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Ce manuscrit présente le développement de nouvelles diphosphines et phosphoramidites atropoisomères dissymétriques et leurs applications en catalyse énantiosélective. Dans une première partie, nous nous sommes intéressés à la synthèse de deux nouvelles diphosphines atropoisomères dépourvues de symétrie C2. Ces nouveaux ligands optiquement purs, appelés MeO-NAPhePHOS et TriMe-NAPhePHOS, possédent chacun un squelette biaryle dissymétrique obtenu par couplage intramoléculaire diastéréosélectif entre deux cycles aromatiques reliés par une agrafe chirale. L'évaluation de ces ligands dans des réactions de catalyse énantiosélectives a montré leur véritable efficacité. En effet, de très bonnnes sélectivités ont été obtenus en hydrogénation asymétrique catalysée par des complexes du ruthénium, pour la réaction d'addition-1,4 d'acides boroniques sur des cétones a,b-insaturées catalysée par des complexes du rhodium et pour la réaction de cycloisomérisation d'énynes-1,7 catalysée par des complexes du palladium. De plus, les propriétés stériques du MeO-NAPhePHOS et TriMe-NAPhePHOS ont été réalisées grâce à des calculs de modélisation moléculaire. Des tests comparatifs d'hydrogénation asymétrique réalisés avec nos deux ligands, le BINAP et le MeO-BIPHEP ont montré que les caractéristiques géométriques des diphosphines atropoisomères étaient hautement corrélées aux énantiosélectivités observées. Dans une deuxième partie, nous avons utilisé l'approche synthétique développée pour l'obtention de nouveaux ligands phosphoramidites dissymétriques présentant un phosphore stéréogène. Leur évaluation en catalyse énantiosélective, comme l'hydrogénation et les additions conjuguées, a montré qu'il était indispensable de disposer de ligands énantio- et diastéréomériquement purs afin d'identifier l'espèce la plus active et sélective.

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<p>The first part of the work describes a procedure of oligonucleotide purification using a reversed-phase cartridge. The developed method employs a very efficient yet mild oligonucleotide detritylation on the cartridge support allowing fast purification of oligonucleotides regardless of their 5´-modification. Thiol- and amino-modified oligonuc-leotides were detritylated and purified with the same high efficiency as non-modified oligonucleotides. The method enables fast, parallel and automated purification of many oligonucleotide probes that was not possible before. In combination with the method of removal of tritylated failure fragments oligonucleotides were produced with purity superior to that of oligonucleotides purified using RP HPLC.</p><p>In the second part of the present study a method of solid-phase RNA synthesis using 2´-tert-butyldithiomethyl (2´-O-DTM) is discussed. The stability of the DTM group during oligonucleotide assembly and deprotection in ammonia, together with its ability for rapid deprotection under mild conditions, allowed the synthesis of RNA with the quality similar to that of synthetic DNA oligonucleotides. The advantage of the 2´-O-DTM group is that it is completely orthogonal to all protecting groups used for the traditional solid-phase DNA synthesis. Therefore, the synthesis can be performed using a standard DNA synthesis procedure – no changes are needed for the product assembly. RNA oligonucleotides synthesized with retained 5´-terminal trityl group can be subjected to a cartridge-based purification using the procedure described in the first part of the study. The phosphoramidite synthesis was optimized for a large scale preparation and gives versatility for introduction of other alkyldithiomethyl groups according to the preference to their certain properties.</p><p>The third part of the thesis describes the synthesis of a dithiomethyl linker and its utility for reversible conjugation of oligonucleotides. A dithiomethyl group, cleavable under mild conditions, was introduced onto 3´-OH of tritylated nucleosides via 3´-O-methylthiomethyl derivatives. The influence of different alkyl substituents on the disulfide bond stability was investigated, and stable analogues were employed in oligosyntheses. Two applications were developed using the present linker: 1) purification of oligonucleotides linked to the solid support; and 2) cartridge-based purification of tritylated oligonucleotides having an additional hydrophobic group on their 3´- terminus.</p>

The first part of the work describes a procedure of oligonucleotide purification using a reversed-phase cartridge. The developed method employs a very efficient yet mild oligonucleotide detritylation on the cartridge support allowing fast purification of oligonucleotides regardless of their 5´-modification. Thiol- and amino-modified oligonuc-leotides were detritylated and purified with the same high efficiency as non-modified oligonucleotides. The method enables fast, parallel and automated purification of many oligonucleotide probes that was not possible before. In combination with the method of removal of tritylated failure fragments oligonucleotides were produced with purity superior to that of oligonucleotides purified using RP HPLC. In the second part of the present study a method of solid-phase RNA synthesis using 2´-tert-butyldithiomethyl (2´-O-DTM) is discussed. The stability of the DTM group during oligonucleotide assembly and deprotection in ammonia, together with its ability for rapid deprotection under mild conditions, allowed the synthesis of RNA with the quality similar to that of synthetic DNA oligonucleotides. The advantage of the 2´-O-DTM group is that it is completely orthogonal to all protecting groups used for the traditional solid-phase DNA synthesis. Therefore, the synthesis can be performed using a standard DNA synthesis procedure – no changes are needed for the product assembly. RNA oligonucleotides synthesized with retained 5´-terminal trityl group can be subjected to a cartridge-based purification using the procedure described in the first part of the study. The phosphoramidite synthesis was optimized for a large scale preparation and gives versatility for introduction of other alkyldithiomethyl groups according to the preference to their certain properties. The third part of the thesis describes the synthesis of a dithiomethyl linker and its utility for reversible conjugation of oligonucleotides. A dithiomethyl group, cleavable under mild conditions, was introduced onto 3´-OH of tritylated nucleosides via 3´-O-methylthiomethyl derivatives. The influence of different alkyl substituents on the disulfide bond stability was investigated, and stable analogues were employed in oligosyntheses. Two applications were developed using the present linker: 1) purification of oligonucleotides linked to the solid support; and 2) cartridge-based purification of tritylated oligonucleotides having an additional hydrophobic group on their 3´- terminus.

This thesis deals with the development of transition metal-catalyzed silaborations of 1,3-dienes and 1,6-enynes. The first part of the thesis describes the development of the enantioselective 1,4-silaboration of 1,3-cyclohexadiene. A number of chiral metal-ligand complexes were evaluated. Up to 82% enantiomeric excess was obtained using a catalyst system derived from Pt(acac)2 and a phosphoramidite ligand. The product formed was employed in allylborations of aldehydes, giving homo-allylic alcohols in good yields with good to moderate diastereoselectivity. In attempts to widen the scope of silaborations to include acyclic, terminally substituted 1,3-dienes, products from H-B exchange with, and H-Si addition to, the dienes were obtained. The second part describes the development of silaborative carbocyclization of 1,6-enynes. A Pd N-heterocylic carbene complex was found to be effective for the silaborative carbocyclization of unsubstituted enynes, giving the products in good to excellent yields. Employing terminally substituted enynes resulted in low or no yields. The last part describes investigations into the reaction mechanisms of the processes developed in the first part. It was found that the silylborane undergoes oxidative addition to a Pt(0) complex generated from Pt(acac)2 and DIBALH. After insertion of 1,3-cyclohexadiene into the Pt-B bond a π-allyl complex was observed experimentally. In the addition of silylborane to acyclic, terminally substituted, 1,3-dienes it was shown by deuterium labeling experiments that one diene loses a hydride via H-B exchange and that this hydride is then added to another diene via H-Si addition. A reaction mechanism was proposed for this process. / QC 20100924

Récemment, la chimie des phosphoramidites s’est montrée efficace et polyvalente en tant que plateforme pour accéder à des poly(phosphodiester)s à séquence définies abiotiques. Grâce à cette stratégie, les monomères peuvent être placés dans la chaîne à des positions choisies, ouvrant la voie à de nombreuses possibilités pour la préparation de macromolécules fonctionnelles. Ici, la méthode phosphoramidite a été explorée pour la synthèse de polymères dits numériques, qui contiennent des séquences de monomères encodées binairement. Des polymères dont les longueurs de chaînes et les séquences numériques sont contrôlées ont été préparés en utilisant une stratégie phosphoramidite classique impliquant des groupements protecteurs diméthoxytrityles, ou bien un procédé photocontrôlé faisant intervenir des groupements nitrophénylpropyloxycarbonyles clivables à la lumière. En outre, plusieurs stratégies pour modifier l’information contenue dans les chaînes latérales ont été étudiées dans cette thèse. Une modification binaire post-polymérisation à travers deux cycloadditions alcyne-azoture catalysées par le cuivre(I) consécutives a été examinée pour optimiser les chaînes latérales des poly(phosphodiester)s à séquences définies. De plus, la libération photocontrôlée de différents motifs éthers ortho-nitrobenzyliques latéraux a été étudiée. Ces fonctions ont permis la conception d’oligo(phosphodiester)s numériques dont les séquences d’information peuvent être effacées ou révélées grâce à la lumière. / Phosphoramidite chemistry has recently been evidenced to be an efficient and versatile platform to access sequence-defined abiotic poly(phosphodiester)s. Using this strategy, monomers can be placed at defined positions positions in a chain, thus opening up wide possibilities for the preparation of functional macromolecules.Here, the phosphoramidite platform was explored to synthesize so-called digital polymers, which contain monomer-coded binary sequences. Polymers with controlled chain lengths and digital sequences were prepared using either a standard phosphoramidite strategy involving dimethoxytrityl protective groups or a photo-controlled process involving light-cleavable nitrophenylpropyloxycarbonyl protective groups. Additionally, several strategies to modify the side chain information were investigated in this thesis. A binary post-polymerization modification by means of sequential copper(I)-catalyzed alkyne-azide cycloadditions was investigated for tuning the side chain functionality of sequence-defined poly(phosphodiester)s. Moreover, the photo-controlled release of several ortho-nitrobenzylic ether side chain motifs was studied. These moieties allowed the design of digital oligo(phosphodiester)s whose sequence information can be erased or revealed with light as a trigger.