yohimbine and RX821002, the marked parallel shifts of dose–response curves were observed, with the antagonistic effects of RX821002 more pronounced. In vivo pharmacodynamics experiment suggests that α_2D-adrenoceptor subtype is mainly engaged in mydriatic effects evoked in rats by imidazoline derivatives, in particular by clonidine.

Circulatory effect of TCS-80, a new imidazoline compound, in rats

BACKGROUND

Synthesis and hypotensive properties of centrally acting imidazoline agents: 1-[(imidazolidin-2-yl)imino]-1H-indazole (Marsanidine) and 7-chloro-1-[(4,5-dihydro-1H-imidazol-2-yl)methyl]-1H-indazole (TCS-80) were tested in rats. We have recently synthesized two novel Marsanidine analogues which decrease blood pressure and heart rate in rats: 1-[(4,5-dihydro-1H-imidazol-2-yl)methyl]-1H-indole (TCS-54), and 7-chloro-1-[(4,5-dihydro-1H-imidazol-2-yl)methyl]-1H-indole (TCS-213). Among all these analogues, compound TCS-80 exhibits the highest affinity to I1-imidazoline receptors and the lowest α2/I1 selectivity ratio. The observed cardiovascular effects of the compounds might be mediated through α2-adrenergic and I1-imidazoline receptors and subsequent decrease of the symphathetic nerve activity. The present studies were performed to determine whether α2-adrenergic and/or I1-imidazoline receptors are involved in the decrease of blood pressure and heart rate induced by Marsanidine, TCS-54, TCS-80, and TCS-213 in rats.

METHODS

Anesthetized rats were infused iv with the tested compounds and selective α2-adrenoceptor antagonist, RX821002, or nonselective α2-adrenergic/I1-imidazoline receptor antagonist, Efaroxan. The mean arterial blood pressure and heart rate were monitored directly and continuously throughout the experiment.

RESULTS

Efaroxan inhibited the hypotensive effect of TCS-80 stronger than RX821002. The degree of inhibition of the hypotensive effect of the remaining compounds was similar for both antagonists. The presence of Efaroxan and RX821002 diminished the heart rate decrease induced by all compounds administration, though the influence on the maximal chronotropic effect was attenuated significantly in the TCS-80 and TCS-213 treated animals only.

CONCLUSION

Our results indicate that hypotensive and negative chronotropic activities of all tested compounds are mediated by both the α2-adrenergic and I1-imidazoline receptors. Moreover, the circulatory effect of TCS-80 might be mediated to relatively higher degree by the I1-imidazoline receptors than by the α2-adrenergic ones.

Polymeric (anion-π)n interactions in crystals of 2-(2,4,6-trioxo-[1,3,5]triazinan-1-yl)ethylammonium iodide

2-(2,4,6-Trioxo-[1,3,5]triazinan-1-yl)ethyammonium halides

Structural diversity of copper(II) complexes with N-(2-pyridyl)imidazolidin-2-ones(thiones) and their in vitro antitumor activity

Six series of structurally different mono- and binuclear copper(II) complexes 5-10 were obtained by reacting N-(2-pyridyl)imidazolidin-2-ones (1a-l), N,N'-bis(2-pyridyl)imidazolidin-2-ones (2a,b), N-acyl-N'(2-pyridyl)imidazolodin-2-ones (3a-j) and N-(2-pyridyl)imidazolidine-2-thiones (4a-g) with copper(II) chloride at an ambient temperature. The coordination modes of the complexes obtained were established by elemental analysis, IR spectroscopic data and single crystal X-ray diffraction studies. The in vitro cytotoxic activities of both the free ligands and copper(II) complexes were evaluated using a crystal violet microtiter plate assay on five human tumor cell lines: LCLC-103H, A-427, SISO, RT-4 and DAN-G. The free ligands 1-4 at concentration attainable in cancer cells of 20 μM showed no meaningful cytotoxic effect with cell viability in the range of 88%-100%. The most potent copper(II) complex of 1-(6-ethoxy-2-pyridyl)imidazolidin-2-one (6b) exhibited selective cytotoxicity against A-427 lung cancer cell line, while the complexes of 1-(5-methyl-2-pyridyl)imidazolidine-2-thione (5h) and 1-(4-tert-butyl-2-pyridyl)imidazolidine-2-thione (5j) showed cytostatic effect against a whole panel of five human tumor cell lines. In conclusion, the only complexes that showed remarkably increased activity in comparison to the free ligands were those obtained from N-(2-pyridyl)imidazolidine-2-thiones 4c and 4e substituted with alkyl group at position 4 or 5 of pyridine ring.

Vagotomy reveals the importance of the imidazoline receptors in the cardiovascular effects of marsanidine and 7-ME-marsanidine in rats

BACKGROUND

The recently synthesized novel benzazole derivates - marsanidine (1-[(imidazolidin-2-yl)imino]indazole) and 7-Me-marsanidine (1-[(imidazolidin-2-yl)imino]-7-methylindazole) display promising effects on the circulatory system. We previously indicated that i.v. administration of both compounds decreased the mean arterial blood pressure (MAP) and heart rate (HR) in rats. The cardiovascular effect of the tested compounds may consist not only in inhibiting the sympathetic, but also in activating the parasympathetic pathways related to vagal nerves. Present experiments were performed to determine how vagotomy, with or without an α2 adrenoreceptor blockade, may affect hypotensive and HR limiting actions of marsanidine and 7-Me-marsanidine.

METHODS

Both compounds were infused i.v. (10 μg/kg b.w.) to anesthetized rats, half of which underwent vagotomy. Half the intact, and half the vagotomised rats received RX821002, an α2 adrenorereceptor inhibitor. MAP and HR were monitored directly throughout the experiment.

RESULTS

Vagotomy enhanced hypotension observed after marsanidine administration. The α2 adrenergic blockade abolished the action of marsanidine in both the intact and vagotomised rats. Vagotomy did not affect the 7-Me-marsanidine-induced decrease of MAP or HR. However, it abolished the reducing effect of the α2 adrenergic receptor blockade on the hypotension triggered by 7-Me-marsanidine.

CONCLUSION

The results show that although cardiovascular effects of marsanidine and 7-Me-marsanidine are not mediated by the vagal nerves, vagotomy enhanced sensitivity of the sympathetic pathways for the tested compounds. While the action of marsanidine in vagotomised and intact rats may be explained by activation of the α2 adrenoreceptors, the effects of 7-Me-marsanidine seem to be α2 adrenoreceptor-independent. It seems likely that activation of I1 imidazoline receptors could mediate the observed effects.

Biological activities of guanidine compounds, 2008 - 2012 update

INTRODUCTION

Compounds incorporating guanidine moiety have found many practical applications in diverse areas of chemistry, such as nucleophilic organocatalysis, anion recognition and coordination chemistry. Moreover, guanidine functional group is found in natural products, pharmaceuticals and cosmetic ingredients produced by synthetic methods. Thus, knowledge of their biological activities and therapeutic uses is of utmost importance for researchers involved in drug discovery processes.

AREAS COVERED

In this review the authors highlight the continued development and therapeutic applications of newly synthesized guanidine-containing compounds including small peptides and peptidomimetics incorporating arginine. The review presents patents and patent applications filed in the years 2008 - 2012 with emphasis placed on new mechanisms of pharmacological action of guanidine derivatives.

EXPERT OPINION

While guanidines are often thought of as strong organic bases and compounds hydrophilic in nature, over the last 4 years there has been an enormous increase in discovery of new promising lead structures with guanidine core, suitable for development of potential drugs acting at central nervous system, anti-inflammatory agents, anti-diabetic and chemotherapeutic agents as well as cosmetics.

5-Methyl-3,6,7,8a-tetra-hydro-2H-diimidazo[1,2-c:1',2'-e]pyrido[1,2-a][1,3,5]triazin-5-ium iodide

The structure of the title compound, C(12)H(16)N(5) (+)·I(-), shows that the methyl-ation reaction with CH(3)I occurred at the imine N atom at position 5 of the 3,6,7,8a-tetra-hydro-2H-diimidazo[1,2-c:1',2'-e]pyrido[1,2-a][1,3,5]triazine system. In the cation, the sp(3)-hybridized C atom belonging to the fused dihydro-pyrine and dihydro-1,3,5-triazine rings deviates by 0.514 (3) Å from the best plane defined by the remaining cationic non-H atoms. The fused dihydro-pyridine and dihydro-1,3,5-triazine rings are each in a half-chair conformation with the sp(3)-hybridized C atom as a flap. The iodide anion is 3.573 (2) Å from the methyl-ated N atom and exhibits five short C-H⋯I(-) contacts with distances less than 3.16 Å. The structure has been determined from a non-merohedral twin with twin law [-1 0 0 0 - 1 0 0.115 0 1], minor domain = 0.1559 (12).