8-Methylureido-10-amino-10-methyl-imidazo[1,2-a]indeno[1,2-e] pyrazine-4-ones: highly in vivo potent and selective AMPA receptor antagonists

Water soluble 8-methylureido-10-amino-10-methyl-imidazo[1,2-a]indeno[1,2-e]pyraz ine-4-one 4 represents a novel class of highly potent and selective AMPA receptors antagonists with in vivo activity. The dextrorotatory isomer (+)-4 was found to display the highest affinity with an IC50 of 10 nM. It also exhibited very good anticonvulsant effects after i.p., s.c. and i.v. administration in mice subjected to electrical convulsions (MES) and i.p. in audiogenic seizure-e in DBA/2 mice (ED50's < or = 10 mg/kg).     

Synthesis and antifungal evaluation of pyrido[1,2-a]indole-1,4-diones and benzo[f]pyrido[1,2-a]indole-6,11-diones

Pyrido[1,2-a]indole-1,4-diones and benzo[f]pyrido[1,2-a]indole-6,11-diones were synthesized and tested for in vitro antifungal activity against two pathogenic strains of fungi. Among them tested, many compounds showed good antifungal activity. The results suggest that pyrido[1,2-a]indole-1,4-diones and benzo[f]pyrido[1,2-a]indole-6,11-diones would be potent antifungal agents.     

Synthesis of a [1,2-3H]-labeled pregnanolone.

A method is described for the synthesis and purification of 3 alpha-hydroxy-5 alpha-[1,2-3H]pregnan-20-one. [1,2-3H]progesterone (55 Ci/mmol) was incubated with a homogenate of rat brain tissue. The product was purified by Sephadex chromatography and thin-layer chromatography. The identity and purity of the product were established by successive recrystallizations and high-performance liquid chromatography. A 34% portion of the starting material was converted to 3 alpha-hydroxy-5 alpha-[1,2-3H]pregnan-20-one. The final radiopurity of 3 alpha-hydroxy-5 alpha-pregnan-20-one obtained from four independent preparations was 94% to 99%.     

Bioisosteres of 9-carboxymethyl-4-oxo-imidazo[1,2-a]indeno-[1,2-e]pyrazin-2-carboxylic acid derivatives. Progress towards selective, potent in vivo AMPA antagonists with longer durations of action

A novel series of 2- and 9-disubstituted heterocyclic-fused 4-oxo-indeno[1,2-e]pyrazin derivatives was synthesized. One of them, the 9-(1H-tetrazol-5-ylmethyl)-4-oxo-5,10-dihydroimidazo[1,2-a]indeno[1,2-e]pyrazin-2-yl phosphonic acid 4i exhibited a strong and a selective binding affinity for the AMPA receptor (IC50 = 13 nM) and demonstrated potent antagonist activity (IC50 = 6nM) at the ionotropic AMPA receptor. This compound also displayed good anticonvulsant properties against electrically-induced convulsions after ip and iv administration with ED50 values between 0.8 and 1 mg/kg. Furthermore, a strong increase in potency was observed when given iv 3 h before test (ED50 = 3.5 instead of 25.6 mg/kg for the corresponding 9-carboxymethyl-2-carboxylic acid analogue). These data confirmed that there is an advantage in replacing the classical carboxy substituents by their bioisosteres such as tetrazole or phosphonic acid groups.     

Synthesis and biological evaluation of benzo[4,5]imidazo[1,2-c]pyrimidine and benzo[4,5]imidazo[1,2-a]pyrazine derivatives as anaplastic lymphoma kinase inhibitors

Chromosomal translocations involving anaplastic lymphoma kinase (ALK) are the driving mutations for a range of cancers and ALK is thus considered an attractive therapeutic target. We synthesized a series of functionalized benzo[4,5]imidazo[1,2-c]pyrimidines and benzo[4,5]imidazo[1,2-a]pyrazines by an aza-Graebe–Ullman reaction, followed by palladium-catalyzed cross-coupling reactions. A sequential regioselective cross-coupling route is reported for the synthesis of unsymmetrically disubstituted benzo[4,5]imidazo[1,2-a]pyrazines. The inhibition of ALK was evaluated and compound 19 in particular showed good activity against both the wild type and crizotinib-resistant L1196M mutant in vitro and in ALK-transfected BaF3 cells.     

Synthesis and initial structure-activity relationships of a novel series of imidazolo[1,2-a]pyrimid-5-ones as potent GnRH receptor antagonists

SAR studies of 2-arylimidazolo[1,2-a]pyrimid-5-ones 10a-m, which were derived from initial lead 3a, resulted in the discovery of a series of potent nonpeptide human GnRH receptor antagonists. Compounds with good potency (e.g., 10e, K(i)=7.5 nM) were prepared by introduction of a 2-(2-pyridyl)ethyl at the basic nitrogen and a 3-pentyl ester at the 6-position of the bicyclic core.     

Synthesis of New Aromatic Pyrrolo[2,1- c] [1,4]benzodiazepines and Pyrrolo[1,2- a] thieno[3,2- e] [1,4]diazepines as Anti-tumoral Agents

Diazepine analogs of thieno[2,3- b] pyrrolizin-8-ones were synthesized by aromatization of 2-hydroxypyrrolo[1,2- a] thieno[3,2- e] [1,4]diazepines. These compounds were evaluated in vitro for their antiproliferative activity against the L1210 leukemia cell line. The activity of these compounds was in the micromolar range, the best result being for the mixture of the isomers 5 and 6 which showed a 0.35 μM IC 50 against cell growth.     

Loss of tritium from coprostanone derived from [1,2(n)-3H]cholesterol or [7(n)-3H]cholesterol

After oral administration of a mixture of [1,2(n)-3H]cholesterol and [4-14C]cholesterol to a baboon, fecal coprostanone had a 46% lower 3H/14C ratio than the dose administered. Loss of 3H by enolization of the 3-ketone could account for the decrease in 3H/14C. If [7(n)-3H]cholesterol was administered instead of [1,2(n)-3H]cholesterol a 23% loss of 3H from coprostanone was found. Procedures requiring measurement of 3H-coprostanone derived from [1,2(n)-3H]- or [7(n)-3H]cholesterol could be seriously in error unless an appropriate correction for loss of 3H is made.     

Synthesis and antiprotozoal activity of novel bis-benzamidino imidazo[1,2-a]pyridines and 5,6,7,8-tetrahydro-imidazo[1,2-a]pyridines

The key dinitrile intermediates 4a-d were synthesized by reaction of phenacyl bromide 1 and the appropriate 2-amino-5-bromopyridines to yield 3a-d. Suzuki coupling of 3a-d with 4-cyanophenylboronic acid yielded the 2,6-bis(4-cyanophenyl)-imidazo[1,2-a]pyridine derivatives 4a-d. The bis-amidoximes 5a-d, obtained from 4a-d by the action of hydroxylamine, were converted to the bis-O-acetoxyamidoximes which on catalytic hydrogenation in a mixture of ethanol/ethyl acetate gave the acetate salts of 2,6-bis[4-(amidinophenyl)]-imidazo[1,2-a]pyridines 7a-d. In contrast, catalytic hydrogenation of the bis-O-acetoxyamidoxime of 5a in glacial acetic acid gave the saturated analogue 2,6-bis[4-(amidinophenyl)]-5,6,7,8-tetrahydro-imidazo[1,2-a]pyridine 8. O-Methylation of the amidoximes 5a-d gave the N-methoxyamidines 6a-d. The diamidines showed strong DNA binding affinity, were very active in vitro against T. b. r. exhibiting IC(50) values between 7 and 38nM, but were less effective against P. f. with IC(50) values between 23 and 92nM. Two of the diamidines 7c and 7d were slightly more active than furamidine but less active than azafuramidine in the T. b. r. STIB900 mouse model. Only one prodrug 6b showed moderate activity in the same mouse model.     

Metabolism of alpha-D-[1,2-13C]glucose pentaacetate and alpha-D-glucose penta[2-13C]acetate in rat hepatocytes

Hepatocytes from fed rats were incubated for 120 min in the presence of alpha-D-[1,2-13C]glucose pentaacetate (1.7 mM), both D-[1,2-13C]glucose (1.7 mM) and acetate (8.5 mM), alpha-D-glucose penta[2-13C]acetate (1.7 mM), or D-[1,2-13C]glucose (8.3 mM). The amounts of 13C-enriched L-lactate and D-glucose and those of acetate and beta-hydroxybutyrate recovered in the incubation medium were comparable under the first two experimental conditions. The vast majority of D-glucose isotopomers consisted of alpha- and beta-D[1,2-13C]glucose. The less abundant single-labeled isotopomers of D-glucose were equally labeled on each C atom. The output of 13C-labeled L-lactate, mainly L-[2-13C]lactate and L-[3-13C]lactate, was 1 order of magnitude lower than that found in hepatocytes exposed to 8.3 mM D-[1,2-13C]glucose, in which case the total production of the single-labeled species of D-glucose was also increased and that of the C3- or C4-labeled hexose was lower than that of the other 13C-labeled isotopomers. In cells exposed to alpha-D-glucose penta[2-13C]acetate, the large majority of 13C atoms was recovered as [2-13C]acetate and, to a much lesser extent, beta-hydroxybutyrate labeled in position 2 and/or 4. Nevertheless, L-[2-13C]lactate, L-[3-13C]lactate, and single-labeled D-glucose isotopomers were also produced in amounts higher or comparable to those found in cells exposed to alpha-D-[1,2-13C]glucose pentaacetate. However, a modest preferential labelling of the C6-C5-C4 moiety of D-glucose, relative to its C1-C2-C3 moiety, and a lesser isotopic enrichment of the C3 (or C4), relative to that of C1 (or C6) and C2 (or C5), were now observed. These findings indicate that, despite extensive hydrolysis of alpha-D-glucose pentaacetate (1.7 mM) in the hepatocytes, the catabolism of its D-glucose moiety is not more efficient than that of unesterified D-glucose, tested at the same molar concentration (1.7 mM) in the presence of the same molar concentration of unesterified acetate (8.5 mM), and much lower than that found at a physiological concentration of the hexose (8.3 mM). The present results also argue against any significant back-and-forth interconversion of D-glucose 6-phosphate and triose phosphates, under conditions in which sizeable amounts of D-glucose are formed de novo from 13C-enriched Krebs cycle intermediates generated from either D-[1,2-13C]glucose or [2-13C]acetate.     

Synthesis of new 4-[2-(alkylamino) ethylthio]pyrrolo[1,2-a]quinoxaline and 5-[2-(alkylamino) ethylthio]pyrrolo[1,2-a]thieno[3,2-e]pyrazine derivatives, as potential bacterial multidrug resistance pump inhibitors

The synthesis of new 4-[2-(alkylamino)ethylthio]pyrrolo[1,2-a]quinoxaline derivatives la-1 is described in five or six steps starting from various substituted nitroanilines 2a-e. The bioisostere 5-[2-(alkylamino)ethylthio]pyrrolo[1,2- a]thieno[3,2-e]pyrazine 1m was also prepared. The new derivatives were evaluated as efflux pump inhibitors (EPIs) in a model targeting the NorA system of Staphylococcus aureus. The antibiotic susceptibility of two strains overproducing NorA, SA-1199B and SA-1, was determined alone and in combination with the neo-synthesised compounds by the agar diffusion method and MIC determination, in comparison with reserpine and omeprazole taken as reference EPIs. A preliminary structure-activity relationship study firstly allowed to clarify the influence of the substituents at positions 7 and/or 8 of the pyrrolo[1,2-a]quinoxaline nucleus. Methoxy substituted compounds, 1b and 1g, were more potent EPIs than the unsubstituted compounds (1a and 1f), followed by chlorinated derivatives (1c-d and 1h). Moreover, the replacement of the N,N-diethylamino group (compounds 1a-e) by a bioisostere such as pyrrolidine (compounds 1f-h) enhanced the EPI activity, in contrast with the replacement by a piperidine moiety (compounds 1i-k). Finally, the pyrrolo[1,2-a]thieno[3,2-e]pyrazine compound 1m exhibited a higher EPI activity than its pyrrolo[1,2-a]quinoxaline analogue la, opening the way to further pharmacomodulation.     

Cerebral metabolism of [1,2-13C2]acetate as detected by in vivo and in vitro 13C NMR

The metabolism of [1,2-13C2]acetate in rat brain was studied by in vivo and in vitro 13C NMR spectroscopy, in particular by taking advantage of the homonuclear 13C-13C spin coupling patterns. Well nourished rats were infused with [1,2-13C2]acetate or [1-13C]acetate in the jugular vein, and the in situ kinetics of 13C labeling during the infusion period was followed by 13C NMR techniques. The in vivo 13C NMR spectra showed signals from (i) the C-1 carbon of [1,2-13C2] acetate or [1-13C]acetate, (ii) 13CO3H-, and (iii) the natural abundance 13C carbons of sufficiently mobile fatty acids. Methanol/HCl/perchloric acid extracts of the brains were prepared and were further analyzed by high resolution 13C NMR. The homonuclear 13C-13C spin coupling patterns after infusion of [1,2-13C2]acetate showed very different isotopomer populations in glutamate, glutamine, and gamma-aminobutyric acid. Analyzing the relative proportions of these isotopomers revealed (i) two different glutamate compartments in the rat brain characterized by the presence and absence, respectively, of glutamine synthase activity, (ii) two different tricarboxylic acid cycles, one preferentially metabolizing [(1,2-13C2]acetate, the other mainly using unlabeled acetyl-coenzyme A, (iii) a hitherto unknown cerebral pyruvate recycling system associated with the tricarboxylic acid cycle, metabolizing primarily unlabeled acetyl-coenzyme A, and (iv) a predominant production of gamma-aminobutyric acid in the glutamate compartment lacking glutamine synthase.     

Imidazo[1,2-a]pyrazin-8-ones, imidazo[1,2-d][1,2,4]triazin-8-ones and imidazo[2,1-f][1,2,4]triazin-8-ones as alpha2/alpha3 subtype selective GABA A agonists for the treatment of anxiety

Imidazo[1,2-a]pyrazin-8-ones, imidazo[1,2-d][1,2,4]triazin-8-ones and imidazo[2,1-f][1,2,4]triazin-8-ones are high affinity GABA(A) agonists. Compound 16d has good oral bioavailability in rat, functional selectivity for the GABA(A)alpha2 and alpha3-subtypes and is anxiolytic in a conditioned animal model of anxiety with minimal sedation observed at full BZ binding site occupancy.     

DNA adducts in rats and mice following exposure to [4-14C]-1,2-epoxy-3-butene and to [2,3-14C]-1,3-butadiene

1,3-Butadiene (BD) is a major industrial chemical and a rodent carcinogen, with mice being much more susceptible than rats. Oxidative metabolism of BD, leading to the DNA-reactive epoxides 1,2-epoxy-3-butene (BMO), 1,2-epoxy-3,4-butanediol (EBD) and 1,2:3,4-diepoxybutane (DEB), is greater in mice than rats. In the present study the DNA adduct profiles in liver and lungs of rats and mice were determined following exposure to BMO and to BD since these profiles may provide qualitative and quantitative information on the DNA-reactive metabolites in target tissues. Adducts detected in vivo were identified by comparison with the products formed from the reaction of the individual epoxides with 2'-deoxyguanosine (dG). In rats and mice exposed to [4-14C]-BMO (1-50 mg/kg, i.p.), DNA adduct profiles were similar in liver and lung with N7-(2-hydroxy-3-butenyl)guanine (G1) and N7-(1-(hydroxymethyl)-2-propenyl)guanine (G2) as major adducts and N7-2,3,4-trihydroxybutylguanine (G4) as minor adduct. In rats and mice exposed to 200 ppm [2,3-14C]-BD by nose-only inhalation for 6 h, G4 was the major adduct in liver, lung and testes while G1 and G2 were only minor adducts. Another N7-trihydroxybutylguanine adduct (G3), which could not unambiguously be identified but is either another isomer of N7-2,3,4-trihydroxybutylguanine or, more likely, N7-(1-hydroxymethyl-2,3-dihydroxypropyl)guanine, was present at low concentrations in liver and lung DNA of mice, but absent in rats. The evidence indicates that the major DNA adduct formed in liver, lung and testes following in vivo exposure to BD is G4, which is formed from EBD, and not from DEB.     

Synthesis and cytotoxicity of methyl-4,8-dihydrobenzo[1,2-b:5,4-b']dithiophene-4,8-dione derivatives.

2- and 3-Methyl-4,8-dihydrobenzo[1,2-b:5,4-b']dithiophene-4,8-dione and related derivatives were synthesized and evaluated in vitro by NCI against eight cancer types. Compounds 12-15 showed significant activity against melanoma, NCI-H23 non-small cell lung cancer, and MDA-MB-435 and MDA-N breast cancer cell lines; 2-hydroxymethyl-4,8-dihydrobenzo[1,2-b:5,4-b']dithiophene-4,8-dion e (13) showed the highest activity against melanoma (mean log GI50 = -7.74) and the highest overall potency (mean log GI50 = -6.99).     

New ferrocenic pyrrolo[1,2-a]quinoxaline derivatives: synthesis, and in vitro antimalarial activity

Following our search for antimalarial compounds, novel series of ferrocenic pyrrolo[1,2-a]quinoxaline derivatives 1-2 were synthesized from various substituted nitroanilines and tested for in vitro activity upon the erythrocytic development of Plasmodiumfalciparum strains with different chloroquine-resistance status. The pyrrolo[1,2-a]quinoxalines 1 were prepared in 6-8 steps through a regioselective palladium-catalyzed monoamination by coupling 4-chloropyrrolo[1,2-a]quinoxalines with 1,3-bis(aminopropyl)piperazine or -methylamine using Xantphos as the ligand. The ferrocenic bispyrrolo[1,2-a]quinoxalines 2 were prepared by reductive amination of previously described bispyrrolo[1,2-a]quinoxalines 9 with ferrocene-carboxaldehyde, by treatment with NaHB(OAc)(3). The best results were observed with ferrocenic pyrrolo[1,2-a]quinoxalines linked by a bis(3-aminopropyl)piperazine. Moreover, it was observed that a methoxy group on the pyrrolo[1,2-a]quinoxaline nucleus and no substitution on the terminal N-ferrocenylmethylamine function enhanced the pharmacological activity. Selected compounds 1b, 1f-h, 1l and 2a were tested for their ability to inhibit beta-haematin formation, the synthetic equivalent of hemozoin, by using the HPIA (heme polymerization inhibitory activity) assay. Of the tested compounds, only 2a showed a beta-haematin formation inhibition, but no inhibition of haem polymerization was observed with the other selected ferrocenic monopyrrolo[1,2-a]quinoxaline derivatives 1b, 1f-h and 1l, as the IC(50) values were superior to 10 equivalents.     

Synthesis and biological evaluation of novel hexahydro-pyrido[3',2':4,5]pyrrolo[1,2-a]pyrazines as potent and selective 5-HT(2C) receptor agonists

Further lead optimization efforts on previously described 1,2,3,4,10,10a-hexahydro-1H-pyrazino[1,2-a]indoles led to the new class of 5,5a,6,7,8,9-hexahydro-pyrido[3',2':4,5]pyrrolo[1,2-a]pyrazines culminating in the discovery of (5aR,9R)-2-[(cyclopropylmethoxy)methyl]-5,5a,6,7,8,9-hexahydro-9-methyl-pyrido[3', 2':4,5]pyrrolo[1,2-a]pyrazine 18 as a potent, full 5-HT(2C) receptor agonist with an outstanding selectivity profile and excellent hERG and phospholipidosis properties.     

8-Methylureido-4,5-dihydro-4-oxo-10H-imidazo[1,2-a]indeno[1,2-e]pyrazines: highly potent in vivo AMPA antagonists

A novel series of readily water soluble 8-methylureido-4,5-dihydro-4-oxo-10H-imidazo[1,2-a]indeno[1,2-e]++ +pyrazines were synthesized. The -10-yl acetic acid ((+)-3) and -10-carboxylidene (4) derivatives exhibit potent affinities (IC50=4 and 19 nM, respectively) and antagonist properties (IC50 = 2 and 3 nM, respectively) at the ionotropic AMPA receptor. These compounds also display anticonvulsant properties against both electrically and sound-induced convulsions in mice after ip, sc and iv administration with ED50 values between 0.9 and 11 mg/kg, thus suggesting adequate brain penetration.     

Experimental and theoretical studies of anthelmintics: oxfendazole and its imidazo[1,2-a]pyridine-2-carbamate isomer

Mice experimentally infected with Trichinella spiralis were used to test the therapeutic effectiveness of an anthelmintic, methyl 6-(phenylsulfinyl)imidazo[1,2-a]pyridine-2-carbamate, against the immature and adult worms during the intestinal phase of infection. A single oral dose of 100 mg kg-1 of the drug on the third day after exposure to infection was totally ineffective against the adult worms as determined at necropsy on day 6. Neither higher unit dosages of the drug, division of the daily oral dose, nor increasing the length of the treatment period from 1 to 4 days enhanced drug activity in vivo. Furthermore the drug was inactive as a single oral dose against the immature worms at all of the dosages tested (12.5-400 mg kg-1). These results are in marked contrast to those obtained previously with oxfendazole (methyl 5[6]-(phenylsulfinyl)benzimidazole-2-carbamate) under comparable experimental conditions and clearly indicate that the two compounds are not anthelmintically equivalent in the T. spiralis-infected mouse system in spite of their similar structural features. A quantum mechanical study of these drugs was undertaken and a hypothesis for the inactivity of the imidazo[1,2-a]pyridine-2-carbamate isomer is proposed.