2,5-diketopiperazines peculiar heterocyclic system found in several natural products constitutes a rich source of new biologically active compounds. The wide spectrum of their biological properties points to various therapeutic possibilities. Introduction of structural rigidity, resulting in diketopiperazine derivatives containing a pyridine ring that can form an intramolecular hydrogen bond,and shows an interesting activity. In our research, we hope to probe further the importance of structural rigidity with regards to biological activity. We hope to replace the hydrogen bonding between the pyridine ring and amide nitrogen with a covalent link. This will further restrict the rotation and isomerization of the Z-double bond.

Perfumery compounds isoeugenol and isosafrole can be oxidized to their aldehydes, vanillin and heliotropin respectively. The aldehydes obtained are very useful and commercially valuable products. Apart from their importance as perfumery compounds, they form important intermediates in the Pharmaceuticals and pesticide industries. Liquid phase oxidation of isosafrole using different oxidizing agents were tried. Sodium dichromate as oxidizing agent in aqueous acetic acid was found to be most suitable because of its higher yields and mild reaction conditions. This reaction was taken up for detailed study. Since the kinetic study of dichromate oxidation in aqueous acetic acid medium of isosafrole has not been mentioned in the literature, various parameters like isosafrole, dichromate and acetic acid concentrations were studied. The experiments were conducted at different temperatures to estimate the activation energy of the reaction. The effect of added salts like manganese sulfate, manganese acetate and cobaltous acetate has also been studied. For all the experiments the change in isosafrole concentration was observed. The rate of reaction increases with increase in isosafrole concentration. The order of the reaction with respect to isosafrole concentration is found to be one. The rate of reaction increases with increase in initial sodium dichromate concentration. The reaction is found to be half order in dichromate ion concentration. The rate of reaction increases with increase in acetic acid concentration with an order two. The atmospheric oxygen does not affect the reaction rate suggests that the reaction may not be free radical reaction. The rate of reaction increases with increase in temperature. The activation energy was found to be equal to 14.59 kcal/mol.

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The di-O-acetyl derivative of 4,6-O-benzylidene-1-deoxy-1-nitromethyl-β-D-glucopyranose was reduced by a mixture of elemental iron and nickel in aqueous tetrahydrofuran under CO2, with concurrent O → N acetyl migration to 1-acetamido-4-O-acetyl-2,6-anhydro-5,7-O-benzylidene-1-deoxy-D-glycero-D-guloheptitol. Its 2-O-mesyl derivative was converted by base into the D-manno-2,3-epoxide. The epoxide ring was opened by NH3 to give the 3-amino-β-D-altropyranose derivative, which was subsequently N-benzoylated to 1-acetamido-2,6-anhydro-4-benzoylamino-5,7-O-benzylidene-1,4-dideoxy-D-glycero-D-glucoheptitol. Attempts to prepare 1-acetamido-2,6-anhydro-4-benzoylamino-5,7-O-benzylidene-1,4-dideoxy-3-methanesulfonyl-Dglycero-D-glucoheptitol gave spontaneously the D-allo-oxazoline derivative. However, a 3-O-mesyl derivative could be obtained by mesylation of 1,4-di-acetamido-2,6-anhydro-5,7-0-benzylidene-I,4-dideoxy-D-glycero-D-glucoheptitol. 2,6-Anhydro-5,7-O-benzylidene-1-deoxy-1-nitro-D-glycero-D-guloheptitol was reduced and N-acetylated to the acetamidomethyl derivative. 3,4-Di-O-mesylation of 1-acetamido-2,6-anhydro-5,7-O-benzylidene-1-deoxy-D-glycero-D-guloheptitol gave 1-acetamido-2,6-anhydro-5,7-O-benzylidene-1-deoxy-3,4-dimethanesulfonyl-D-glycero-D-guloheptitol, which reacted with methoxide to give the D-manno-2,3-epoxide, and mostly 2,6-anhydro-5,7-O-benzylidene-1-deoxy-D-glycero-D-gluco-heptitol [1,2,3, : 4',5',6']- 2'-methyl-2'-oxazine, presumably via a D-allo-2,3-epoxide. The condensation of 4,6-O-benzylidene-D-glucopyranose with nitroethane gave 2,6-anhydro-1,3-O-benzylidene-7,8-dideoxy-7-nitro-D-threo-L-gulooctitol and its diastereomer, which was obtained by an acetylation-deacetylation procedure. 2,6-Anhydro-1,3-O-benzylidene-7,8-dideoxy-7-nitro-L-erythro-L-gulooctitol was reduced by a mixture of elemental Fe°/Ni° in aqueous FHF under CO2 to 7-amino-2,6-anhydro-1,3-O-benzylidene-7,8-dideoxy-L-erythro-L-gulooctitol with retention of the 4,6-O-benzylidene blocking group. Acetylation of 2,6-anhydro-1,3-O-benzylidene-7,8-dideoxy-7-nitro-D-threo-L-gulooctitol produced an open chain compound. Cyclic product was not isolated. The oxime derivative, 4,5-di-O-acetyl-3,7-anhydro-6,8-O-benzylidene-1,2-dideoxy-2-oxime-D-glycero-D-guloheptitol, was separated as a byproduct from the acetylation. The condensation of nitropropane with 4,6-O-benzylidene-B-D-glucopyranose, followed by acetylation of the reaction solution, gave 4,5-di-O-acetyl-2,6-anhydro-1,3-O-benzylidene-7-nitro-7,8,9-trideoxy-D-threo-L-gulononitol and its diastereomer. Deacetylation of 4,5-di-O-acetyl-2,6-anhydro-1,3-O-benzylidene-7-nitro-7,8,9-trideoxy-D-threo-L-gulononitol gave 2,6-anhydro-1,3-O-benzylidene-7-nitro-7,8,9-trideoxy-D-threo-L-gulononitol, which could be reduced to the free amino compound by a mixture of elemental Fe°/Ni° in aqueous THF under CO2.

Cheung, Wing Ki. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 100-112). / Abstracts in English and Chinese. / Acknowledgments / Abbreviations / Abstract 一 English --- p.i / - Chinese --- p.iii / Chapter Chapter 1 --- General Introduction / Chapter 1.1. --- Colon Cancer / Chapter 1.1.1. --- Colon cancer statistic in Hong Kong --- p.1 / Chapter 1.1.2. --- Development of Colon cancer --- p.1 / Chapter 1.1.3. --- Treatment --- p.2 / Chapter 1.2. --- Chemistry of ascorbates / Chapter 1.2.1. --- Sodium-L-ascorbate --- p.3 / Chapter 1.2.2. --- "Sodium 5,6-benazylidene-L-ascorbate" --- p.4 / Chapter 1.3. --- "Reactive oxygen species and reactive nitrogen species, and their biological consequences" --- p.5 / Chapter 1.4. --- Cell cycle --- p.7 / Chapter 1.5. --- Autophagy --- p.8 / Chapter 1.6. --- Human colon cancer HT29 cells for anti-tumor study --- p.9 / Chapter 1.7 --- Aim of study --- p.10 / Chapter Chapter 2 --- Comparative studies of cytotoxicity of SAA and SBA in short term treatment / Chapter 2.1. --- Introduction --- p.11 / Chapter 2.2. --- Materials and Methods --- p.14 / Chapter 2.3. --- Results --- p.17 / Chapter 2.4. --- Discussion --- p.26 / Chapter Chapter 3 --- Comparative studies of SAA and SBA in oxidative stress induction and their corresponding ROS inhibitors / Chapter 3.1. --- Introduction --- p.28 / Chapter 3.2. --- Materials and Methods --- p.31 / Chapter 3.3. --- Results --- p.35 / Chapter 3.4. --- Discussion --- p.42 / Chapter Chapter 4 --- "Effects of SAA and SBA treatments on cell cycle regulatory proteins and the induction of transient cell cycle arrests in Gl, S and G2 phases Cell Cycle" / Chapter 4.1. --- Introduction --- p.45 / Chapter 4.2. --- Materials and Methods --- p.49 / Chapter 4.3. --- Results --- p.53 / Chapter 4.4. --- Discussion --- p.69 / Chapter Chapter 5 --- Autophagy induction during SBA treatment and autophagy inhibition during SAA treatment / Chapter 5.1. --- Introduction --- p.72 / Chapter 5.2. --- Materials and Methods --- p.74 / Chapter 5.3. --- Results --- p.77 / Chapter 5.4. --- Discussion --- p.91 / Chapter Chapter 6 --- General Discussion --- p.93 / References --- p.100

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Les symbioses bactérie-légumineuse (nodulation) et champignon-plante (mycorhization) présentent un intérêt agrobiologique et écologique majeur ; elles permettent aux plantes de croître naturellement sur un sol aride et peu fertile. Il a été démontré très récemment que les signaux impliqués dans la mise en place de la symbiose endomycorhizienne à arbuscule (facteurs "Myc") sont très proches de ceux de la nodulation. Il s'agit de molécules appartenant à la famille des lipo-chitooligosaccharides. Afin de réaliser la synthèse de ces molécules, deux nouvelles méthodologies ont été développées. L'ouverture oxydante d'acétals de 4,6-O-benzylidène de plusieurs glycopyranosides (en série gluco, galacto et manno) par le diméthyldioxirane (DMDO) a été étudiée. Le contrôle de la régiosélectivité a été effectué grâce au groupement protecteur introduit sur la fonction alcool de la position 3. La formation directe de β-glycosides de la N-acétyl-D-glucosamine par catalyse au triflate de fer (III) a été étudiée. La réaction a été menée sous irradiation micro-ondes ou en flux continu (système minifluidique Vapourtec®). Une nouvelle stratégie pour la synthèse du facteur [Myc-IV (C16:0, S)] a ensuite été établie. Nous avons utilisé un réactif peu toxique et non odorant pour introduire le motif thio nécessaire à la formation de deux liaisons glycosidiques. Le disaccharide précurseur de l'unité réductrice a été obtenu grâce à la première méthodologie développée au cours de cette thèse. / Arbuscular mycorrhiza (AM) is a root endosymbiosis between plants and fungi. It has an agrobiological interest and a crucial ecological importance because it allows plants to grow on aride and infertile soil. Recently, the structure of the symbiotic signal "Myc factor" was identified as a mixture of lipochitooligosaccharides (LCOs). In order to propose a new synthesis of LCOs, we developed two green methodologies in glycochemistry. We performed the oxidative cleavage of 4,6-O-benzylidene acetals of various glycopyranosides (gluco, manno and galacto series) with dimethyldioxirane (DMDO) and its regioselective control with a suitable protecting group at position 3. We investigated the formation of β-glycoside of N-acetyl-D-glucosamine using catalytic iron (III) triflate. The reaction can be performed using microwave irradiation or, for scale-up synthesis, flow chemistry using Vapourtec® minifluidic system. We establish a new strategy for the total synthesis of the most abundant Myc factor [Myc-IV (C16:0, S)]. We used odorless and few toxic MbpSH reagent to introduce the activated thio residue involved in two glycosylation reactions. The disaccharide acceptor precursor of the reducing end was obtained after oxidative cleavage of the 4,6-O-benzylidene moiety by DMDO.