In the interests of synthetic efficiency several cascade reactions involving iminium ion intermediates have developed to allow for the rapid assembly of complex molecules from relatively simple starting materials. A cascade methodology for the rapid, diastereoselective synthesis of quinolizidine ring systems has been expanded to encompass a greater range of substrates. The utility of this extension was demonstrated in the efficient syntheses of the tricyclic core structures found in halichlorine and the cylindricine family of alkaloids. Additionally a second cascade sequence has been developed that progresses through an S[subscript N]1 followed by nucleophilic attack on an N-acyl iminium ion to deliver the products of a formal [4+3] cycloaddition. This methodology has been successfully employed to synthesize a [3.3.2] bridgehead system that serves as a key intermediate in a proposed synthesis of (±)-actinophyllic acid. Synthesis of this compound represent progress in the ongoing effort to synthesize this natural product.

Hrušková M.: Alkaloids from the wood of the species Liriodendron tulipifera L. and their activity against human cholinesterase. Diploma thesis, Charles University, Faculty of Pharmacy in Hradec Králové, Department of Pharmaceutical Botany, Hradec Králové, 2018. Key words: Liriodendron tulipifera, alkaloids, biological activity. The alkaloids from the wood of the species Liriodendron tulipifera L. were isolated and their inhibitory activity against acetylcholinesterase, butyrylcholinesterase and propyl oligopeptidase, which are enzymes involved in the pathophysiology of Alzheimer's disease (AD), was investigated. The search and testing of new substances, which are used in AD treatment, is very relevant, as this disease cannot be casually treated yet. An alkaloid extract of Liriodendron tulipifera L. wood was tested in a preliminary testing for inhibitory activity against human cholinesterase. Because of the promising results, it was chosen for an isolation and identification of possible effective alkaloids. The extract was carried out by column chromatography with a step gradient elution. A preparative TLC was used to isolate alkaloids. The identification of alkaloids was done by structural analyses (NMR and MS). Optically active substances were measured for their optical rotation. A modified...

Charles University Faculty of Pharmacy in Hradec Králové Department of Pharmaceutical Botany Candidate: Kamila Lipovská Supervisor: doc. Ing. Lucie Cahlíková, Ph.D. Title of Diploma thesis: Preparation of lycorine derivatives and their biological activity The plants of the Amaryllidaceae family are one of the most important sources of biologically active alkaloids. Lycorine, a phenanthridine alkaloid, isolated from various species of the Amaryllidaceae plant family, has attracted considerable attention due to its promising biological activities. Specifically, its anticancer properties have been evaluated in vitro and in vivo in various preclinical models of human cancers. Further biological effects manifested by lycorine are: antiviral, antibacterial, antifungal, antiplasmodial, anti-oxidant, anti-inflammatory and insect antifeedant effects, as well as ascorbic acid biosynthesis and RNA inhibitory activity. So far, lycorine was used for preparation of many derivatives by modification of different functional groups in its molecule, and screened for a various biological activities such as anticancer activity, inhibition of cholinesterases, antiplasmodial, antitrypanosomal, antiviral and anti-Trichomonas vaginalis activity. The present work deals with the preparation of lycorine derivatives and their...

A proposta deste trabalho experimental in vitro foi avaliar se a incorporação de 1% - em peso - do alcalóide teobromina (Sigma Aldrich, Darmstadt, Alemanha) ao cimento de ionômero de vidro (CIV) convencional (GC Gold Fuji 9, GC Corp, Japão) tem a capacidade de alterar as propriedades físico-químicas desse material. Para tanto, dois grupos experimentais foram propostos: G1 - CIV convencional e G2 - CIV com adição de teobromina. Foram confeccionados 160 discos de CIV de acordo com as instruções do fabricante, utilizando matrizes circulares. Para analisar as mencionadas propriedades, os discos foram submetidos a testes específicos, de acordo com as normas da International Standard Organization (ISO) para cada uma das propriedades. Discos de 15mmx1mm de diâmetro foram utilizados para as provas de sorção (n=5) e de solubilidade (n=5), com o auxílio de balança analítica, dissecadores e estufa a 23 e 37ºC por várias semanas. O ensaio de microdureza foi realizado em amostras (n=20) de 15mm×1mm submetidas a cinco edentações, com carga de 25 gramas e 30 segundos, à temperatura ambiente. Para a avaliação da cor, discos (n=20) de 15mm×1mm foram submetidos ao espectrofotômetro, adotando-se a guia colorimétrica da Comissão internacional de Iluminação (CIE). No ensaio de resistência flexural, os espécimes (n=60) de 12mm×1mm foram armazenados em estufa a 37ºC durante 24 horas para posterior analise na máquina de ensaios universal. Para avaliar a influência da teobromina adicionada ao CIV na formação de biofilme por Streptococcus mutans,, sobre os corpos da prova (n=40) de 12mm×1mm biofilmes foram desenvolvidos. As cepas de S.mutans foram cultivadas em Tryptic Soy Agar (TSA, Difco) a 37°C. Também a dosagem de flúor foi avaliada, em discos de prova (n=10) armazenados em saliva artificial e submersos em solução TISAB para posterior análise com eletrodo de flúor e obtenção da curva da liberação dessa substância. Os dados obtidos nos testes de sorção e solubilidade, microdureza, cor e resistência flexural foram submetidos à análise de variância ANOVA um fator e ao teste de Tukey para comparação entre os grupos, adotando-se 5% de nível de significância (p<0,05). O ensaio da influência da teobromina adicionada ao CIV na quantidade de biofilme de Streptococcus mutans formado e o teste de dosagem de flúor foram submetidos à análise de variância two-way ANOVA e ao teste de Tukey, com nível de significância de 5% para comparação entre os grupos experimentais. O segundo fator avaliado nestes dois ensaios foi o tempo. Os resultados não revelaram alteração da sorção e da solubilidade no CIV que recebeu teobromina (p>0,05). A microdureza aumentou com a adição de teobromina ao CIV (p<0,05). Não houve alteração de cor do CIV que recebeu teobromina (p>0,05). A resistência na flexão biaxial diminuiu quando da adição de teobromina ao CIV (p<0,05). Já a quantidade de biofilme formado foi menor em G2 (p<0,05). Em relação à liberação de flúor, observou-se que a adição de teobromina não altera essa propriedade do CIV (p>0,05). Com base em tais achados, conclui-se que a adição de teobromina a 1% ao cimento do ionômero de vidro convencional não produz alterações significativas nas propriedades desse material, podendo até mesmo otimizar algumas dessas propriedades. Ainda assim, estudos adicionais sobre o assunto devem ser realizados. / The purpose of this experimental in virtro work, was to evaluate if the incorporation of the 1% in weight of an alkaloid: theobromine (Sigma Aldrich Darmstadt, Germany) to the conventional glass ionomer cement (GIC) (GC Gold Fuji 9; GCC Japan Corp) has the capacity to change the properties physicochemical of this material. Whereby, it was proposed two experimental groups: G1 - Conventional GIC and G2 GIC incorporated with theobromine. According to the instructions of the creator, there were created 160 specimens, for which it was used circular matrices. To analyze the mentioned properties, the specimens were analyzed under the International Standard Organization (ISO) for each property. It was used matrices of 15mmx1mm diameter for the sorption (n=5) solubility (n=5) tests. With the help of an analytical balance, desiccators and a stove at 23º and 37° for various weeks; it was made essays of micro firmness using 20 matrices of 15mmx1mm, were submitted to five indentations with a charge of 26 grams and 30 seconds in environmental temperature. For the color evaluation it was used 20 matrices of 15mmx1mm, that were submitted to a spectrophotometer following the colorimetric guide of the International Commission of Illumination (CIE). An essay of biaxial flexural strength was made in 60 matrices of 12mmx1mm that were stored in a stove at 37º for 24 hours, for a later analysis in a universal testing machine. To evaluate the influence of the theobromine incorporated to the glass ionomer cement (GIC) in the creation of biofilm Streptococcus mutans, there were developed 40 matrices of 12mmx1mm of biofilm. The strains of the Streptococcus mutans were cultivated in Tryptic Soy-Agar at 37°. It was also evaluated the fluorine release capacity using 10 test matrices stored in artificial saliva and submerged in TISAB substance for a later analysis with an fluorine electrode, to obtain the release curve of that substance. The obtained information from the test of sorption, solubility, micro strength, color and biaxial flexural strength, were submitted to an analysis of variance ANOVA one factor and Tukey\'s test for a comparison between groups assuming the 5% level of significance (p <0,05). The essay of the influence of the theobromine added to the GIC in the amount of biofilm Streptococcus mutans formed and the test of fluorine release were submitted to the Bidirectional Variance Analysis ANOVA and Tukey\'s test, with a significant level of 5% to the comparison between experimental groups; the second factor evaluated in this two essays was time. The results didn\'t show an alteration in the sorption and solubility in the GIC that received theobromine (p >0,05). The micro strength increased with the addition of the theobromine to the GIC (p< 0,05). There were not any alterations in the color of the GIC that received theobromine (p >0.05). The resistance to the biaxial flexural strength decreased when the theobromine was added to the GIC (p <0.05). The amount of formed biofilm was less in the G2. In relation to the fluorine release it was observed that the addition of theobromine does not change the properties of GIC (p >0.05). Based on these findings, it is concluded that the addition of theobromine in 1% to the conventional glass ionomer cement, does not produce significant changes over this material properties and also, it can optimize some of these properties. However, more studies should be done about this topic.

A ipalbidina é um alcaloide indolizidínico com propriedades analgésica e antirradicais livres. Este alcaloide possui como fonte natural a Ipomoea alba L., uma espécie de dama-da-noite, sendo isolado das suas sementes na forma de aglicona da ipalbina (ligada à D-glicose). A ipalbidina possui estrutura química relativamente simples, porém sua síntese na forma enantiomericamente pura se apresenta como um desafio sintético. Dentre as inúmeras rotas de síntese da ipalbidina, apenas quatro são enantiosseletivas. Neste trabalho de dissertação é apresentada uma nova estratégia sintética visando a preparação da S-(+)-ipalbidina. A estratégia tem como etapas chaves: uma reação de olefinação (Wittig e Horner-Wadsworth-Emmons); a preparação de uma diazocetona e de &alpha;-clorocetonas; e a conversão destas no esqueleto indolizidínico por uma reação de ciclização. Como material de partida para a reação de olefinação foi empregado o S-prolinal protegido (Boc e Cbz). Este aminoaldeído foi empregado como fonte do centro estereogênico e de um dos anéis presentes na estrutura final. A partir das reações de olefinação, foram obtidos compostos carbonílicos &alpha;, &beta;-insaturados que, em seguida, sofreram redução da dupla ligação (28-94%). A partir dos produtos hidrogenados, foram preparados ácidos carboxílicos (66-83%) que, em seguida, foram convertidos na diazocetona (32%) e nas &alpha;-clorocetonas (34-70% a partir de ilídeos &beta;-ceto sulfoxônios). As &alpha; -clorocetonas também foram preparadas a partir de ésteres com bons rendimentos (60-70%). O esqueleto indolizidínico foi obtido a partir da reação de ciclização da diazocetona e das &alpha; -clorocetonas, porém os rendimentos não foram satisfatórios e a metodologia deve ser melhorada. Uma &alpha;-clorocetona mais simples foi reduzida ao álcool correspondente. A &beta;-cloridrina obtida foi convertida no aminoálcool cíclico (indolizidina monoidroxilada, 16%). A preparação deste aminoálcool cíclico sugere que a metodologia desenvolvida é promissora. A nova estratégia sintética pode levar à síntese da (+)-ipalbidina em seis ou sete etapas (uma rota curta). A funcionalização da &alpha;-clorocetona e o melhoramento do método a partir da diazocetona podem também levar à síntese outras indolizidinas. / Ipalbidine is an indolizidine alkaloid with analgesic and antioxidant properties. This alkaloid is isolated from the seeds of Ipomoea alba L., as the aglycone of ipalbine (associated to the D-glucose). The ipalbidine has a relatively simple chemical structure, but its synthesis in the enantiomerically pure form is a synthetic challenge. Although a great number of synthetic routes of ipalbidine have been reported, only four are enantioselective. This dissertation reports new studies toward the synthesis of (+)-ipalbidine. The key steps of the synthetic strategy are: olefination reaction (Wittig or Horner-Wadsworth-Emmons); preparation of a diazoketone and &alpha; -chloroketones; and the cyclization reaction from the diazoketone and &alpha; -chloroketones. A (Boc and Cbz) protected-S-prolinal was used as the initial reagent. This amino aldehyde was employed as the chiral pool and it provides one the rings necessary to build the indolizidine skeleton. A Wittig reaction (88-94%) and a Horner-Wadsworth-Emmons reaction (60-70%) were evaluated for the first step of the synthesis. &alpha;, &beta;-Unsaturated carbonyl compounds were prepared from the olefination reactions and, after that, double bond reduction was carried out under some hydrogenation conditions (28-90%). The carboxylic acids were prepared from the hydrogenated compounds (66-83%). The carboxylic acids were used to prepare the diazoketone (32%) and the &alpha; -chloroketones (34-70% from sulfoxonium ylides). The cyclization reaction from the diazoketone and &alpha; -chloroketones afforded the indolizidine skeleton, but the yields were not satisfactory. The reaction conditions, in this case, need to have to be improved. The &alpha; -chloroketones were also prepared from esters in good yields (60-70%). A simple &alpha; -chloroketone was reduced to the corresponding &beta;-chlorohydrin. After the preparation of this &beta;-chlorohydrin, the cyclization afforded a cyclic amino alcohol (a mono hydroxylated indolizidine, in 16% yield). These results suggest a promising methodology. The present strategy on the synthesis of (+)-ipalbidine can provide this alkaloid in six or seven steps (a short route) and can also be applicable to the syntheses of other indolizidine alkaloids.

Cyanobacteria, also known as blue-green algae, are known to produce a number of biologically active compounds. Extracts of cultured cyanobacteria isolated from South Florida sources were screened for possible developmental toxins using the zebrafish (Danio rerio) embryo as a model of vertebrate development. A strain of cyanobacteria, Fischerella 52-1, isolated from the Florida Everglades, was found to produce metabolites that caused a consistent developmental dysfunction in embryos exposed to lipophilic extract. Initial chemical characterization of the bioactive fraction identified a series of eight apparent indole-containing compounds. The two main components were purified using the zebrafish embryo model to guide the fractionation. Chemical characterization using 1- and 2-dimensional NMR, HESIMS, HRHESIMS, and IR determined that the two main compounds were the previously identified 12-epi-Hapalindole H Isonitrile, and a novel compound 12-epi-Ambiugine B Nitrile. The major contributor of the developmental defects detected in the zebrafish embryos was 12-epi-Hapalindole H Isonitrile.

Significant attention from the medicinal and pharmaceutical communities has been pushed towards the design and development of natural products for defence against many forms of illnesses. The Amaryllidaceae plant family has shown their prevalence over time aiding towards our needs and becoming viable sources of alkaloids due to their wide variety of bioactivities presented. The low availability towards these often-complex structures with at times comprising up to six contiguous chiral centers have made practical testing scarce. More dominantly the isocarbostyrils are well recognized, being hydroxylated phenanthridones providing increased activities making them model targets to test and develop new synthetic strategies towards. These compounds represent a subset of the Amaryllidaceae alkaloids that lack a basic nitrogen center. This thesis describes the total synthesis of four derivatives of the antiviral natural product (+)-trans-dihydronarciclasine from α-azidoacetone and m-anisaldehyde. Herein we demonstrate constructive routes towards ring-A modified, fully functionalized rings-B/C derivatives synthesized via asymmetric chemical syntheses providing further insight into SAR studies. This thesis expands on the organocatalytic [3+3]-cycloaddition sequence to produce aminocyclitol cores providing effective routes towards the development of five stereogenic centers in all targeted ring-C structures. Such studies were attributed to the enal adducts isolated from the Wittig reaction towards four natural product derivatives gaining knowledge related to the targeted molecules mode of action. One additional (+)-transdihydrolycoricidine analogue will be communicated, that enables the imaging while inside live cells with use of alkyne-tag Raman imaging. Limitations of the alkaloids include the toxicity that accompanies these agents and the poor aqueous solubilities they provide, eliciting an increased need for new antiviral agents. The syntheses communicated provide effective routes towards unnatural alkaloids and can be pushed towards alternative chiral aminocyclitol targets for future studies. All compounds have been sent away for screening including against coronavirus at Johns Hopkins. / Thesis / Bachelor of Science (BSc) / This thesis is primarily driven towards the development of four antiviral lycorane structural type alkaloids, and an analogue synthesized via a copper-cocatalyzed Sonogashira reaction, utilizing a labile phenol-derived sulfonated hydroxyl group in its coupling towards an alkyne tagged structure. This method provides easy access for a variety of compounds without a fluorescent tag, taking steps forward in elucidating how the Amaryllidaceae alkaloids are delivering their biological effects. The densely substituted ring-C was obtained via an asymmetric organocatalytic [3+3] sequence for the assembly of the aminocyclitol core and is described. This sequence has provided effective regio, diastereo, and enantioselective access to five unnatural products. Preparation of the precursors were prepared using a Wittig methodology previous reported by the McNulty group that has been used in many syntheses for various Amaryllidaceae alkaloids

no / Leishmania donovani are the causative agents of visceral leishmaniasis worldwide. Lack of vaccines and emergence of drug resistance warrants the need for improved drug therapy and newer therapeutic intervention strategies against leishmaniasis. In the present study, we have investigated the effect of the natural indoloquinoline alkaloid cryptolepine on L. donovani AG83 promastigotes. Our results show that cryptolepine induces cellular dysfunction in L. donovani promastigotes, which leads to the death of this unicellular parasite. Interestingly, our study suggest that cryptolepine-induced cell death of L. donovani is counteracted by initial autophagic features elicited by the cells. For the first time, we show that autophagy serves as a survival mechanism in response to cryptolepine treatment in L. donovani promastigotes and inhibition of autophagy causes an early increase in the amount of cell death. This study can be exploited for designing better drugs and better therapeutic strategies against leishmaniasis in future.

Lycorin gilt bei vielen Amaryllidaceae als Hauptalkaloid und die Aufnahme dieser Pflanzen ist eine häufige Vergiftungsursache bei Mensch und Tier. Als Hauptsymptome infolge dieser Pflanzenvergiftungen werden Nausea und Emesis genannt, aber systematische Untersuchungen zu diesen biologischen Effekten, zum Wirkmechanismus und zur Pharmakokinetik von Lycorin, das als auslösendes Agens angenommen wird, existieren bislang nicht. In der vorliegenden Arbeit werden die Zusammenhänge zwischen verabreichter Lycorin-dosis und Lycorin-induzierter Nausea und Emesis, die Beeinflussbarkeit dieser emetischen Effekte durch etablierte Antiemetika und die Pharmakokinetik von Lycorin in einem cross-over und vehikel-kontrollierten Design in vivo untersucht. Die Studie wurde an elf Beagle-Hunden beider Geschlechter durchgeführt. Die Lycorin-induzierten emetischen Effekte wurden quantifiziert und über Videoaufzeichnungen zeitnah dokumentiert. Nausea wird hierbei mittels eines Scoring-Systems quantifiziert, während die Parameter Latenzzeit, Dauer und Anzahl der Brechakte zur Beurteilung der Emesis herangezogen werden. Die subkutane Applikation von Lycorin induziert, beginnend ab einer Dosis von 0,5 mg/kg KGW Nausea und Vomitus. Eine statistische Signifikanz ist allerdings erst ab 1,0 mg/kg und ein maximaler emetischer Effekt bei einer Dosis von 2 mg/kg (ED100) zu verzeichnen. Die Ergebnisse zeigen eine Korrelation zwischen applizierter Lycorin-Dosis und Nausea-Score sowie der Anzahl der Brechakte. Lycorin-induzierte Nausea und Emesis sind in den vorliegenden Untersuchungen selbstlimitierend und dauern maximal 2,5 Stunden an. Lycorin weist in den untersuchten Dosierungen von 0,25 mg/kg bis 2,0 mg/kg eine lineare Plasmakinetik auf. Nach subkutaner Gabe werden maximale Plasmakonzentrationen (Cmax) nach 0,5 h gemessen, die mittlere Plasma-Halbwertszeit beträgt 0,67 h nach subkutaner, respektive 0,51 h nach intravenöser Applikation. Die errechnete orale Bioverfügbarkeit beträgt ca. 40 %. Das Auftreten von Nausea und Emesis, sowie deren Verlauf decken sich weitestgehend mit dem Verlauf der Lycorinkonzentration im Plasma. In keiner der untersuchten Dosisstufen sind blutchemische oder hämatologische Abweichungen aufgetreten. Um Rückschlüsse auf die Zielstrukturen von Lycorin und somit auf den emetischen Wirkungsmechanismus der Lycorin-induzierten Emesis und Nausea zu gewinnen, wurden die Hunde jeweils mit Diphenhydramin, Maropitant, Metoclopramid, Ondansetron oder Scopolamin vorbehandelt. Diese therapeutisch etablierten Antiemetika besitzen eine selektive Rezeptoraffinität und entfalten ihre antiemetische Wirkung über einen Antagonismus an histaminergen H1- (Diphenhydramin), dopaminergen D2- (Metoclopramid), muskarinergen M1-3- (Scopolamin), serotoninergen 5-HT3- (Ondansetron) oder Neurokinin-1-Rezeptoren (NK1) (Maropitant). Durch die Bindung des jeweiligen Antiemetikums an die spezifischen Rezeptoren, soll die anschließende Bindung von Lycorin an den gleichen Rezeptoren verhindert oder reduziert werden, was sich in einer Reduktion oder Abwesenheit von Nausea und Emesis auswirkt. Die Vorbehandlung mit Ondansetron ist mit einer signifikanten Verminderung der Anzahl der Brechakte verbunden und durch die Vorbehandlung mit Maropitant kann Lycorin-induzierte Emesis komplett verhindert werden. Einzig Ondansetron reduziert darüber hinaus den Ausprägungsgrad der Nausea und verlängert die Latenzzeit bis zum Auftreten von Vomitus, was eine Beteiligung von 5-HT3 Rezeptoren bei lycorin-induzierter Nausea nahe legt. Histaminerge (H1), dopaminerge (D2) und muskarinerge (M1-3) Rezeptoren sind vermutlich nicht an Lycorin-induzierter Nausea und Emesis beteiligt. Die Befunde der vorliegenden Arbeit weisen darauf hin, dass Lycorin bei Vergiftungen mit Pflanzen oder Pflanzenteilen, die zu den Amaryllidaceae gehören, eine entscheidende Bedeutung für die klinische Symptomatik und den Verlauf von Intoxikationen hat. Nach den Ergebnissen dieser Arbeit sind eine prädominierende Beteiligung von NK1- und eine etwas geringer ausgeprägte Beteiligung von 5-HT3-Rezeptoren im emetischen Wirkmechanismus wahrscheinlich. Somit erscheint die therapeutische Anwendung von Maropitant beim Hund (und evtl. Apreptitant beim Menschen) und/oder Ondansetron zur symptomatischen Behandlung anhaltender Nausea und Emesis bei Pflanzenvergiftungen mit Amaryllidacaen bei denen die Wirkung von Lycorin dominiert, wissenschaftlich begründet und klinisch von Vorteil gegenüber anderen antiemetischen Prinzipien zu sein.

Une approche hors ‘pool chiral' du système tricyclique 8b-azaacenaphthylène de l'alcaloïde (-)-205B a été développé. Cet alcaloïde, caractérisé par son squelette tricyclique rarement rencontré dans les produits naturels, a suscité un intérêt scientifique important ces dernières années du à son activité biologique potentiel vis à vis de maladies neurodégénératives. Cependant, due à sa très faible bio-disponsibilitié son mode d'action détaillée est actuellement inconnue. Notre stratégie se caractérise par plusieurs transformations remarquables. Une cycloaddition thermique [2 + 2] hautement stéréosélective et une expansion de cycle via un réarrangement de Beckmann donnent accès à un lactame fonctionnalisé. Une réaction de Mannich vinylogue fournit efficacement un buténolide qui est ensuite rapidement transformé en un motif indolizidinone. Après méthylation de cet intermediaire bicyclique, une réaction de cyclisation de type aza-Prins, rarement utilisée en synthèse, conduit à un intermédiaire avancé possédant le système tricyclique qui caractérise le produit naturel. Ainsi, cette approche défini une base solide pour une nouvelle voie d'accès à cet important et particulièrement rare alcaloïde isolé à partir de peau de grenouille néotropicales Dendrobates pumilio considerée comme espèce protégée. / A non-chiral pool approach to the 8b-azaacenaphthylene ring system of the frog poison alkaloid (-)-205B has been developed. This rare tricyclic alkaloid has been of considerable synthetic interest in recent years owing to its potential biological activity against neuronal disorders. However, due to lack of material, a detailed study of the mode of action of this natural product has not yet been reported. Our strategy features several noteworthy transformations. A highly diastereoselective thermal [2+2] cycloaddition and a ring expansion through Beckmann rearrangement generates the functionalised lactam intermediate. An efficient vinylogous Mannich reaction then provides access to a butenolide, which subsequently leads to an indolizidinone ring system. After installation of a methyl group on this bicyclic intermediate, a relatively unexplored aza-Prins cyclization has been successfully employed to obtain an advanced intermediate, possessing the desired tricyclic system found in the natural product. This approach has laid a solid foundation for a novel access to this potentially important but scarce alkaloid extracted from a neotropical frog Dendrobatus pumilio that is threatened to be endangered.