Enantioselective synthesis of indole alkaloids and their application as NMDA antagonists

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Publications

Synthesis of phenylalaninol-derived oxazolopyrrolidone lactams and evaluation as NMDA receptor antagonists

Publication . Pereira, Nuno A. L.; Sureda, Francesc X.; Turch, M.; Amat, Mercedes; Bosch, Joan; Santos, Maria M. M.

N-Methyl-d-aspartate (NMDA) receptor antagonists are known to rescue neuronal cell death caused by excessive activation of glutamate receptors. This phenomenon, known as excitotoxicity, is implicated in the pathogenesis of several neurodegenerative disorders including ischemia, Alzheimer's disease, Parkinson's disease, and Huntington's disease. Unfortunately, some NMDA receptor antagonists have shown discouraging results when tested in clinical trials. However, recent advances in the physiology and pharmacology of the NMDA receptor have kept interest alive in modulating NMDA receptors for therapeutic intervention. We present here the synthesis of a small library of phenylalaninol-derived oxazolopyrrolidone lactams and their evaluation as NMDA receptor antagonists. The compounds were easily synthesized in yields up to 92 %. In addition, one of the compounds has a 50 % inhibitory concentration (IC (50)) of 62 mu M and offers potential to develop more potent NMDA receptor antagonists.

2013Journal article

Open access

Efficient synthesis of spiroisoxazoline oxindoles

Publication . Ribeiro, Carlos J. A.; Kumar, S. Praveen; Moreira, Rui; Santos, Maria M. M.

The synthesis of spiroisoxazoline oxindoles containing ester groups at position 4′ and aromatic or ester groups at position 3′ of the isoxazoline ring is reported. The compounds were synthesized in yields up to 94% by 1,3-dipolar cycloaddition of 3-methylene indolin-2-ones and chlorooximes in the presence of triethylamine or zinc.

2012Journal article

Restricted access

Desenvolvimento de novos antagonistas do recetor NMDA

Publication . Pereira, Nuno Alexandre Lousa; Santos, Maria M. M.; Santos, Daniel J. V. A. dos

O recetor N-metil-D-aspartato (NMDAR) exerce um papel fundamental no controlo da plasticidade sinática nomeadamente nos processos de aprendizagem e memória. No entanto, foi demonstrado que uma atividade exacerbada destes recetores está implicada no desenvolvimento de doenças neurodegenerativas como as doenças de Alzheimer e de Parkinson através de um fenómeno designado por excitotoxicidade. Neste processo, a acumulação na fenda sinática do neurotransmissor glutamato excitatório ativa os NMDAR localizados na membrana neuronal, permitindo o influxo de iões cálcio (Ca2+) para o compartimento celular. A excessiva entrada de Ca2+ ativa uma cascata de sinalização intracelular que culminam em dano mitocondrial assim como em morte neuronal por apotose ou necrose. Nos últimos 30 anos tem-se verificado uma vasta procura por novos antagonistas deste recetor que sejam vantajosos no tratamento da demência mental. De especial interesse são os casos de sucesso dos adamantanos – memantina e amantadina – atualmente utilizados no tratamento de fases avançadas das doenças de Alzheimer e de Parkinson. Esta dissertação consiste no desenvolvimento de novos antagonistas do NMDAR através de modernas técnicas de síntese enantioseletiva para a produção de estudos de estrutura-atividade. Foram sintetizadas pequenas bibliotecas de oxazolo-isoindolinonas, oxazolo-pirrolidonas, oxazolo-piperidonas, indolo[2,3a]quinolizidinas e spiro-indolinas para avaliação biológica como antagonistas do NMDAR. As oxazolo-isoindolinonas revelaram-se como uma nova classe de antagonistas, sendo que o composto mais eficaz desenvolvido apresentou um IC50 de 154μM. Também foram obtidos bons resultados para as oxazolo-pirrolidonas, em que o composto mais eficiente desta série exibiu um IC50 de 62 μM, sendo assim 1.5x mais potente que a amantadina (IC50 = 92 μM). Da mesma forma, as oxazolo-piperidonas também demonstraram ser uma nova classe de antagonistas com um IC50 de 63 μM para o composto ativo mais potente, novamente sendo 1.5x mais potente que a amantadina. No que diz respeito às indolo[2,3a]quinolizidinas, estas também apresentaram atividade como antagonistas do NMDAR. Nesta série, o composto detetado mais potente apresentou um IC50 de 30.4 μM e sendo por isso 3x mais ativo que a amantadina. Quanto às spiro-indolinonas, estes compostos encontram-se de momento em avaliação biológica. Todos os resultados obtidos foram racionalizados com recurso a técnicas de química computacional, nomeadamente por docking molecular e por geração de farmacóforos. Os resultados obtidos sugerem que os novos antagonistas revelados possuem um modo de ação ainda desconhecido. Através deste trabalho foi possível elaborar estudos de estrutura-atividade com estas séries de compostos que revelaram os requisitos estruturais necessários para a atividade como antagonistas do NMDAR.

2014Master thesis

Open access

Design and synthesis of small molecule modulators of p53

Publication . Ribeiro, Carlos Jorge Azevedo Costa, 1980-; Santos, Maria Manuel Duque Vieira Marques dos; Moreira, Rui, 1960-; Rodrigues, Cecília M. P., 1968-

Among the tumor suppressor genes, p53 is one of the most studied. It is widely regarded as the “guardian of the genome”, playing a pivotal part in the preservation of genomic integrity by regulating cell cycle, apoptosis, DNA repair, senescence and angiogenesis, and consequently has a major role in carcinogenesis. The function played by p53 in tumor suppression is further highlighted by the fact that direct inactivation of this gene occurs in more than 50% of malignancies. In addition, in tumors that retain wild type p53 status, its function is usually inactivated by overexpression of negative regulators, primarily murine double minute-2 (MDM2), mainly through MDM2 gene amplification or by activity loss of MDM2 inhibitor ARF. Hence, restoring p53 function in cancer cells represents a valuable anticancer approach. Several strategies are being developed, and in particular targeting p53-MDM2 interaction has emerged as a promising viable approach when dealing with cancers that retain wild type p53 function. These two proteins regulate each other through an autoregulatory feedback loop: activation of p53 stimulates the transcription of MDM2, which in turn binds to the Nterminal transactivation domain of p53, disabling its transcriptional function. p53- MDM2 interaction inhibitors share common structural features: a rigid heterocyclic scaffold with three lipophilic groups that mimic the three pivotal p53 Phe19, Trp23 and Leu26 that interact with MDM2. Seven compounds have already entered clinical trials. The main goal of this PhD thesis was to develop new anticancer agents containing a spirooxindole scaffold with different spiro five-membered rings: isoxazoline, oxadiazoline, and triazolines. The spirocycle can potentially function as the rigid heterocyclic scaffold, from which three lipophilic groups are projected to mimic the three pivotal p53 amino acids. This work followed three major strategies: synthesis of spirooxindole derivatives by 1,3 dipolar cycloaddition; biological evaluation of the compounds synthesized; and stability assessment. Overall this PhD thesis contributed with three new families of spirooxindoles with in vitro anti-cancer activity. The most active derivative possessed a GI50 of 1.72 μM in HCT116 p53(+/+) cell line. Furthermore their ability to disrupt the interaction between p53 and MDM2 was confirmed by implementing a cell-base in vitro bimolecular fluorescence complementation assay (BiFC) and the apoptotic outcome verified by immunoblotting analysis and luminescent caspase 3/7 activity assay.

2015Doctoral thesis

Open access

Enantiopure Indolizinoindolones with in vitro activity against blood- and liver-stage malaria parasites

Publication . Pereira, Nuno A. L.; Monteiro, Ângelo; Machado, Marta; Gut, Jiri; Molins, Elies; Perry, Maria Jesus; Dourado, Jorge; Moreira, Rui; Rosenthal, Philip J.; Prudêncio, Miguel; Santos, Maria M. M.

Malaria continues to be a major cause of morbidity and mortality to this day, and resistance to drugs like chloroquine has led to an urgent need to discover novel chemical entities aimed at new targets. Here, we report the discovery of a novel class of potential antimalarial compounds containing an indolizinoindolone scaffold. These novel enantiopure indolizinoindolones were synthesized, in good-to-excellent yields and excellent diastereoselectivities, by cyclocondensation reaction of (S)- or (R)-tryptophanol and 2-acyl benzoic acids, followed by intramolecular α-amidoalkylation. Interestingly, we were able to synthesize for the first time 7,13b-cis indolizinoindolones in a two-step route. The novel compounds showed promising activity against erythrocytic stages of the human malaria parasite, Plasmodium falciparum, and liver stages of the rodent parasite Plasmodium berghei. In particular, an (S)-tryptophanol-derived isoindolinone was identified as a promising starting scaffold to search for novel antimalarials, combining excellent activity against both stages of the parasite's life cycle with low cytotoxicity and excellent metabolic and chemical stability in vitro.

2015Journal article

Restricted access