Synthesis of bridged piperazines with sigma receptor affinity

Bridged piperazines 4 were designed as conformationally restricted piperazine sigma receptor ligands. The chiral pool synthesis started from (S)-glutamate, which was transformed in five reaction steps into the piperazinediones 5 bearing a propionic acid ester side chain. A two-step Dieckmann analogous cyclization provided the bicyclic ketones 7 as key intermediates. The alcohols 8 were prepared by LiAlH4 reduction of the ketones 7. NaBH4 reduction, Williamson ether synthesis and LiAlH4 reduction led to the methyl and benzyl ethers 12 and 13. High sigma1 affinity is attained when one large substituent is introduced either at N-8 or O-2. The most potent sigma1 ligand in this series of compounds is the methyl ether 12b with the N-butyl substituent (K(i)=13.2 nM, selectivity sigma2:sigma1 = 16). Moreover, the N-methyl derivatives 13a (sigma2: K(i)=30.4 nM) and 12a (sigma2 preference) represent promising starting points for the development of potent and selective sigma2 ligands.     

Substituted benzo[d]oxazol-2(3H)-one derivatives with preference for the sigma1 binding site

We describe here the synthesis and the binding interaction with sigma(1) and sigma(2) receptors of a series of new benzo[d]oxazol-2(3H)-one derivatives variously substituted on the N-benzyl moiety. The results of binding studies confirm the notion that the benzoxazolone moiety confers preference towards sigma(1) sites and establish that the ability to bind to sigma(1), but not to sigma(2) receptors, is strongly affected by the kind and the position of the substituents introduced in the N-benzyl ring. In fact, compounds with substitutions in para-position with atoms of Cl, H or F or with a CH(3) group exhibit a higher affinity for sigma(1) receptors than the corresponding ortho-substituted compounds. The highest affinity and selectivity, with K(i) values of 0.1 and 427 nM for sigma(1) and sigma(2) receptors, respectively, and a corresponding K(i)sigma(2)/K(i)sigma(1) selectivity ratio of 4270 were found for the Cl-substituted compound. These results indicate that benzo[d]oxazol-2(3H)-one derivatives are among the most selective and sigma(1) receptor-preferring ligands currently available.     

Angiotensin II--AT1 receptor antagonists: design, synthesis and evaluation of substituted carboxamido benzimidazole derivatives

A series of 5-(alkyl and aryl)carboxamido benzimidazole derivatives had been designed, synthesized and evaluated for in vitro angiotensin II--AT1 receptor antagonism and in vivo antihypertensive activities. The pharmacological activities were inversely related to the size of alkyl and aryl substituents. It can be suggested that compounds with lower alkyl groups at 5-position of benzimidazole nucleus demonstrated potent antihypertensive activity.     

Substituted benzylaminoalkylindoles with preference for the sigma2 binding site

In the attempt to develop new sigma ligands we synthesized a series of N-benzyl-3-[1-(4-fluorophenyl)-1H-indol-3-yl]-N-methylpropan-1-amines and N-benzyl-4-[1-(4-fluorophenyl)-1H-indol-3-yl]-N-methylbutan-1-amines variously substituted on the phenyl ring. The displacement percentages of [3H]-DTG and [3H]-(+)-pentazocine determined in rat liver homogenates by these compounds at the fixed 100 nM concentration have been determined as a preliminary evaluation of their sigma1 and sigma2 affinity, respectively. The results suggested that the phenyl substituents may positively modulate, in comparison with the unsubstituted compound, the ability to displace [3H]-DTG from sigma2 sites, whereas the same phenyl substituents reduced the displacement percentages of [3H]-(+)-pentazocine from sigma1 sites. Some of these compounds were selected for radioligand binding assays. Compounds with a butylene intermediate chain displayed the greatest binding affinity for sigma2 over sigma1 receptors. The butylene derivative with 2,4-dimethyl substitution on the phenyl ring showed the greatest sigma2 affinity (sigma2Ki=5.9 nM) and an appreciable sigma2 over sigma1 selectivity (sigma1Ki/sigma2Ki=22). The obtained results suggest that a butylene chain separating the indole moiety from variously substituted benzylamino groups may be required to their interaction with a hypothetical secondary sigma2 binding site.     

Synthesis and cytotoxic activity of new alkyl[3-(2-chloroethyl)ureido]benzene derivatives

Several alkyl[3-(2-chloroethyl)ureido] (CEU) benzene derivatives were prepared as potential anticancer agents. These new compounds were readily prepared in good yields by addition of anilines to 2-chloroethylisocyanate. Their cytotoxic activity was evaluated on human breast cancer (MDA-MB-231), human colon adenocarcinoma (LoVo) and mouse lymphocytic leukemia (P388D₁) tumor cell lines. Several new CEUs were significantly more cytotoxic than the nitrogen mustard chlorambucil. The biological activity of these aromatic urea derivatives seems to be related to the nature and position of the alkyl substituents on the aromatic ring. Substitution by branched alkyl groups on position 4 of the aromatic ring led to cytotoxic molecules which are up to 5 times more potent than the standard chlorambucil.     

4β-[(4-Alkyl)-1,2,3-triazol-1-yl] podophyllotoxins as anticancer compounds: design, synthesis and biological evaluation

A series of 4β-[(4-alkyl)-1,2,3-triazol-1-yl] podophyllotoxin derivatives were designed in silico, synthesised by employing click chemistry approach, and evaluated for cytotoxicity against a panel of human cancer cell lines (SF-295, A-549, PC-3, Hep-2, HCT-15 and MCF-7). Majority of the compounds proved to be more potent than etoposide and select compounds exhibited significant anticancer activity with IC50 values in the range of 0.001-1 μM. DNA fragmentation and flow-cytometric results reveals that 4β-[(4-alkyl)-1,2,3-triazol-1-yl] podophyllotoxin derivatives induce dose dependent apoptosis. Docking experiments showed a good correlation between their calculated interaction energies with the topoisomerase-II and the observed IC50 values of all these compounds.     

Synthesis of N-substituted 2-[(1E)-alkenyl]-4-(1H)-quinolone derivatives as antimycobacterial agents against non-tubercular mycobacteria

In an effort to improve biological activities and to examine antimycobacterial-lipophilicity relationships of 2-[(1E)-alkenyl)]-4-(1H)-quinolones, we have synthesized a series of 30 quinolones by introducing several alkyl groups, an alkenyl and an alkynyl group at N-1. All synthetic compounds were first tested in vitro against Mycobacterium smegmatis and the most active compounds (MIC values ～3.0-7.0 μM) were further examined against three other rapidly growing strains of mycobacteria using a microtiter broth dilution assay. The Clog P values of the synthetic compounds were calculated to provide an estimate of their lipophilicity. Compounds 18e, 19a and 19b displayed the most potent inhibitory effect against M. smegmatis mc(2)155 with an MIC value of ～1.5 μM, which was twenty fold and thirteen fold more potent than isoniazid and ethambutol, respectively. On the other hand, compounds 17e, 18e and 19a were most active against Mycobacterium fortuitum and Mycobacterium phlei with an MIC value of ～3.0 μM. In the human diploid embryonic lung cell line MRC-5 cytotoxicity assay, the derivatives showed moderate to strong cytotoxic activity. Although the antimycobacterial activity of our synthetic compounds could not be correlated with the calculated log P values, an increase in lipophilicity enhances the antimycobacterial activity and C13-C15 total chain length at positions 1 and 2 is required to achieve optimal inhibitory effect against the test strains.     

Design, synthesis and binding properties of novel and selective 5-HT3 and 5-HT4 receptor ligands

This work reports the synthesis and the binding tests on the 5-HT3 and 5-HT4 receptors of new thienopyrimidopiperazine and piperazinylacylaminodimethylthiophene derivatives, in order to identify potent and selective ligands for each receptor. The 3-amino-2-(4-benzyl-1-piperazinyl)-5,6-dimethyl-thieno[2,3-d]pyrimidin-4(3H)-one derivative 28 showed the highest affinity and selectivity for the 5-HT3 over the 5-HT4 receptor (5-HT3 Ki=3.92 nM, 5-HT4 not active), whereas the 2-[4-[4-(2-pyrimidinyl)-1-piperazinyl]butanoylamino]-4,5-dimethyl-3-thiophenecarboxylic acid ethyl ester (41) showed the highest affinity and selectivity for the 5-HT4 over the 5-HT3 receptor (5-HT4 Ki=81.3 nM, 5-HT3 not active). Conformational analyses were carried out on the compounds of the piperazinylacylaminodimethylthiophene series (39-42) taking compound 41 as the template.     

Solution-phase parallel synthesis and evaluation of anticonvulsant activity of N-substituted-3,4-dihydroisoquinoline-2(1H)-carboxamides

In our previous studies we identified several isoquinoline derivatives displaying potent anticonvulsant effects in different animal models of epilepsy. With the aim to exploit the main structure-activity relationships (SAR) for this class of compounds we planned a solution-phase parallel synthesis (SPPS) of new N-substituted-3,4-dihydroisoquinoline-2(1H)-carboxamides exploring the effect of introduction of different (cyclo)alkyl groups at carboxamide moiety linked to N-2 atom of isoquinoline scaffold. The pharmacological effects were evaluated against audiogenic seizures in DBA/2 mice and, even if some new derivatives were more active than valproate, the designed modifications did not improve the anticonvulsant efficacy with respect to their precursors.     

Synthesis and binding studies of epibatidine analogues as ligands for the nicotinic acetylcholine receptors

Neuronal nicotinic acetylcholine receptors (nAChRs) are transmembrane ligand-gated ion channels. Recent research demonstrated that selective nAChR ligands may have therapeutic potential in a number of CNS diseases and disorders. The alkaloid epibatidine is a highly potent non-opioid analgesic and nAChR agonist, but too toxic to be a useful ligand. To develop ligands selective for distinct nAChR subtypes and with reduced toxicity, a series of epibatidine and homoepibatidine analogues were synthesized. (+/-)-8-Methyl-3-(pyridin-3-yl)-8-azabicyclo[3,2,1]oct-2-ene, showed high affinity towards alpha4beta2 (Ki=2 nM), subtype selectivity (alpha4beta2/alpha7 affinity ratio>100) and relatively low toxicity in mice and can be labeled with 11C and 18F as positron emission tomography (PET) tracers for imaging of nAChRs.     

Design, synthesis and binding properties of novel and selective 5-HT(3) and 5-HT(4) receptor ligands

This work reports the synthesis and the binding tests on the 5-HT(3) and 5-HT(4) receptors of new thienopyrimidopiperazine and piperazinylacylaminodimethylthiophene derivatives, in order to identify potent and selective ligands for each receptor. The compound with higher affinity and selectivity for the 5-HT(3) over the 5-HT(4) receptor was the 3-amino-2-(4-benzyl-1-piperazinyl)-5,6-dimethyl-thieno[2,3-d]pyrimidin-4(3H)-one 28 (5-HT(3) K(i)=3.92 nM, 5-HT(4) not active), the compound with higher affinity and selectivity for the 5-HT(4) over the 5-HT(3) receptor was the 2-[4-[4-(2-pyrimidinyl)-1-piperazinyl]butanoylamino]-4,5-dimethyl-3-thiophenecarboxylic acid ethyl ester 41 (5-HT(4) K(i)=81.3 nM, 5-HT(3) not active). Conformational analyses were carried out on the compounds of the piperazinylacylaminodimethylthiophene series (39-42) taking compound 41 as the template.     

Discovery, synthesis, and investigation of the antitumor activity of novel piperazinylpyrimidine derivatives

Protein kinases play several pertinent roles in cell proliferation, and targeting these proteins has been shown to be a successful strategy toward controlling different malignancies. Despite the great discovery stories during the last two decades, there is still a demand for anticancer small molecules with the potential of being selective on both the protein kinase and/or the cellular level. A series of novel piperazinylpyrimidine compounds were synthesized and tested for their potential to selectively inhibit the growth of certain tumor cell lines included within the NCI-60 cell line panel. MDA-MB-468, a triple-negative/basal-like breast carcinoma, cell line was among the most sensitive cell lines towards compounds 4 and 15. The three most interesting compounds identified in cellular screens (4, 15, and 16) were subjected to kinase profiling and found to have an interesting selective tendency to target certain kinase subfamily members; PDGFR, CK1, RAF and others. Compound 4 showed a selective tendency to bind to and/or inhibit the function of certain KIT and PDGFRA mutants compared to their wild-type isoforms. Piperazinylpyrimidine based derivatives represent a new class of selective kinase inhibitors. Significantly 4 is more potent at inhibiting oncogenic mutant forms of PDGFR family kinases, which is relevant in terms of its potential use in treating tumors that have become resistant to treatment or driven by such mutations. The clinical demand for agents useful in the control of triple-negative/basal-like breast cancer justifies our interest in compound 15 which is a potent growth inhibitor of MDA-MB-468 cell line.     

New quinoxalinecarbonitrile 1,4-di-N-oxide derivatives as hypoxic-cytotoxic agents

We report the synthesis and biological in vitro activities of 16 new 2-quinoxalinecarbonitrile 1,4-di-N-oxides. These compounds present new basic lateral chains (piperazines and anilines) in the 3 position as well as different substituents in the 6 and/or 7 positions of the quinoxaline ring. Among piperazine derivatives, 4b (a 7-chloro-3-(4-methylpiperazin-1-yl) derivative) was the most potent (P = 0.5 x10(-6) M). In general, aniline derivatives were more potent and selective than the former, compound 12b (with a 4-(methylphenyl)amino moiety in the 3 position and a chlorine atom in the 7 position) being the best one (P = 3 x 10(-6) 16).     

Recent developments in the field of A2A and A3 adenosine receptor antagonists

In the last years adenosine receptors have been extensively studied, and mainly at present we understand the importance of A(2A) and A(3) adenosine receptors. A(2A) selective adenosine receptors antagonists are promising new drugs for the treatment of Parkinson's disease, while A(3) selective adenosine receptors antagonists have been postulated as novel anti-inflammatory and antiallergic agents; recent studies also indicated a possible employment of these derivatives as antitumour agents. Lately different classes of compounds have been identified as potent A(2A) and A(3) antagonists. In this article we report the past and present efforts which led to development of more potent and selective A(2A) and A(3) antagonists. Our group has mainly worked on the pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine nucleus both as A(2A) and A(3) antagonists, aiming to improve the affinity, selectivity and the hydrophilic profile. In fact, we have synthesised several compounds endowed with high affinity and selectivity versus A(2A) adenosine receptors, as 2, 2a-c (K(i)A(2A)=0.12-0.19 nM), or A(3) adenosine receptors, as 4p (K(i)A(3)=0.01 nM) and 4q (K(i)A(3)=0.04 nM).     

1,8-Naphthyridines VII. New substituted 5-amino[1,2,4]triazolo[4,3-a][1,8]naphthyridine-6-carboxamides and their isosteric analogues, exhibiting notable anti-inflammatory and/or analgesic activities, but no acute gastrolesivity

The [1,2,4]triazolo[4,3-a][1,8]naphthyridine-6-carboxamide derivatives 5-amino (2) or 5-alkoxy (3) substituted and the 5-amino[1,2,4]triazolo[4,3-a]quinoline-4-carboxamide derivatives (4), designed to obtain new effective analgesic and/or anti-inflammatory agents were synthesized. Ten compounds 2 and 4 showed an interesting analgesic activity: the most potent ones are 2j (36% inhibition, P<0.05) and 4b (77% inhibition, P<0.01) at 6.25 and 25mgkg(-1) doses, respectively. Compounds 2i-l and 4c showed notable anti-inflammatory properties: the most potent ones are 2i (68% inhibition, P<0.01) and 2l (42% inhibition, P<0.05) at 12.5 and 6.25mgkg(-1) doses, respectively. The replacement in compounds 2 of the N-substituted 5-amino substituents with similar alkoxy groups usually afforded less active compounds 3.     

Synthesis and inhibitory activity of dimethylamino-chalcone derivatives on the induction of nitric oxide synthase

A series of nine dimethylamino-chalcone derivatives (1,3-diaryl-propenones) was synthesized and screened as potential inhibitors of NO and PGE(2) production in the RAW 264.7 macrophage cell line. 4-Dimethylamino-2',5'-dimethoxychalcone (6) was found to be the most potent and dual inhibitor (IC(50s) in the submicromolar range) of NO and PGE(2) production. 2',6'-Dimethoxylation appeared to be an effective requirement for selective and potent inhibition of nitric oxide synthase induction as it was confirmed by Western blot analysis. Chalcone (6) at 25 mg kg(-1) by oral route, inhibited significantly the formation of oedema in the carrageenan-induced model of inflammation in mice.     

Design,synthesis and biological evaluation of new endocannabinoid transporter inhibitors

In the present work we describe the synthesis and the in vitro evaluation of a series of arachidonic acid derivatives of general structure I as endocannabinoid transporter inhibitors. In addition, we report the first in vivo studies of the most potent derivative (4, UCM707) within this series. The majority of compounds studied are highly potent (IC(50)=24-0.8 micro M) and selective endocannabinoid uptake inhibitors with very low affinities for either the enzyme fatty acid amide hydrolase (IC(50)=30-113 micro M) or for cannabinoid receptor subtype 1 (CB(1)), cannabinoid receptor subtype 2 (CB(2)) and vanilloid receptor subtype 1 (VR(1)) (K(i)=1000-10000 nM). Among them, (5Z,8Z,11Z,14Z)-N-(fur-3-ylmethyl)icosa-5,8,11,14-tetraenamide (UCM707) behaves as the most potent endocannabinoid transporter inhibitor described to date (IC(50)=0.8 micro M) and exhibits improved potency for the anandamide transporter, high selectivity for CB(1) and VR(1) receptors, and modest selectivity for CB(2). In vivo it enhances the analgesia and hypokinetic effects induced by a subeffective dose of anandamide.     

Synthesis, DNA binding and cytotoxicity of new pyrazole emodin derivatives

A series of new anthrapyrazoles were derived from emodin by attaching various cationic alkyl amino side chains onto a pyrazole ring which had been incorporated into the anthraquinone chromophore. Compared with emodin, the derivatives had significantly higher DNA binding affinity based on interaction with calf thymus DNA, and much more potent cytotoxicity against different tumor cells. The derivatives with a mono-cationic alkyl side chain exhibited the highest DNA binding affinity and cytotoxicity.     

Asymmetric synthesis of chiral piperazinylpropylisoxazoline ligands for dopamine receptors

The asymmetric synthesis of chiral piperazinylpropylisoxazoline analogues, (R)-(+)-1, 2 and (S)-(-)-1, 2 was accomplished through a seven-step sequence of reactions, which involved asymmetric 1,3-dipolar cycloaddition, alkyl chain extension, and reductive amination as key reactions. Chiral ligands (R)-(+)-1, 2 exhibited the higher binding affinity and selectivity for the D(3) receptor over the D(4) receptor than (S)-(-)-1, 2 ligands.     

Synthesis of 4-(aminoalkyl) substituted 1,3-dioxanes as potent NMDA and σ receptor antagonists

Elongation of the distance between the oxygen heterocycle and the basic amino moiety or ring expansion of the oxygen heterocycle of the NMDA receptor antagonists dexoxadrol and etoxadrol led to compounds with promising NMDA receptor affinity. Herein the combination of both structural features, i.e. elongation of the O-heterocycle--amine distance with a 1,3-dioxane ring is envisaged. The synthesis of aminoethyl-1,3-dioxanes 13, 22, 23 and 29 was performed by transacetalization of various acetals with pentane-1,3,5-triol, activation of the remaining free OH moiety with tosyl chloride and subsequent nucleophilic substitution. The corresponding 3-aminopropyl derivatives 33-35 were prepared by substitution of the tosylates with KCN and LiAlH4 reduction. The highest NMDA receptor affinity was found for 1,3-dioxanes with a phenyl and an ethyl residue at the acetalic position (23) followed by diphenyl (22) and monophenyl derivatives (13). Generally the NMDA affinity of primary amines is higher than the NMDA affinity of secondary and tertiary amines. Altogether the primary amine 23a (Ki=24 nM) represents the most promising NMDA receptor antagonist of this series exceeding the NMDA affinity of the mono-homologues (2-aminoethyl)-1,3-dioxolanes (3,4) and (aminomethyl)-1,3-dioxanes (5,6). Whereas the primary amine 23a turned out to be selective against σ1 and σ2 receptors the benzylamine 13d was identified as potent (Ki=19 nM) and selective σ1 antagonist, which showed extraordinarily high antiallodynic activity in the capsaicin assay.