Terminalia glabrata et Rauvolfia nukuhivensis sont deux espèces végétales polynésiennes endémiques et menacées d’extinction. T. glabrata cohabite avec T. catappa, commune du Pacifique, ce qui contribuerait à sa vulnérabilité par interfertilité. R. nukuhivensis souffre de problèmes de régénération en raison de stress climatiques, de prédation et d’exploitation anthropique. Des approches de génétique et de chimie ont été developpées afin d’étudier ces deux espèces. Pour T. glabrata, les résultats de « barcoding » ont permis d’établir une très forte proximité génétique avec T. catappa. L’analyse métabolomique a révélé une forte variabilité intraspécifique. Les études génétiques de R. nukuhivensis ont permis de relier des espèces distinctes et d’origines géographiques différentes. Elles ont aussi démontré la présence d’un seul groupe de Rauvolfia dont les individus proviennent des îles de Nuku Hiva et de Ua Huka. Ces travaux ont permis d’établir des relations entre les diversités génétiques et chimiques. L’étude des métabolites secondaires de l’écorce de R. nukuhivensis et de la préparation médicinale a permis d’identifier 13 composés, appartenant à 4 familles chimiques (ajmalanes, sarpaganes, macrolines et  carbolines). 8 de ces composés sont nouvellement identifiés dans la nature et une hypothèse de biosynthèse inédite permettant d’expliquer leur co occurrence chez R. nukuhivensis a été établie. Enfin, ces produits ont été soumis à des tests d’activité pharmacologique. La préparation médicinale a stimulé la prolifération cellulaire et la cicatrisation (tissus FHN). Ces tests ont aussi montré la forte inhibition des canaux ioniques Kv11.1 par les nukuhivensiums. / Terminalia glabrata and Rauvolfia nukuhivensis are endangered Polynesian plant species and endemic. T. glabrata co-exists with a common species from the Pacific T. catappa, thus contributing to its vulnerability by interfertility. R nukuhivensis endures regeneration issues due to climate stress, predation and overexploitation. Hence, these species have been classified as protected species by the authorities and are subjected to conservation plans. Because of their heritage value and their traditional uses, they represent species of cultural importance for the country. Genetics and chemistry approaches were conducted for this study. Concerning T. glabrata, barcoding assays established great similarity with T. catappa. Metabolomics data showed infraspecific variability. Phylogenetic data of Rauvolfia species are consistent with their biogeography, and revealed the existence of an only group of individuals from Nuku Hiva and Ua Huka. Genetic diversity is linked to phytochemical occurence. Investigation of R. nukuhivensis bark metabolites and the traditional remedy led to identification of 13 isolated compounds within 8 new ones, belonging to the ajmalan, sarpagan, macroline and β-carboline skeleton. The co-occurrence of these alkaloid skeletons led to establish an unprecedented biosynthesis route. Finally, isolated compounds and the traditional remedy were submitted to bioassays. The traditional remedy induced cell proliferation and wound healing activities on FHN cells and ion channels Kv11.1 were strongly inhibited by

The presented master thesis is focused on an integration of plant alkaloids' curriculum into education process at eight-year grammar schools or their equivalent at primary and secondary schools. The aims of the thesis are to provide a basic data about plant alkaloids, to specify an integration of the plant alkaloids into the curricular documents and to select specific and suitable methods for teaching of the alkaloid topic at schools. These teaching methods were practically verified at the Karel Čapek's Grammar School at Dobříš by using author's proposals of the school lesson, the project teaching and laboratory exercises. In the terms of benefits for students, it has been verified that the teaching of plant alkaloids using the teaching project and the laboratory exercises, can be performed more efficiently than those during an "ordinary" school lesson. Key words: plant alkaloids, teaching methods, teaching lesson, project method, laboratory exercise, biology, chemistry

Datura metel is a herbaceous plant found in almost all tropical parts of the world. It belongs to the family Solanaceae whose members, viz. Duboisia, Atropa, Hyoscyamus and Datura plants are known to produce tropane alkaloids- hyoscyamine and scopolamine which are most noted for their therapeutic use as anti-cholinergic agents. Since these alkaloids are produced in very low amounts in plants, alternative sources and methods of production for these alkaloids have been crucial in meeting the demands for these drugs. Endophytic fungi inhabiting a plant may have the potential to produce the same compounds as the host plants. The aim of the present study was to search for tropane alkaloid producing endophytic fungal isolates from Datura metel. Eighteen endophytic fungi were isolated from various tissues of Datura metel and screened for the presence of three tropane alkaloid biosynthetic genes- putrescine N-methyltransferase (PMT), tropinone reductase I (TRI) and hyoscyamine 6β-hydroxylase (H6H) using PCR-based screening approach. Six endophytic fungal isolates were found to possess the PMT, TR1 and H6H genes. The fungi were identified using molecular taxonomy as Col letotrichum boninense, Phomopsis sp., Fusarium solani, Col letotrichum incarnatum, Col letotrichum siamense and Col letotrichum gloeosporioides and the identity was confirmed using colony and spore morphology. The production of tropane alkaloids hyoscyamine and scopolamine by the fungi has been ascertained using various techniques like TLC, HPLC and ESI-MS/MS by comparison with the authentic reference standards. The amount of tropane alkaloids produced by all six fungi in liquid cultures was quantified using HPLC analysis. Among the six tropane alkaloid-producing fungi Col letotrichum incarnatum gave the highest yields of hyoscyamine and scopolamine which were 3.906 mg/L and 4.13 mg/L, respectively. With an aim to characterize the tropane alkaloid biosynthetic genes in these fungi, the PMT gene was isolated from five of the endophytic fungi- Col letotrichum boni-nense, Fusarium solani, Col letotrichum incarnatum, Col letotrichum siamense and Col-letotrichum gloeosporioides for the first time and the sequence analysis showed high ho-mology (98%) to the Datura metel PMT cDNA. The gene was found to be devoid of introns in the fungi. Further phylogenetic analysis of the full length PMT sequence from the fungi strongly supports the hypothesis of horizontal gene transfer between the host plant and endophytic fungi. For further in detail characterization of fungal PMT, the Col letotrichum boninense PMT gene was taken as a representative. CbPMT gene was cloned in pRSET A expres-sion vector and heterologously expressed in E. coli and biochemically characterized. For optimal yield of soluble protein upon heterologous expression different conditions such as IPTG concentration, temperature and time post induction were optimized. Optimal yield was obtained by inducing the culture by 0.25 mM IPTG once it had reached and O.D. of 0.6 and incubating at 37◦ C for 3 h. The recombinant CbPMT enzyme expressed as histidine tagged fusion protein was purified using Ni-NTA affinity chromatography. Gel elution studies were carried out to determine molecular weight of the protein and it was found that the protein exists as a homodimer in solution with some amount also present as a monomer. Catalytic activity of the purified recombinant enzyme was studied for its dependence on both substrates putrescine as well as S-adenosylmethionine (SAM). The Km and Vmax values for putrescine were found to be 464 µM and 18.55 nkat/mg, respectively, while those for S-adenosylmethionine were found to be 628 µM and 18.63 nkat/mg, respectively. Optimum temperature for activity was found to be 37◦ C and optimum pH range was found to be 8-9. Fluorescence spectroscopy was used to study the binding affinity of both the sub-strates to the enzyme. Fluorescence quenching data for each substrate was analysed by using a nonlinear regression curve fit and Kd values were found to be 0.309 mM for pu-trescine and 0.118 mM for SAM, respectively. Circular dichroism spectrum of the enzyme indicated a pattern typical for alpha helix in the secondary structure. Binding of either substrate led to increase in ellipticity of the protein. Fluorescence quenching studies with collisional quenchers- acrylamide, potassium iodide, and cesium chloride indicated that the native protein is folded in a conformation that allows tryptophan residues to be acces-sible for quenching. The fraction of tryptophan residues (fa ) accessible for quenching by acrylamide (1.06) was found to be higher than that for potassium iodide (0.54) while that cesium ions was the least (0.38). The neutral quencher acrylamide could access all the tryptophans meaning that none of tryptophans are completely buried inside hydrophobic cores. the differential accessibility to the charged quenchers, however, indicates that more of the tryptophans are surrounded by positively charged amino acids. The unfolding of the protein was studied with the aid of chaotropic agents guanidine-HCl and urea and thermodynamic parameters were determined. The denaturant m-values were found to be 2.313 kcal/mol/M for Gdn-HCl and 2.345 kcal/mol/M for urea respectively. The free energy of unfolding was estimated to be 2.635 kcal/mol for Gdn-HCl and 4.630 kcal/mol for urea. Since no reports are available about the thermodynamics of folding and unfolding of PMT from any plant source, this study contributes towards the understanding of protein stability. Although a lot of reports are available on the biochemical characterization of PMT from different plant sources, the crystal structure of PMT is not yet available. In the current work, homology based modelling studies on CbPMT were carried out to get some idea about the protein tertiary structure. Homology based modelling studies showed that a significant amount of protein is present as α-helices which are present on the surface while the β-sheets are present in the interior of the protein. Each monomer of the protein is capable of binding both the substrates and hence the dimerization property of the enzyme could be a purely structural one leading to more stability and solubility of the protein. In conclusion, this study has shown for the first time that endophytic fungi have significant potential to be used for tropane alkaloid production and six such fungal strains have been identified. Although the production of tropane alkaloids by endophytic fungi is not very high, it can be scaled up by over-expressing the biosynthetic gene putrescine N-methyltransferase in the highest producer- Col letotrichum incarnatum to further increase the yield. These endophytic fungi have significant potential to be applied in fermentation technology to meet the demands for these drugs economically.

The thesis entitled “Enantiospecific total synthesis of indole alkaloids eburnamonine, aspidospermidine, quebrachamine, henrycinols A and B and synthesis of azepino[4,5-b]indolones” is divided into three chapters. In the first chapter, a unified strategy for the enantiospecific total synthesis of monoterpene indole alkaloids (+)-eburnamonine (1), (–)-aspidospermidine (2) and (–)-quebrachamine (3) is described. The chiral pool synthesis commenced with (S)-ethyl lactate 4, which was elaborated to the allylic alcohol 5. Johnson-Claisen orthoester rearrangement of the allylic alcohol 5 furnished the key chiral building block 6 possessing a quaternary stereogenic center. Pictet-Spengler cyclization of tryptamine with the corresponding aldehydes obtained by appropriate functionalization of the chiral building block 6 and ring closing metathesis were the key reactions employed en route the total synthesis of the indole alkaloids 1–3 (Scheme 1). Scheme 1. Unified strategy for the synthesis of monoterpene indole alkaloids (+)-eburnamonine (1), (–)-aspidospermidine (2) and (–)-quebrachamine (3). The second chapter of the thesis pertains to the synthesis of azepino[4,5-b]indolones 7 via Brønsted acid mediated intramolecular cyclization of unsaturated tryptamides 8. Various ,-unsaturated acids 9 derived from different -hydroxy esters 10, were converted to the corresponding unsaturated tryptamides 8 and subjected to the optimized reaction conditions. The results of the study indicated that -substituted unsaturated secondary tryptamides derived from (S)-ethyl lactate were the most effective in undergoing an intramolecular cyclization to furnish the corresponding azepino[4,5-b]indolones 7, possessing a quaternary stereogenic center in good yields. The presence of an alkenyl moiety in the quaternary center allowed the functionalization of these compounds and was subsequently employed to access the ABCD core 11 of tronocarpine and the tetracyclic cores 12 of some iboga alkaloids. The loss of chirality in the formation of the azepino[4,5-b]indolones indicated that the reaction proceeds predominantly by an SN1 pathway. During the course of the study an interesting formation of an azonino[5,4-b]indolone 13 by a competing SN1 pathway and a tetracyclic azepino[4,5-b]indolone 14 via a cascade cyclization were noticed (Scheme 2). Scheme 2. Synthesis of azepino[4,5-b]indolones 7 possessing a quaternary stereogenic center. The first total synthesis of two new indole alkaloids, henrycinols A (15) and B (16) which were isolated from the plant Melodinus henryi CRAIB is described in the third chapter of the thesis. The key reaction in the synthetic sequence is the Pictet-Spengler cyclization of L-tryptophan methyl ester 17a and the aldehyde 18 derived from D-tartaric acid which leads to the installation of all the stereogenic centers present in the natural products. Interestingly, a switch in the diastereoselectivity of the reaction was observed by varying the substituent on the amine in L-tryptophan methyl ester 17. When L-tryptophan methyl ester 17b possessing an N-allyl substitution was employed, the desired 1,3-trans tetrahydro--carboline 19b could be obtained in good yields, which was subsequently elaborated to the natural products 15 and 16 (Scheme 3). Scheme 3. Total synthesis of henrycinols A (15) and B (16).

Les travaux présentés dans ce mémoire décrivent une nouvelle voie de synthèse d'aminoalcools 1,2 à partir de γ-bromo-β-cétosulfoxydes, dans lesquels seul le centre stéréogène du soufre est défini. Cette synthèse s'appuie sur deux processus hautement stéréocontrôlés dirigés par le groupement sulfoxyde : le dédoublement cinétique dynamique lors de la substitution nucléophile du brome par la dibenzylamine et la réduction diastéréosélective du carbonyle. Les syn-γ-N,N-dibenzylamino-β-hydroxysulfoxydes correspondants ont été obtenus avec des excès diastéréoisomériques supérieurs à 95%. Les syn-γ-N,N-dibenzylamino-β-hydroxysulfoxydes se sont avérés être des intermédiaires très intéressants pour la synthèse de produits comportant le motif aminoalcool 1,2. Ainsi, nous avons décrit la préparation d'un 3-N,N-dibenzylamino-1,2-diol et son utilisation dans une nouvelle stratégie de déprotection régiodivergente d'acétals cycliques. Nous avons également décrit un nouvel accès aux cis-2-méthyl-6-alkylpipéridin-3-ols, via l'ouverture de cycle d'un 3-N,N-dibenzylamino-1,2-époxyde par l'azaénolate dérivé d'une hydrazone, et l'avons appliqué à la synthèse d'un alcaloïde, la (+)-déoxocassine. Parallèlement, nous avons débuté une étude de synthèse d'aminoalcools 1,3 par la réduction diastéréosélective d'une oxime dérivée d'un δ-céto-β-hydroxysulfoxyde. / In this thesis manuscript, we report on a new pathway to 1,2-aminoalcohols starting from chiral nonracemic γ-bromo-β-ketosulfoxides. This two-step approach, where the stereo control is provided by the sulfoxide group, relies on a highly stereocontrolled nucleophilic substitution of the bromine by dibenzylamine, combined with a dynamic kinetic resolution process, and the reduction of the carbonyl group. The corresponding syn-γ-N,N-dibenzylamino-β-hydroxysulfoxides were obtained with more than 95% diasteroisomeric excess. These syn-γ-N,N-dibenzylamino-β-hydroxysulfoxides turned out to be very useful intermediates for the synthesis of aminoalcohol containing products. Thus, we described the preparation of a 3-N,N-dibenzylamino-1,2-diol, and its use in an original strategy of regiodivergent cyclic acetals deprotection. We also developed a new access to "all cis"-2-methyl-6-alkylpiperidin-3-ols, by the mean of a 3-N,N-dibenzylamino-1,2-epoxide ring opening reaction with the azaenolate derived from an hydrazone. We applied this methodology to the synthesis of an alkaloid, (+)-deoxocassine. In addition, we studied a synthesis of 1,3-aminoalcohols using a diasteroselective reduction of a δ-keto-β-hydroxysulfoxyde-derived oxime.

This work describes the results obtained from the phytochemical study, chemometric analysis and activity cytotoxic in vitro and in vivo of the leaves Guatteria pogonopus Mart., a species of Annonaceae that occurs in Sergipe. The leaves were subjected to two processes. In the first, the leaves were conducted extraction and the study of the chemical composition of the essential oil, considering the seasonality effect; in the second, the isolation of fixed compounds was performed on order to identify alkaloids. Both studies were evaluated towards the antitumor activity in vitro and in vivo. Yields of essential oils ranged from 0.34 % for the month of October/2012 to 0.10 % for the month of September/2012. This variation can be explained by the climate, which the rainfall was higher in September compared to October. This means that the greater the amount of precipitation, reduced yield. The sesquiterpene hydrocarbons were the main constituents of the oils in the samples, with the highest concentration in the month of July/2012 (71.93 %). They were identified as á- and â-pinene, bicyclogermacrene, germacrene B, ã-patchoulene, spathulenol, á-santalene, (E)-caryophyllene, ã-elemene and globulol. In Principal Component Analysis (PCA), both CP1 and CP2 components can explain 90 % of the total variance. It is remarkable that several compounds have focused on the right of the axis of CP1. This phenomenon explains the regularity of the percentage that appears in each month. The ã-patchouleno, spathulenol and bicyclogermacrene compounds protrude to the left of the axis of CP1. Which are the major compounds of the composition of essential oils predominant in all sampling months. In addition to these one can see (E)-caryophyllene and á-santalene, to a lesser prominence this axis. In Hierarchical Cluster Analysis (HCA) formed groups because of similarities. The results of the in vitro antitumor activity of essential oil showed pronounced cytotoxic activity against NCI-H358M, PC-3M and OVCAR-8 lines. In vivo study oil was able to inhibit tumor growth, thus indicating that the essential oil has a significant antitumor potential. Phytochemical study the alkaloidal sheets from the fraction of methanol extract was possible to date the isolation of six alkaloids encoded as GP-1 (nornuciferine), GP-2 (isocorydine), GP-3 (mixture of the nornuciferine and anonaine), GP-4 (lisycamine) and GP-5 (liriodinene). The identification of the alkaloids was performed by 1D/2D 1H and 13C NMR, MS and GC/MS, and comparison with authentic standards and literature data. The cytotoxicity assay performed with single concentration in the extracts and fractions (50 mg/ml) and basic substances (25 mg/mL) revealed promising results with minimal inhibition of 50 % of at least one tumor cell lines. Among the extracts, fractions and evaluated substance, the alkaloidal fraction and compounds GP-1 were the most active against strains B16-F10 and HepG2. Because the activities presented and in order to obtain the IC50 for these two samples front lines K562, HL-60 cells and PBMC were also evaluated. Both the alkaloidal fraction and the compound GP-1 showed good results. The results indicated that G. pogonopus is a biologically active cytotoxic properties with promising source of compounds. / Este trabalho descreve os resultados do estudo fitoquimico, analise quimiometrica e investigacao citotoxica in vitro e in vivo das folhas de Guatteria pogonopus Mart. uma especie de Annonaceae de ocorrencia em Sergipe. As folhas foram submetidas a dois processos: no primeiro, foi realizada a extracao e o estudo da composicao quimica do oleo essencial, levando em consideracao o efeito da sazonalidade. Enquanto que no segundo, foi realizado o isolamento de compostos fixos visando a identificacao de alcaloides. Ambos estudos foram avaliados frente a atividade antitumoral in vitro e in vivo. Os rendimentos dos oleos essenciais variaram de 0,34% para o mes de outubro/2012 a 0,10% para o mes de setembro/2012. Essa variacao pode ser explicada pelo clima, o qual o indice pluviometrico foi maior para setembro em relacao a outubro. Isso significa, que quanto maior a quantidade de precipitacao, menor o rendimento. Os sesquiterpenos hidrocarbonetos foram os constituintes majoritarios nas amostras dos oleos, com maior concentracao no mes de julho/2012 (71,93%). Os constituintes majoritarios identificados foram Ñ- e £]-pineno, biciclogermacreno, germacreno B, £^-patchouleno, espatulenol, £-santaleno, (E)-cariofileno, £^-elemeno e globulol. Na Analise de Componentes Principais (ACP), as duas componentes CP1 e CP2 conseguem explicar mais de 90% da variancia total dos dados. E possivel notar que varios compostos se concentraram na direita do eixo da CP1. Esse fenomeno explica a regularidade da porcentagem que aparece em cada mes. Os compostos £^-patchouleno, espatulenol e biciclogermacreno se sobressaem para esquerda do eixo da CP1. Os quais sao os compostos majoritarios da composicao dos oleos essenciais predominante em todos os meses de coleta. Na Analise de Agrupamento Hierarquico (AAH) formaram-se grupos devido a semelhancas. Os resultados da atividade antitumoral in vitro do oleo essencial indicaram pronunciada atividade citotoxica contra as linhagens de NCI-H358M, PC-3M e OVCAR-8. No estudo in vivo o oleo foi capaz de inibir o crescimento tumoral, indicando assim, que o oleo essencial apresenta um potencial antitumoral significativo. Do estudo fitoquimico da fracao alcaloidica do extrato metanolico foi possivel ate o momento o isolamento de seis alcaloides codificados como GP-1 (nornuciferina), GP-2 (isocoridina), GP-3 (nornuciferina e anonaina em mistura), GP-4 (lisicamina), GP-5 (liriodenina). A identificacao dos alcaloides foi realizada por RMN de 1H e 13C 1D/2D, EM e CG/EM, bem como comparacao com padroes autenticos e dados da literatura. O ensaio de atividade citotoxica em concentracao unica realizado com os extratos e fracoes (50 £gg/mL) e substancias puras (25 £gg/mL), revelaram resultados promissores com inibicao minima de 50% de pelo menos uma das linhagens tumorais. Entre os extratos, fracoes e substancia avaliadas, a fracao alcaloidica e o composto GP-1 foram os mais ativos contra as linhagens B16-F10 e HepG2. Devido as atividades apresentadas e com o objetivo de se obter a CI50 essas duas amostras tambem foram avaliadas frente as linhagens de celulas K562, HL-60 e PBMC. Tanto a fracao alcaloidica como o composto GP-1 apresentaram bons resultados. Os quais indicaram que G. pogonopus e uma fonte promissora de compostos biologicamente ativos com propriedades citotoxicas.

Polycyclic nitrogen containing heterocycles form the basic skeleton of numerous alkaloids and physiologically active drugs. Alloyohimbane was obtained from 3,4-dihydro-â-carboline using an iron-mediated [2+2+1] cycloaddition as the key-step. The bis-TMS-diyne was conveniently obtained by the C-alkylation of 3,4-dihydro-â-carboline followed by N-alkylation. Demetalation of the iron-complex followed by hydrogenation, E-ring expansion, and reduction provided alloyohimbane, a structurally and biologically interesting substance, via a linear eight-step sequence in 7% overall yield based on 3,4-dihydro-â-carboline. Another sequence provided (±)-alloyohimbane and (±)-3-epi-alloyohimbane in nine steps. The pyrrole unit occurs in a variety of naturally occurring compounds, pharmaceutical products and polymers. A novel two-step procedure for the synthesis of pyrroles by addition of a propargyl Grignard reagent to a Schiff base and subsequent silver(I)-promoted oxidative cyclization of the resulting homopropargylamine has been developed. The generality of this reaction was proven by the synthesis of a broad variety of substituted pyrroles using silver(I)-promoted cyclization. A three-step synthesis of (±)-harmicine, a natural product isolated from the Malaysian plant Kopsia griffithii having strong anti-leishmania activity, from 3,4-dihydro-â-carboline is achieved by addition of 3-trimethylsilylpropargyl Grignard reagent, Ag(I)-promoted oxidative cyclization to a pyrrole, and chemoselective hydrogenation of pyrrole ring. Total synthesis of anti-tumor active crispine A and biologically active 1,2,3,5,6,10b-hexahydropyrrolo[2,1-a]isoquinoline have been achieved in three steps using silver(I)-promoted oxidative cyclization as key step.

Pavuková, S.:Vinca minor L. alkaloids and their biological activity II. Diploma thesis, Charles University, Faculty of Pharmacy in Hradec Králové, Department of Pharmaceutical Botany, Hradec Králové 2020. Vinca minor L. is a species of species of flowering plant, native mainly to central and southern Europe, which containst more than 50 indole alkaloids. During screening of potential plant inhibitors against human acetylcholinesterase (hAChE) and butyrylcholinesterase (HBChE) at our department, an alkaloidal extract from dried aerial parts of Vinca minor demonstrated strong and selective hBChE inhibitory activity with an IC50 value of 13.60 ± 0.83 μg/mL, however, against hAChE was inactive (IC50 value >100 μg/mL). The fraction VM 323 - 327 (4,72 g) was separated by column chromatography on silica gel again with stepwise elution by using chloroform and ethanol and overall 7 joined fractions were obtained.Subsequently, repeated preparative TLC on silica gel led to isolation of three compounds; the newly isolated substance SP-1, (-)-picrinine (SP-2) and deacetylakuammiline (SP-3). Their structures were elucidated with mass spectrometry (ESI), NMR and optical rotation. Isolated alkaloids were tested on ability to inhibit AChE, BuChE, POP a GSK-3β, which are enzymes playing an important role in...

L’étude chimique de 11 plantes du Gabon, dont certaines utilisées en médecine traditionnelle, a été réalisée à la recherche de composés antiplasmodiaux de structures nouvelles. Deux Apocynaceae (Pleiocarpa mutica Benth., Callichilia inaequalis Stapf) et une Gelsemiaceae (Mostuea brunonis Didr.) ont été plus spécifiquement étudiées, via une stratégie de déréplication fondée sur des réseaux moléculaires générés à partir de données CLHP-MS/MS (Molecular Networking) et annotés avec une base de données d’alcaloïdes indolomonoterpéniques mise au point au laboratoire (MIADB). Cette investigation a guidé un travail de fractionnement et d’isolement, qui a permis l’obtention d’alcaloïdes indolomonoterpéniques très originaux, en termes de décorations ou de modes d’assemblage.Des écorces de tiges de P. mutica, 7 dimères indolomonoterpéniques non décrits dans la littérature ont été obtenus : 5 sont des bis-aspidofractanes dont 4 sont reliés par un pont méthylène (pléiokomenines A-D) ; deux sont des dimères du type aspidofractane-éburnamine, analogues de la pléiomutine.Les tiges et les racines de C. inaequalis ont livré 2 bis-indoles nouveaux, analogues de la criophylline, dont le premier porteur d’un sulfate dans cette classe d’alcaloïdes, ainsi que l’inaequalisine A, premier indolomonoterpène monomérique lié à un reste phénylpropène via une liaison C-C.L’étude des tiges et des feuilles de M. brunonis a conduit à l’isolement de quatre nouveaux composés : un monomère de type sarpagine (16-epi-méthylester-panarine) et 3 dimères bis-vobasines inédits à pont sulfide (théionbrunonines A-C). Des molécules connues, mais pas toujours identifiées dans les genres étudiés, ont également été isolées. Plusieurs des composés nouveaux présentent une activité antiplasmodiale de l’ordre du µM in vitro sur une souche de Plasmodium falciparum chloroquino-résistante. / The chemical study of 11 Gabonese plant species, some being used in traditional medicine, was performed in search of antiplasmodial compounds with new structures. Two Apocynaceae (Pleiocarpa mutica Benth., Callichilia inaequalis Stapf) and a Gelsemiaceae (Mostuea brunonis Didr.) were more specifically investigated, using LC-MS/MS data in a dereplicative approach based on the “molecular networking” strategy, with an annotation performed using an “in-house” monoterpene indole alkaloids database (MIADB). This approach was used to guide the isolation of original alkaloids, in terms of substitution patterns or of linkage. From the stem bark of P. mutica, 7 previously undescribed bis-indoles were obtained: five are bis-aspidofractanes, four of them being linked by a methylene bridge (pleiokomenines A-D); Two are aspidofractane-eburnane dimers analogous to pleiomutine. The twigs and roots of C. inaequalis yielded 2 new bis-indoles analogous to criophylline, among which one is the first natural sulfate-bearing indole monoterpene. Inaequalisine A, the first monomeric indole monoterpene linked to a phenylpropene moiety by a C-C linkage was also obtained.The study of the twigs and leaves of M. brunonis lead to 4 new compounds: A monomeric sarpagine (16-epi-methylester-panarine) and 3 unknown bis-vobasines which constituting monomers are linked by a sulfide bridge (theionbrunonines A-C).Known compounds were also isolated, some of which were previously undescribed in the genera studied here. Several of the new molecules exhibited antiplasmodial in vitro activity in the micromolar range against a chloroquine-resistant strain of P. falciparum.

Die Ziele dieser Arbeit waren die Darstellung der Naturstoffe Murrayachinon-B–E und Pyrayachinon-A–C, sowie die Synthese einiger nicht natürlicher, potentiell anti-Tuberkulose-aktiver Carbazole und Carbazolchinone. Für die Darstellung der aus der Pflanze Murraya euchrestifolia Hayata isolierten Naturstoffe wurden verschiedene synthetische Herangehensweisen untersucht: Die Transformation eines 7 Hydroxycarbazolchinons in die Zielverbindungen gelang nicht, ebenso wie die Syntheseroute über eine trioxygenierte Vorstufe. 7-Methoxy-3-methyl-1-tosyloxycarbazol (A) ließ sich jedoch in einer Ausbeute von 76 % über drei Stufen darstellen. Ausgehend von A konnten die Zielverbindungen regioselektiv in fünf bis sieben Stufen in Gesamtausbeuten von 10 % bis 46 % synthetisiert werden. Der Pyranring in Pyrayachinon-A wurde dabei über eine Sequenz aus Bromierung, Prenylierung, Cyclisierung und Oxidation aufgebaut. Die Anellierung der Pyranringe in Pyrayachinon-B und –C erfolgte, nach Methyletherspaltung an A in zwei Stufen. Die Einführung der Prenyl- und Geranylgruppen für die Synthese der Murrayachinone gelang durch reduktive Pyranringöffnung bzw. über eine Sequenz aus Methyletherspaltung, Propargylierung, partieller Hydrierung und Umlagerung. Außerdem wurde für Murrayafolin-B, Bismurrayafolin-B und -D über diese Syntheseroute ein Zugang geschaffen. Diese Verbindungen konnten, ausgehend von A, in sechs bzw. sieben Stufen in Gesamtausbeuten von 39 % bis 53 % dargestellt werden. Im Vergleich zu den bislang beschriebenen Synthesen dieser Verbindungen konnten alle Gesamtausbeuten signifikant gesteigert werden. Besonders hervorzuheben sind die Synthesen von Murrayafolin-B (bislang: 0.4 %, in dieser Arbeit: 40.0 %) und Pyrayachinon-A (bislang: 3.0 %, in dieser Arbeit: 22.1 %). Überdies wurde erstmalig die palladiumkatalysierte oxidative Cyclisierung eines O-tosylgeschützten Diarylamins zu einem Carbazol beschrieben. In Fortführung vorangegangener Arbeiten wurden zehn bislang nicht beschriebene Derivate des anti-Tuberkulose-aktiven 3-Methoxy-2-methylcarbazol-1,4-chinons dargestellt, darunter neun Carbazolchinone und ein Carbazol. Die Synthese der Carbazolchinone gelang palladiumkatalysiert in je vier bis sechs Stufen. Das Carbazol wurde eisenvermittelt über fünf Stufen dargestellt. Die Untersuchung der Aktivität gegenüber Mycobacterium tuberculosis steht noch aus.