The interaction of [Ru(NH3)5Cl]2+ and [Ru(NH3)6]3+ ions with DNA

The interaction of [Ru(NH3)5Cl]2+ and [Ru(NH3)6]3+ complex ions with calf thymus DNA has been studied at various r values (r = [Mn+]/[DNA-P]). Electronic spectra of metal-DNA solutions have been recorded and compared to the spectra of metal, as well as of DNA, solutions. Melting curves have been taken for the determination of DNA melting temperature (Tm) in the presence of the above complex ions. The results showed a biphasic melting of the DNA strands for relatively high r values. The Tm for the first phase increased with increasing r values, indicating metal ion interaction with the phosphate moieties of the DNA. The appearance of a second-phase melting, in connection with electronic spectra, pH values, and conductivity measurements of metal ion solutions, is indicative of the initial complexes' transformation to [Ru(NH3)5OH]2+, which binds preferentially to double-stranded rather than single-stranded DNA, thus leading to a second melting curve at a higher temperature than the first one.     

Similar binding of the carcinostatic drugs cis-[Pt(NH3)2Cl2] and [Ru(NH3)5Cl] Cl2 to tRNAphe and a comparison with the binding of the inactive trans-[Pt(NH3)2Cl2] complex - reluctance in binding to Watson-Crick base pairs within double helix.

A comparative study of the binding of square planar cis- and trans-[Pt(NH3)2Cl2] complexes and the octahedral [Ru(NH3)5(H2O)]3+ complex to tRNAphe from yeast was carried out by X-ray crystallography. Both of the carcinostatic compounds, cis-[Pt(NH3)2Cl2] and [Ru(NH3)5(H2O)]3+ show similarities in their mode of binding to tRNA. These complexes bind specifically to the N(7) positions of guanines G15 and G18 in the dihydrouridine loop. [Ru(NH3)5(H2O)]3+ has an additional binding site at N(7) of residue G1 after extensive soaking times (58 days). A noncovalent binding site for ruthenium is also observed in the deep groove of the acceptor stem helix with shorter (25 days) soaking time. The major binding site for the inactive trans-[Pt(NH3)Cl2] complex is at the N(1) position of residue A73, with minor trans-Pt binding sites at the N(7) positions of residues Gm34, G18 and G43. The similarities in the binding modes of cis-[Pt(NH3)2Cl2] and [Ru(NH3)5(H2O)]3+ are expected to be related to their carcinostatic properties.     

1-[4-[3-[4-[bis(4-fluorophenyl)hydroxymethyl]-1- piperidinyl]propoxy]-3-methoxyphenyl]ethanone(AHR-5333): a selective human blood neutrophil 5-lipoxygenase inhibitor

In this study we report the in vitro inhibition of leukotriene synthesis in calcium ionophore (A23187)-stimulated, intact human blood neutrophils by AHR-5333. The results showed that AHR-5333 inhibits 5-HETE, LTB4 and LTC4 synthesis with IC50 values of 13.9, 13.7 and 6.9 microM, respectively. Further examination of the effect of AHR-5333 on individual reactions of the 5-lipoxygenase pathway (i.e. conversion of LTA4 to LTB4, LTA4 to LTC4, and arachidonic acid to 5-HETE) showed that this agent was not inhibitory to LTA4 epoxyhydrolase and glutathione-S-transferase activity in neutrophil homogenates. However, conversion of arachidonic acid (30 microM) to 5-HETE was half maximally inhibited by 20 microM AHR-5333 in the cell-free system. The inhibition of LTB4 and LTC4 formation in intact neutrophils by AHR-5333 appears to be entirely due to a selective inhibition of 5-lipoxygenase activity and an impaired formation of LTA4, which serves as substrate for LTA4 epoxyhydrolase and glutathione-S-transferase. AHR-5333 did not affect the transformation of exogenous arachidonic acid to thromboxane B2, HHT and 12-HETE in preparations of washed human platelets, indicating that this agent has no effect on platelet prostaglandin H synthase, thromboxane synthase and 12-lipoxygenase activity. The lack of inhibitory activity of AHR-5333 on prostaglandin H synthase activity was confirmed with microsomal preparations of sheep vesicular glands.     

Identification of 4-[1-[3-chloro-4-[N'-(5-fluoro-2-methylphenyl)ureido]phenylacetyl]-(4S)-fluoro-(2S)-pyrrolidinylmethoxy]benzoic acid as a potent, orally active VLA-4 antagonist

Optimization of benzoic acid derivatives by introducing substituents into the diphenyl urea moiety led to the identification of compound 20l as a potent VLA-4 antagonist. Compound 20l inhibited eosinophil infiltration into bronchial alveolar lavage fluid in a murine asthma model by oral dosing and its efficacy was comparable to anti-mouse alpha4 antibody (R1-2). Furthermore, this compound significantly blocked bronchial hyper-responsiveness in the model.     

3-[2-Amino-2-imidazolin-4(5)-yl]alanine (enduracididine) and 2-[2-amino-2-imidazolin-4(5)-yl] acetic acid in seeds of Lonchocarpus sericeus

3-[2-Amino-2-imidazolin-4(5)-yl]alanine (enduracididine) and 2-[2-amino-2-imidazolin-4(5)-yl] acetic acid have been isolated from seeds of Lonchocarpus sericeus. The concentration of each compound was ca 0.5 % of the fresh seed weight.     

Structure-dependent in vitro cytotoxicity of the isomeric complexes [Ru(L)2Cl2] (L=o-tolylazopyridine and 4-methyl-2-phenylazopyridine) in comparison to [Ru(azpy)2Cl2]

The dichlorobis(2-phenylazopyridine)ruthenium(II) complexes, [Ru(azpy)(2)Cl(2)], are under renewed investigation due to their potential anticancer activity. The three most common isomers alpha-, beta- and gamma-[RuL(2)Cl(2)] with L= o-tolylazopyridine (tazpy) and 4-methyl-2-phenylazopyridine (mazpy) (alpha indicating the coordinating Cl, N(pyridine) and Nazo atoms in mutual cis, trans, cis positions, beta indicating the coordinating Cl, N(pyridine) and Nazo atoms in mutual cis, cis, cis positions, and gamma indicating the coordinating Cl, N(pyridine) and Nazo atoms in mutual trans, cis, cis positions) are synthesized and characterized by NMR spectroscopy. The molecular structures of gamma-[Ru(tazpy)(2)Cl(2)] and alpha-[Ru(mazpy)(2)Cl(2)] are determined by X-ray diffraction analysis. The IC(50) values of the geometrically isomeric [Ru(tazpy)(2)Cl(2)] and [Ru(mazpy)(2)Cl(2)] complexes compared with those of the parent [Ru(azpy)(2)Cl(2)] complexes are determined in a series of human tumour cell lines (MCF-7, EVSA-T, WIDR, IGROV, M19, A498 and H266). These data unambiguously show for all complexes the following trend: the alpha isomer shows a very high cytotoxicity, whereas the beta isomer is a factor 10 less cytotoxic. The gamma isomers of [Ru(tazpy)(2)Cl(2)] and [Ru(mazpy)(2)Cl(2)] display a very high cytotoxicity comparable to that of the gamma isomer of the parent compound [Ru(azpy)(2)Cl(2)] and to that of the alpha isomer. These biological data are of the utmost importance for a better understanding of the structure-activity relationships for the isomeric [RuL(2)Cl(2)] complexes.     

Differential Absorption, Translocation and Metabolism of Metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)one] by Soybean Cultivars

Soybean (Glycine max (L.) Merr.) cultivars have been reported to range in tolerance to injury by 4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)one (metribuzin), from tolerant (e.g.‘Bragg’) to susceptible (e.g.‘Coker 102’ and ‘Semmes’). ‘Bragg,’‘Coker 102’, and ‘Semmes’ soybeans were grown in sand subirrigated with nutrient solution containing labelled (¹⁴C-carbonyl metribuzin) and nonlabelled metribuzin to determine cultivar variability in absorption, translocation, and metabolism of metribuzin. Plants were periodically harvested, autoradiographed, and radioactivity in tissue extracts quantified. Data indicated that all 3 cultivars readily absorbed and translocated metribuzin. However, ‘Bragg’ tissues accumulated greater quantities of metribuzin metabolites than the other two cultivars. The major ¹⁴C-containing metabolite in ‘Semmes’ and ‘Coker’ roots and stems was 6-tert-butyl-as-triazine-3-5-(2H,4H)-dione, whereas the major ¹⁴C-metabolite isolated from‘Bragg’ roots and stems was a glucose conjugate. Results indicated that differential-intraspecific responses to metribuzin may result from differential capacities for herbicide detoxification by conjugation.     

Studies on formation and stability of the d[G(AG)5]* d[G(AG)5]·d[C(TC)5] and d[G(TG)5]* d[G(AG)5]· d[C(TC)5] triple helices

We have targeted the d[G(AG)₅] · d[C(TC)₅] duplex for triplex formation at neutral pH with either d[G(AG)₅] or d[G(TG)₅]. Using a combination of gel electrophoresis, uv and CD spectra, mixing and melting curves, along with DNase I digestion studies, we have investigated the stability of the 2:1 pur*pur · pyr triplex, d[G(AG)₅] * d[G(AG)₅] · d[C(TC)₅], in the presence of MgCl₂. This triplex melts in a monophasic fashion at the same temperature as the underlying duplex. Although the uv spectrum changes little upon binding of the second purine strand, the CD spectrum shows significant changes in the wavelength range 200–230 nm and about a 7 nm shift in the positive band near 270 nm. In contrast, the 1:1:1 pur/pyr*pur · pyr triplex, d[G(TG)₅] * d[G(AG)₅] · d[C(TC)₅], is considerably less stable thermally, melting at a much lower temperature than the underlying duplex, and possesses a CD spectrum that is entirely negative from 200 to 300 nm. Ethidium bromide undergoes a strong fluorescence enhancement upon binding to each of these triplexes, and significantly stabilizes the pur/pyr*pur · pyr triplex. The uv melting and differential scanning calorimetry analysis of the alternating sequence duplex and pur*pur · pyr triplex shows that they are lower in thermodynamic stability than the corresponding 10-mer d(G₃A₄G₃) · d(C₃T₄C₃) duplex and its pur*pur · pyr triplex under identical solution conditions. © 1997 John Wiley & Sons, Inc.     

Synthesis and monoamine transporter binding properties of 2beta-[3'-(substituted benzyl)isoxazol-5-yl]- and 2beta-[3'-methyl-4'-(substituted phenyl)isoxazol-5-yl]-3beta-(substituted phenyl)tropanes

A series of 2beta-[3'-(substituted benzyl)isoxazol-5-yl]- and 2beta-[3'-methyl-4'-(substituted phenyl)isoxazol-5-yl]-3beta-(substituted phenyl)tropanes were prepared and evaluated for affinities at dopamine, serotonin, and norepinephrine transporters using competitive radioligand binding assays. The 2beta-[3'-(substituted benzyl)isoxazol-5-yl]-3beta-(substituted phenyl)tropanes (3a-h) showed high binding affinities for the dopamine transporter (DAT). The IC(50) values ranged from 5.9 to 22nM. On the other hand, the 2beta-[3'-methyl-4'-(substituted phenyl)isoxazol-5-yl]-3beta-(substituted phenyl)tropanes (4a-h), with IC(50) values ranging from 65 to 173nM, were approximately 3- to 25-fold less potent than the corresponding 2beta-[3'-(substituted benzyl)isoxazol]tropanes. All tested compounds were selective for the DAT relative to the norepinephrine transporter (NET) and serotonin transporter (5-HTT). 3Beta-(4-Methylphenyl)-2beta-[3'-(4-fluorobenzyl)isoxazol-5-yl]tropane (3b) with IC(50) of 5.9nM at the DAT and K(i)s of 454 and 113nM at the NET and 5-HTT, respectively, was the most potent and DAT-selective analog. Molecular modeling studies suggested that the rigid conformation of the isoxazole side chain in 4a-h might play an important role on their low DAT binding affinities.     

Correlation of antibacterial activity of some N-[5-(2-furanyl)-2-methyl-4-oxo-4H-thieno[2,3-d]pyrimidin-3-yl]-carboxamide and 3-substituted-5-(2-furanyl)-2-methyl-3H-thieno[2,3-d]pyrimidin-4-ones with topological indices using Hansch analysis

The antimicrobial activity of the N-[5-(2-furanyl)-2-methyl-4-oxo-4H-theino[2,3-d]pyrimidin-3-y1]-carboxamides and 3-substituted-5-(2-furanyl)-2-methyl-3H-thieno[2,3-d]pyrimidin-4-ones was correlated with different topological indices using Hansch analysis. Good correlations were obtained through a simple regression equation with third order molecular connectivity index (3chi). The developed QSAR models were crossvalidated by leave-one-out technique.     

Synthesis and antimycobacterial activity of 4-[5-(substituted phenyl)-4, 5-dihydro-3-isoxazolyl]-2-methylphenols

Compounds based on the isoxazoline moiety were screened for their antimycobacterial activity in vitro against Mycobacterium tuberculosis H37R (MTB), and INH (isoniazid) resistant Mycobacterium tuberculosis (INHR-MTB) using the agar dilution method and bactec 460. Among the synthesized compounds, 4-[5-(4-bromophenyl)-4,5-dihydro-3-isoxazolyl]-2-methylphenol (4l) was found to be the most active agent against MTB and INHR-MTB with minimum inhibitory concentration of 0.62 μM. When compared to INH, compound (4l) was 1.12 fold and 3.0 fold more active against MTB and INHR-MTB, respectively.     

Synthesis and Anti-Tubercular (Tb) Evaluation of Bis[4-Ethylidineamino[1,2,4]Triazole-3-Thiol] Tethered by 1,4-Dihydropyridine

Russian Journal of Bioorganic Chemistry - A new series of 5,5'-(2,6-dimethyl-4-phenyl-1,4-dihydropyridine-3,5-diyl)bis[4-(ethylideneamino)-4H-[1,2,4]-triazole-3-thiol) was synthesized via...     

The oxygenation of [3-methyl-3H]desacetoxycephalosporin C [7beta-(5-D-aminadipamido)-3-methylceph-3-em-4-carboxylic acid] to [3-hydroxymethyl-3H]desacetylcephalosporin C by 2-oxoglutarate-linked dioxygenases from Acremonium chrysogenum and Streptomyces clavuligerus.

Cell-free extracts of Acremonium chrysogenum and Streptomyces clavuligerus oxidize the 3-methyl group of desacetoxycephalosporin C to a 3-hydroxymethyl group. The enzyme responsible for this reaction in these organisms was purified 20- and 30-fold respectively by chromatography on DEAE-cellulose. The enzymes, which were assayed with [3-methyl-3H]desacetoxycephalosporin C as substrate, have the properties expected of 2-oxoglutarate-linked dioxygenases. They require 2-oxoglutarate, Fe2+ cations and a mixture of reducing agents (dithiothreitol and ascorbate) for full activity. The enzyme from A. chrysogenum, but not that S. clavuligerus, is activated about 10-fold when it is preincubated with a reaction mixture from which either desacetoxycephalosporin C or 2-oxoglutarate is omitted. Fe2+ cations seem to play a key role in this activation. Both enzymes seem highly specific for cephalosporins with the natural 7beta-(5-D-aminoadipamido) side chain and are likely to be responsible for the oxidation of the 3-methylcephem nucleus in vivo.     

Separation of [Sp]-3'-O-(5'-dimethoxytritylthymidyl)-5'-O-(3'camphanoyl thymidyl)-O-methyl phosphite.

First isolation of diastereoisomerically enriched (d.p. 95%) [Sp]-3'-O-(5'-dimethoxytrityl tjymidyl)-5'-O-(3'-camphanoyl thymidyl)-O-methyl phosphite (1) allowed to assign, via sulfuration and deprotection, its absolute configuration as Sp. Its reactions with methyl iodide, dimethoxytrityl chloride, or water, respectively, allowed to confirm correctness of assignment of absolute configuration in diastereisomers of TPMeT, and to assign absolute configuration in corresponding diastereoisomers of TPDMTT and TPHT.     

The kinetics and stereochemistry of base hydrolysis of the seven isomers of [Co(dien)(ampy)Cl] and [Co(dien)(ibn)Cl]

The kinetics and stereochemistry for the base catalysed substitution reactions of all seven isomers (4 mer and 3 fac) of both [Co(dien)(ibn)Cl]²⁺ and [Co(dien)(ampy)Cl]²⁺ have been studied in detail, for water and azide ion as entering groups. The stereochemistry for the azide ion anation of some of the [Co(dien)(diamine)OH]²⁺ species have also been investigated. The mer isomers are of comparable reactivity and amongst the fastest reacting pentaaminechlorocobalt(III) complexes known. They are also much faster to hydrolyse than the fac species. In both the ibn and ampy systems, a common product stereochemistry is observed for the four reactant mer isomers (the product is a mixture of all four mer configurations), for both azide ion and water as nucleophiles, but not for the three fac reactants (H₂O as nucleophile). The kinetic and equilibrium distributions are quite different. For the mer isomer reactions, a common trigonal bipyramidal five-coordinate intermediate deprotonated at the sec-NH of the dien is overwhelmingly implicated. The substitution mechanisms are argued in detail. Other data reported include isomerisation rates and equilibrium distributions for some mer-hydroxo and a mer-aqua complex of exceptional reactivity, equilibrium distributions for the mer-phosphato complexes in the ampy system under different pH conditions, the crystal structure for the isolated m1-[Co(dien)(ampy)OP(OH)₃]Cl₃ · 2H₂O species, and a rationale for its predominance at neutral pH based on internal H-bonding.     

NMR study of ammonium ion binding to d[G3T4G4]2 and d[G4(T4G4)3] G-quadruplexes

Quantitative NMR study has shown a significant difference in affinity of (15)NH(4)(+) ions for cation binding sites within G-quadruplexes adopted by d[G3T4G4]2 and d[G4(T4G4)3].     

Synthesis and antibacterial activities of new piperidine substituted (5R)-[1,2,3]triazolylmethyl and (5R)-[(4-F-[1,2,3]triazolyl)methyl] oxazolidinones

A novel series of 5(R)-[1,2,3]triazolylmethyl and (5R)-[(4-F-[1,2,3]triazolyl)methyl]oxazolidinones having various piperidine group were synthesized and evaluated antibacterial activity against clinically isolated resistant strains of Gram-positive and Gram-negative bacteria. The compound 12a having exo-cyanoethylidene group in the 4-position of piperidine ring was found to be two to threefold more potent than the linezolid against penicillin-resistant Staphylococcus pneumonia and Staphylococcus agalactiae, and also exhibited reduced MAO-B inhibitory activity.     

Determination of 3-(5-cyclopropyl-1,2,4-oxadiazol-3-yl)-5-(1-methylethyl)imidazo[1,5-a]quinoxalin-4(5H)-one in serum by high-performance liquid chromatography

A high-performance liquid chromatographic assay with solid-phase extraction (SPE) for the rapid and sensitive quantitation of 3-(5-cyclopropyl-1,2,4-oxadiazol-3-yl)-5-(1-methylethyl)imidazo[1,5-a]quinoxalin-4(5H)-one (I, U-78875) in serum is described. The validation results indicated that the present method had excellent intra- and inter-assay precision (≤ 9.5%, mean ± S.D. = 3.9±3.0%, n = 25) and accuracy (≤ 10.0%, mean ± S.D. = 3.0 ± 2.9%, n = 25), as well as improved sensitivity (2 ng/ml, using a 100-μl injection). Each chromatographic run is only 10 min and the organic solvent for the extraction of I and internal standard (U-82217) from serum was only 300 μl. The application results obtained from the SPE method were in good agreement with the advanced automated sample preparation method.     

Synthesis and activity of 2-[4-(4-[3H]-2-cyanophenyl)piperazinyl]-N-(2,4,6-[3H]3-3-methylphenyl)acetamide: a selective dopamine D4 receptor agonist and radioligand

The first selective dopamine D4 agonist radioligand is described. The synthesis of these piperazine radioligands relied on the transformation of brominated precursors 4a and 4b with tritium gas in the presence of a sensitive cyano functional group. The specific activity of these two radioligands was measured and [3H]6b found to be suitable for use in D4 saturation and competition binding studies. The synthesis, biological, and radioactivity of this new agonist radioligand as well as preliminary SAR will be discussed.