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PubMed1990

Reduction potentials of imine-substituted, biologically active pyridines: possible relation to activity.

Cyclic voltammetry data were obtained for a number of biologically active compounds which incorporate imine substitution on the pyridine nucleus. The reductions in acid (iminium ion formation) were for the most part reversible, and in the range of -0.5 to -0.7V. The toxic effect of these drugs is thought to be caused by the generation of reactive oxygen radicals that arise via charge transfer, or by disruption of electron transport chains.

Chemical Phenomena↗
PubMed1987

Antimalarial and anticoccidial activity of 3-aryl-7-chloro-3,4-dihydroacridine-1,9-(2H,10H)-diones. 1-Imines, 1-amines, 1-oximes, 1-hydrazones and related compounds.

Out of more than 130 synthesized derivatives of floxacrine and of 10-deoxyfloxacrine, such as 3-(4-trifluoromethyl-phenyl) or 3-(4-chlorophenyl)-7-chloro-10-hydroxy- or -10-deoxy-3,4-dihydroacridine- 1,9(2H,10H)-dione 1-imines and 1-hydrazones, more than 45 showed an activity against asexual stages of Plasmodium berghei in the mouse which was comparable with or superior to that of floxacrine. More than 25 derivatives of the 3-(4-chlorophenyl)-floxacrine series and 3-(4-chlorophenyl)-10-deoxy-floxacrine series are more effective than floxacrine against Eimeria tenella infection in chickens. 1-Amino compounds of the various series proved of be generally inactive, as did fragments of the structure of and compounds related to floxacrine. Structure-activity relations are suggested on the basis of examples.

Acridines↗
PubMed1985

Mechanisms of N-acetyl-p-benzoquinone imine cytotoxicity.

N-Acetyl-p-benzoquinone imine (NAPQI), a reactive metabolite of acetaminophen, rapidly reacts at physiological pH with glutathione (GSH) forming an acetaminophen-glutathione conjugate and stoichiometric amounts of acetaminophen and glutathione disulfide (GSSG). The same reaction products are formed in isolated hepatocytes incubated with NAPQI. In hepatocytes which have been treated with 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) in order to inhibit glutathione reductase, the initial rise in GSSG concentration in the presence of NAPQI is maintained, whereas GSSG is rapidly reduced back to GSH in untreated hepatocytes. Oxidation by NAPQI of GSH to GSSG and the reduction of GSSG back to GSH by the NADPH-dependent glutathione reductase appear to be responsible for the rapid oxidation of NADPH that occurs in hepatocytes incubated with NAPQI in that the effect is blocked by pretreatment of cells with BCNU. When added to hepatocytes, NAPQI not only reacts with GSH but also causes a loss in protein thiol groups. The loss in protein thiols occurs more rapidly in cells pretreated with BCNU or diethylmaleate. Whereas both of these treatments enhance cytotoxicity caused by NAPQI, BCNU pretreatment has no effect on the covalent binding of [14C-ring]NAPQI to cellular proteins. Furthermore, dithiothreitol added to isolated hepatocytes after maximal covalent binding of [14C-ring]NAPQI but preceding cell death protects cells from cytotoxicity and regenerates protein thiols. Thus, the toxicity of NAPQI to isolated hepatocytes may result primarily from its oxidative effects on cellular proteins.

Acetaminophen↗
PubMed1979

[Biologically active N-Mannich bases of isatin-3-(phenyl)-imines (author's transl)].

By the condensation of isatin and 5-nitroisatin with substituted aromatic amines, isatin- and 5-nitroisatin-3-(phenyl)-imines (azomethines) are formed which are converted into N-Mannich-bases by aminomethylation and may be formulated as azomethines with E configuration. A biotest of Lepidium sativum L. was used to prove mitodepressive properties. Some compounds showed a significant growth-inhibiting activity. It was found that a change in activity is produced by condensation on the carbon atom in position 3 and by aminomethylation on the nitrogen atom in the isatin nucleus.

Imines↗
PubMed1997

The response of germ cells to ethylene oxide, propylene oxide, propylene imine and methyl methanesulfonate is a matter of cell stage-related DNA repair.

We describe the consequences of a defect for nucleotide excision repair (NER) in oocytes for alkylation-induced mutagenesis in different germ-cell stages of Drosophila males. Mutant frequencies induced in NER+ condition (cross NER+female female x NER+male) were compared with those fixed in a NER- background (cross NER-female female x NER+male), using the X-linked recessive lethal assay (SLRL) for the measurement of forward mutations in 700 loci. In successive male germ-cell stages exposed to a low dose of 2.4 mM x h methyl methanesulfonate, efficient repair of premutational damage in spermatogonia and by the maternal repair system after fertilization was observed. Ethylene oxide (EO) and propylene oxide (PO) did not induce high mutant frequencies in postmeiotic germ cells when mutagenized males were mated with NER+ females: a 32-fold increase in dose from 750 ppm x h to 24,000 ppm x h EO (approximately LD50) led to no more than a 3-fold enhancement in mutant frequency. However, up to a 17-fold increase in mutant frequencies were obtained with NER- females. In matings with NER+ females, PO was about 10 times less mutagenic than EO. Suppression of the maternal NER system caused a hypermutability, which, on the average, was 2.4-fold lower than for EO. This indicates that the 2-hydroxyethyl adduct generated by EO is more efficiently repaired than the 2-hydroxypropyl adduct caused by PO. The low SLRL frequencies (0.2-0.9%) estimated for propylene imine (PI) in NER+ genotypes showed no relation to dose in the range from 1,500 to 48,000 ppm x h. In the absence of NER, mutant frequencies were increased up to 29-fold, and a dose-dependent increase in mutations was observed for PI over the entire dose range. This study shows mutation induction by EO in postmeiotic Drosophila germ cells at exposure doses that are 800-fold below those applied previously in the mouse specific-locus test on spermatogonia [with negative response; Russell et al. (1984): Mutat Res 129:381-388] and 11-fold below the EO dose for which increased dominant-lethal responses and heritable translocations were documented in mice spermatozoa and spermatids [Generoso et al. (1990): Environ Mol Mutagen 16:126-131].

Animals↗
PubMed2001

Cobaltocenium-functionalized poly(propylene imine) dendrimers: redox and electromicrogravimetric studies and AFM imaging.

The first four generations of cobaltocenium-functionalized, diaminobutane-based poly(propylene imine) dendrimers DAB-dend-Cb,(PFb)x (x = 4, 8, 16, and 32; Cb=[Co(eta5-C5H4CONH)(eta5-C5H5)] (1-4) have been synthesized and characterized. The redox activity of the cobaltocenium centers in 1-4 has been characterized by using cyclic voltammetry and the electrochemical quartz-crystal microbalance (EQCM). All of the dendrimers exhibit reversible redox chemistry associated with the cobaltocenium/cobaltocene redox couple. Upon reduction. the dendrimers exhibit a tendency to electrodeposit onto the electrode surface, which is more pronounced for the higher generations. Pt and glassy carbon electrodes could be modified with films derived from 1-4,exhibiting a well-defined and persistent electrochemical response. EQCM measurements show that the dendrimers adsorb, at open circuit, onto platinum surfaces at monolayer or submonolayer coverage. Cathodic potential scanning past -0.75 V at which the cobaltocenium sites are reduced, gave rise to the electrodeposition of multilayer equivalents of the dendrimers. The additional material gradually desorbs upon re-oxidation so that only a monolayer equivalent remains on the electrode surface. Changes in film morphology as a function of dendrimer generation and surface coverage were studied by using admittance measurements of the quartz-crystal resonator on the basis of its electrical equivalent circuit, especially in terms of its resistance parameter. In general, we find that films of the lower dendrimer generation 1 behave rigidly, whereas those of the higher generation 4 exhibit viscoelastic behavior with an intermediate behavior being exhibited by 2 and 3. Using tapping-mode atomic force microscopy (AFM). we have been able to obtain molecularly resolved images of dendrimer 4 adsorbed on a Pt(111) electrode.

Journal Article↗
PubMed1993

Platelet aggregation inhibiting and anticoagulant effects of oligoamines, XIX: 4,4'-Phenylene-bis-sydnone imines.

Fourteen 4,4'-m-phenylene- and two 4,4'-p-phenylene-bis-sydnone imine hydrochlorides have been synthesized. All compounds exhibited good solubility in water. In the m-series the 3-(3-phenylpropyl)-derivative 5c and the 3-hexyl compound 5l showed antiplatelet activities at or below 10 mumol/L (IC50, Born-test with collagen). The corresponding p-compounds had the same (6l) or slightly lower (6c) activity. No effect on the fibrin formation (Quick-test) could be observed.

Anticoagulants↗
PubMed1993

Platelet aggregation inhibiting and anticoagulant effects of oligoamines, XXI: 4,4'-Alkylene-bis-sydnone imines.

Two methylene-, seven ethylene-, eleven propylene- and two 4,4'-butylene-bis-sydnone imines have been synthesized and tested for their antiplatelet (Born-test, collagen) and anticoagulant (Quick-test) activity in vitro. The most active compounds were found in the ethylene and propylene series. The most favourable substituents in 3-position of the sydnone were hexyl to octyl or phenylethyl to phenylbutyl groups. Six compounds exhibit an IC50 < or = 10 mumol/L against platelet aggregation. Three compounds showed an IC75 < or = 200 mumol/L concerning the fibrin formation (Quick delta t > or = 7 s).

Anticoagulants↗
PubMed2005

Catalytic, asymmetric aza-Baylis-Hillman reaction of N-sulfonated imines with activated olefins by quinidine-derived chiral amines.

The chiral nitrogen Lewis base, tricyclic cinchona alkaloid derivative TQO, is an effective promoter in the catalytic, asymmetric aza-Baylis-Hillman reaction of N-sulfonated imines Ar-CH=NR' 1 (R' = Ts, Ms, Ns, SES) with various activated olefins such as methyl vinyl ketone (MVK), ethyl vinyl ketone (EVK), acrolein, methyl acrylate, phenyl acrylate, or alpha-naphthyl acrylate to give the corresponding adducts in moderate to good yields with good to high ee (up to 99 %) at -30 degrees C or 45 degrees C in various solvents, including DMF/MeCN (1:1, v/v). The first such reaction of 1 with the simplest Michael acceptor MVK and methyl acrylate has been achieved with excellent enantioselectivity. The adducts derived from MVK and EVK had the opposite absolute configuration to those from acrolein, methyl acrylate, phenyl acrylate, and alpha-naphthyl acrylate. A plausible mechanism has been proposed on the basis of previous reports and the authors' investigations. An effective bifunctional chiral nitrogen Lewis base-Brønsted acid system has been revealed in this type of aza-Baylis-Hillman reaction.

Journal Article↗
PubMed2006

Deamination of the amino acid fragment in imine metallacycles: unexpected synthesis of an NH-aldimine organometallic compound.

We report that the action of Lewis bases, such as triphenylphosphine, pyridine, or trimethylamine, on imine metallacycles derived from amino acids leads to the formation of the first organometallic compound of an NH aldimine, a highly reactive organic species, and the corresponding alpha-ketoester, in a deamination reaction that mimics the metabolism of alpha-amino acids. The synthesis of different cyclopalladated compounds by a reaction between palladium acetate and the Schiff bases 2,4,6-Me(3)C(6)H(2)CH=NCH(R(1))COOR(2) (R(1) = CH(2)Ph, R(2) = Et and R(1) = Ph, R(2) = Me) is also reported.

Organometallic Compounds↗
PubMed2006

Protonic and temperature modulation of constituent expression by component selection in a dynamic combinatorial library of imines.

The constitutional recomposition of a dynamic library of imines displays a complex behavior under the effect of two parameters, acidity and temperature. A qualitative analysis of the quantitative data is presented. The results illustrate the response of such a dynamic system to a physical stimulus (temperature) and a chemical effector (H+), thus demonstrating its adaptive behavior under the pressure of external factors. They also point to the possibility of modulating a given functional property (optical, electronic, ionic) by constitutional recomposition induced by a specific trigger. Such features are of great interest for the development of stimuli-responsive, functional dynamic materials.

Journal Article↗
PubMed2006

Mechanistic investigations of imine hydrogenation catalyzed by dinuclear iridium complexes.

Treatment of [Ir2(mu-H)(mu-Pz)2H3(NCMe)(PiPr3)2] (1) with one equivalent of HBF4 or [PhNH=CHPh]BF4 affords efficient catalysts for the homogeneous hydrogenation of N-benzylideneaniline. The reaction of 1 with HBF4 leads to the trihydride-dihydrogen complex [Ir2(mu-H)(mu-Pz)2H2(eta2-H2)(NCMe)(PiPr3)2]BF4 (2), which has been characterized by NMR spectroscopy and DFT calculations on a model complex. Complex 2 reacts with imines such as tBuN=CHPh or PhN=CHPh to afford amine complexes [Ir2(mu-H)(mu-Pz)2H2(NCMe){L}(PiPr3)2]BF4 (L = NH(tBu)CH2Ph, 3; NH(Ph)CH2Ph, 4) through a sequence of proton- and hydride-transfer steps. Dihydrogen partially displaces the amine ligand of 4 to form 2; this complements a possible catalytic cycle for the N-benzylideneaniline hydrogenation in which the amine-by-dihydrogen substitution is the turnover-determining step. The rates of ligand substitution in 4 and its analogues with labile ligands other than amine are dependent upon the nature of the leaving ligand and independent on the incoming ligand concentration, in agreement with dissociative substitutions. Water complex [Ir2(mu-H)(mu-Pz)2H2(NCMe)(OH2)(PiPr3)2]BF4 (7) hydrolyzes N-benzylideneaniline, which eventually affords the poor hydrogenation catalyst [Ir2(mu-H)(mu-Pz)2H2(NCMe)(NH2Ph)(PiPr3)2]BF4 (11). The rate law for the catalytic hydrogenation in 1,2-dichloroethane with complex [Ir2(mu-H)(mu-Pz)2H2(OSO2CF3)(NCMe)(PiPr3)2] (8) as catalyst precursor is rate = k[8]{p(H2)}; this is in agreement with the catalytic cycle deduced from the stochiometric experiments. The hydrogenation reaction takes place at a single iridium center of the dinuclear catalyst, although ligand modifications at the neighboring iridium center provoke changes in the hydrogenation rate. Even though this catalyst system is also capable of effectively hydrogenating alkenes, N-benzylideneaniline can be selectively hydrogenated in the presence of simple alkenes.

Journal Article↗
PubMed2006

Asymmetric aza-Henry reaction of N-tosyl imine.

An efficient stereoselective aza-Henry reaction of N-tosyl imine, catalyzed by the coordination of diethylzinc with a chiral semi-aza-crown ligand, with moderate to high ee (up to 83%) is reported.

Journal Article↗
PubMed2005

EPR characterisation of Cu(II) complexes of poly(propylene imine) dendromesogens: using the orienting effect of a magnetic field.

Liquid-crystalline derivatives of poly(propylene imine)dendrimers of the 0th, 1st and 2nd generations, complexed with copper(II) ions, were studied by EPR spectroscopy. The structures of copper (II) complexes with different Cu(II) loadings x per dendrimer ligand L (x = Cu/L) were determined. At the lowest concentration, the Cu(II) ions form monomeric complexes with approximately square-planar N2O2 coordination of both carbonyl oxygen and amido nitrogen atoms. At higher copper content, two kinds of Cu(II) complex sites with different geometries exist. The orienting effect of a high magnetic field was used to investigate the structure and magnetic properties of the copper(II) complexes. This effect, for the first time in dendrimers, allowed the resolution of five nitrogen super-hyperfine lines on g(z) components with the unusual coupling constant of a(Nz)= 35.9 x 10(-4) cm(-1). The combination of the magnetic parameters and the orienting effect indicates the presence of a monomeric complex with pseudotetrahedral N2O2 coordination of the Cu(II) ion, as well as a "dimer" structure with fivefold coordination, presumably due to an N3O2 environment. Higher copper loadings lead to increased exchange coupling between the complex sites.

Journal Article↗
PubMed2006

Magnetic properties of poly(propylene imine)-copper dendromesogenic complexes: An EPR study.

Copper(II) complexes formed by coordination of the Cu(II) ion with liquid-crystalline poly(propylene imine) dendrimer ligand (L) of the first (complex 1) and second (complex 2) generations with various Cu(II) contents (x = Cu/L) have been studied by electron paramagnetic resonance (EPR) spectroscopy. The existence of a redox-active blue complex 1 (x = 1.9) and the copper(II) nitrate electron transfer associated with the valence tautomerism are revealed for the first time in copper-based dendrimers. It has been shown that the electronic structure of the blue complex 1 (x = 1.9) is adequately described as a mixed-valence dimer containing d9- and diamagnetic d10-configurated copper ions, and an antiferromagnetically coupled NO3* radical arising on the nitrate-bridged counter ligand. The activation energy value found for the electron transfer is about 0.35 meV, which indicates a low-energy charge dynamic. The ability of the blue and green complexes 1 (x = 1.9) dissolved in isotropic solvents to orient themselves in the magnetic field was revealed by EPR spectroscopy. The degree of orientation of the molecular z axis (S(z)) of these complexes in the magnetic field differs, depending on the type of copper(II)-complexing site in the dendrimer ligand, and can reach 0.76, which is close to S(z) = 1 (completely aligned system). A combination of magnetic and orientational parameters indicates an NO4 environment of the Cu(II) ion in green complex 1 (x = 1.9), and confirms the chain structure with intermolecular Cu(II)-NO3-Cu(II) bridges between Cu(II) centres in columns.

Copper↗
PubMed2005

Recent advances in rational gene transfer vector design based on poly(ethylene imine) and its derivatives.

The continually increasing wealth of knowledge about the role of genes involved in acquired or hereditary diseases renders the delivery of regulatory genes or nucleic acids into affected cells a potentially promising strategy. Apart from viral vectors, non-viral gene delivery systems have recently received increasing interest, due to safety concerns associated with insertional mutagenesis of retro-viral vectors. Especially cationic polymers may be particularly attractive for the delivery of nucleic acids, since they allow a vast synthetic modification of their structure enabling the investigation of structure-function relationships. Successful clinical application of synthetic polycations for gene delivery will depend primarily on three factors, namely (1) an enhancement of the transfection efficiency, (2) a reduction in toxicity and (3) an ability of the vectors to overcome numerous biological barriers after systemic or local administration. Among the polycations presently used for gene delivery, poly(ethylene imine), PEI, takes a prominent position, due to its potential for endosomal escape. PEI as well as derivatives of PEI currently under investigation for DNA and RNA delivery will be discussed. This review focuses on structure-function relationships and the physicochemical aspects of polyplexes which influence basic characteristics, such as complex formation, stability or in vitro cytotoxicity, to provide a basis for their application under in vivo conditions. Rational design of optimized polycations is an objective for further research and may provide the basis for a successful cationic polymer-based gene delivery system in the future.

Cross-Linking Reagents↗
PubMed1994

Synthesis and some physiochemical properties of 2-hydroxy-N-(3,4-dimethyl-5-isoxazolyl)-1,4-naphthoquinone 4-imine derivatives.

Some derivatives of 2-hydroxy-N-(3,4-dimethyl-5-isoxazolyl)- 1,4-naphthoquinone 4-imine (3), a poorly soluble drug, were synthesized in an attempt to improve their physicochemical properties. The new compounds were characterized by spectroscopic methods including an iterative NMR method (the LAOCOON III program). The physicochemical properties such as solubility, relative lipophilicity (RM), and partition coefficients (Leo-Hansch fragmental system) were determined. Some derivatives were more lipophilic than 3 and one was water soluble. In vitro antibacterial activity was also reported for some derivatives.

Animals↗
PubMed2006

Evaluation of Gd(III)DTPA-terminated poly(propylene imine) dendrimers as contrast agents for MR imaging.

Different generations of Gd(III)DTPA-terminated poly(propylene imine) dendrimers {G1 [n = 4 Gd(III) ions per molecule], G3 (n = 16) and G5 (n = 64)} and reference Gd(III)DTPA complex [G0 (n = 1)] were characterized in terms of (i) longitudinal (r1) and transverse (r2) relaxivities in mouse blood plasma, (ii) concentration detection limits in vitro and (iii) in vivo contrast-enhanced MR imaging (CE-MRI) in mice at 1.5 T. Serial and dynamic CE-MRI were performed to monitor the distribution of MRI contrast agent in the heart, arteries, renal system, liver, spleen, bladder and tumor periphery. The relaxivities increased non-linearly with molecular weight (for G0 ionic r1 = 8.1 mM(-1) s(-1) and ionic r2 = 8.6 mM(-1) s(-1) to G5 19.3 and 25.0, respectively). The minimal detectable dendrimer concentration was more than two orders of magnitude lower for G5 (8.1 x 10(-8) M) than for G0 (3.1 x 10(-5) M). Sub-millimeter-sized blood vessels were well visualized with serial CE-MRI with each contrast agent. Dynamic CE-MRI showed timely renal clearance for all contrast agents, but a stronger and a prolonged blood signal enhancement for the higher generations of the dendritic contrast agent. Moreover, G0 and G1 showed a rapid tumor wash-in and wash-out, whereas G3 and G5 displayed a more gradual and prolonged tumor wash-in. In conclusion, both G0 and dendritic contrast agents G1, G3 and G5 are well suited for non-tissue-specific MRI of sub-millimeter-sized blood vessels and evaluating tumor microcirculatory characteristics in mice. Higher generations of dendritic contrast agents display lower concentration detection limits, which suggests their future use for molecular imaging.

Animals↗