Over the last decade, the domain of click chemistry has grown exponentially and has significantly impacted the fields of organic synthesis, medicinal chemistry, molecular biology, and materials science. The ideal model of a click reaction has become the copper-catalyzed azide-alkyne cycloaddition (CuAAC). Inherent limitations of CuAAC, including high temperatures, long reaction times, and difficult purifications, have been minimized by the development of nitrogen-based ligands. Herein, we present a novel application of 1,2,4-triazines by investigating their use as accelerants for CuAAC. A diverse library of 1,2,4-triazines were synthesized in order to examine the molecular determinants of their catalytic activity. These ligands were found to be potent accelerants, at catalytic concentrations, in the presence of both copper(I) and copper(II) salts. Remarkably, these catalyzed reactions proceeded at room temperature, generating high isolated yields, in both polar and nonpolar solvents. 5,6-Diphenyl-3-(pyridin-2-yl)1,2,4-triazine was the most active ligand studied, producing an 89% yield in a model click reaction within one hour. Additional experiments with an array of azides and alkynes yielded similar results, defining a broad substrate scope for 1,2,4-triazines as catalysts for click chemistry. Heterogeneous 1,2,4-triazines were designed using different solid supports and different sites of attachment with respect to the 1,2,4-triazine ligand. The primary advantages offered by these immobilized catalysts are the prevention of metal contamination in 1,2,3-triazole products and the recyclability of the catalyst. Results indicated that 1,2,4-triazine-functionalized silica was a more effective accelerant of CuAAC, whereas polystyrene-supported 1,2,4-triazines displayed modest activity. In coordination with copper(II), 1,2,4-triazines appended onto silica generated isolated yields greater than 90% after four consecutive reaction cycles with minimal copper leaching. Further research will utilize both homogeneous and heterogeneous 1,2,4-triazine-accelerated CuAAC in the derivatization of solid supports for energy-related chemical processes and in the synthesis of novel enzyme inhibitors.

Copper-catalyzed regeneration in atom transfer radical addition (ATRA) utilizes reducing agents, which continuously regenerate the activator (CuI) from the deactivator (CuII) species. This technique was originally found for mechanistically similar atom transfer radical polymerization (ATRP) and its application in ATRA and ATRC has allowed significant reduction of catalyst loadings to ppm amounts. In order to broaden the synthetic utility of in situ catalyst regeneration technique, this was applied in copper-catalyzed atom transfer radical cascade reaction in the presence of free radical diazo initiators such as 2,2’-azobis(isobutyronitrile) (AIBN) and (2,2’-azobis(4-methoxy-2,4-dimethyl valeronitrile) (V-70), which is the first part of this dissertation. This methodology can be translated to sequential ATRA/ATRC reaction, in which the addition of CCl4 to 1,6-dienes results in the formation 5-hexenyl radical intermediate, which undergoes expedient 1,5-ring closure in the exo- mode to form 1,2-disubstituted cyclopentanes. When [CuII(TPMA)Cl][Cl] complex was used in conjunction with AIBN at 60 0C, cyclic products derived from the addition of CCl4 to 16-heptadiene, diallyl ether and N,N­-diallyl-2,2,2-trifluoroacetamide were synthesized in nearly quantitative yields using as low as 0.02 mol% of the catalyst (relative to 1,6-diene). Even more impressive were the results obtained utilizing tert­-butyl-N,N-diallylcarbamate and diallyl malonate using only 0.01 mol% of the catalyst. Cyclization was also found to be efficient at ambient temperature when V-70 was used as the radical initiator. High product yields (>80%) were obtained for mixtures having catalyst concentrations between 0.02 and 0.1 mol%. Similar strategy was also conducted utilizing unsymmetrical 1,6-diene esters. It was found out that dialkyl substituted substrates (dimethyl-2-propenyl acrylate and ethylmethyl-2-propenyl acrylate) underwent 5-exocyclization producing halogenated g-lactones after the addition of CCl4 in the presence of 0.2 mol% of [CuII(TPMA)Cl][Cl]. Based on calculations using density functional theory (DFT) and natural bond order (NBO) analysis, cyclization of 1,6-diene esters was governed by streoelectronic factors. <br>As a part of broadening the synthetic usefulness of in situ copper(I) regeneration, scope was further extended to sequential organic transformations. Based on previous studies, copper(I) catalyzed [3+2] azide-alkyne cycloaddition is commonly conducted via in situ reduction of CuII to CuI species by sodium ascorbate or ascorbic acid. At the same time, ATRA reactions have been reported to proceed efficiently via in situ reduction of CuII complex to the activator species or CuI complex has been fulfilled in the presence of ascorbic acid. Since the aforementioned reactions share similar catalyst in the form of copper(I), a logical step was taken in performing these reactions in one-pot sequential manner. Reactions involving azidopropyl methacrylate and 1-(azidomethyl)-4-vinylbenzene in the presence of a variety of alkynes and alkyl halides, catalyzed by as low as 0.5 mol-% of [CuII(TPMA)X][X] (X=Br-, Cl-) complex, proceeded efficiently to yield highly functionalized (poly)halogenated esters and aryl compounds containing triazolyl group in almost quantitative yields (>90%). Additional reactions that were carried out utilizing tri-, di- and monohalogenated alkyl halides in the ATRA step provided reasonable yields of functionalized trriazoles. A slightly different approach involving a ligand-free catalytic system (CuSO4 and ascorbic acid) in the first step followed by addition of the TPMA ligand in the second step was applied in the synthesis of polyhalogened polytriazoles. Sequential reactions involving vinylbenzyl azide, tripropargylamine and polyhalogenated methane (CCl4 and CBr4) provided the desired products in quantitative yield in the presence of 10 mol% of the catalyst. Modest yields of functionalized polytriazoles were obtained from the addition of less active tri- and dihalogenated alkyl halides utilizing the same catalyst loading. <br>The last part focuses on copper(I) complexes, which were used catalysts in cyclopropanation reaction. One class represented cationic copper(I)/2,2-bipyridine complexes with p-coordinated styrene [CuI(bpy)(p-CH2CHC6H5)][A] (A = CF3SO3- (1) and PF6- (2) and ClO4- (3). Structural data suggested that the axial coordination of the counterion in these complexes observed in the solid state weak to non-coordinating (2.4297(11) Å 1, 2.9846(12) Å 2, and 2.591(4) Å 3). When utilized in cyclopropanation, complexes 1-3 provided similar product distribution suggesting that counterions have negligible effect on catalytic activity. Furthermore, the rate of decomposition of EDA in the presence of styrene catalyzed by 3 (kobs=(7.7±0.32)´10-3 min-1) was slower than the rate observed for 1 (kobs=(1.4±0.041)´10-2 min-1) or 2 (kobs=(1.0±0.025)´10-2 min-1). On the other hand, tetrahedral copper(I) complexes with bipyridine and phenanthroline based ligands have been reported to have strongly coordinated tetraphenylborate anions. CuI(bpy)(BPh4), CuI(phen)(BPh4) and CuI(3,4,7,8-Me4phen)(BPh4) complexes are the first examples in which BPh4- counterion chelates a transition metal center in bidentate fashion through h2 p-interactions with two of its phenyl rings. The product distribution revealed that the mole percent of trans and cis cyclopropanes were very similar. The observed rate constants (kobs) shown in for decomposition of EDA in the presence of externally added styrene were determined to be kobs=(1.5±0.12)´10-3 min-1, (6.8±0.30)´10-3 min-1 and (5.1±0.19)´10-3 min-1. / Bayer School of Natural and Environmental Sciences / Chemistry and Biochemistry / PhD / Dissertation

Die Kombination von Polymeren mit Peptiden vereint die Eigenschaften beider Stoffklassen miteinander. Dabei können die strukturbildenden Eigenschaften der Peptide genutzt werden, um Polymere zu organisieren. In der vorliegenden Arbeit wurde ein Polymer-Peptid-Konjugat verwendet, das sich in Wasser zu Bändern anordnet. Die treibende Kraft für diesen Prozess ist die Anordnung des Peptidteils zu β-Faltblattstrukturen. Das Polymer-Peptid-Aggregat besitzt einen Peptidkern mit funktionalen Oberflächen, der lateral von einer Polyethylenoxidschale umgeben ist. Durch Änderung der Peptidsequenz war es bisher möglich, die Eigenschaften dieser Fasern zu variieren. In der Arbeit wird ein modularer Ansatz zur vielfältigen Modifizierung einer Polymer-Peptid-Faser entwickelt. So ist es möglich, die Eigenschaften der Fasern einzustellen, ohne die strukturbildende β-Faltblattsequenz verändern zu müssen. Um weitere Funktionen an den Fasern anzubringen, wurde die 1,3-dipolaren Addition verwendet. Diese Reaktion beschreibt die konzertierte Umlagerung eines Azides mit einem Alkin. Sie ist in den meisten Lösungsmitteln unter hohen Ausbeuten durchführbar. Im Rahmen der Arbeit wird die Erzeugung von Aziden untersucht und auf die Polymer-Peptid-Fasern übertragen. Der Diazotransfer stellte dabei die Methode der Wahl dar, so können Azidgruppen aus Aminen gewonnen werden. Unter Verwendung der 1,3-dipolaren Addition konnten verschiedene alkinfunktionale Moleküle kovalent an die azidfunktionalisierten Polymer-Peptid-Fasern gebunden werden. So wurde ein Fluoreszenzfarbstoff an die Fasern gebunden, der eine Abbildung der Fasern mittels konfokaler Mikroskopie erlaubte. Weiterhin wurden die Eigenschaften der Fasern durch Addition dreier carboxylfunktionaler Moleküle modifiziert. Diese Fasern konnten weiter genutzt werden, um Kalzium zu binden. Dabei variierte die Anzahl der gebundenen Kalziumionen in Abhängigkeit der jeweiligen Fasermodifikation erheblich. Weitere Untersuchungen, die Morphologie von Kalziumcarbonatkristallen betreffend, werden aktuell durchgeführt. Die kovalente Anbringung eines reduzierenden Zuckers an die Polymer-Peptid-Fasern erlaubt die Abscheidung von Silber aus Tollens Reagenz. Durch eine Entwicklung analog zur Schwarz-Weiss-Photographie können in nachfolgenden Arbeiten so Silberdrähte in Nanogröße erzeugt werden. An die azidfunktionalen Fasern können weitere funktionale Moleküle angebracht werden, um die Eigenschaften und das Anwendungsspektrum der Polymer-Peptid-Fasern zu erweitern. / The combination of polymer with peptides combines the advantages of both substance classes. It is possible to use peptide structure-forming properties to assemble polymers. In my current research, a self assembling Polymer-Peptide-Conjugate was used, which forms ribbon-like structures in water. The peptide tendency to form β-sheets is the driving force for this process. The resulting Polymer-Peptide-Aggregate is build up of a core shell model, where the peptides are the core and the polymer (polyethylene oxide) is the lateral suited shell. A new peptide synthesis was necessary in order to change the functional groups in the peptide core. In my present work a modular strategy was developed to get access to various types of modified Polymer-Peptide-Fiber. This allows adjustiment to the fiber properties without changing the structure forming b‑sheet sequence. To apply these functions, 1,3‑dipolar addition was used. This reaction described the simultaneous reactions of alkynes and azides. The reaction occurs in most solvents under high yields. In the context of this work, the generation of azides was investigated and transferred to the Polymer-Peptide-Fibers. Diazotransfer was the chosen method to transfer primary amines into azidefunctions at the fiber surface. With the use of 1,3‑dipolar addition it was possible to bind alkyne functionalized molecules covalent to the azide functionalized fibers. A fluorescent dye was bound to the fibers to image these fibers with confocal microscopy. The properties of the azide fibers were further modified to incorporation three different carboxylic molecules. These fibers were used to estimate the calcium binding affinity. Thus, differing the number of bonded calcium is a function of the used fiber attachment. Investigations concerning the morphology of Calcium carbonate crystals can be done. The covalent attachment of reducing sugar to the Polymer-Peptide-Fibers should will allow the production of silver(0)clusters along the fibers with the use of Tollens´ reagent. With the help of a developer solution, similar to black and white photography, the possibility to archive silverrods in nanometer size can be obtained. The applied modifications on fibers is hence a promising first step in altering fibers in which by adjusting its properties, we broaden the applications of these Polymer-Peptide-Fibers.

In this work, the synthesis of biopolymer-based hydrogel networks with defined architecture is presented. In order to obtain materials with defined properties, the chemoselective copper-catalyzed azide-alkyne cycloaddition (or Click Chemistry) was used for the synthesis of gelatin-based hydrogels. Alkyne-functionalized gelatin was reacted with four different diazide crosslinkers above its sol-gel transition to suppress the formation of triple helices. By variation of the crosslinking density and the crosslinker flexibility, the swelling (Q: 150-470 vol.-%;) and the Young’s and shear moduli (E: 50 kPa - 635 kPa, G’: 0.1 kPa - 16 kPa) could be tuned in the kPa range. In order to understand the network structure, a method based on the labelling of free functional groups within the hydrogel was developed. Gelatin-based hydrogels were incubated with alkyne-functionalized fluorescein to detect the free azide groups, resulting from the formation of dangling chains. Gelatin hydrogels were also incubated with azido-functionalized fluorescein to check the presence of alkyne groups available for the attachment of bioactive molecules. By using confocal laser scanning microscopy and fluorescence spectroscopy, the amount of crosslinking, grafting and free alkyne groups could be determined. Dangling chains were observed in samples prepared by using an excess of crosslinker and also when using equimolar amounts of alkyne:azide. In the latter case the amount of dangling chains was affected by the crosslinker structure. Specifically, 0.1% of dangling chains were found using 4,4’-diazido-2,2’-stilbene-disulfonic acid as cosslinker, 0.06% with 1,8-diazidooctane, 0.05% with 1,12-diazidododecane and 0.022 % with PEG-diazide. This observation could be explained considering the structure of the crosslinkers. During network formation, the movements of the gelatin chains are restricted due to the formation of covalent netpoints. A further crosslinking will be possible only in the case of crosslinker that are flexible and long enough to reach another chain. The method used to obtain defined gelatin-based hydrogels enabled also the synthesis of hyaluronic acid-based hydrogels with tailorable properties. Alkyne-functionalized hyaluronic acid was crosslinked with three different linkers having two terminal azide functionalities. By variation of the crosslinking density and crosslinker type, hydrogels with elastic moduli in the range of 0.5-3 kPa have been prepared. The variation of the crosslinking density and crosslinker type had furthermore an influence also on the hydrolytic and enzymatic degradation of gelatin-based hydrogels. Hydrogels with a low crosslinker amount experienced a faster decrease in mass loss and elastic modulus compared to hydrogels with higher crosslinker content. Moreover, the structure of the crosslinker had a strong influence on the enzymatic degradation. Hydrogels containing a crosslinker with a rigid structure were much more resistant to enzymatic degradation than hydrogels containing a flexible crosslinker. During hydrolytic degradation, the hydrogel became softer while maintaining the same outer dimensions. These observations are in agreement with a bulk degradation mechanism, while the decrease in size of the hydrogels during enzymatic degradation suggested a surface erosion mechanism. Because of the use of small amount of crosslinker (0.002 mol.% 0.02 mol.%) the networks synthesized can still be defined as biopolymer-based hydrogels. However, they contain a small percentage of synthetic residues. Alternatively, a possible method to obtain biopolymer-based telechelics, which could be used as crosslinkers, was investigated. Gelatin-based fragments with defined molecular weight were obtained by controlled degradation of gelatin with hydroxylamine, due to its specific action on asparaginyl-glycine bonds. The reaction of gelatin with hydroxylamine resulted in fragments with molecular weights of 15, 25, 37, and 50 kDa (determined by SDS-PAGE) independently of the reaction time and conditions. Each of these fragments could be potentially used for the synthesis of hydrogels in which all components are biopolymer-based materials. / In dieser Arbeit wird die Synthese Biopolymer-basierter Hydrogelnetzwerke mit definierter Architektur beschrieben. Um Materialien mit definierten und einstellbaren Eigenschaften zu erhalten, wurde die chemoselektive Kupferkatalysierte Azid-Alkin-Cycloadditionsreaktion (auch als Click-Chemie bezeichnet) für die Synthese Gelatine-basierter Netzwerke eingesetzt. Alkin-funktionalisierte Gelatine wurde mit vier verschiedenen Diazid-Quervernetzern oberhalb der Gel-Sol-Übergangstemperatur umgesetzt, um die Formierung tripelhelikaler Bereiche durch Gelatineketten zu unterdrücken. Durch Variation der Menge an Quervernetzer (und damit der Netzdichte) sowie der Länge und Flexibilität der Quervernetzer konnten u.a. die Quellung (Q: 150-470 vol.-%) sowie der Young’s - und Schermodul im kPa Bereich eingestellt werden (E: 50 kPa - 635 kPa, G’: 0.1 kPa - 16 kPa). Um die Netzwerkarchitektur zu verstehen, wurde eine Methode basierend auf dem Labeln unreagierter Azid- und Alkingruppen im Hydrogel entwickelt. Die Gelatine-basierten Hydrogele wurden mit Alkin-funktionalisiertem Fluorescein umgesetzt, um freie Azidgruppen zu detektieren, die bei einem Grafting entstehen. Darüber hinaus wurden die Hydrogele mit Azid-funktionalisiertem Fluorescein reagiert, um die Menge an freien Alkingruppen zu bestimmen, die zudem potentiell für die Anbindung bioaktiver Moleküle geeignet sind. Quervernetzung, Grafting, und die Anzahl freier Alkingruppen konnten dann mit Hilfe der konfokalen Laser Scanning Mikroskopie und der Fluoreszenzmikroskopie qualitativ und quantitativ nachgewiesen werden. Gegraftete Ketten wurden in Systemen nachgewiesen, die mit einem Überschuss an Quervernetzer hergestellt wurden, entstanden aber auch beim Einsatz äquimolarer Mengen Alkin- und Azidgruppen. Im letzteren Fall wurde in Abhängigkeit von der Struktur des Diazids unterschiedliche Anteile gegrafteter Ketten festgestellt. 0.1 mol-% von gegrafteten Ketten wurden für 4,4’-Diazido-2,2’-stilbendisulfonsäure gefunden, 0.06 mol-% für 1,8-Diazidooktan, 0.05 mol% für 1,12-diazidododecan und 0.022 mol-% für PEG-Diazid. Diese Beobachtung kann durch die unterschiedliche Flexibilität der Vernetzer erklärt werden. Während der Netzwerkbildung werden die Bewegungen der Gelatineketten eingeschränkt, so dass kovalente Netzpunkte nur erhalten werden können, wenn der Vernetzer lang und flexibel genug ist, um eine andere Alkingruppe zu erreichen. Die Strategie zur Synthese von Biopolymer-basierten Hydrogelen mit einstellbaren Eigenschaften wurde von Gelatine- auf Hyaluronsäure-basierte Gele übertragen. Alkin-funktionalisierte Hyaluronäure wurde mit drei verschiedenen Diaziden quervernetzt, wobei Menge, Länge, und Flexibilität des Quervernetzers variiert wurden. In dieser Weise wurden sehr weiche Hydrogele mit E-Moduli im Bereich von 0.5-3 kPa hergestellt. Die Variation der Vernetzungsdichte und des Vernetzertyps beeinflusste weiterhin den hydrolytischen und enzymatischen Abbau der Hydrogele. Hydrogele mit einem geringerem Anteil an Quervernetzer wurden schneller abgebaut als solche mit einem höheren Quervernetzeranteil. Darüber hinaus konnte gezeigt werden, dass Hydrogele mit Quervernetzern mit einer rigiden Struktur deutlich langsamer degradierten als Hydrogele mit flexibleren Quervernetzern. Während des hydrolytischen Abbau wurden die Materialien weicher, behielten aber ihre Form bei, was mit einem Bulk-Abbau-Modell übereinstimmt. Während des enzymatischen Abbaus hingegen änderten sich die Materialeigenschaften kaum, jedoch wurden die Proben kleiner. Diese Beobachtung stimmt mit einem Oberflächenabbaumechanismus überein. Da in allen vorgestellten Systemen nur eine kleine Menge synthetischer Vernetzer eingesetzt wurde (0.002 – 0.02 mol%), können die Materialien noch als Biopolymer-basierte Materialien klassifiziert werden. Jedoch enthalten die Materialien synthetische Abschnitte. In Zukunft könnte es interessant sein, einen Zugang zu Materialien zu haben, die ausschließlich aus Biopolymeren aufgebaut sind. Daher wurde der Zugang zu Biopolymer basierten Telechelen untersucht, die potentiell als Vernetzer dienen können. Dazu wurden durch die kontrollierte Spaltung von Gelatine mit Hydroxylamin Gelatinefragmente mit definiertem Molekulargewicht hergestellt. Hydroxalamin reagiert unter Spaltung mit der Amidbindung zwischen Asparagin und Glycin, wobei Aspartylhydroxamate und Aminoendgruppen entstehen. Die Reaktion von Gelatine mit Hydroxylamin ergab Fragmente mit Molekulargewichten von 15, 25, 37, und 50 kDa (bestimmt mit SDS-PAGE), und die Formierung dieser Fragmente war unabhängig von den weiteren Reaktionsbedingungen und der Reaktionszeit. Jedes dieser Fragmente kann potentiell für die Synthese von Hydrogelen eingesetzt werden, die ausschließlich aus Biopolymeren bestehen.

Immobilization of different bio- and organic molecules on solid supports is fundamental within many areas of science. Sometimes, it is desirable to obtain a directed orientation of the molecule in the immobilized state. In this thesis, the copper (I) catalyzed Huisgen 1,3-dipolar cycloaddition, referred to as a “click chemistry” reaction, was explored as a means to perform directed immobilization of small molecule ligands on gold surfaces. The aim was to synthesize alkyne- and azide-terminated alkanethiols that would form well-organized self assembled monolayers (SAMs) on gold from the commercially available substances orthoethylene glycol and bromo alkanoic acid. N-(23-azido-3,6,9,12,15,18,21-heptaoxatricosyl)-n-mercaptododekanamide/hexadecaneamide (n = 12, 16) were successfully synthesized and allowed to form SAMs of different compositions to study how the differences in density of the functional groups on the surface would influence the structure of the monolayer and the click chemistry reaction. The surfaces were characterized by different optical methods: ellipsometry, contact angle goniometry and infrared reflection-absorption spectroscopy (IRAS). The click reaction was found to proceed at very high yields on all investigated surfaces. Finally, the biomolecular interaction between a ligand immobilized by click chemistry on the gold surfaces and a model protein (bovine carbonic anhydrase) was demonstrated by surface plasmon resonance using a Biacore system.

Ce travail a pour objet l'obtention et la caractérisation de nouveaux copolymères amphiphiles et d'hydrogels à hydrophilie contrôlée, à partir de polymères naturels, avec comme utilisations potentielles la vectorisation de principes actifs. En conséquence, il est donc nécessaire que les polymères utilisés pour l'obtention de ces architectures répondent à un certain nombre de contraintes, notamment être non-toxiques, biocompatibles et biodégradables. Pour ces raisons, on retient le plus souvent comme matériaux de départ des polymères naturels, en particulier les polysaccharides. Quelques polymères synthétiques répondent aussi à ces contraintes, telle que la polycaprolactone. Ainsi, le matériau de base utilisé dans ce travail est l'amidon sur lequel a été greffé soit la poly (ε-caprolactone), soit une chaîne grasse. La thèse est structurée en cinq chapitres consacrés d'une part au greffage de structures hydrophobes sur l'amidon et la formation d'hydrogels à hydrophobie modulable, d'autre part à la vectorisation de la lévofloxacine par ces composés. La première partie traite du greffage de la polycaprolactone sur l'amidon par "click chemistry" (CuAAC) entre l'amidon fonctionnalisé par des fonctions alcynes et des polycaprolactones à fonction azoture en bout de chaîne, ces dernières étant préalablement obtenues par POC de la caprolactone. Les réactions de CuAAC ont été effectuées non seulement selon les protocoles habituels, mais aussi par micro ondes. Par ailleurs, l'amidon a aussi été hydrophobisé par les méthodes usuelles d'estérification par une chaîne grasse via le chlorure de l'acide palmitoique. Les produits ainsi obtenus ont été caractérisés par RMN, IR, XPS et leur comportement dans différents solvants (solubilité, gonflement) a été étudié. Une seconde partie est consacrée à l'élaboration d'hydrogels à base d'amidon et d'amidon modifié avec des chaînes d'acides gras et de PCL par réticulation avec l'acide citrique. Afin d'atteindre les objectifs, une stratégie multifactorielle expérimentale avec deux variables indépendantes a été utilisée. La modélisation mathématique des données expérimentales permet de remonter aux paramètres physico-chimiques pertinents, montre les effets de synergie et établit les conditions d'optimisation. Une dernière partie a permis d'évaluer les cinétiques de libération de la lévofloxacine, un antibiotique de dernière génération, par les hydrogels obtenus. Les matériaux obtenus ont montré des propriétés de libération contrôlée potentiellement intéressantes. Les résultats obtenus au cours de cette thèse ont été évalués par la publication de trois articles et par dissémination des résultats au six conférences internationales.

Oligonucleotides are short fragments of DNA (10-100nt) which are of great interest because their applications in molecular biology, biomedicine and nanotechnology. As a result of their ability to base pairing, oligonucleotides can be used as primers, hybridization probes in biosensors, agents for controlling gene expression, structural material in nanotechnology or as substrates for a variety of biochemical and biophysical studies. Chemical modification of oligonucleotides as well as conjugation to different functional molecules allows for modulation of both therapeutical and biotechnological properties. This thesis is focused in the nucleic acid chemistry field and the main objective is the synthesis of modified oligonucleotides for obtaining structures with therapeutical and/or biotechnological interest. Oligonucleotides capable to form structures other than the canonical DNA double helix have received considerable attention in the last years. The ability of triplex forming oligonucleotides (TFOs) to bind specifically to certain duplex DNA regions provides a strategy for site-directed modification of genomic DNA. Besides, G-quadruplexes are four-stranded DNA structures stabilized by stacking of guanine tetrads which have been found in telomeres and some promoters and play a role in regulation of transcription and translation. In addition, they are also interesting for nanotechnological devices. In this context, the first part of the research work was addressed to synthesize parallel stranded oligonucleotide clamps carrying LNA (locked nucleic acid) residues and study the stability of the triplex formed with DNA and RNA target sequences. Secondly, a novel strategy to obtain parallel clamps using the non-templated chemical ligation of two oligonucleotides by 5’-5’ linkages was developed. For this purpose, several protocols for introduce azido and alkyne moieties in the 5’-end of different sequences were developed so that the modified DNA strands could form a parallel hairpin after their chemical ligation by click chemistry. Thirdly, a system composed of four DNA strands whose 5’ ends are covalently attached was designed to form a monomolecular parallel G-quadruplex, which was used to study the effects of some nucleobase modifications in quadruplex structure. Finally, oligonucleotide conjugates carrying Cu(II) complexes were synthesized to construct arrays of electrochemical oscillators for nanotechnology applications.

Les MOFs résultent de l'organisation de polyèdres métalliques reliés par des molécules organiques chélatantes pour former un réseau poreux. La construction de solides hybrides organiques/inorganiques permet d'imaginer un très grand nombre de matériaux aux propriétés structurales et physico-chimiques variées. Le confinement du substrat dans une structure rigide, associé à des propriétés particulières des clusters métalliques ainsi qu'à des parois pouvant être fonctionnalisées, fournissent un environnement catalytique unique, plaçant les MOF à la frontière entre les espèces types zéolites et les enzymes. Cependant, il existe aujourd'hui très peu de MOFs possédant plus d'une fonction catalytique. Néanmoins, les propriétés catalytiques des MOFs peuvent être améliorées de façons non négligeables grâce aux méthodes de post-fonctionalisation. Dans ce travail, nous reportons le développement d'une méthode de post-fonctionnalisation originale des amino-MOFs. La première étape consiste à convertir la fonction amine en fonction azoture. Puis, sans isolation ni purification, le MOF fonctionnalisé est obtenu par " Click Chemistry " en ajoutant l'alcyne correspondant. Cette méthode peut être appliquée à tous les types d'amino-MOFs et à quasi toutes les fonctions chimiques que l'on souhaite greffer. Une large librairie de nouveaux matériaux a ainsi été obtenue et complètement caractérisée. Cette méthode a aussi été utilisée pour créer des MOFs catalytiques à façon pour une réaction de transesterification, ainsi que pour l'investigation de nouvelles applications plus fines (niches industrielle)

An antenna for light harvesting is an organized multicomponent system in which several chromophoric molecular species absorb the incident light and channel the excitation energy to a common acceptor component. In this study, Click chemistry has been successfully applied in the synthesis of a bay region tetraboron dipyrrin (BODIPY) appended perylenediimide (PDI). This light-harvesting molecule presents a large cross section for the absorption of light in the visible region. Excitation energy is efficiently channeled to the perylenediimide core. This novel antenna system is the first demonstration of the efficiency of energy transfer in a BODIPY- PDI bichromophoric system and appears to be highly promising for the design and synthesis of similar dendritic structures.

Modular polyketide synthases (PKSs) are the largest enzymes known to man and are responsible for synthesizing some of the most important human medicines. Their ability to construct stereochemically-rich carbon chains containing diverse substituents has inspired the biosynthetic community to engineer these factories for the in vitro synthesis of a small library of polyketide compounds. New complex polyketides are discovered every year, yet the lack of compound prohibits characterization and testing of these new compounds for medicinal properties. Smaller polyketide compounds generated in vitro could be organically manipulated to generate larger, more complex polyketide natural products and natural product analogs. Chemoenzymatic approaches like this would be extremely beneficial to the scientific community; however, there are still obstacles that must be overcome before the use of PKS for the preparative synthesis of an in vitro generated polyketide library would prove fruitful: purchasing substrates such as methylmalonyl-CoA is cost-prohibitive, PKSs are often difficult to express and purify, and the products generated are typically nonchromophoric. The use of a malonyl-CoA ligase from Streptomyces coelicolor (MatB) was investigated for the enzymatic synthesis of polyketide extender units such as methylmalonyl-CoA (Chapter 2). MatB synthesized a total of 5 CoA-linked extender units in vitro: malonyl-, methylmalonyl-, ethylmalonyl-, hydroxymalonyl- and methoxymalonyl-CoA. Two ternary complex structures of MatB with bound product and leaving group were also solved to sub-2Å resolution. MatB generated extender units were employed in the module-catalyzed synthesis of a triketide pyrone. The selectivity of a PKS module to incorporate a variety of side chains into triketide pyrones was also investigated (Chapter 3). A total of 10 triketide pyrone compounds were synthesized, 5 produced via modular "stuttering" and one possessing a terminal alkyne chemical handle. Lastly, nonchromphoric polyketide products were made visible upon copper(I)-catalyzed azide alkyne cycloaddition (CuAAC) with fluorescent sulforhodamine B azide revealing insights into in vitro reactivites of a PKS module (Chapter 4). The work described in this dissertation has helped advance the scientific community towards procuring an in vitro synthesized polyketide library for future synthetic applications. / text