Diamidines are compounds with antiparasitic properties that target the minor groove of DNA. The mechanism of action of these compounds is unknown, but topological changes to DNA structure are a possibility. In this study, we have developed a polyacrylamide gel based screening method to determine topological effects of diamidines on four target sequences: AAAAA, TTTAA, AAATT, and ATATA. The changes caused are sequence dependent, but generally the effect on AAAAA and AAATT is the same while the effect on TTTAA and ATATA is the same. A few compounds show interesting sequence dependent topological effects in the polyacrylamide screening method that could be caused by the compound forming a dimer. Mass spectrometry is used to determine the stoichiometry of DNA-compound complexes. Once compounds show topological effects in the screening method, a bent fragment of kinetoplast DNA is isolated to determine if the same effects occur with DNA from a parasite.

Dicationic diamidines synthesized in the Boykin group a have shown broad range of activity against a wide variety of microbial pathogens such as Cryptosporidium parvum, Leishmania donovani, Plasmodium falciparum, Trypanosoma burcei, and Trichomonas vaginalis. Thiophene based dicationic diamidines have been especially impressive versus Trichomoniasis, and several species of the leishmania parasite. The best compound in vitro against leishmania was 2,5-bis-(4-amidophenyl)thiophene [DB 351]. In an attempt to improve upon antileishmanial activity, several analogs of DB 351 have been synthesized. Previously the central heterocyclic ring has been changed (furan, pyrrole, etc.), and the phenyl has been substituted with a pyridine ring, however, in the thiophene series, the 3 and 4 position of the central thiophene ring has remained unmodified. By modifying the 3 and 4 position of the thiophene ring, and taking advantage of the substituent effect, the pharmacodynamic and distribution properties of DB 351 will altered; hopefully leading to more potent antileishmanial compounds.

Dicationic diamidines synthesized in the Boykin group a have shown broad range of activity against a wide variety of microbial pathogens such as Cryptosporidium parvum, Leishmania donovani, Plasmodium falciparum, Trypanosoma burcei, and Trichomonas vaginalis. Thiophene based dicationic diamidines have been especially impressive versus Trichomoniasis, and several species of the leishmania parasite. The best compound in vitro against leishmania was 2,5-bis-(4-amidophenyl)thiophene [DB 351]. In an attempt to improve upon antileishmanial activity, several analogs of DB 351 have been synthesized. Previously the central heterocyclic ring has been changed (furan, pyrrole, etc.), and the phenyl has been substituted with a pyridine ring, however, in the thiophene series, the 3 and 4 position of the central thiophene ring has remained unmodified. By modifying the 3 and 4 position of the thiophene ring, and taking advantage of the substituent effect, the pharmacodynamic and distribution properties of DB 351 will altered; hopefully leading to more potent antileishmanial compounds.

Dans cette thèse, j'ai essayé d'identifier le mode d'action de composés biscationiques récemment synthétisés et leurs interactions avec les parasites résistants à la chloroquine. Les activités de divers représentants des composés ammonium bisquaternaire, des amidines alkyl (provenant du groupe de professeur Vial, Montpellier, France), des amidines bisbenzyl (provenant du groupe Chimie de l'Université de Liverpool, Royaume-Uni) ont été comparés à la chloroquine et la pentamidine. Leurs potentiels de résistance croisée avec la chloroquine ont également été étudiés. Dans ce but, deux lignées cellulaires modifiées génétiquement par échange allélique, C3Dd2 et C2GCO3 furent utilisées.Parmi les amidines bisbenzyl, une série de composés appartenant aux guanidines, thiazoles et triazoles ont été criblés pour leur activité contre des souches résistantes et sensibles à la chloroquine chez Plasmodium falciparum. Une hypersensibilité significative est observée pour les amidines bisbenzyl parmi les isolats affichant un PfCRT mutant. Aucune différence n'est observée pour les composés provenant du groupe Vial. Pour comprendre le mode d'action et le rôle de PfCRT, j'ai réalisé des expériences de fixation compétitives (competitive binding') et de cristallisation d'hème. Tous les composés ont montré à différents degrés des interactions avec l'hème, cependant il fut observé que leur activité ne corrélait pas avec l'inhibition de la cristallisation d'hème. Une des raisons possibles à cela est que les différences structurales peuvent jouer un rôle important dans le transport du composé. De plus, j'ai étudié l'effet du pH sur l'activité des composés en utilisant les lignées cellulaires modifiées génétiquement par échange allélique afin d'observer l'effet du gradient de proton sur le transport de la chloroquine et de la pentamidine. Des différences significatives de l'activité de la chloroquine furent observées chez les deux souches. Malgré les valeurs de pKa élevées pour la pentamidine, il y avait une différence significative dans la sensibilité pour ce composé chez les souches quand le pH a changé.Car les diamidines requièrent des transporteurs pour traverser les barrières membranaires et qu'un possible transporteur de choline a été caractérisé chez Plasmodium falciparum, j'ai également réalisé des études initiales sur la caractérisation moléculaire de ce transporteur. Un gène qui encode une protéine chez P. falciparum avec une similarité significative aux eucaryotes supérieurs fut identifié en utilisant des analyses bioinformatiques et fut employé dans une transformation et des études analyses fonctionnelles.En conclusion, ce travail suggère qu'il est possible d'utiliser de nouveaux amidines bisbenzyl pour cibler spécifiquement les souches résistantes à la quinoléine chez Plasmodium falciparum, arborant des allèles de PfCRT mutantes. En adhérant à cette hypothèse et sachant que les deux classes de composés fixent la même cible non parasitaire (soit l'hème), il serait possible de créer rationnellement une combinaison de composés quinoléine / diamidine. Ainsi, les souches résistantes à un des deux composés seraient plus sensibles à l'autre partenaire, retardant ainsi l'apparition de résistance. / In this thesis I have attempted to subject the issues of mode of action of recently synthesized bis cationic compounds and their possible interactions with chloroquine resistance. Antimalarial activities of representatives of various bis quarternary ammonium compounds, alkyl amidines (received from Dr.Vial group, Montpellier) and of bisbenzyl amidines (received from Chemistry group, Liverpool) activity have been investigated with chloroquine and pentamidine and looked for cross resistance with chloroquine. For this purpose two genetically modified allelically exchanged cell lines C3Dd2 and C2GCO3 modified on the chloroquine resistance-related PfCRT (P.falciparum chloroquine Resistance Transporter) gene were used. Among the benzyl amidines, a significant hypersensitivity tobis benzyl amidines was observed among the isolates bearing the mutant PfCRT. No such difference is observed for the bisalkyl amidines. To understand the mode of action and role of PfCRT, competitive binding assay to heme (which may mediate the well-known cellular accumulation of the compounds) and effect on heme crystallization assays (which is involved in the toxic effect against the intracellular parasite) were performed. All these compounds were shown to interact with heme in various degrees. Their activity was observed not to be correlating with heme crystallization inhibition. This is likely due to the structural differences between the compound which discriminate the compounds in the transport of the compound to the parasite and their mechanism of antimalarial activities. In addition I have studied the effect of pH on the pharmacological activity of the drugs using allelically exchanged genetically modified cell lines (for PfCRT) to characterize the importance of proton gradient on the transport of chloroquine and pentamidine to the intracellular parasite. Significant difference (reduced antimalarial activity with increased pH) in the activity of chloroquine was observed for both the strains. Despite of the high pKa values for pentamidine, there was significant difference in the sensitivity of the strains to this compound, when the pH is changed. As both the diamidines and choline analogs require transporters to cross the membrane barriers and enter the parasite where they accumulate I have also performed initial studies on the molecular characterization of a potential carrier in P.falciparum. Using basic bioinformatic tools, a gene encoding a P.falciparum protein with significant similarity to higher eukaryotes choline transporter was identified and preliminary work for its functional analysis was performed. In conclusion, this work establishes substantial differences between the various classes of bis-cationic compounds essentially (based on benzamidine and choline-analogs alkylkamidine series) concerning their interaction with the infected erythrocyte and their antimalarial activity. The series are diffentallly affected by the PfCRT mutation and the chloroquine resistance. Results suggest that it may be possible to use novel bisbenzyl amidines to specifically target quinoline resistant Plasmodium falciparum malaria, harbouring mutant pfcrt alleles. Taking this idea further and since both classes of compound target the same non-parasite target (heme), it may even be possible to rationally design a quinoline / diamidine drug combination, in which isolates resistant to one partner drug become more sensitive to the other partner, thus delaying the onset of resistance.

The objective of this thesis was to study whether heterocyclic dicationic compounds that are minor groove binders have the ability to inhibit the digestive properties of type II restriction enzymes which bind to the major groove of the DNA. If these compounds do possess the ability to inhibit restriction enzymes, then what factors influence their ability to inhibit the restriction enzymes? The methods used to study the interactions of DNA, compounds, and enzymes are gel electrophoresis, DNA thermal melting, and circular dichroism. The results from this project reveal that the minor grove binding compounds are able to inhibition type II restriction enzymes. The inhibition is heavily influenced by compound structure and the DNA binding sequence of the enzyme.

Diamidines are a class of compounds that target the minor groove of DNA and have antiparasitic and antimicrobial properties. Their mechanism of action has not been fully elucidated, but may include changes in DNA topology. In this study we have investigated such changes using methods of gel electrophoresis including ligation ladders and cyclization assays. We found that topology changes were sequence dependent. Compounds typically caused non-anomalously migrating ATATA sequences to migrate as if they were bent, while A5 sequences that normally migrated anomalously became less so in the presence of certain diamidines. Select compounds induced changes in cyclization efficiency that were also sequence dependent; DB75 significantly abolished cyclization in A5 containing sequences but enhanced it in sequences containing ATATA sites.

DNA minor groove binding compounds have had limited therapeutic uses, in part due to problems with sequence specificity. A two-site model has been developed to enhance specificity, in which compounds bind to two short AT sites separated by one or two GC base pairs. Using thermal melting, heterocyclic dications with this capability were tested with various oligonucleotides for binding affinity and specificity. Compounds of interest were further probed using circular dichroism, mass spectrometry, biosensor-SPR, and molecular modeling. Several compounds were found to “jump” a GC base pair, binding to AT sites in the minor groove of DNA with a two-site recognition mode. One compound was also found to recognize a single intervening GC base pair. Compounds with terminal, non-polar amidine extensions were found to have increased DNA binding compared to analogs with terminal amidines. This unique, two-site DNA recognition mode offers novel design principles to recognize entirely new DNA motifs.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The aim of this study was to develop and to evaluate the therapeutic efficacy of liposomes diminazene aceturate and in vitro and by using mice experimentally infected with Trypanosoma evansi. In vitro tests were performed in culture medium at concentrations of 0.25, 0.5, 1, 2 and 3 mg/ml of diminazene aceturate convetional (CDMZ) and liposomal (L-DMZ). A total of 114 rats (Rattus norvegicus) were used of in vivo test. These rats were divided into 6 groups (A, B, C, D, E and F). Group A served as a negative control (uninfected and untreated). Rats in Group B served as a positive control and were infected with T. evansi. Animals in Group C were infected and treated with L-DMZ (single dose, 3.5 mg/kg-1), Group D was composed with infected and treated with C-DMZ animals (single dose, 3.5 mg/kg-1), Group E infected treated with L-DMZ animals for 5 consecutive days (3.5 mg/kg-1/dia) and Group F infected treated with C-DMZ animals for 5 consecutive days (3.5 mg/kg-1/dia). In vitro, a dose-dependent trypanocidal effect of L-DMZ was observed against the parasite. In vivo, the efficacy of L-DMZ and C-DMZ in different therapeutic protocols was similar. The analysis of biochemical and histological parameters on the 7th and 40th post-treatment revealed alterations in liver and kidney enzymes, and histological alterations in the structure of organs, especially in the animals treated with L-DMZ at 5 consecutive days. The results of this study showed that liposomal formulations may be a new alternative for the treatment of tripanosomoses, but future research could be undertaken to improve the conduction of liposomes and direction for greater efficiency. / Este estudo teve como objetivo desenvolver e testar lipossomas de aceturato de diminazeno em testes in vitro e in vivo visando o controle de Trypanosoma evansi. O teste in vitro foi realizado em meio de cultura nas concentrações de 0,25, 0,5, 1, 2 e 3 μg/mL de aceturato de diminazeno convencional (C-DMZ) e lipossomal (L-DMZ). Para os testes in vivo foram utilizados 114 ratos (Rattus norvegicus) divididos em seis grupos (A, B, C, D, E e F) em dois experimentos, um para avaliar a eficácia e outro para analisar os parâmetros bioquímicos e histológicos. O grupo A foi utilizado como controle (animais sadios), B (animais infectados e não tratados), C (animais infectados e tratados com aceturato de diminazeno lipossomal com dose única 3,5 mg/kg-1), D (animais infectados e tratados com aceturato de diminazeno convencional com dose única 3,5 mg/kg-1), E (animais infectados e tratados com aceturato lipossomal por 5 dias consecutivos com a dose de 3,5 mg/kg-1/dia) e grupo F (animais e infectados tratados com aceturato convencional por 5 dias consecutivos com a dose de 3,5 mg/kg-1/dia). O teste in vitro com o lipossoma de aceturato de diminazeno mostrou uma maior mortalidade dose-dependente do T. evansi em meio de cultura se comparado ao medicamento comercial e os parasitos morreram mais rapidamente que nos grupos de aceturato de diminazeno convencional e controle. Nos resultados dos testes in vivo, a eficácia do aceturato de diminazeno lipossomal e convencional nos diferentes protocolos terapêuticos foram similares. A análise dos parâmetros bioquímicos e histológicos realizados no 7º e 40º pós-tratamento revelaram alterações nas enzimas hepáticas e renais, além de modificações na estrutura dos órgãos, principalmente nos animais tratados com lipossomas na maior dosagem. Os resultados obtidos neste estudo demonstraram que as formulações lipossomais podem ser uma nova alternativa para o tratamento das tripanossomoses. Futuras pesquisas poderiam ser realizadas para melhorar o carreamento e a direção dos lipossomas para uma maior eficácia.

A class of linear diamidines was synthesized for the evaluation as a treatment of Human African Trypanosomiasis. These fused heterocyclic compounds are thiazole[5,4-d]thiazoles and are of interest because the parent compound, 2,5-Bis(4-amidinophenyl)-thiazolo[5,4-d]thiazole HCl salt, which is also called DB 1929, has exhibited a low nanomolar IC50 value against Trypanosoma brucei rhodesiense and has shown selectivity for binding to the human telomere G-quadruplex over that of DNA duplex. A fluoro and a methoxy derivative have been synthesized and are currently undergoing testing for activity and binding affinity. In addition, fluorescence studies of selected diamidines were done to study the effect of structural variation on fluorescence. This data is useful since it can determine what types of moieties are needed to yield a compound that will fluoresce in the higher wavelengths (500 nm and above) of the visible spectrum, which would be advantageous in determining the uptake of the drug in the trypanosome within the endemic areas of Africa with a simple microscope.

Les amines homoallyliques sont des synthons clés pour la construction de nombreuses molécules d'intérêt biologique. Du fait de la double liaison carbone-carbone du fragment allylique, facilement fonctionnalisable, elles sont également très utilisées en synthèse organique. Ce travail de recherche s'oriente sur la synthèse d'amines homoallyliques grâce à des complexes de titane. En effet, le couplage réducteur d'imines et de diènes promu par du titane permet la formation d'amines homoallyliques diastéréoisomères syn et anti. La diastéréosélectivité de la réaction est directement affectée par le substituant porté par l'atome d'azote. Selon qu'il s'agit d'un groupement benzyle ou phényle, la sélectivité sera marquée en faveur de l'amine syn ou anti respectivement. De plus, l'ajout de l'acide de Lewis BF3.OEt2 permet de diminuer considérablement le temps de réaction mais également d'inverser la diastéréosélectivité obtenue avec la réaction sans acide de Lewis.L'instabilité des amines homoallyliques durant le processus de purification a permis d'autre part de mettre en lumière un réarrangement cationique 2-Aza-Cope. Ce réarrangement a été appliqué à la synthèse catalytique d'homocrotylamines et d'un acide aminé , insaturé. Ce manuscrit rapporte également la synthèse d'amines homoallyliques par couplage entre des diènes et des dérivés benzotriazole. Ces dérivés génèrent des iminiums qui réagissent plus efficacement que les imines pour former les amines souhaitées. De plus, la réaction effectuée avec des dérivés de type bis(benzotriazole) conduit sélectivement à des homoallyl-(E)- homocrotylamines. Cette réactivité est expliquée par une triple réaction en cascade à savoir : allyltitanation - réarrangement cationique 2-Aza-Cope - allyltitanation.D'autre part, une partie de ce manuscrit s'intéresse à la réaction entre le complexe Ti(NMe2)4 et des dioxocyclames qui forment de nouvelles diamidines macrocyliques. Les propriétés chimiques de ces amidines présentent de nombreux intérêts pour la formation de complexes avec des métaux tels que le Cu, le Ni et le Pd. Les analyses des complexes méritent d'être approfondies afin de déterminer sans ambigüité leur structure et de mieux comprendre le mode de coordination de ces nouveaux macrocycles azotés.