Caused by the organism Mycobacterium tuberculosis (Mtu), the globally distributed disease tuberculosis was responsible for the deaths of 1.4 million people in 2011. Anthranilate phosphoribosyltransferase (AnPRT) is an enzyme that catalyses the second committed step of the tryptophan biosynthetic pathway within Mtu, and is a promising target for antibiotics. This research aimed to further understand the mechanics of the AnPRT active site, in order to provide useful information towards AnPRT drug design. AnPRT inhibition and alternate substrates were investigated as well as variant AnPRT proteins, the results of which aided in unravelling a complex active site mechanism and illuminating several decisive inhibition strategies.

La chimie des hétérocycles est un des domaines les plus importants en chimie organique. En effet, 65% de la littérature en chimie organique traite des hétérocycles. Ils sont largement présents dans la nature, essentiels à la vie et leurs applications sont infinies. Parmi eux, les structures dites privilégiées, attirent une attention particulière. Ces structures privilégiées, dont font partie les quinoléines et les indoles, jouent un rôle central dans la chimie médicinale, pour la production de librairies de cibles thérapeutiques. De ce fait, le développement de nouvelles méthodes de synthèse de structures privilégiées, simples, efficaces et sensibles à l’impact environnemental reste un défi pour les chimistes. De nombreuses méthodes de synthèse requièrent l’emploi de dérivés d’anilines acylées en position ortho, mais ces substrats sont peu disponibles. La réaction d’addition en cascade, catalysée au cuivre, d’un réactif de Grignard sur l’anthranilate de méthyle permet l’obtention d’une aniline acylée en position ortho, jamais reportée au préalable, avec un rendement quantitatif. Cette dernière servira alors de substrat de départ pour la synthèse de plusieurs hétérocycles privilégiés dont les quinoléines et les indoles. La réaction de Friedlander est utilisée depuis plusieurs siècles mais souffre de l’emploi de conditions réactionnelles extrêmes et nocives pour l’environnement. Elle a donc été modernisée pour donner accès à une série de huit quinoléines trisubstituées, sans solvant, ni acide fort, ni hautes températures. Par ailleurs, le procédé de Heumann consiste en la synthèse d’indoles substitués en position par alkylation d’anilines acylées en position ortho, suivie d’une étape de saponification et de cyclisation intramoléculaire. Breveté par l’entreprise B.A.S.F., en 1895, ce procédé est rapidement devenu obsolète dû à de faibles rendements et des conditions réactionnelles difficiles. La chimie en flux continu a alors permis la renaissance de ce procédé grâce à l’élaboration d’un protocole plus efficace et plus sécuritaire. Somme toute, les travaux présentés dans cette thèse contribuent au développement de méthodologies simples, efficaces, sensibles aux enjeux environnementaux et menant à des structures plus complexes. / The heterocycle chemistry is one of the most important fields in organic chemistry. Indeed, 65% of the literature in organic chemistry is about heterocycles. They are widely present in nature, essential to life and their applications are endless. Among them, the so-called privileged structures, attract particular attention. Privileged structures, of which quinolines and indoles are a part, play a crucial role in medicinal chemistry, for the production of libraries of therapeutic targets. Therefore, the development of new synthetic methods, simple, efficient and sensitive to environmental impact remains a challenge for chemists. Many synthetic methods require the use of o-acylated anilines, but these substrates are not easily available. The copper catalyzed addition reaction of a Grignard reagent on methyl anthranilate allows to form an o-acylated aniline, never reported before, with a quantitative yield. The latter will then serve as starting material for the synthesis of several privileged heterocycles including quinolines and indoles. The Friedlander reaction has been used for several centuries but suffers from the use of extreme reaction conditions which are harmful to the environment. It has therefore been modernized to give access to a series of eight trisubstituted quinolines, without solvent, strong acid or high temperatures. Furthermore, Heumann's process consists of the synthesis of indoles substituted in position by o-acylated anilines alkylation, followed by saponification and intramolecular cyclization steps. Patented by B.A.S.F. in 1895, this process quickly became obsolete due to low yields and difficult reaction conditions. Continuous flow chemistry has resurrected this process through the development of a more efficient and safer protocol. All in all, the work presented in this thesis contributes to the development of simple, effective methodologies, sensitive to environmental issues and leading to increasingly complex structures.

Les plantes produisent une grande variété de produits naturels pour faire face aux conditions environnementales. Les enzymes de la famille CYP98 des cytochromes P450 sont des enzymes clés dans la production des composés dérivés de la voie des phénylpropanoïdes. Ces enzymes sont impliquées dans l'hydroxylation des esters phénoliques pour la biosynthèse des monolignols chez les angiospermes, mais elles sont également impliquées dans la production de divers autres composés phénoliques solubles. Nous avons caractérisé des CYP98 représentatifs des mousses, Lycopodes, fougères, Gymnospermes, Angiospermes basales, Monocotylédones et Eudicotylédones et démontré que leur préférence de substrat a changé au cours de l'évolution. Un mutant knock-out de CYP98 de mousse a révélé un phénotype sévère et que le p-coumaroyl-thréonate est substrat de l’enzyme in vivo. Une duplication des CYP98s ne peut être observée que dans le génome des Angiospermes, qui présentent généralement une isoforme potentiellement impliquée dans la biosynthèse de la lignine et autres isoformes, résultant de duplications indépendantes, dont le spectre de substrats est plus large in vitro. / Plants produce a rich variety of natural products to face environmental constraints. Enzymes of the cytochrome P450 CYP98 family are key actors in the production of phenolic bioactive compounds. They hydroxylate phenolic esters for lignin biosynthesis in angiosperms, but also produce various other bioactive phenolics. We characterized CYP98s from a moss, a lycopod, a fern, a conifer, a basal angiosperm, a monocot and from two eudicots. We found that substrate preference of the enzymes has changed during evolution of land plants with typical lignin-related activities only appearing in angiosperms, suggesting that ferns, similar to lycopods, produce lignin through an alternative route. A moss CYP98 knock-out mutant revealed coumaroyl-threonate as CYP98 substrate in vivo and showed a severe phenotype. Multiple CYP98s per species exist only in the angiosperms, where we generally found one isoform presumably involved in the biosynthesis of monolignols, and additional isoforms, resulting from independent duplications, with a broad range of functions in vitro.

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<p>The hydrogen bond is one of nature’s ubiquitous molecular interactions. Its role ranges from that of a static provider of structural integrity in proteins to that of a dynamic coordinate, along which excited state deactivation in sunscreen molecules is achieved. The work in this dissertation employs a supersonic expansion to collisionally cool peptide oligomers and a sunscreen chromophore to the zero-point vibrational level of their low lying conformational minima. These species are interrogated using high-resolution, conformer-specific ultraviolet and infrared laser spectroscopic techniques with the aim of elucidating their intrinsic conformational preferences, hydrogen bonding networks, and excited state deactivation mechanisms.</p><p>Synthetic foldamers are oligomers composed of non-natural building blocks, such as b- and g-amino acids. Incorporation of such residues into a peptide backbone results in secondary and tertiary structures that are distinct from those found in nature. Herein, the folding propensity of a series of mixed a/b and pure b-peptides is presented. In each case, both the left- and right-handed emergence of mixed-helical secondary structures, the 11/9- and the 12/10-helix, are observed. Next, the intrinsic conformational preferences of a series of increasingly complex asparagine-containing peptides are characterized. Asparagine, with its flexible carboxamide sidechain, is omnipresent within the prion forming domain of the misfolded proteins associated with several neurodegenerative diseases. Asparagine’s propensity for b-turn structures is discussed and compared with that of analogous peptide sequences found in nature.</p><p>Methyl anthranilate is a natural product that contains an identical electronic chromophore to the sunscreen agent, meradimate. The excited state deactivation mechanism of methyl anthranilate and its water complex is determined with extensive ultraviolet spectroscopic characterization, and is discussed within the broader context of its role as a sunscreen agent. Vibronic analysis coupled with computational results indicate extensive heavy-atom rearrangement leading to hydrogen atom dislocation, rather than full transfer, on the S₁ surface. This phenomenon is further characterized with infrared spectroscopy and theoretical modeling, in which the NH stretch is adiabatically separated from other internal coordinates. Extensive dilution of the dislocated NH stretch oscillator strength over many transitions and ~1,300 cm^-1 is predicted. These results may have implications for similar molecules, such as salicylic acid and its derivatives.</p>