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Die Pseudodistomine gehören zu den ersten Piperidinalkaloiden marinen Ursprungs, die 1987 von Ishibashi et al. aus der Tunikate (Ascidie) Pseudodistoma kanoko isoliert wurden. Aus der gleichen Tunikate wurde 1995 das Pseudodistomin C isoliert. Die amphiphilen Piperidinalkaloide zeigen eine Antitumor-Aktivität gegen bestimmte Mäuseleukämiezellen, wobei Pseudodistomin C auch eine Cytotoxizität gegen menschliche HeLa-abgeleitete Krebszellen KB aufweist. In der Einleitung wird ausführlich auf Vorkommen, Struktur, Biogenese, pharmakologische Perspektiven und literaturbekannten Synthesen dieser amphiphilen Piperidin-Alkaloide eingegangen. Im Hauptteil wird zunächst eine gescheiterte Synthese ausgehend von D-Ribose über das Konzept einer Tandem Wittig-[3+2]-Cycloaddition beschrieben. Daraufhin wird ein völlig neuer Syntheseweg vorgestellt, welcher den formalen Aufbau des Pseudodistomin C über einen bekannten Piperidin-Grundkörper ermöglich. Des weiteren konnte das vollständig geschützte Pseudodistomin E synthetisiert werden. / Pseudodistomines belong to the first known piperidine alkaloids of marine origin, isolated by Ishibashi et al. from the tunicate (ascidie) pseudodistoma kanoko in 1987. From the same tunicate Pseudodistomin C was isolated in 1995. The amphiphilic piperidin alkaloids show an antitumor activity against certain leukemic cells derived from mice, whereas Pseudodistomin C also exhibits an antitumor activity against human HeLa-derived cancer cells KB. The introduction goes into details about occurrence, structure, biogenesis, pharmacological perspectives and literature known synthesis of these amphiphilic piperidine alkaloids. The main part starts with a failed synthesis based on D-ribose by the concept of a tandem wittig-[3+2]-cycloaddition. Consequently an entirely new synthesis pathway is presented, which enables the formal buildup of Pseudodistomin C by a known piperidine compound. Furthermore I was able to synthesize the fully protected Pseudodistomin E.

Ziel dieser Arbeit ist die Synthese neuer optisch aktiver Hydroxyalkylheterocyclen durch Ringtransformationen von chiralen -Alkylidenlactonen. Hierzu wurden letztere gezielten Additionen von Binucleophilen, 1,3-dipolaren Cycloadditionen, Cupratadditionen und Epoxidierungsreaktionen unterworfen. Die erhaltenen Produkte konnten durch weitere gezielte Folgereaktionen, Spaltungen oder Reaktionen mit Nucleophilen zu interessanten enantiomerenreinen Hydroxyalkylheterocyclen umgesetzt werden. Eine Deutung der acyclischen Seitendifferenzierung gelang mit Hilfe des antiperiplanaren Effektes und des inside alkoxy effects. Umsetzungen mit Hydrazinen führten in guten Ausbeuten zu trans-Hydroxyalkyl-3-pyrazolidinonen. Aus Nitromethan und -Alkylidenlactonen erhält man DBU-katalysiert Nitroethyllactone die sich unter hydrogenolytischen Reaktionsbedingungen zu trans-3-Hydroxyalkyl-2-pyrrolidinonen ringtransformieren lassen. Über o-Aminothiophenoladditionen und Ringtransformationen werden enantiomerenreine 3-(2-Hydroxyalkyl-2,3-dihydro-1,5-benzothiazepin-4(5H)-one erhalten, die neuartige Analoga der Pharmaka Dilthiazem und Thiazesim darstellen. Neue D1-Pyrazoline entstehen durch 1,3-dipolare Cycloadditionen von Diazoalkanen an -Alkylidenlactone. Durch photolytische Extrusion von Stickstoff werden neue chirale Cyclopropanderivate erhalten. Enantiomerenreine , -Diaminosäurederivate werden durch hydrogenolytische N-N-Bindungsspaltung der D1-Pyrazoline generiert. Über Epoxidierung der -Alkylidenlactone mittels Dimethyldioxiran und Umsetzung der erhaltenen Oxirane mit verschiedenen N- und S-Nucleophilen und anschließender Ringtransformation, ist ein Zugang zu Benzothiazepin-4(5H) -on, 1,5-Benzodiazepin-2-on, 1,4-Thiazepan-5-on, Thiomorpholin-2-on, 1-Phenyl-2-acetidion sowie über Lithium-Halogenaustausch-Reaktion zu 2-Hydroxy-2-hydroxyethyl- thiochromen-4-on erarbeitet worden. Mit Organokupferverbindungen gelingt hochregioselektiv die 1,4-Addition. Unter Bedingungen der Iodlactonisierung werden aus den Addukten neuartig substituierte -Butyro- und -Valerolactone erhalten. / The thesis is focused on the synthesis of new optically active hydroxyalkyl heterocycles by ring-chain-transformation of chiral -alkylidenlactones. The latter were subjected to specific additions of binucleophiles to 1,3-dipolare cycloadditions to addition of cuprates and to epoxidation. The product obtained could be further applied in the synthesis of interesting enantiomerically pure hydroxyalkyl heterocycles by specific reactions like ring-cleavage or reactions with nucleophiles. The acyclic side differentiation could be explained with the help of the antiperiplanar effect and the inside alkoxy effects. Reactions with hydrazines led to trans-hydroxyalkyl-3-pyrazolidinones in good yields. Nitroethyllactones were obtained from -alkylidenlactones and nitromethane under DBU-catalysis. In a following step they are ring-transformed into trans-3-hydroxyalkyl-2-pyrrolidinones by hydrogenation. Enantiomerically pure 2-hydroxyalkyl-2,3-dihydro-1,5-benzothiazepin-4-(5H)ones could be prepared by addition of o-aminothiophenol and following ring-chain-transformation. These compounds represent novel analogs of the drugs Dilthiazem&#8482 and Thiazesim&#8482. Novel D1-pyrazoline results from 1,3-dipolare cycloadditions of -alkylidenlactone with diazoalkanes. New chiral derivatives of cyclopropanes were obtained by photolytic extrusion of nitrogen. Enantiomerically pure ,-diaminoacid derivatives were generated by hydrogenolytic cleavage of the N-N-bond of the pyrazolines. Epoxidation of -alkylidenlactones with dimethyldioxirane and opening of the oxirane ring obtained by various N- and S-nucleophiles provided new methods for the synthesis of benzothiazepin-4(5H)-one, 1,5-benzodiazepin-2-one, 1,4-thiazepan-5-one, thiomorpholin-2-one and 1-phenyl-2-acetidione. 2-Hydroxy-2-hydroxyethyl-thiochromen-4-one could be obtained by lithium-halogens exchange reaction. The 1,4-additions of organocuprates to -alkylidenlactones succeeded with high regioselectivity. Novel substituted [gamma]-butyro- and -valerolactones were obtained by iodolactonisations of these adducts.

Foi estudado o efeito da lactona sesquiterpênica licnofolido sobre o \"burst\" respiratório de leucócitos polimorfonucleares inflamatórios (PMN) estimulados por forbol (PMA), pelo peptídeo quimiotático fMLP ou zimozan opsonizado (OZ). O licnofolido inibiu de forma dose-dependente a liberação de O2•- pelos PMN, sem alteração do período \"Iag\" do complexo NADPH. oxidase. O efeito foi mais acentuado quando os PMN foram estimulados diretamente pela via de proteína quinase C. A adição de ditiotreitol ou glutationa reduzida (GSH) às suspensões celulares antes da incubação com licnofolido preveniu parcialmente o efeito inibitório. O tratamento dos PMN com a lactona determinou uma queda drástica dos níveis celulares de GSH livre, sem incremento de glutationa oxidada (GSSG). A reação direta entre GSH e licnofolido foi confirmada com a detecção de um aduto glutationil-licnofolido através de identificação por espectrometria de massa (ESI-MS/MS). A S-tiolação protéica induzida pelo PMA foi reduzida em PMN tratados com Iicnofo/ido, como detectado através de determinação de incorporação de [35S], sendo que 80% desses tióis foram identificados como GSH. Uma série de proteínas S-glutationadas foi detectada através de autoradiografias, sendo que aquelas correspondentes a 38 e 24 kDa tiveram essa modificação póstraducional suprimida pelo tratamento com dose de licnofolido capaz de suprimir o \"burst\" respiratório dos PMN. Estes resultados indicam que a depleção celular de GSH causada pelo licnofolido impede a sustentação do \"burst\" respiratório pelos PMN, em correlação direta com a diminuição de S-glutationação protéica. / An investigation was made into the action of the sesquiterpene lactone lychnopholide on the respiratory burst of inflammatory polymorphonuclear leukocytes. Lychnopholide determined concentration-related inhibition of the generation of phorbol 12-myristate 13-acetate-, chemotatic peptide-, and opsonized zymozan-induced superoxide anion with no effect on the lag time of the assembly of the NADPH oxidase complex, such action was greater on the protein kinase C pathway that on both membrane receptor dependent stimuli via. Subsequent additions of D-glucose, Ca2+, Mg2+, dithiothreitol ar reduced glutathione (GSH) did not reverse the inhibitory action. The addition of both thiols prior to the lychnopholide treatment partially hindered the inhibition rate. The endogenous level of GSH in leukocytes was drastically depleted under the lychnopholide treatment, without corresponding increases occurring in the oxidized form (GSSG). A direct reaction between glutathione and lychnopholide was confirmed from a glutathionyl-lychnopholide adduct detected by electrospray mass spectrometry analysis and identified by tandem mass analysis in cellular extracts. Protein S-thiolation induced by PMA stimulation was decreased in lactone-treated PMN as detected by [35S] scintillation count, which indicated that about 80% of the thiols were glutathione. A subset of S-glutathionylated proteins was identified through gel electrophoresis, which revealed that the modification of the phorbol-triggered protein sulfhydryl in the protein bands corresponding to 38 and 24 kDa was precluded by the lychnopholide treatment correlated with respiratory burst inhibition. These results show that GSH depletion determined by lychnopholide treatment renders PMN to sustain respiratory burst, whose action is proportional to protein S-glutahionylation decrease.

A busca por novos fármacos inspirados em substâncias de origem natural é uma estratégia conhecida e há tempos utilizada. As lactonas sesquiterpênicas (LST) são um grupo de substâncias amplo e diverso com várias atividades farmacológicas descritas, e cuja característica estrutural determinante é a de um esqueleto principal contendo 15 átomos de carbono e um anel lactônico. O mecanismo de ação das LST está intrinsicamente relacionado com reações de adição do tipo Michael frente a biomoléculas, provocando alquilações. Há na literatura estudos aprofundados sobre a química medicinal das LST, entretanto pouco há sobre o metabolismo desse grupo de substâncias em ambientes fisiológicos. Neste sentido, este trabalho é focado no estudo do metabolismo e também das vias de fragmentação por eletrospray da budleína A, que possui estrutura química do tipo furanoeliangolido, e pertence à classe dos germacranolidos. Foram realizados ensaios in vitro utilizando-se os modelos de oxidação biomimética com metaloporfirina, microssomas hepáticos e metabolismo pela microbiota intestinal de ceco de porco (pig cecum model), sendo nos dois últimos testado também o correlato 4,5-dihidro-2\',3\'-epoxi-15-desoxigoyazensolido. O estudo de fragmentação também abordou a comparação entre budleína A e a centraterina - um estereoisômero que se diferencia apenas pela orientação da cadeia lateral ligada ao C-8 - em espectrômetros distintos e com suporte de métodos computacionais para cálculos de energia (Gaussian 03 em base B3LYP/6-31G(d)). Nos estudos de fragmentação observou-se a diferença de intensidade dos sinais para íons fragmento comuns às duas LST (m/z 275, 257 e 83), além da presença do íon fragmento de m/z 293 apenas para a budleína A, permitindo a diferenciação destes isômeros por meio de espectrometria de massas com ionização por eletrospray, sem a necessidade de ressonância de magnética nuclear. Os produtos de oxidação detectados na reação com metaloporfirinas acusaram a epoxidação na cadeia lateral envolvendo C-2\' e C-3\' com a formação de diastereoisômeros. No ensaio com microssomas não foram detectados produtos para a budleína A, enquanto que para a substância correlata observou-se a abertura do epóxido na cadeia lateral e adição de uma hidroxila, formando um diol vicinal. No modelo de ceco de porco observaram-se a formação de adutos de LST com o aminoácido cisteína, os quais foram posteriormente degradados pela ação da microbiota intenstinal, dando origem a diversos metabólitos compostos pela LST e partes de cisteína. Sendo assim, este trabalho lança bases para a maior compreensão do metabolismo de LST do tipo furanoeliangolido em modelos distintos e também contribui para os estudos de espectrometria de massas para este tipo de substância, além de descrever uma ferramenta analítica útil na diferenciação de dois estereoisômeros. / The search for new drugs inspired on compounds from natural products is a wellknown strategy with several successful cases. Sesquiterpene lactones (STL) are a wide and diversified group of compounds which has already many pharmacological activities reported. Their fundamental moiety includes a skeleton containing 15 carbons and a lactone ring and the mechanism of action is related to Michael addition type reactions with biomolecules, promoting alkylation. There are a high amount of studies regarding the medicinal chemistry of the STL, however there are few information about the metabolism of these compounds under physiological environments. On this way, the aims of this work are focused on the study of the metabolism as well as the fragmentation pathways of budlein A, which is a furanoheliangolide and belongs to the germacranolides class. On this work the following experiments were carried out: in vitro oxidative metabolism with metalloporphyrin and microsomes; intestinal metabolism by using the pig cecum model (microbiota). For microsomes and intestinal metabolism the compound 4,5- dihydro-2\',3\'-epoxy-15-deoxy-goyazensolide was also applied. Fragmentation studies compared the fragmentation patterns of budlein A and centratherin - which is a stereoisomer with -orientation for the side chain bonded at C-8 - by using different spectrometers being supported by computational methods for energies calculations (Gaussian 03 at level B3LYP/6-31G(d)). For the fragmentation studies it was observed the difference of signal intensities for fragment ions which are common for both STL (m/z 275, 257 e 83), moreover the ion m/z 293 was detected only for budlein A, allowing the differentiation between these isomers by electrospray ionization mass spectrometry instead nuclear magnetic resonance. The reactions with metalloporphyrin yielded two diastereoisomers of the STL with an epoxide at the side chain between C-2\'and C-3\'. On the microsome assay any product was detected for budlein A, while for the correlated compound the epoxide ring was opened and a hydroxyl was added at C-3\', forming a vicinal diol. On the pig cecum model it was observed the formation of adducts due to the reaction of the STL and the amino acid cysteine. These adducts were later degraded by the action of the microbiota yielding different metabolites composed by STL and residues of cysteine. Thus, this work may contribute to the improvement of the knowledge about the metabolism of STL furanoheliangolide type in different models as well as for the studies regarding the mass spectrometry of this type of compound. The development of a useful analytical tool for the differentiation of two isomers was also an important achievement.

A presente tese relata o estudo químico de duas espécies vegetais pertencentes à família Asteraceae: Mikania sp. nov; e Wunderlichia crulsiana. Da espécie Mikania sp. nov. foram estudados os extratos diclorometânicos das folhas e dos galhos, tendo sido isolados e identificados sete ácidos diterpênicos; dos óleos voláteis das folhas e dos galhos foram identificadas vinte substâncias entre monoterpenos e sesquiterpenos. Da espécie Wunderlichia crulsiana foram estudados os extratos diclorometânicos das flores e dos galhos. Das flores foram isolados e identificados palmitatos e acetatos de triterpenoílas. Dos galhos foram isolados e identificados acetatos de triterpenoílas e triterpenonas e identificados por CG triterpenóis acetilados e palmitatos de triterpenoílas hidrolisados e posteriormente acetilados. Deste extrato foram também isolados e identificados três lactonas sesquiterpênicas e um sesquiterpeno. A identificação das substâncias foi realizada através de RMN de 1H, de 13C (BBD e DEPT 135º), CG/EM e co-injeção de padrões. Os extratos brutos de ambas as plantas apresentaram discreta atividade, quando submetidos a um ensaio antifúngico. As frações, contendo os triterpenóis, acetatos e palmitatos de triterpenoflas e as lactonas sesquiterpênicas, foram testadas quanto à atividade anti-infíamatória mostrando-se bastante ativas. Tanto os extratos brutos quanto as fraqões supracitadas não se mostraram ativos em um ensaio antitumoral. Estes resultados indicam a seletividade da atividade dos extratos e frações, possivelmente não contendo substâncias citotóxicas. / This work describes the chemical study of two plants which belong to the family Asteraceae: Mikania sp. nov. and Wunderlichia crulsiana. The dichlorometane extracts from leaves and stems of Mikania sp. nov. we studied and seven diterpenic acids were isolated and identified. The volatile oil from leaves and stems of this plant were also studied and twenty substances among monoterpenes and sesquiterpenes were identified. From Wunderlichia crulsiana we analysed the dichlorometane extracts from flowers and stems. From flowers we isolated and identified triterpenes esterified with palmitic acid and acetic acid. From stems we isolated and identified triterpenes esterified with acetic acid and 3-oxo-triterpenes. By GC, we identified hydroxylated triterpenes that were acetylated, and triterpenes esterified with palmitic acid that were hydrolysed and acetylated. From stems we also isolated and identified three sesquiterpene lactones and a sesquiterpene. The compounds were identified by PMR, CMR (BBD and DEIT 135º), GC/MS and co-injection with authentic samples The extracts of both plants showed low activity when submitted to bioassay with Cladosporium sphaerospermum. The fractions which contain the hydroxylated triterpenes, triterpenes esterified with acetic and palmitic acids and sesquiterpene lactones were submitted to anti-inflammatory bioassay and showed 42%, 29%, 29% and 47% of activity, respectively. The above mentioned extracts and the fractions did not show significant activity on the Saccharomyces cerevisae bioassay, so there were not citotoxic substances in them.

Chiral Baeyer-Villiger (BV) oxidation of cyclic ketones allows rapid access to asymmetric lactones as valuable intermediates in organic chemistry and frequently encountered precursors in enantioselective synthesis. In the first part, BV oxidation of functionalized ketones, especially cyclic &amp / #61537 / -hydroxy and acetoxy ketones is described which could be a straightforward route to the &amp / #61537 / -hydroxy lactones and &amp / #61537 / -hydroxyalkanoic acid derivatives. The &amp / #61537 / -acetoxylation of indanone, tetralone and chromanone derivatives by using Mn(OAc)3 followed by the enzyme catalyzed kinetic resolution of acetoxy ketones gives both of the enantiomers of &amp / #61537 / -acetoxy ketones in good chemical and optical yields. The Bayer-Villiger oxidation of &amp / #61537 / -acetoxy ketones with m-CPBA, CF3SO3H, and CH2Cl2, at rt gives the corresponding lactones without racemization. The phenyl moiety migrates selectively in order to form lactones. The mild hydrolysis of lactones affords phenolic &amp / #61537 / -hydroxycarboxylic acid derivatives. Because of the high importance of pyrrole derivatives which exist in the structure of many natural products possessing biological activity beside their valuable feature of being versatile building blocks in organic synthesis and important starting materials for various synthetic transformations, a convenient method for the synthesis of 1,2,3,5-tetrasubstituted pyrrole derivatives starting from 1,3,-dicarbonyl compounds throuh acid catalyzed cyclization reaction is presented in the second part of the thesis. Alkylation of 1,3-dicarbonyl compound with propargyl bromide followed by one step cyclization with the introduction of primary amines in the presence of catalytic amount of trifluoroacetic acid (TFA) affords the corresponding pyrrole derivatives in high yields. The third part of the thesis describes the cyano-phosphorylation of various alkyl and aryl phosphonates in the presence of diethyl cyanophosphonate (DEPC) as the phosphorylating agent under the promotion of the KCN catalyst. Reaction of acyl phosphonates with DEPC forms the phosphonocyanohydrin-O-phosphates which are the important starting materials of quaternary &amp / #945 / -hydroxy carboxylic acid and phosphonate containing &amp / #946 / -aminoalcohol derivatives.

This thesis entitled ‘ Unusual Acylation Properties of Type II Fatty Acid Biosynthesis Acyl Carrier Proteins’ describes the discovery of self-acylation and malonyl transferase activity in acyl carrier proteins involved in type II fatty acid biosynthesis and assigns a physiological role to these processes inside the cellular milieu. Acyl carrier protein (ACP) is one of the most abundant proteins present inside the cell and almost 4% enzymes require it as a cofactor. Acyl carrier proteins can exist either as discrete proteins or as domains of large functional proteins. They function in a variety of synthases as central molecules to which growing acyl intermediates and nascent product molecules are covalently tethered during the elongation and modification steps required to produce the final product. A prototypical bacterial ACP is composed of 70-80 amino acids and is generally expressed in the apo form. It is post-translationally modified to active holo form by the addition of 4'-phosphopantetheine moiety to an absolutely conserved serine residue in a reaction catalyzed by holo-ACP synthase or 4'-phosphopantetheine transferase. Chapter 1 surveys literature related to carrier proteins inside the cell and describes the thesis objective. It also presents an overview of the acyl carrier proteins and their involvement in various metabolic pathways inside the cell. The chapter details the structural organization of acyl carrier proteins from various sources revealing the conservation in their structure and also details the molecular basis of interaction of ACP with other enzymes inside the cell. The discovery of unusual self-acylation property in acyl carrier proteins involved in polyketide biosynthesis and its absence in acyl carrier proteins involved in fatty acid biosynthesis prompted me to investigate the reasons for this selective behavior. Discovery of self-acylation property in acyl carrier proteins Plasmodium falciparum and chloroplast targeted Brassica napus acyl carrier proteins involved in type II fatty acid biosynthesis and the mechanism of this reaction forms the basis of Chapter 2. In this chapter it has been shown that self-acylation property is intrinsic to a given acyl carrier protein and is not dependent on the pathway in which it is involved. Based on primary sequence analysis and site directed mutagenesis studies presence of an aspartate/glutamate has been identified to be critical for the self-acylation event. Furthermore, it has also been shown that the self-acylation event in type II fatty acid biosynthesis acyl carrier proteins is highly specific in nature employing only dicarboxylic acid –CoAs as substrates unlike the polyketide biosynthesis acyl carrier proteins which utilize both dicarboxylic acid and β-keto acid thiol ester -CoAs as substrates. The detailed kinetics of these reactions has also been worked out. Combining all the results a plausible mechanism for the self-acylation reaction has been proposed. Chapter 3 describes the discovery of a novel malonyl transferase behavior in acyl carrier proteins involved in type II fatty acid biosynthesis. Malonyl transferase property in ACPs of type II FAS from a bacterium (Escherichia coli), a plant (Brassica napus) and a parasitic protozoon (Plasmodium falciparum) were investigated to present a unifying paradigm for the mechanism of malonyl transferase behavior in ACPs. Identification of malonyl transferase property in Plasmodium falciparum ACP and Escherichia coli ACP (EcACP) and the absence of this property in Brassica napus ACP has been described in this chapter. Detailed investigations demonstrated that presence of an arginine or a lysine in loop II and an arginine or glutamine at the start of helix III as the residues that are critical for the transferase activity. In order to assign a physiologic function to these unusual acylation properties, fabD(Ts) mutant strain of Escherichia coli was utilized for heterologous complementation by the various wild type and mutant ACPs that are able to catalyze either or both of the activities. Growth of the mutant strain at non-permissive temperature, when complemented with ACPs catalyzing both the reactions confirmed that these properties have a physiologic relevance. Extensive mutagenesis experiments in conjunction with complementation studies allowed me to propose a plausible mechanism on how the self-malonylation and malonyl transferase properties operate in tandem. Chapter 4 describes the thermodynamic characterization of self-acylation process using Isothermal Titration Calorimetry. Isothermal Titration Calorimetric studies on the binding of malonyl, succinyl, butyryl and methylmalonyl –CoA to Plasmodium falciparum and Brassica napus acyl carrier proteins were performed to investigate the role of thermodynamic parameters in the specificity of self-acylation reaction. Calculation of the parameters showed that the thermodynamics does not control the self-acylation reaction. The evolution of self-acylation property in various acyl carrier proteins and its possible significance in the evolution of various metabolic events is described in Chapter 5. Extensive bioinformatics search was performed and phylogenetic analysis on acyl carrier proteins from 60 different taxa was done using the MEGA4 program. Analysis showed that this property was first found in cyanobacterium. Later, during the course of evolution this property was lost in most acyl carrier proteins, and was retained either in acyl carrier proteins that are targeted to organelles of cyanobaterial orgin viz. apicoplast in apicomplexans and chlorplasts in plants or in acyl carrier proteins involved in secondary metabolic events such as polyketide biosynthesis. Chapter 6 summarizes the findings of the thesis. Acyl carrier protein from Plasmodium falciparum, Brassica napus and Escherichia coli were characterized for their self-acylation and malonyl transferase properties and a combined mechanism for these two properties is proposed. The work done also provides an in vivo rationale to these in vitro processes. Furthermore, the evolutionary significance of the self-acylation behavior is also discussed in the thesis. The thesis also probes into the thermodynamics of the self-acylation reaction in Plasmodium falciparum and Brassica napus acyl carrier proteins. Thus, the thesis adds a new dimension to the much unexplored ACP biology and paves the way to study in vivo roles of these processes in detail. Appendix I describes the Isothermal Titration calorimetric characterization of binding of various acyl-PO4 molecules to Escherichia coli PlsX (Acyl-phosphate acyltransferase). PlsX, the first enzyme of phosphatidic acid biosynthesis pathway catalyzes the conversion of acyl-ACP into acyl-PO4, which is further used by other enzymes leading to the formation of phosphatidic acid. ITC results presented in this section show that longer chain length acyl-PO4 molecules show better binding to PlsX, as compared to the smaller ones demonstrating that long chain acyl molecules serve as better substrates for phosphatidic acid synthesis.

Natural products are essential tools for basic cellular studies leading to the identification of medically relevant protein targets and the discovery of potential therapeutic agents. We have developed a set of second generation diazo reagents with small steric footprints, namely an alpha-trifluoroethyl (HTFB) diazo reagent, for simultaneous arming and SAR studies of bioactive natural products. The Rh(II)-catalyzed O-H insertions of several alcohol-containing natural products, including the potent translation inhibitor lactimidomycin, are investigated and useful reactivity and both chemo- and site- (chemosite) selectivities are observed. The alpha-trifluoroethyl diazo reagents (HTFB) shows clear differences in the IL-2 reporter assay with FK506 derivatives and provides greater retention of biological activity in a hMetAP2 proliferation assay of fumagillol derivatives compared to the first generation pbromophenyl diazo reagent (HBPA). The synthetic utilities of the new alpha-trifluoroethyl diazo reagent (HTFB) provide a great new tool for basic cellular studies facilitating the discovery of new drug candidates for human disease. Furthermore, we are interested in methodologies for beta-lactone synthesis and transformations. In this study, we demonstrated synthetic versatilities of beta-lactones for the synthesis of beta-lactam congeners of orlistat as fatty acid synthase inhibitors via SnCl4- promoted tandem Mukaiyama aldol-lactonization (TMAL) reaction and a one-pot, mild conversion of beta-lactones to beta-lactams. The inhibitory activities of the derived beta-lactam derivatives are determined in a biochemical fluorogenic assay using recombinant FASTE, and the micro-molar range FAS-TE inhibitory activities were observed. Additionally, we pursued synthetic studies toward the total synthesis of spongiolactone, which is a unique beta-lactone-containing marine diterpenoid, isolated from the marine sponge Spongionella gracilis. This natural product bears a unique tricyclic beta-lactone core possessing four contiguous stereogenic centers and an additional stereogenic quaternary carbon on a cyclohexyl appendage. We completed the total synthesis of 6,15-bis-epi-spongiolactone by employing an intramolecular nucleophilecatalyzed aldol-lactonization (NCAL) process as the key step to construct the fused tricyclic beta-lactone core. Importantly, we developed a double diastereoselective and, for the first time, a kinetic resolution via the NCAL process that enables an enantioselective strategy to the tricyclic beta-lactone core of (+)-spongiolactone.