A principal limitação do uso de MgO em refratários é a facilidade com que reage com água formando hidróxido de magnésio (Mg(OH)2) que, devido à sua menor densidade, causa tensões destrutivas nesses materiais. Para outras aplicações, no entanto, a reação de hidroxilação do MgO é necessária, como em produção de agentes antichamas, em compósitos poliméricos e na correção de pH de solos. Observações empíricas na literatura demonstraram que diferentes fontes de MgO possuem reatividades e sensibilidades à hidroxilação distintas. Este estudo analisou o impacto de variáveis externas (por exemplo, a liberação de calor que ocorre durante a reação ou o volume das amostras) que ainda não foi completamente compreendido. O impacto auto-catalítico da temperatura reacional e da exotermia da reação foi avaliado. Por meio de medidas de temperatura in situ e de grau de hidroxilação termogravimétrico, também foram estudados os impactos do volume das amostras testadas e da concentração de sólidos nas suspensões, por meio de medidas de temperatura in situ e termogravimetria. Analisou-se também as principais diferenças estruturais entre duas principais fontes de MgO (sínter de MgO e magnésia cáustica): morfologia de partículas, densidade e área superficial específica. Em seguida, os mecanismos de hidroxilação em suspensões aquosas e seus efeitos foram avaliados por meio de testes de hidroxilação seguidos de termogravimetria, difração de raios-X, medidas de condutividade iônica, densidade, área superficial específica e microscopia eletrônica, e relacionado com as características físico-químicas e morfológicas das respectivas fontes de MgO. Pôde-se constatar que diferenças significativas entre a temperatura nominal do meio reacional e no interior da amostra podem afetar a cinética de hidroxilação do material. O volume e a concentração de sólidos variáveis também podem acentuar consideravelmente os efeitos da exotermia e gerar gradientes de hidroxilação. Também se verificou que a morfologia e a quantidade do Mg(OH)2 formado mudam significativamente dependendo do precursor e em função das condições de tempo-temperatura. / The use of MgO in refractories is restrict due to the easy reaction with water forming magnesium hydroxide (Mg(OH)2). Its lower density causes compressive stresses that can crack their structure. On the other hand, for applications such as the production of flame retardant agents for polymer composites and pH correcting of contaminated soil, this reaction is necessary. Empirical observations in the literature have shown that different sources of MgO have district levels of chemical reactiveness. The present study analyzed the main structural differences between the two main sources of MgO (magnesia sinter and caustic magnesia): particle morphology, density and specific surface area. The mechanisms of hydroxylation of these raw materials in aqueous suspensions and their effects were followed by hydroxylation tests, X-ray diffraction, ionic conductivity, density, specific surface area and scanning electron microscopy. They were associated with the physical characteristics morphological, chemical of these MgO sources. The impact of external variables (e.g., heat release during the reaction or the sample volume), that was not yet completely understood, was also evaluated through temperature measurements carried out in situ and hydroxylation degree accessed by thermogravimetry. The effects of samples volume and solid concentration in aqueous suspension were also investigated. The results showed that differences between the ambient temperature and reaction inside sample temperature can affect the kinetics of hydroxylation of the material. The samples volume and solids concentration can also enhance significantly the effects of heat release and generate gradients of hydroxylation. It was also found out that the morphology and the amount of Mg(OH)2 formed can change depending on the precursor and on the time-temperature conditions.

No description available.

No / The minerals involved in the formation of metazoan skeletons principally comprise glassy silica, calcium phosphate or carbonate. Because of their ancient heritage, glass sponges (Hexactinellida) may shed light on fundamental questions such as molecular evolution, the unique chemistry and formation of the first skeletal silica-based structures, and the origin of multicellular animals. We have studied anchoring spicules from the metre-long stalk of the glass rope sponge (Hyalonema sieboldi; Porifera, Class Hexactinellida), which are remarkable for their size, durability, flexibility and optical properties. Using slow-alkali etching of biosilica, we isolated the organic fraction, which was revealed to be dominated by a hydroxylated fibrillar collagen that contains an unusual [Gly-3Hyp-4Hyp] motif. We speculate that this motif is predisposed for silica precipitation, and provides a novel template for biosilicification in nature.

N-hydroxylating monooxygenases (NMO) are members the class B flavoprotein monooxygenases. They catalyze the N-hydroxylation of lysine and ornithine and play and essential role in the biosynthesis of hydroxamate containing siderophores. Siderophores are high affinity iron-chelators composed of catechol and hydroxamate functional groups that are synthesized and secreted by several microorganisms and plants. It has been showed that many NMOs are essential for virulence in many opportunistic pathogens such as Aspergillus fumigatus and Pseudomonas aeruginosa. The focus of my research is on the N-hydroxylating enzymes: Siderophore A (SidA) from Aspergillus fumigatus and Amycolatoposis alba monooxygenase (AMO). One of my projects is focusing on identifying inhibitors of SidA that will ultimately block the siderophore biosynthesis in A. fumigatus. Out of 973 compounds screened using an activity high-throughput assays two compounds were identified. These were, wortmannin a steroid metabolite and ebselen a benzoselenazole as SidA inhibitors with IC50 values of 369 µM and 11 µM respectively. A second part of this works investigates the hydroxamate formation of the siderophore albachelin in Amycolatoposis alba with the purpose of better understanding this class of enzymes and their catalytic mechanism. The enzyme was purified and characterized in its holo (FAD-bound) and apo (unbound) forms. Pre-steady and steady state kinetics shows that the two forms have different coenzyme preference; apo-AMO prefers NADH while holo-AMO has a higher affinity to NADPH. / Master of Science in Life Sciences

Les catalyseurs chimiques sont utilisés dans différents procédés de synthèse. Cependant, la pollution qu'ils causent sur l'environnement n’est pas prise en considération. Les procédés de synthèse chimique nécessitent généralement un grand volume de solvants organiques, produisant d’énormes quantités de déchets chimiques, souvent toxiques et non dégradables. Le remplacement des catalyseurs chimiques par des biocatalyseurs (enzymes) pourrait donc bénéficier de leur nature écologique et de leur grande sélectivité envers les produits désirés. Néanmoins, la faible activité et stabilité des enzymes ainsi que leurs coûts élevés sont des obstacles majeurs au développement des systèmes enzymatiques. Par conséquent, des études axées sur le développement de systèmes biocatalytiques plus actifs, stables et rentables, pouvant ouvrir les portes vers un environnement plus vert, sont très souhaitables. Parmi les enzymes qui catalysent des réactions d’importance dans de nombreux procédés de synthèse, le cytochrome P450 BM3 issu de Bacillus megaterium fait l'objet de cette thèse. L'enzyme est capable d’hydroxyler les liaisons C–H des acides gras (C₁₂-C₂) à température ambiante et pH physiologique. Pour cette réaction, BM3 n'a besoin que d’oxygène et de deux électrons habituellement obtenus de son cofacteur naturel, le NADPH. Cependant, pour engager cette enzyme dans les réactions d'hydroxylation, quelques obstacles importants doivent être surmontés : (i) le cofacteur coûteux (NADPH), devrait être remplacé par une source d'électrons moins chère ou régénérée, (ii) la stabilité enzymatique devrait être améliorée et (iii) l'enzyme devrait être facilement récupérable du milieu de réaction pour être réutilisée. Dans ce contexte, cette étude propose pour la première fois l'immobilisation d'un BM3 sur des nanoparticules magnétiques (NMP) d’oxyde de fer. Ce système enzymatique bénéficie (i) de la préférence de l'enzyme pour les cofacteurs NADH et BNAH (moins chers que le NADPH), (ii) de la réutilisation facile du biocatalyseur et (iii) d’une stabilité significative de l’enzyme lors du stockage. Les NMP synthétisées ont été fonctionnalisées pour permettre l’immobilisation de l'enzyme par adsorption ou liaison covalente. Par conséquent, les BM3-NMP adsorbées / réticulées ou liées de façon covalente ont été obtenues en immobilisant P450 BM3 (R966D / W1046S) sur Ni²⁺-PMIDA-NMP ou sur des NMP activés par glutaraldéhyde, respectivement. / L'activité de l’enzyme immobilisée a été comparée avec celle de l’enzyme libre dans la réaction d'hydroxylation du 10-pNCA comme substrat modèle. L'acide myristique a également été utilisé comme substrat modèle pour confirmer la capacité d’hydroxylation sélective de l’enzyme sur les atomes de carbone ω-1, -2 ou -3. Pour les mêmes conditions opératoires, le BM3 adsorbé / réticulé a montré plus de 85% de l'activité de l’enzyme libre, alors que pour les BM3-NMP liées de manière covalente cela représente 60%. La séparation facile des NMP du milieu réactionnel à l’aide d’un aimant a permis de réutiliser le système enzymatique cinq fois consécutives. Après 5 cycles de réaction, l'enzyme réticulée a conservé 100% de son activité initiale. Compte tenu que le recyclage de l’enzyme libre n’est pas faisable, ce résultat est d’une importance considérable dans les applications pratiques. De plus, la stabilité de l’enzyme pendant un mois de stockage à 4 ºC a été évaluée pour chaque système de BM3. Les résultats ont montré que l’enzyme libre n’était plus active après seulement une semaine de stockage dans ces conditions. L'enzyme réticulée n'a montré qu'une activité relative de 41% après un mois de stockage, mais pour le BM3 fixée de façon covalente, la valeur correspondante a été de 80%. La cinétique de l'hydroxylation du 10-pNCA en présence de l’enzyme libre ou immobilisée a été également étudiée. Sur la base des données expérimentales, un modèle de Hill (coefficient de Hill égal à 2) a été obtenu pour l'enzyme libre. Il a été démontré que les mêmes paramètres cinétiques sont capables de prédire le comportement du système BM3-adsorbé et BM3-réticulé dans la réaction d’hydroxylation, étant donné sa similarité avec celui de l’enzyme libre. En conclusion, les résultats de cette thèse ont montré qu'un système enzymatique actif, stable et rentable peut être obtenu en immobilisant le BM3 sur des NMP fonctionnalisées. Il bénéficie autant des avantages de l'enzyme que du support. Ainsi, l'immobilisation sur des NMP d’une enzyme spécialement conçue pour remplacer le couteux NADPH par des cofacteurs moins chers mais efficaces (NADH et BNAH) offre en même temps une amélioration significative de sa stabilité et facilite son recyclage. / MNPs have been synthesized and surface functionalized to attach the enzyme via two different methods, adsorption and covalent binding. Moreover, glutaraldehyde was used to treat the adsorbed enzyme molecules on MNPs (crosslinking-adsorption). Therefore, adsorbed, crosslinked-adsorbed, or covalently bound BM3-MNPs were obtained by immobilizing P450 BM3 on synthesized Ni²⁺-functionalized MNPs or glutaraldehyde pre-activated MNPs, respectively. The immobilized enzyme activity was compared to its free counterpart in hydroxylation reaction of 10-pNCA (10-(4-Nitrophenoxy) decanoic acid) as a substrate model. Myristic acid was also used as a substrate model to confirm the enzyme selective hydroxylation at ω-1, -2, or -3 carbon positions. The effect of cofactor (NADH and its analogue, BNAH) on the enzyme activity was also investigated. The adsorbed/crosslinked-adsorbed BM3 showed more than 85% of the free enzyme activity while the covalently bound BM3-MNPs presented 60% of the free enzyme activity under the same reaction conditions. An important feature of BM3-MNPs system is the possibility of recycling the biocatalyst. Facile separation of the magnetic nanoparticles from the reaction medium by applying a magnet provided the opportunity of reusing the enzymatic system for five times. After 5 cycles of reaction, the crosslinked-adsorbed enzyme retained 100% of its initial activity. Although the covalently bound enzyme showed, only half of the crosslinked-adsorbed enzyme activity, its storage stability was more significant. Taking into account that the enzyme reuse is an essential concern in many large-scale applications and the free BM3 cannot be recovered and reused, this result is noteworthy. Storage stability tests revealed that the free enzyme became inactive after one-week while the crosslinked-adsorbed enzyme and the covalently attached BM3 on MNPs showed 41% and 80% relative activity after one month, respectively. Finally, the steady-state kinetics of 10-pNCA hydroxylation by free and immobilized BM3 was investigated. Based on the experimental data, a non-Michaelis-Menten, Hill model (Hill coefficient of 2) was obtained for the free enzyme which could also predict the adsorbed and crosslinked-adsorbed BM3-MNPs system performance. This sigmoidal behavior was found to be independent of enzyme concentration and type of cofactor. However, since the enzyme activity was only 60% of the free enzyme for covalently bound BM3, further studies are necessary for a better understanding of this system. In summary, the results of this thesis show that an active, stable, and cost-effective BM3-MNPs system can be obtained by immobilizing an engineered BM3 on functionalized MNPs. Such systems benefit from the advantages of both enzyme and support. An engineered enzyme can fulfill the desired targets including the replacement of costly NADPH by less-expensive, yet effective cofactors namely NADH and BNAH. Furthermore, immobilization of this enzyme on MNPs improves its stability and facilitates the recycling process. / Chemical catalysts are used in different synthetic processes from lab to industrial scales. High reaction yields usually achieved by this type of processes favor their application in many industries without considering the pollution they cause to the environment. Chemical synthesis processes usually require a high volume of organic solvents and produce tons of chemical wastes which are often toxic and not degradable. Replacing conventional catalysts by biocatalysts (enzymes) can benefit from their environmentally friendly nature and high selectivity toward the desired products. Although the advantages of biocatalysts over chemical catalysts have been proven, the application of enzymes in an industrial level is still not considerable. The enzyme low activity, stability, and high cost are the main concerns in developing large-scale enzymatic systems. Therefore, in the context of a greener environment, studies focusing on the development of more active, stable, and cost-effective enzymatic systems are in great demand. Among several enzymes that can catalyze essential synthesis reactions, cytochrome P450 BM3 from Bacillus megaterium is the subject of this thesis. This enzyme hydroxylates the saturated and unsaturated C–H bonds of medium to long chain fatty acids at room temperature and physiological pH. For this reaction, BM3 only needs molecular oxygen and two electrons usually obtained from its natural cofactor, NADPH. However, to engage this enzyme in hydroxylation reactions, some important obstacles should be overcome: (i) the costly cofactor (NADPH) should be replaced by a cheaper source of electrons or regenerated, (ii) the enzyme stability should be improved, and (iii) the enzyme should be easily recovered from the reaction medium to be reused. In this context, this study proposes for the first time the immobilization of an optimized BM3 mutant on functionalized iron oxide magnetic nanoparticles (MNPs). This enzymatic system benefits from (i) the enzyme preference towards cofactors like the reasonably priced NADH and the very cheap BNAH, (ii) facile recovery and reuse of the biocatalyst (enzyme-MNPs), and (iii) the enzyme significant storage stability.

This thesis explores roles of 2-oxoglutarate-dependent (2OG) oxygenases as interfaces that modulate steps in the flow of genetic information in cells in response to oxygen availability. Chapter 1 introduces mechanistic, biochemical and physiological aspects of major subfamilies of 2OG oxygenases, and their established regulatory roles in cells. In addition, structural and functional aspects of the ribosome and the translation process are discussed, with a focus on post-translational ribosome modifications. Chapter 2 investigates histone demethylases, which mediate chromatin-dependent regulation of gene expression and provides proof-of-concept for the rational, structure-guided design of small-molecules for selective inhibition of 2OG oxygenases with roles in cancer and inflammatory disease. Chapter 3 suggests regulatory roles for ten-eleven-translocation (TET)- catalysed DNA hydroxylation; calorimetric and thermal analyses reveal a duplex-stabilizing effect of the epigenetic 5-methylcytosine mark that is reversed upon conversion to 5- hydroxymethylcytosine (also termed the ‘sixth’ DNA base), raising the possibility that 2OG oxygenase catalysis might affect transcription via biophysical effects. Chapter 4 investigates fluoride release assays as a technology to enable medicinal chemistry studies on 2OG oxygenases with roles in fat mass regulation and obesity, cancer and inflammation; studies on the ALKBH5 enzyme show that it is a hypoxically upregulated 2OG oxygenase with a substrate preference distinct from previously characterized ALKBH enzymes. Chapter 5 identifies OGFOD1 as a 2OG-dependent ribosomal protein hydroxylase. OGFOD1 catalysis is conserved from yeast to humans. OGFOD1 catalyses formation of trans-3- hydroxy-L-proline in a highly conserved loop of ribosomal protein S23 proximal to the ribosomal decoding centre, possibly to modulate the interactions of eukaryotic ribosomes with tRNA, mRNA and translation factors in an oxygen-dependent manner. OGFOD1 is the functionally most well-conserved protein-modifying 2OG oxygenase; likewise, ribosomal protein S23 hydroxylation is the most well-conserved post-translational ribosome modification in eukaryotes. Some cell lines require OGFOD1 for proliferation, and scaffolds for OGFOD1- selective inhibitors are developed for use as potential antiproliferative agents and probes for cellular function. Chapter 6 shows the development of assays to investigate whether OGFOD1 catalysis affects ribosome assembly and function, including processivity, accuracy of initiation, elongation and termination, in yeast and mammalian cell lines. Chapter 7 concludes that ribosome hydroxylation might present an additional layer of regulatory complexity by which 2OG oxygenases could enable cells to respond to fluctuating oxygen levels.

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Over the recent years, increasing scientific attention has been paid to pharmaceuticals, other drugs and their metabolites. These substances are of particular interest because of their physiological, toxicological and ecotoxicological effects in the human body and respectively in the environment. Cytochrome P450 enzymes (P450s) play a key role in the conversion and detoxification of bioactive compounds including many pharmaceuticals and drugs. Most of these enzymes belong to the monooxygenases; they are intracellular and rather unstable biocatalysts that are difficult to purify and require expensive, complex cofactors, which alltogether hampers their use in isolated form. The investigations carried out here with fungal peroxygenases have shown that this enzyme sub-subclass (EC 1.11.2.x) has a promising potential for oxyfunctionalizations and can catalyze a variety of reactions typical for P450s. Peroxygenases are extracellular, i.e. secreted fungal enzymes with high stability, which merely need peroxide for function. Results obtained with the unspecific/aromatic peroxygenases (APOs) of Agrocybe aegerita, Coprinellus radians and Marasmius rotula have demonstrated that APOs catalyze numerous H2O2-dependent monooxygenations of pharmaceuticals and psychoactive drugs. Among them are i) the monooxygenation of aromatic compounds, ii) the benzylic hydroxylation of toluene derivatives, iii) the O-dealkylation of different ether structures including the scission of benzodioxoles (O-demethylenation) and esters as well as iv) the N-dealkylation of secondary and tertiary amines. The peroxygenases studied considerably differ in their substrate spectrum and the preferred positions of oxidation. This finding opens the possibility to develop in the future an “enzymatic toolbox“ on the basis of fungal peroxygenases for the oxyfunctionalization of pharmaceutically relevant compounds. Mechanistic studies showed that (1) the monooxygenations always proceed via incorporation of one oxygen atom from the peroxide, (2) the demethylation of phenacetind1 established a deuterium isotope effect similar to P450s, (3) the catalytic efficiencies for the studied oxidations are in the same range as those of P450s (though the kcat- and Km values are noticeably higher), (4) the kinetic studies with nitro-1,3-benzodioxole gave parallel double reciprocal plots suggestive of a “ping pong” mechanism, (5) the substrate spectrum and the activity pattern of APOs follows in a wide range those of the human key P450s as well as that (6) the difference spectra obtained in bindings studies are of the phenol type of P450s. Furthermore, APOs were found to be stable and active in long term experiments over two weeks and they oxidized pharmaceuticals at low, environmentally relevant concentration (ppb range). All the above properties strongly indicate that APOs respresent an interesting alternative for the enzymatic conversion of pharmaceuticals as well as for the preparation of human drug metabolites, for example, in medicinal and pharmacological research or the bioremediation sector (removal of pharmaceuticals from environmental media). / In den letzten Jahren sind Pharmazeutika und deren Metabolite mehr und mehr in den Fokus der Wissenschaft gerückt. Diese Substanzen sind aufgrund ihrer physiologischen und toxikologischen sowie ökotoxikologischen Wirkungen im menschlichen Körper bzw. in der Umwelt von besonderem Interesse. Cytochrom-P450-Enzyme (P450s) spielen eine Schlüsselrolle bei der Umsetzung und Detoxifizierung bioaktiver Substanzen, darunter vieler Pharmazeutika und Drogen. Es handelt sich bei diesen Enzymen in erster Linie um Monooxygenasen, die intrazellulär lokalisiert und relativ instabil sind; sie benötigen komplexe, teure Kofaktoren und sind nur unter hohem Aufwand zu reinigen, was ihre Anwendung in isolierter Form insgesamt erschwert. Die hier durchgeführten Untersuchungen zu pilzlichen Peroxygenasen haben gezeigt, dass diese Enzymsubklasse (EC 1.11.2.x) ein hohes Oxyfunktionalisierungspotenzial besitzt und eine Vielzahl P450-typischer Reaktionen zu katalysieren vermag. Peroxygenasen sind extrazelluläre, d.h. sekretierte Pilzenzyme, die eine hohe Stabilität aufweisen und lediglich ein Peroxid als Kosubstrat benötigen. Die unter Verwendung der unspezifischen/aromatischen Peroxygenasen (APOs) von Agrocybe aegerita, Coprinellus radians und Marasmius rotula gewonnenen Ergebnisse belegen, dass APOs verschiedene H2O2-abhängige Monooxygenierungen von Pharmazeutika und psychoaktiven Substanzen realisieren. Dazu gehören i) die Monooxygenierung von Aromaten, ii) die benzylische Hydroxylierung von Toluolderivaten, iii) die O-Dealkylierung verschiedener Etherstrukturen einschließlich der Spaltung von Benzodioxolen (O-Demethylenierung) und Estern sowie iv) die N-Dealkylierung von sekundären und tertiären Aminen. Die untersuchten Peroxygenasen wiesen teilweise deutliche Unterschiede im Substratspektrum und den präferierten Oxidationspositionen auf. Dieser Befund eröffnet die Möglichkeit, zukünftig einen „enzymatischen Werkzeugkasten“ auf Basis pilzlicher Peroxygenasen für die Oxyfunktionalisierung von pharmazeutisch relevanten Wirkstoffen zu entwickeln. Mechanistische Experimente zeigten, dass (1) die Monooxygenierungen stets unter Einbau eines aus dem Peroxid stammenden Sauerstoffatoms erfolgen, (2) die Deethylierung von Phenacetin-d1 einen Deuteriumisotopeneffekt ähnlich dem der P450s aufweist, (3) die katalytischen Effizienzen für die untersuchten Oxidationen im gleichen Bereich wie die der P450s liegen (wobei die kcat- und Km-Werte deutlich höher ausfallen), (4) die kinetischen Untersuchungen zur Oxidation von Nitro-1,3-Benzodioxol parallele Verläufe der ermittelten Ausgleichsgeraden in der doppelt reziproken Darstellung ergaben, was für einen “Ping-Pong-Mechanismus“ spricht, (5) sich das Substratspektrum und die Aktivitätsmuster der APOs in einem weiten Bereich mit denen der wichtigsten menschlichen P450s decken sowie dass (6) die in Bindungsstudien gewonnenen Differenzspektren denen des Phenoltyps der P450s entsprechen. Desweiteren erwiesen sich APOs in Langzeitexperimenten über zwei Wochen als stabil und aktiv und sie waren in der Lage, Pharmazeutika in umweltrelevanten Konzentrationen (ppb-Bereich) zu oxidieren. All die genannten Eigenschaften legen nahe, dass APOs eine interessante Alternative zur enzymatischen Umsetzung von Pharmazeutika sowie zur Herstellung von humanen Pharmazeutika-Metaboliten darstellen, die z.B. Einsatz in der medizinischpharmakologischen Forschung oder im Umweltbereich (Entfernung von Pharmazeutika aus Umweltmedien) finden könnten.

The objective of this presented study was to synthesize optically active compounds considered to be key intermediates in the synthesis of Oseltamivir (Tamiflu) by performing chemical and biotechnological methods. Thereof, the carboethoxy cyclohexenone skeleton first was synthesized utilizing easily available substances. The synthesis of alpha-hydroxy ketones in enantiomerically pure form offers a great importance in the synthesis of biologically active compounds. Toward this fact, the enantioselective synthesis of alpha-hydroxy carboethoxy cyclohexenone scaffold has been accomplished by following the routes which were manganese(III) acetate-mediated chemical oxidation followed by enzyme-mediated hydrolysis and additionally microbial direct biooxidation by whole cells of fungi expressly A. oryzae and A. flavus. A very satisfying results have been obtained by both of the methods.

In the first part of this thesis is related to the regioselectivity in ene reaction of singlet oxygen with cyclic alkenes. The photooxygenation of 1-methyl-, 2,3-dimethyl-, 1,4-dimethylcyclohexa-1,4-dienes, 1,2,3,4,5,8-hexahydronaphthalene (16) and 2,3,4,7-tetrahydro-1H-indene (17) which are readily available through Birch reduction, yielded the ene products. The formed endocyclic dienes were trapped by the addition of singlet oxygen to give corresponding bicyclic endoperoxy-hydroperoxides. In the case of 1-methylcyclohexa-1,4-diene (13) and 1,4-dimethyl-cyclohexa-1,4-diene (15), cis-effect determined the product distribution. Photooxygenation of 2,3-dimethylcyclohexa-1,4-dienes (14) gave mainly exocyclic olefin, which was attributed to the lowered rotational barrier of the methyl group and increased reactivity of the methyl groups. Photooxygeneation of 1,2,3,4,5,8-hexahydronaphthalene (16) and 2,3,4,7-tetrahydro-1H-indene (17) shows importance of the geometry of the allylic hydrogen in the ground state. In the second part of this thesis is related to the stereoselective synthesis of carbaheptopyranose derivatives. Two new carbaheptopyranoses, 5a-carba-6-deoxy-&alpha / -DL-galacto-heptopyranose (184) and 5a-carba-6-deoxy-&alpha / -DL-gulo-heptopyranose (185) have been prepared starting from cyclohexa-1,4-diene. The addition of dichloroketene to cyclohexa-1,4-diene followed by subsequent reductive elimination and Baeyer-Villiger oxidation formed the bicyclic lactone 188. Reduction of the lactone moiety followed by acetylation gave the diacetate 182b with cis-configuration. Introduction of additional acetate functionality into the molecule was achieved by singlet oxygen ene-reaction. The formed hydroperoxide 189 was reduced and then acetylated. The double bond in triacetate was further functionalized either by direct cis-hydroxylation using OsO4 or epoxidation followed by ring-opening reaction to give the hepto-pyranose derivatives 184 and 185.