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PubMed1992

Application of infrared spectrometry to the study of tautomerism and conformational and configurational isomerism in medical and biochemical agents: N,N'-disubstituted amidines.

Infrared investigations on the v(NH) and v(C = N) vibrations of N,N'-disubstituted formamidines, acetamidines and benzamidines, containing the same or different groups at the amino and imino nitrogen atoms, and of some model compounds (N-monosubstituted amides, imidazoles and 2-aminopyridines), carried out in CCl4 at various temperatures and concentrations, and in other solvents, show that all the amidines studied have the E configuration on the C = N double bond and display conformational isomerism on the C-N single bond. Formamidines exist predominantly in the form of a conformer with a hydrogen atom synperiplanar to the imino nitrogen atom, and can form a cyclic dimer. In acetamidines and benzamidines the other conformer, with a hydrogen antiperiplanar to the imino nitrogen, prevails, and hence they can form mainly linear dimers. Different positions of the v(NH) and v(C = N) bands observed for N,N'-diaryl and N,N'-dialkyl derivatives permit determination of the composition of tautomeric mixtures in N-alkyl-N'-arylamidines.

Amidines↗
PubMed2004

Structural diversity in the coordination of amidines and guanidines to monovalent metal halides.

A series of structurally characterised, monovalent metal-halide complexes incorporating neutral amidine and guanidine ligands is reported. N,N'-diphenylbenzamidine reacted with copper(I) chloride to afford the bis-ligand complex [CuCl(PhC[NPh][NHPh])2]2 (1), that exists as a chlorine bridged dimer in the solid state, with a non-symmetrical distribution of NH...Cl interactions within the 'Cu2Cl2' metallacycle. In contrast, only one equivalent of the guanidine, Me2NC[NiPr][NHiPr] (2), is coordinated in the copper(I) iodide complex [CuI(Me2NC[NiPr][NHiPr])]2 (3), which was also isolated as the dimer with bridging halide atoms. The molecular structure of the bicyclic guanidine, 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-alpha]pyrimidine (hppH), is reported, revealing a hydrogen bridged dimer with extensive delocalisation throughout the ligand framework. Coordination of hppH to lithium chloride afforded the dimeric bis-ligand complex [LiCl(hppH)2]2 (4) in which each hppH molecule interacts with a different chlorine atom of the central 'Li2Cl2' core of the molecule via NH...Cl hydrogen bonding. In contrast the 2:1 ligand to metal complex is formed with silver(I) chloride to afford AgCl(hppH)2 (5), a unique example of a monomeric, three-coordinate silver chloride supported by nitrogen-based ligands. The series of mixed ligand complexes [CuX(hppH)(PPh3)]n (6, X = Cl, n= 1; 7, X = Br, n= 2; 8 X = I, n= 2) have also been synthesised and structurally characterised, allowing comparisons of the relative coordinating behaviour of hppH and PPh3 as neutral donors at copper(I) centres to be made.

Amidines↗
PubMed2006

Microwave-assisted cyclic amidine synthesis using TiCl4.

Microwave-assisted treatment of various heterocyclic amides (benzodiazepinone, phthalazone) with TiCl(4) in the presence of primary or secondary amines provides the corresponding amidines. In addition to the interest of the microwaves for this reaction, our study highlights the higher reactivity of the cyclic acetamide moiety compared to the cyclic benzamide moiety towards this TiCl(4)-mediated reaction.

Amidines↗
PubMed2001

Sequence-dependent binding of bis-amidine carbazole dications to DNA.

The conventional wisdom argues that DNA intercalators possess a condensed polyaromatic ring whereas DNA minor groove binders generally contain unfused aromatic heterocycles, frequently separated by amide bonds. Recently, this view has been challenged with the discovery of powerful intercalating agents formed by unfused aromatic molecules and groove binders containing a polyaromatic nucleus. Bis-amidinocarbazoles belong to this later category of drugs having a planar chromophore and capable of reading the genetic information accessible within the minor groove of AT-rich sequences [Tanious, F.A., Ding, D., Patrick, D.A., Bailly, C., Tidwell, R.R. & Wilson, W.D. (2000) Biochemistry 39, 12091-12101]. But in addition to the tight binding to AT sites, we show here that bis-amidinocarbazoles can also interact with GC sites. The extent and mode of binding of 2,7 and 3,6 substituted amidinocarbazoles to AT and GC sequences were investigated by complementary biochemical and biophysical methods. Absorption, fluorescence, melting temperature and surface plasmon resonance (SPR) measurements indicate that the position of the two amidine groups on the carbazole ring influences significantly the drug-DNA interaction. SPR and DNase I footprinting data confirm the AT-preference of the compounds and provide useful information on their additional interaction with GC sequences. The 3,6-carbazole binds approximately twice as strongly to the GC-containing hairpin oligomer than the 2,7-regioisomer. The high tendency of the 3,6 compound to intercalate into different types of DNA containing G.C base pairs is shown by electric linear dichroism. This work completes our understanding of the sequence-dependent DNA binding properties of carbazole dications.

Amidines↗
PubMed2002

Effects of amidine derivatives on parasite-macrophage interaction and evaluation of toxicity.

In this work, the effect of amidine derivatives (with bromine and methoxy as substituents) in the "in vitro" parasite-macrophage interaction was evaluated. The potential toxicity was also analyzed. The results show that the methoxy-derivative was able to decrease the percentage of "in vitro" infection, being not hazardous to the host cell. Furthermore, experiments using Balb/c mice showed that this compound was very effective in avoiding infection in these animals. On the other hand, the compound with bromine as substituent was toxic to macrophages and unable to prevent infection in Balb/c mice. Pentamidine isethionate, used as reference drug, was not efficient in both experiments.

Amidines↗
PubMed1980

Properties of amidinated glucagons.

Porcine glucagon has been reacted with a series of alkyl imidates. The epsilon-amino group and both the alpha and epsilon-amino groups were modified and the subsequent glucagon derivatives were purified by ion-exchange chromatography and characterized. The modified glucagons were compared with native glucagon in their ability to activate hepatic adenylate cyclase and to compete with 125I-glucagon for binding to sites specific for glucagon in hepatic plasma membranes. N epsilon-acetamidino-glucagon was as biologically potent, in both activity and binding, as native glucagon, whereas N epsilon-4-hydroxyphenylamidinoglucagon required a twofold higher concentration to obtain similar levels. These findings suggest that modification through the epsilon-amino group with alkyl imidates possessing reporter groups should result in glucagon derivatives with significant biological potency, thus providing a new approach to the study of this peptide hormone. Amidination of both epsilon and alpha-amino groups resulted in glucagon derivatives which were agonists with respect to adenylate cyclase activation and which displayed unexpected anomylous behavior on chromatography.

Adenylyl Cyclases↗
PubMed1963

Radioprotection by pressor amidines.

In the mouse, radioprotection is not always associated with the effect of hypertensive amidines and related amines. The protection resulting from this group of agents follows the pharmacological reduction of intercellular oxygen tension. oxygen tension of radiosensitive tissues.

Amidines↗
PubMed1984

Effect of synthetic protease inhibitors of the amidine type on cell injury by Rickettsia rickettsii.

To evaluate the importance of proteolytic activity in the pathogenesis of cell injury by Rickettsia rickettsii, a series of four aromatic amidine inhibitors of trypsin-like proteases were introduced into the plaque model. The compounds were shown to be active toward plaque reduction with their order of effectiveness parallel to their antitrypsin activity. One of the compounds, bis(5-amidino-2-benzimidazolyl)-methane, at a concentration of 10(-5) M demonstrated complete inhibition of plaque formation on day 6. Bis(5-amidino-2-benzimidazolyl)methane at the same concentration reduced cell injury even when added to the system after 72 h of rickettsial infection. The reduction in morbidity in guinea pigs experimentally infected with R. rickettsii and treated with bis(5-amidino-2-benzimidazolyl)methane as compared with morbidity in infected, untreated animals, comprised delay in the onset of fever and slightly fewer febrile animals. Because bis(5-amidino-2-benzimidazolyl)methane had no effect on phospholipase A2, the enzyme activity associated with penetration-induced cell injury, it is likely that a trypsin-like protease also plays an essential role either in the physiology of R. rickettsii or as its pathogenic mechanism.

Amidines↗
PubMedDate not supplied

New amidine derivatives of indole.

A series of new derivatives of indole of expected biological activity was prepared. Amidines 7 and 8 were obtained from the corresponding nitriles 3 and 4 and iminoethers 6.

Amidines↗
PubMed1975

[Relationships between structure and the noradrenaline depleting effects of guanidine and amidine derivatives (author's transl)].

In guinea pigs we studied the noradrenaline (NA) depletion in the sympathetic nerve terminals of the heart exerted by 24 derivatives of guanidine and amidine; the effects of these substances being considerably similar in their chemical structure were compared to those of reserpine, guanethidine, guanoxan and cyclazenin. Substitution of the free guanidine group to give an imidazoline or imidazolidine ring diminished the activity of the compounds. If the benzodioxane ring of guanoxan was "opened" to give a diether of catechol, the activity of the substances was not altered. We also observed a NA depletion after injection of some guanidine derivatives substituted with piperazine. The elongation of the aliphatic chain between guanidine and the aromatic substituent considerably decreased the activity of the compounds.

Amidines↗
PubMed1992

[Synthesis of N-(2-carboxy-thieno(2,3-b)pyridin-3-yl)-amidines by the reaction with 4-oxo-4H-pyrido(3',2':4,5)-thieno(3,2-d)-1,3-oxazines with secondary cycloaliphatic amines].

4-Oxo-4H-pyrido[3',2':4,5]thieno[3,2-d]1,3-oxazines react with secondary cycloaliphatic amines to give besides the expected bisamides the amine salts of N-(2-carboxy-thieno[2,3-b]pyridine-3-yl)amidines. These compounds showed inhibitory activity against different lipoxygenases, but a small chemical stability.

Amidines↗
PubMed1988

Aromatic amidines: inhibitory effect on purified plasma serine proteinases, blood coagulation and platelet aggregation.

The inhibitory effect of benzamidine as well as of 1,3-di-(p-amidinophenoxy)-2,2-bis-(p-amidinophenoxymethyl)propane (TAPP-H) and TAPP-halo derivatives (with Cl, Br or I) on (i) the catalytic properties of purified plasma serine proteinases (notably, factor Xa, factor VIIa, thrombin and plasmin), (ii) blood coagulation, and (iii) platelet aggregation was investigated in vitro. For all the enzyme/inhibitor systems examined, the inhibition patterns were strictly competitive, and titrations conformed to simple equilibria. The inhibitory effect of TAPP-H and TAPP-halo derivatives is higher, by at least 10-fold, than that of benzamidine, which binds at the primary specificity subsite (S1) of serine proteinases and is commonly taken as a molecular inhibitor model. The high inhibitory effect of aromatic tetraamidines has been interpreted taking into account an additional productive binding for a second benzamidine or halo-benzamidine moiety to the enzyme surface. As a whole, the data reported here indicate that aromatic amidines inhibit the plasma serine proteinases involved in different steps of haemostasis (coagulation and platelet aggregation) as well as clot lysis under physiological-like conditions in vitro.

Amidines↗
PubMed1986

Quantitative structure-activity relationships and molecular graphics in ligand receptor interactions: amidine inhibition of trypsin.

Quantitative structure-activity relationships have been formulated for four sets of amidine inhibitors of trypsin. The quantitative results from these equations are compared with qualitative models constructed from the X-ray crystallographic coordinates of a benzamidine bound to trypsin. The good agreement between the mathematical and graphics models provides further support for the use of substituent constants and regression analysis in the study of enzyme-ligand interactions.

Amidines↗
PubMedDate not supplied

Studies on pyrazine derivatives. Part VII. Synthesis and tuberculostatic activity of some pyrazine amidines and amidoximes.

In the reaction of 2-cyano-6-alkylaminopyrazines with sec. amines in the presence of anhyd. AlCl3 amidines 1-13 were obtained. From pyrazine-2-imidoesters, 2-cyano-pyrazines and pyrazine-2-carbothioamides and hydroxylamine, amidoximes 14-49 were easily prepared. These new compounds were, however, of little tuberculostatic activity (MIC between 31.5-2000 mug/cm3).

Amidines↗
PubMed1984

[The hypotensive effect of aromatic amidines and imidazolines].

Some amidine, diamidine and diimidazoline derivatives were tested on their ability to lower the blood pressure of the rat. Except for 5-amidino-2-phenylindole (271/179) all substances led to a short-lasting hypotension, the dose relationship of some of which was investigated. The biscationic character was a prerequisite for a strong hypotensive action. The predominantly peripheral origin of the blood pressure lowering action was shown for the substances pentamidine, diminazene, 6-amidino-2- (4-amidinophenyl)-indole (102/198), 5-amidino-2-(4-amidinophenyl) - benzofurane (150/49) and 2,6-diamidinoindole (261/115). A parasympathomimetic and histaminic efficiency could be excluded. The pressor effect of norepinephrine (noradrenaline) was reduced under the influence of pentamidine, diminacene and 102/198. With the dog 102/198 and 261/115 showed a diminution of heart rate and force as well as a vasodilatory effect. Using the rat, different cardiovascular parameters behaved analogous. Pentamidine, diminazene, 102/198 and 261/115 increased the force of contraction of the isolated rat atrium. Toxic effects were observed in doses as high as 0,5 mmol/l and l mmol/l. Pentamidine reduced the heart rate of the isolated atrium in a dose-dependent manner. Taking into account the in vitro results, the heart effects were interpreted as being reflectory. In the isolated rat aorta preparation the aforementioned substances in low doses shifted the dose-response curves of norepinephrine to the right, whereas higher doses also reduced the maximum contraction. Considering the results on the intact animal, a direct action of the diamidines on vascular smooth muscle was discussed.

Amidines↗
PubMed1978

[Hydrolysis of the amidine analogs of penicillins].

The products of the hydrolytic degradation of 6-beta-(hexahydro-IH-azepenyl-1)methylenamino) penicillanic acid, 6-beta-(N,N-dimethylformamidino-N1)-penicillanic acid and 6-beta-(morpholinyl-1)methylenamino penicillanic acid were identified with the method of thin-layer chromatography and paper electrophoresis in neutral, acid and alkaline solutions and in the presence of penicillinase. The data of the study showed that acid hydrolysis of the amidine analogues of penicillins resulted in cleavage of the beta-lactame cycle and formation of the respective penicillanic acids. In the alkaline medium the secondary amine (hexamethylenimine, dimethylamine, morpholine) was cleaved from the antibiotic side chain and the resulting N-formyl-6-aminopenicillanic acid was further cleaved up to peniciec acid. The beta-lactame cycle of the antibiotics was cleaved under the effect of penicillinase and the resulting penicilloinic acids degraded into peniciec acid, N-formylpeniciec acid and secondary amines. In the nutral solution the antibiotics were transformed into N-formyl-6-aminopenicillanic acid and penicilloinic acids at the first stage of the hydrolysis followed by their further degradation with formation of N-formylpeniciec acid, peniciec acid and secondary amines.

Amidines↗