Doctor of Philosophy / Department of Chemistry / Duy H. Hua / Three research projects are described in this dissertation, and they are: (i) discovery of piperidine derivatives as T-type calcium channel inhibitors for the treatment of epilepsy and neuropathic pain and as protein disulfide isomerase inhibitors for the treatment of influenza viral infection; (ii) discovery of peptide-based calcitonin gene-related peptide receptor antagonists for the treatment of inflammatory pain; and (iii) synthesis of substituted 6-(dimethylamino)-2-phenylisoindolin-1-ones for the inhibition of luciferase. T-type calcium channels are important regulators of nervous system, and upregulated T-type calcium channel activities have been found to link to various types of neurological disorders, such as epilepsy and neuropathic pain. To discover novel T-type calcium channel blockers, a series of 1,4-disubstituted piperidine derivatives were designed and synthesized. Among them, compound 1-4 was found to be a good T-type calcium channel inhibitor with an IC₅₀ of 1 nM for Ca[subscript v]3.2 inhibition. It also showed 86% suppression of seizure induced death in mice and good in vivo analgesic effects on both thermal and mechanical pain thresholds in Spared Nerve Injury rat models. Therefore 1-4 can potentially be used as a T-type calcium channel blocker in the treatment of epilepsy and neuropathic pain. Influenza is a respiratory viral infection. Since viruses rely on host cell proteins for their entry, survival and replication, development of drugs targeting host cell proteins has identified as an effective strategy in controlling viral infections. We synthesized a series of 1,4-disubstituted piperidine derivatives for the inhibition of protein disulfide isomerase enzyme and influenza. Among them, 1-29 was found to possess strong anti-influenza activity (EC₅₀ = 2.5 µM). This suggests the potential use of piperidine scaffold in designing anti-influenza drugs in future. Calcitonin gene-related peptide (CGRP) receptor antagonism has been identified as a successful approach for the treatment of inflammatory pain. Therefore, a novel class of peptide antagonists of CGRP receptor was synthesized and screened for their binding affinities to the CGRP receptor and their analgesic effects on inflammatory-induced pain in rats. Among them, peptide 2-3 showed a higher binding affinity towards the CGRP receptor than previously reported peptide antagonists and exhibited analgesic effects up to 2 h in both Aδ and c-fiber pain tests. Therefore 2-3 indicates its potential use as a CGRP receptor antagonist in the treatment of inflammatory pain. Firefly luciferase is commonly used as a reporter in cells expressing a luciferase gene or its enzymatic activity under the control of a promoter of interest to assess its transcriptional activity. It has been found that some molecules such as molecules with carboxylic acid moiety can directly inhibit luciferase activity in cells. However, it is suggested that carboxylic acid moiety of the compounds may also be associated with side reactions in cells. Therefore, to study whether carboxylic acid moiety causes side effects, we designed two probe molecules, 3-1 and 3-2. Synthesis of probe molecule 3-2 is discussed. Synthesis of probe molecule 3-1 and further investigation of its luciferase inhibition will therefore be useful to understand the toxicity of carboxylic acid containing drugs in future.

No / Forumla chem. . A variety of 5-chloro-2(H)-1,4-oxazin-2-ones bearing a range of substituents at their 3- and 6-positions undergo Diels-Alder cycloaddition as a 2-azadiene component with electron-rich, electron-deficient, and electron-neutral dienophiles. These reactions proceed with moderate regio- and stereoselectivity to afford relatively stable and readily isolable bridged bicyclic lactone cycloadducts. Chemical manipulation of these cycloadducts affords highly substituted and functionally rich piperidines. The regio- and stereochemical preferences of the cycloadditions of 5-chloro-2(H)-1,4-oxazin-2-ones are investigated computationally using density functional theory (B3LYP/6-31G*).

The aim of the work described in this thesis was to explore the synthesis of glycosidase inhibitors and to evaluate their potential as anti-cancer agents. Glycosidases catalyze the fission of glycosidic bonds and are involved in vital biological functions. With regard to their potential for anti-cancer therapy, two glycosidases were identified: α-N-acetyl-galactosaminidase and β-N-acetyl-hexosaminidase. The former has been implicated in causing immunosuppression in advanced cancer patients by negating the effect of the macrophage activating factor (MAF), while the latter is secreted by invading cancer cells and hence associated with metastasis formation. The synthetic focus was on generating piperidine and azetidine iminosugars, carbohydrate mimetics with their endocylic oxygen replaced by nitrogen. Their structural similarity to carbohydrates make iminosugars excellent inhibitors of glycosidases. Following synthesis of a pipecolic amide, its previously reported potent β-N-acetyl-hexosaminidase inhibition was confirmed. This data, along with inhibition profiles of several pyrrolidines, allowed the generation of a molecular model for predicting activity of β-N-acetyl-hexosaminidase inhibitors. The model was used to select azetidines in the D/L-ribo and D-lyxo configuration as suitable candidates to be explored in novel chemical space, leading to the first synthesis of a fully unprotected 3-hydroxy-2-carboxy-azetidine. The potent α-N-acetyl-galactosamindase inhibitor 2-acetamido-1,2-dideoxy-D-galacto-nojirimycin (DGJNAc) was successfully derivatised via N-alkylation. Important structural discoveries with regard to glycosylation of vitamin D₃-binding protein, the precursor of MAF, were made using MALDI mass-spectrometry. By comparing the enzymatic and cellular inhibition of N-alkylated derivatives of DGJNAc and a pyrrolidine the following generalization on iminosugar biodistribution was found: N-butylation promotes uptake into the cell/organelles, while hydrophilic side-chains restrict cellular access. An in vitro assay evaluating cancer cell invasion was devised and β-N-acetyl-hexoamindase inhibitors were shown to retard cell migration, including with the highly metastatic breast cancer cell line MDA-MB-231. Additive effects where found when the iminosugar was combined with a protease inhibitor, suggesting potential for future combination therapy.

This thesis is an investigation of the natural products deriving from marine algae and cyanobacteria and has resulted in the discovery of eleven new secondary metabolites. The structure elucidations of these new molecules were performed using a variety of spectroscopic techniques. Four new macrolides were isolated and characterized from the Madagascar marine cyanobacterium Geitlerinema sp. These ankaraholides are structurally similar to the potently cytotoxic swinholides and were found to have cytotoxicities ranging from 178 nM to 354 nM against human lung cancer (NCI-H460) and mouse neuro-2a cell lines. Since swinholide-type compounds were previously localized to the heterotrophic bacteria of sponges, these findings raise intriguing questions about their true metabolic source. Geitlerinema sp. was found to be particularly rich in chemistry, and also produced the new linear lipopeptide mitsoamide with unusual structural features including an aminal moiety, a homolysine residue and a polyketide unit (3,7- dimethoxy-5-methyl- nonanedioic acid) (DMNA). A collection of the red marine alga Portieria hornemannii from the south of Madagascar (Tolagniaro, Fort Dauphin), led to the isolation of the previously reported halogenated monoterpene, halomon, and the discovery of three new related metabolites. These molecules were found to inhibit DNA methyltransferase 1 (DNMT-1). As a result of efforts to identify bioactive agents from the marine cyanobacterium Lyngbya majuscula, tanikolide dimer, a novel SIRT2 inhibitor (IC50 = 176 nM), and tanikolide seco-acid were isolated. The depside molecular structure of tanikolide dimer, which is likely a meso compound, was established by NMR, MS and chiral HPLC analyses. The structure of tanikolide dimer raises a number of intriguing configurational and biosynthetic questions for further study. The bioassay guided fractionation of a collection of the brown marine alga Dictyota sp. from Netherland Antilles Playa Fort, led to the identification of a novel HDAC inhibitor with a dolastane carbon skeleton. The novel molecule was also found to possess antimalarial activity. Other known HDAC inhibitors with interesting antimalarial activity have been reported previously, and based on this efficacy against malaria, HDAC appears to be a viable target for the development of antiparasitic agents. / Graduation date: 2006

This thesis describes the development of nitro-Mannich/hydroamination cascade reactions for the synthesis of N-heterocycles, which are important motifs found in a variety of biologically active natural products and pharmaceuticals, such as atorvastatin (Lipitor®). Chapter 2 outlines the development of an efficient synthesis of 2,5-disubstituted pyrroles using a nitro-Mannich/hydroamination cascade. Starting from easily prepared N-protected imines and nitroalkyne substrates, a compatible combination of KOtBu (10 mol%) and AuCl3 (5 mol%) was used to afford the desired pyrrole products, after an alkene isomerisation/HNO2 elimination reaction sequence. Chapter 3 describes the extension of this methodology to the diastereo- and enantioselective synthesis of 1,2,3,4-tetrahydropyridine derivatives using a nitroalkyne substrate with an extended carbon chain. The sequential addition of a bifunctional Brønsted base/H-bond donor organocatalyst and a gold complex was found to facilitate the desired cascade reaction affording substituted 1,2,3,4-tetrahydropyridine products. We then established that highly substituted pyrrolidine compounds could be prepared by replacing the nitroalkyne substrate with a nitroallene substrate (Chapter 4). The combination of KOtBu (5 mol%) and a gold catalyst derived from Au(PPh3)Cl (10 mol%) and AgSbF6 (20 mol%) was found to give an efficient diastereoselective synthesis of pyrrolidine derivatives after an additional nitro group epimerisation step. In addition, the nitro-Mannich/hydroamination cascade using nitroallene substrates was developed into an enantioselective variant using the previously employed bifunctional Brønsted base/H-bond donor organocatalyst. This afforded enantioenriched pyrrolidine derivatives.

Les travaux présentés concernent dans une première partie la synthèse biomimétique d’un alcaloïde indolomonoterpénique : la bipléiophylline. La bipléiophylline est le résultat de l’assemblage complexe de deux unités indoliques identiques ancrées sur une plateforme aromatique. Une stratégie générale de synthèse biomimétique de la bipléiophylline consistant i) à la synthèse de l’unité indolique pléiocarpamine et ii) à l’oxydation de l’acide 2,3-dihydroxybenzoïque a été envisagée. L’accès au squelette complexe de la pléiocarpamine a été étudié selon plusieurs stratégies de synthèse totale mais également par hémisynthèse. Parallèlement une étude des conditions d’oxydation notamment par électrochimie de l’acide 2,3-dihydroxybenzoïque ont permis de déterminer et caractériser son potentiel d’oxydation et de mettre au point les conditions de formation de sa forme oxydée. La seconde partie est consacrée à la synthèse biomimétique d’un modèle du cœur central de l’haliclonine A, un alcaloïde de la famille des manzamines. La synthèse de plusieurs précurseurs a été réalisée ainsi que l’étude de l’étape clé de double addition nucléophile sur un 5,6-dihydropyridinium. / Our work deals in the first part with a biomimetic synthesis of bipleiophyllin, an indolomonoterpenic alkaloid. The bipleiophyllin is the result of a complex anchorage of two identical indolic subunits on an aromatic platform. A general strategy for the biomimetic synthesis of bipleiophyllin consisting of i) the synthesis of the indolic unit pleiocarpamin and ii) the oxidation of 2,3-dihydroxybenzoic acid; was considered. Access to the complex skeleton of pleiocarpamin has been studied by different total synthesis strategies but also by hemisynthesis. Meanwhile this work, a study of the oxidation conditions of 2,3-dihydroxybenzoic acid including by electrochemistry, helped identify and characterize its oxidation potential and develop the required conditions to obtain its oxidized form. The second part is devoted to the biomimetic synthesis of a model compound, mimic of the central core of haliclonin A, an alkaloid of the family of manzamins. The synthesis of several precursors and the study of the key step consisting in a double nucleophilic addition to a 5,6-dihydropyridinium were done.

Les bispidines sont des diamines polycycliques chirales régulièrement utilisées comme ligand pour réaliser de l’induction asymétrique. La bispidine HZ2 est connue pour être agoniste et sélective des récepteurs κ-opioïdes, récepteurs impliqués dans le mécanisme douloureux. Ce travail décrit la mise au point d’une méthode générale de synthèse asymétrique et flexible du squelette bispidine, permettant des modifications structurales, afin d’évaluer le potentiel pharmacologique des analogues synthétisés. Tout d’abord, nous avons synthétisé des pipéridines 2,3,6-trisubstituées grâce à une réaction de Mannich intramoléculaire stéréospécifique entre un β,β’-diaminocétal et divers aldéhydes. Les pipéridones possédant une fonction amino-éthyle en position 3, ainsi obtenues ont été engagées dans une deuxième réaction de Mannich, pour l’obtention de bispidines bicycliques. Ensuite, nous avons souhaité accéder à des bispidines de géométrie plus contrainte. Pour cela, la condensation de divers anhydrides sur les pipéridones possédant une fonction amino-éthyle en position 3, a permis la formation des imides correspondants, précurseurs d’ions N-acyliminium. Les bispidines tricycliques et tétracycliques, sont obtenues par cyclisation en milieu acide en présence des éthers d’énols. Une étude de détermination structurale par RMN a permis de mettre en évidence les différentes conformations adoptées par les bispidines synthétisées (chaise-chaise, chaise-bateau, chaise-twist). Enfin, les composés synthétisés ont fait l’objet de tests in vivo afin d’évaluer leur potentiel antalgique. Ils ont montré une activité modérée. Cependant, l’introduction de groupements aromatiques en α de l’atome d’azote devrait accroître l’efficacité de nos composés, selon les modèles décrits dans la littérature. / Bispidines are polycyclic chirales diamines which are usefull ligands for asymmetric induction. Bispidine HZ2 is known to be an agonist and selective of κ-receptors, receptors invoved in pain mechanism. This work focuses on the development of a versatile asymmetric synthesis of bispidine backbone, allowing structural modifications, in order to evaluate the pharmacologic potential of compounds prepared. Initially, we synthetized 2,3,6-trisubstituted piperidines thanks to an intramolecular stereospecific Mannich reaction between a β,β’-diaminoketal and various aldehydes. Piperidones, thus obtained, which have an amino-ethyl function in position 3, were submitted to a second Mannich reaction, in order to prepare bicyclic bispidines. Then, we wish to obtain bispidines of restricted conformation. The condensation of several aldehydes on piperidones which have an amino-ethyl function in position 3, enabled the formation of the corresponding imides, precursors of N-acyliminium ions. Tricyclic and tetracyclic bispidines were obtained by a cyclisation in acid conditions in presence of enol ethers. A NMR study enabled to give rise to the adopted conformations of the bispidines prepared (chair-chair, chair-boat, chair-twist). Finally, the synthetized compounds were tested in vivo in order to evaluate their analgesic potential. They showed a moderate activity. However, the introduction of aromatic groups in position α of the nitrogen atom would increase the efficiency of our compounds, according to the literature.

L'augmentation de la concentration de dioxyde de carbone (CO2) dans l'atmosphère depuis la révolution industrielle a conduit à l'augmentation de la température moyenne du globe. Pour limiter l’accroissement des températures atmosphériques moyennes, la quantité de dioxyde de carbone émise dans l'atmosphère doit être réduite. Une des solutions envisagée sur les sources fixes est le captage et le stockage du CO2. Ce procédé d’absorption/désorption, bien connu dans le traitement du gaz naturel, est onéreux et peu efficace pour le traitement du gaz des sources fixes et doit être optimisé. La solution proposée s’appuie sur l’utilisation de solvants démixants, présentant une séparation de phase équilibre liquide-liquide (LLE) en solution aqueuse en fonction de la température. Ce manuscrit présente une étude réalisée pour la famille des alkyl-pipéridines connues pour ses séparations de phase. Cette étude permettra d’évaluer l’influence de la taille, de la positionet du nombre de substituants sur les propriétés thermodynamiques d’intérêt pour le procédé. Pour étudier les LLE des solutions aqueuses démixantes, en particulier dans le cas des solutions chargées en gaz, deux instruments ont été mis au point. Il a été possible de démontrer que les changements opérés sur les diagrammes de phase des amines sont liés aux réactions chimiques mises en jeu lors de la dissolution du CO2. Pour les alkyl-pipéridines tertiaire on observe la température de démixtion diminue avec l’addition de CO2, allant avec la formation de carbonates. Avec les alkyl-pipéridines secondaires la température de démixtion augmente, ce qui est lié à la présence en solution de carbamates qui stabilisent la solution aqueuse. Le comportement des amines secondaires très encombrées, qui ne peuvent donc pas formées de carbamates, est similaire à celui des amines tertiaires, ce qui est cohérent avec les conclusions précédentes. Une étude approfondies des propriétés thermodynamiques d’excès (VE, CpE et HE) des alkyl-pipéridines en solution aqueuse a également permis de démontrer des relations structure - propriétés. La position du substituant sur le cycle pipéridine a une influence considérable et prévisible sur l’intensité des propriétés d’excès, alors que la nature de l’amine (secondaire ou tertiaire) va influencer la position de l’extremum de cette propriété. Enfin, une modélisation thermodynamique rigoureuses des solubilités et des enthalpies de dissolution du CO2 dans les solutions aqueuses de pipéridines a permis de déterminer les constantes de formation des carbamates dans les solutions aqueuses de 3- et 4-méthylpipéridines. / The increase of carbon dioxide (CO2) concentration in the atmosphere, since the industrial revolution has led to the rise in the average global climate temperature. To prevent the escalation of global climate temperatures the amount of CO2 emitted into the atmosphere must be reduced. One solution is carbon capture and sequestration which removes CO2 from fixed sources. The absorption/desorption cycle is well known for the treatment of acid gas, but is expensive and not as efficient for the treatment of gas from fixed/industrial sources. A solution to this problem is the use of aqueous demixing amine solvents which present a liquid-liquid phase equilibrium (LLE) as a function of temperature. This manuscript presents a study done to measure the LLE and thermodynamic properties of the alkyl piperidine family, which can be used for carbon capture processes. This work evaluates the effect of the size, position and number of alkyl substituents on the thermodynamic properties of interest in the carbon capture process. To study the LLE of aqueous demixing solutions, particularly gas loaded solutions, two novel apparatuses were developed. The results demonstrate that the changes in the amine phase diagrams are related to the chemical reactions involved with dissolution of CO2. The tertiary alkyl piperidines displayed reduced demixing temperature with the addition of CO2 due to the formation of carbonate species. The secondary alkyl piperidines display an increasing demixing temperature which is related to the formation of carbamate species which stabilizes the solution. Secondary alkyl piperidines that are severely sterically hindered, which cannot produce carbamates, behave similarly to the tertiary amine which is coherent with the preceding conclusion. The structure property relationship concerning the excess thermodynamic properties (VE, CpE et HE) of aqueous solutions were studied in depth. This revealed that the position of the substituents on the cyclic ring has a considerable and obvious influence on the intensity of the excess properties, along with the class of the amine, whether secondary or tertiary, will influence the positions of the extrema of the excess property. To conclude, a rigorous thermodynamic model based on the CO2 solubility and the enthalpy of solution for CO2 in aqueous solutions of alkyl piperidine, allowed for the determination of the carbamate formation constants of 3- and 4-methylpiperidine.

No / A novel series of 1,4-disubstituted aminoanthraquinones were prepared by ipso-displacement of 1,4-difluoro-5,8-dihydroxyanthraquinones by hydroxylated piperidinyl- or pyrrolidinylalkyl-amino side chains. One aminoanthraquinone (13) was further derivatized to a chloropropyl-amino analogue by treatment with triphenylphosphine-carbon tetrachloride. The compounds were evaluated in the A2780 ovarian cancer cell line and its cisplatin-resistant variants (A2780/ cp70 and A2780/MCP1). The novel anthraquinones were shown to possess up to 5-fold increased potency against the cisplatin-resistant cells compared to the wild-type cells. Growth curve analysis of the hydroxyethylaminoanthraquinone 8 in the osteosarcoma cell line U-2 OS showed that the cell cycle is not frozen, rather there is a late cell cycle arrest consistent with the action of a DNA-damaging topoisomerase II inhibitor. Accumulative apoptotic events, using time lapse photography, indicate that 8 is capable of fully engaging cell cycle arrest pathways in G2 in the absence of early apoptotic commitment. 8 and its chloropropyl analogue 13 retained significant activity against human A2780/cp70 xenografted tumors in mice.