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.     

Binding of [H][D-Ala, MePhe, Gly-ol] Enkephalin, [H][D-Pen, D-Pen]Enkephalin, and [H]U-69,593 to Airway and Pulmonary Tissues of Normal and Sensitized Rats

Bhargava, H. N., V. M. Villar, J. Cortijo and E. J. Morcillo. Binding of [³H][D-Ala², MePhe⁴, Gly-ol⁵]enkephalin, [³H][D-Pen², D-Pen⁵]enkephalin, and [³H]U-69,593 to airway and pulmonary tissues of normal and sensitized rats. Peptides 18(10) 1603–1608, 1997.—The role of endogenous opioid peptides in the regulation of bronchomotor tone, as well as in the pathophysiology of asthma is uncertain. We have studied the binding of highly selective [³H]labeled ligands of μ-([D-Ala², MePhe⁴, Gly-ol⁵]enkephalin; DAMGO), δ ([D-Pen², D-Pen⁵]enkephalin; DPDPE), and κ-(U-69,593) opioid receptors to membranes of trachea, main bronchus, lung parenchyma and pulmonary artery obtained from normal (unsensitized) and actively IgE-sensitized rats acutely challenged with the specific antigen. [³H]DAMGO, [³H]DPDPE and [³H]U-69,593 bound to membranes of normal and sensitized tissues at a saturable, single high-affinity site. The rank order of receptor densities in normal tissues was δ- ≥ κ- ≥ μ-, with lung parenchyma exhibiting the greatest binding capacity for δ- and μ- receptors compared to the other regions examined. The K_d values showed small differences between ligands and regions tested. The μ- and δ-opioid receptor densities were decreased in sensitized main bronchus and lung parenchyma, respectively, compared to normal tissues. By contrast, κ-opioid receptor density was augmented in sensitized lung parenchyma but an increase in K_d values was also observed. These differential changes in the density and affinity of opioid receptor types may be related to alterations in endogenous opioid peptides during the process of sensitization.     

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 microM IC50 against cell growth.     

Novel vasopressin V2 receptor-selective antagonists, pyrrolo[2,1-a]quinoxaline and pyrrolo[2,1-c][1,4]benzodiazepine derivatives.

The intent of the work was to study the structure-activity relationships of AVP receptor antagonists bearing a chiral ring as a partial structure since such studies had been reported for only achiral compounds. In the present paper, we deal with compounds consisting of the chiral tricyclic hetero ring (1,2,3,3a,4,5-hexahydropyrrolo[1,2-a]quinoxaline and 1,2,3,10,11,11a-hexahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepine) and 2-phenylbenzanilide analogues. These compounds exhibited a highly selective affinity for V2 receptor, and their stereochemical configuration had a great influence on V2 receptor binding. VP-343 (N-[4-[[(2S,3aR)-2-hydroxy-2,3,3a,4-tetrahydropyrrolo[1,2-a] quinoxalin-5(1H)-yl]carbonyl]phenyl]-4'-methyl[1,1'-biphenyl]-2-ca rboxamide), VP-365 (N-[4-[[(11aS)-2,3,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benz odiazepin-10(5H)-yl]carbonyl]phenyl][1,1'-biphenyl-2-carboxamide) and VP-339 (N-[4-[[(11aS)-5-oxo-2,3,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]+ ++benzodiazepin-10(5H)-yl]carbonyl]phenyl][1,1'-biphenyl]-2-carboxami de) were the most potent compounds in vitro and in vivo. The IC50 values of VP-343, VP-365 and VP-339 against V2 receptor were 0.772, 1.18 and 0.216 nM, respectively. The ED300 values (dose required to increase three times the urine volume of the control rats; oral administration) of VP-343, VP-365 and VP-339 were 0.22, 0.31 and 0.78 mg/kg, respectively.     

Effect of C2-exo unsaturation on the cytotoxicity and DNA-binding reactivity of pyrrolo[2,1-c][1,4]benzodiazepines

A series of novel C2-exo unsaturated pyrrolo[2,1-c][1,4]benzodiazepines (PBDs) has been synthesised via a versatile pro-C2 ketone precursor. C2-exo-unsaturation enhances both DNA-binding reactivity and in vitro cytotoxic potency.     

Extraction selectivities of lower rim substituted calix[4]arene hosts induced by variations in the upper rim substituents

The compound 25,26,27,28-tetra-(2-dimethyldithiocarbamoylethoxy)calix[4]arene has been prepared from 25,26,27,28-tetra-(2-bromoethoxy)calix[4]arene by reaction with sodium dimethyldithiocarbamate. As an extractant for heavy metal ions 25,26,27,28-tetra-(2-dimethyldithiocarbamoylethoxy)calix[4]arene is effective for Hg²⁺, Ag⁺, Pd²⁺ and Au³⁺, but much less effective than 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetra-(2-N,N-dimethyldithiocarbamoylethoxy)calix[4]arene for both Hg₂²⁺ and MeHg⁺. Calixarene alcohols also show selectivity as hosts. The alcohol derivative 25,26,27,28-tetra-(2-hydroxyethoxy)calix[4]arene undergoes slow occlusion of iodine into the lower rim, whereas with the alcohol 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetra-(2-hydroxyethoxy)calix[4]arene no interaction is observed.     

Synthesis and anticancer evaluation of certain indolo[2,3-b]quinoline derivatives

The present report describes the synthesis and anticancer evaluation of certain 11-substituted 6H-indolo[2,3-b]quinolines and their methylated derivatives. These 6H-indolo[2,3-b]quinoline derivatives 11–13 were prepared from the commercially available 1,4-dihydroxyquinoline through alkylation, chlorination, nucleophilic reaction, and ring cyclization. Depending on the ratio of 11, (MeO)₂SO₂, and K₂CO₃, alkylation occurred primarily on N-5 (1:0.8:0.8) or N-6 (1:1.5:1.5) leading to the isolation of 14a or 14b as a major product. Accordingly, major product 15a (2/(MeO)₂SO₂/K₂CO₃ = 1:2:2) or 15b (1:1:1), respectively, was obtained by alkylation of 12 while 16a (13/(MeO)₂SO₂/K₂CO₃ = 1:2:2) or 16b (1:1:1), respectively, was obtained by alkylation of 13. The in vitro anticancer assay indicated 5-methylated derivatives 14a, 15a, 16a are more cytotoxic than their respective 6-methylated counterparts 14b, 15b, 16b and 6H-indolo[2,3-b]quinoline precursors 11, 12, 13. Among them, 11-(4-methoxyanilino)-6-methyl-6H-indolo[2,3-b]quinoline (16a) was the most cytotoxic with a mean GI₅₀ value of 0.78 μM and also exhibited selective cytotoxicities for HL-60 (TB), K-562, MOLT-4, RPMI-8226, and SR with GI₅₀ values of 0.11, 0.42, 0.09, 0.14, and 0.19 μM, respectively.     

Characteristics of [D-Trp]-somatostatin-sensitive B50 phosphorylation

Inhibition of the phosphorylation of the synaptic plasma membrane (SPM) protein B50 by [D-Trp⁸]-somatostatin in vitro is time-dependent. Increasing the time of incubation of hippocampal synaptic plasma membranes with the peptide from 15 sec to 30 min prior to addition of 7.5 μM [γ-³²Ps]ATP results in a complete reduction of B50 phosphorylation. Incubation of synaptic plasma membranes for 30 min in the absence of peptide does not alter basal B50 phosphorylation. Neither ACTH nor β-endorphin produces similar effects—inhibition of B50 phosphorylation by ACTH is maximal at 15 sec and β-endorphin produces only a small inhibition, even after 30 min. [D-Trp⁸]-somatostatin is not activating a membrane-bound protease, since maximal inhibition of B50 phosphorylation by the peptide is seen in the presence of leupeptin or bacitracin. Hippocampal synaptic plasma membranes contain protein phosphatase activity. Assays of B50 phosphorylation in synaptic plasma membranes done under conditions that favor either net phosphorylation or dephosphorylation are consistent with inhibition of protein phosphatase activity by [D-Trp⁸]-somatostatin. This evidence suggests that [D-Trp⁸]-somatostatin interacts with SPM binding sites in the hippocampus, which may alter the activity of an endogenous protein phosphatase to determine the degree of B50 phosphorylation.     

Effect of C2/C3-endo unsaturation on the cytotoxicity and DNA-binding reactivity of pyrrolo[2,1-c][1,4]benzodiazepines

A series of novel C2,C3-endo unsaturated pyrrolo[2,1-c][1,4]benzodiazepines (PBDs) has been synthesised via cleavage of the N10-Alloc protecting group from appropriate precursors. Biophysical and biological evaluations show that the presence of C2/C3-endo unsaturation in the PBD C-ring enhances both DNA-binding reactivity and in vitro cytotoxic potency.     

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 1a-l 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 1a, opening the way to further pharmacomodulation.     

Temperature-dependent regulation of d-cis-[H]diltiazem binding to Ca channels by 1,4-dihydropyridine channel agonists and antagonists

The binding of the Ca²⁺-channel blocker d-cis-[³H]diltiazem to guinea pig skeletal muscle microsomes is temperature-dependent. At 2°C the K_D is 39 nM and B_max is 11 pmol/mg protein. The binding is fully reversible (K₋₁ = 0.02 min⁻¹). The binding sites discriminate between the diastereoisomers 1- and d-cis-diltiazem, recognize verapamil, gallopamil and tiapamil, and are sensitive to La³⁺-inhibition. At 30°C the K_D is 37 nM and the B_max is 2.9 pmol/mg protein. D-cis-diltiazem-labelling is regulated by the 1,4-dihydropyridine Ca²⁺-channel blockers and a novel Ca²⁺-channel activator in a temperature-dependent manner. At 30°C an enhancement of d-cis-diltiazem binding by the channel blockers is observed. This is attributed to a B_max increase. EC₅₀-values for enhancement and the maximal enhancement differ for the individual 1,4-dihydropyridines. At 2°C 1,4-dihydropyridines inhibit d-cis-[³H]diltiazem binding. This is attributed to a B_max decrease. We have directly labelled one of the drug receptor sites within the Ca²⁺-channel which can allosterically interact with the 1,4-dihydropyridine binding sites.     

A radioimmunoassay specific for [Gln]LH-RH: Application in the confirmation of the structure of chicken hypothalamic luteinizing hormone-releasing hormone

In the first report on the chemical structure of a nonmammalian LH-RH, chicken hypothalamic LH-RH was demonstrated to be [Gln⁸]LH-RH [2–4]. However, these studies and subsequent reports [7,8] did not totally exclude the possibility of a reverse sequence of the two amino acids Leu-Gln. In view of the recently described structure of salmon brain LH-RH as [Trp⁷,Leu⁸]LH-RH [9], we undertook to confirm our earlier conclusion that chicken LH-RH is [Gln⁸]LH-RH and not [Gln⁷,Leu⁸]LH-RH. The immunologic, chromatographic and biological properties of natural chicken hypothalamic LH-RH were compared with those of the two synthetic peptides, [Gln⁸]LH-RH and [Gln⁷,Leu⁸]LH-RH. A radioimmunoassay highly specific for [Gln⁸]LH-RH was developed. Natural chicken LH-RH cross-reacted fully with the antiserum which requires the COOH-terminal Gln⁸ to Gly¹⁰-NH₂ for binding, while [Gln⁷,Leu⁸]LH-RH showed less than 0.1% cross-reaction. On a high resolution reverse phase high performance liquid chromatography system, natural chicken LH-RH co-eluted with [Gln⁸]LH-RH and was well separated from [Gln⁷,Leu⁸]LH-RH. In a chicken anterior pituitary cell bioassay, natural chicken LH-RH and [Gln⁸]LH-RH were equipotent in stimulating luteinizing hormone release, while the relative potency of [Gln⁷,Leu⁸]LH-RH was 4.4%. These data, in particular the use of a specific [Gln⁸]LH-RH antiserum, provide conclusive evidence that chicken LH-RH is [Gln⁸]LH-RH.     

A quantitative assay to measure the relative DNA-binding affinity of pyrrolo[2,1-c] [1,4]benzodiazepine (PBD) antitumour antibiotics based on the inhibition of restriction endonuclease BamHI.

An assay has been developed (restriction endonuclease digestion assay--RED100) based on inhibition of the restriction endonuclease BamHI that is capable of quantitative evaluation of the relative DNA-binding affinity of pyrrolo[2,1-c] [1,4]benzodiazepine (PBD) antitumour antibiotics. This method provides comparable results to those obtained from thermal denaturation and ethidium bromide displacement assays but is much more sensitive, discriminating between molecules of similar structure such as DC-81, iso-DC-81 and neothramycin. The results reveal a trend between relative DNA-binding affinity and in vitro cytotoxicity for the PBDs in two tumour cell lines studied.     

Synthesis, structure, and heterogeneous catalytic activity of tungsten chalcogenide cubane cluster containing alkaline earth metal complex

A new compound containing a cubane tungsten chalcogenide cluster [W₄(μ₃-Te)₄(CN)₁₂]⁶⁻ and Ca²⁺ complex units has been prepared by the reaction of aqueous solution of K₆[W₄(μ₃-Te)₄(CN)₁₂] · 5H₂O with the solution of a Ca(NO₃)₂ and phen(1,10-phenanthroline) (1:2 molar ratio) in a solvent mixture of H₂O/EtOH. The structure of [{Ca(phen)₂(H₂O)}{Ca(phen)(H₂O)₄}{Ca(phen)₂(H₂O)₃}][W₄Te₄(CN)₁₂] · 5H₂O 1 has been determined by X-ray crystallography. Compound 1 contains [{Ca(phen)(H₂O)₄}{Ca(phen)₂(H₂O)₃}][W₄(μ₃- Te)₄(CN)₁₂] units bridged by {Ca(phen)₂(H₂O)}²⁺ units to form an one-dimensional zigzag chain structure. Interestingly, compound 1 showed a heterogeneous catalytic activity in the transesterification of a range of esters with methanol under the mild conditions. Moreover, it can be reused without any loss of activity through 10 runs with ester.     

Synthesis and in vitro anti-hepatitis B and C virus activities of ring-expanded ('fat') nucleobase analogues containing the imidazo[4,5-e][1,3]diazepine-4,8-dione ring system

As part of our structure–activity relationship studies, we report here the synthesis and in vitro anti-HBV and anti-HCV activities of a number of ring-expanded (‘fat’) nucleobases containing the imidazo[4,5-e][1,3]diazepine-4,8-dione ring system. One of the compounds, ZP-88, exhibited a good activity/toxicity profile against HBV by inhibition of the synthesis of extracellular virion release (EC₅₀ = 1.7 μM, CC₅₀ = 286 μM, SI = 168) and intracellular HBV replication intermediates (EC₅₀ = 8.4 μM, CC₅₀ = 286 μM, SI = 34) in cultured human hepatoblastoma 2.2.15 cells. By contrast, most of the compounds tested against HCV had only marginal activity/toxicity profile, although that was still better than that of the reference compound ribavirin.     

Differential Interaction of 1-Methyl-4-Phenylpyridinium Ion with the Putatively Vesicular Binding Site of [3H]Tyramine in Dopaminergic and Nondopaminergic Brain Regions

Abstract: The neurotoxin 1-methyl-4-phenylpyridinium ion (MPP⁺) in the brain striatum has recently been shown to bind at a putatively vesicular site labeled by [³H]tyramine ([³H]TY). Whereas in the rat and mouse striatum MPP⁺ antagonized TY binding competitively, in the cerebellum there was a mixed-type antagonism, which suggests the simultaneous occupancy of two different sites. K _i values from displacement curves revealed a fourfold difference in the affinity of MPP⁺ for TY sites in the two brain regions. The degeneration of central noradrenergic terminals induced by an intraperitoneal injection of the toxin N -(2-chloroethyl)- N -ethyl-2-bromobenzylamine in rats decreased by 80% the maximal number of cerebellar TY binding sites, while not affecting striatal binding. Furthermore, guanethidine, a marker for noradrenaline (NA) vesicles, potently inhibited TY binding in NA-innervated regions, such as the cerebellum and the parietal cortex, and poorly in the striatum. It is concluded (a) that both MPP⁺ and TY may also label NA vesicles and (b) that the vesicular carriers for dopamine and NA have different characteristics, which may underlie a regional specificity in the rate of endovesicular sequestration of MPP⁺, with either neurodegenerative or neuroprotective consequences, depending on the brain area involved.     

Prions beget prions: the [PIN] mystery!

Prions are infectious proteins. [PIN⁺] is a non-chromosomal genetic element of Saccharomyces cerevisiae that is necessary for the de novo induction of the [PSI⁺] prion. Recently, [PIN⁺] has been found to be itself a prion of the Rnq1 protein. [URE3], another yeast prion, can also promote [PSI⁺] generation. Thus, one prion can promote the generation of another.     

The new enneanuclear nickel carbonyl anion [Ni9(CO)16] and its relationships with the [Ni12(CO)21] and [Ni6Rh3(CO)17] clusters

The reaction of [N(PPh₃)₂]₂[Ni₆(CO)₁₂] with Cu(PPh₃)_xCl (x=1, 2), as well as the degradation of [N(PPh₃)₂]₂[H₂Ni₁₂(CO)₂₁] with PPh₃, affords the new and unstable dark orange–brown [N(PPh₃)₂]₂[Ni₉(CO)₁₆].THF salt in low yields. This salt has been characterized by a CCD X-ray diffraction determination, along with IR spectroscopy and elemental analysis. The close-packed two-layer metal core geometry of the [Ni₉(CO)₁₆]²⁻ dianion is directly related to that of the bimetallic [Ni₆Rh₃(CO)₁₇]³⁻ trianion and may be envisioned to be formally derived from the hcp three-layer geometry of [Ni₁₂(CO)₂₁]⁴⁻ by the substitution of one of the two outer [Ni₃(CO)₃(μ−CO)₃]²⁻ layers with a face-bridging carbonyl group.     

Cyclic tetranuclear half-sandwich ruthenium(II) complexes with 4,7-phenanthroline and hydroxo bridges: crystal structure, solution behaviour and binding to nucleosides

The reaction between [(η⁶-p-cymene)Ru(H₂O)₃]X₂ and 4,7-phenanthroline (phen) leads to the formation of the rectangular tetranuclear complexes [(η⁶-p-cymene)₄Ru₄(μ-4,7-phen-N⁴,N⁷)₂(μ-OH)₄]X₄ (X = NO₃, 1a; SO₃CF₃, 1b) which have been structurally characterised by X-ray crystallography. ¹H NMR spectroscopic studies suggest the presence of a partially dissociated dinuclear species of type [(η⁶-p-cymene)₂Ru₂(μ-4,7-phen-N⁴,N⁷)(solv)₄]⁴⁺ in equilibrium with the tetranuclear cyclic species found in the solid state. The temperature effect for this equilibrium was studied by variable temperature ¹H NMR experiments in D₂O and MeOD. The results reveal that the proportion of the tetranuclear species increases with the polarity of the solvent which favour stacking interactions between the phenanthroline moieties. In addition, the reactivity of the tetranuclear species towards the nucleosides guanosine (Guo), cytidine (Cyt), 2′-deoxythymidine (Thy) and 2′-deoxyadenosine (dAdo) has been monitored by ¹H NMR as a potential model for the interaction of the 1 species with the probable DNA target. The results reveal that the 1 systems are able to bind the nucleobases endocyclic nitrogen atoms of Guo Cyt, and dAdo.     

Neuropeptide Y receptor agonists: Multiple effects on spontaneous activity in the paraventricular hypothalamus

In vitro rat hypothalamic slices were used to examine the ability of neuropeptide Y (NPY), and the putative Y₁ and Y₂ receptor agonists [Pro³⁴]NPY, and [C²]NPY, to modify spontaneous single-neuron discharge in the paraventricular nucleus (PVN). NPY and [Pro³⁴]NPY, at high concentrations (1500 nM), decreased discharge rates. At intermediate concentrations (150 nM) these peptides produced multiple effects, including increases, decreases, and biphasic changes. At lower concentrations (0.15–15 nM), they typically increased discharge rates. In contrast, [C²]NPY, at all concentrations (1.5–1500 nM), predominantly increased discharge rates. Thus, these NPY sybtype agonists have multiple effects on discharge rate, which may be due to action on multiple NPY receptor subtypes.