Loading...
137 results
Search Results
Now showing 1 - 10 of 137
- Synthesis of 2-{2-[5(4)-aryl-2H-[1,2,3]-triazol-4(5)-yl]vinyl}chromen-4-onesPublication . Albuquerque, Hélio; Santos, Clementina M.M.; Silva, Artur; Cavaleiro, JoséChromones are a family of oxygen-containing heterocyclic compounds that have been shown particular relevant biological activity. In what concerns to 2-methylchromones, their reactivity is well-known and allowed to exploit many different kinds of chemical reactions. The acidic character of the 2-methyl group, due to the low electron density at C-2 caused by carbonyl group enable this class of compounds to undergo oxidation, photolysis, cycloaddition and condensation reactions
- Six-membered ring systems: with O and/or S atomsPublication . Santos, Clementina M.M.; Silva, ArturA large variety of publications have emerged in 2012 involving O- and S-6- membered ring systems. The increasing number of reviews and other communica- tions dedicated to natural and synthetic derivatives and their biological significance highlights the importance of these heterocycles. Reviews on natural products involve biosynthesis and isolation of enantiomeric derivatives h12AGE4802i, biosynthesis, isolation, synthesis, and biological studies on the pederin family h12NPR980i and xanthones obtained from fungi, lichens, and bacteria h12CR3717i and on the potential chemotherapeutic value of phyto- chemical products and plant extracts as antidiabetic h12NPR580i, antimicrobial, and resistance-modifying agents h12NPR1007i. A more specific review covers a structure–activity relationship of endoperoxides from marine origin and their antitry- panosomal activity h12OBC7197i. New synthetic routes to naturally occurring, biologically active pyran derivatives have been the object of several papers. Different approaches have been discussed for the total synthesis of tetrahydropyran-containing natural products (")-zampanolide h12CEJ16868, 12EJO4130, 12OL3408i, (")-aspergillides A and B h12H(85)587, 12H(85)1255, 12TA252i, (þ)-neopeltolide h12JOC2225, 12JOC9840, 12H(85) 1255i, or their macrolactone core h12OBC3689, 12OL2346i. The total synthesis of bistramide A h12CEJ7452i and (þ)-kalihinol A h12CC901i and the stereoselec- tive synthesis of a fragment of bryostatin h12S3077, 12TL6163i have also been sur- veyed. Other papers relate the total synthesis of naturally occurring carbocyclic and heterocyclic-fused pyran compounds, such as (")-dysiherbaine h12CC6295i, penos- tatin B h12OL244i, Greek tobacco lactonic products, and analogues h12TL4293i and on the structurally intriguing limonoids andhraxylocarpins A–E h12CEJ14342i. The stereocontrolled synthesis of fused tetrahydropyrans was used in the preparation of blepharocalyxin D h12AGE3901i. Polyphenolic heterocyclic compounds have also received great attention in 2012. The biological activities and the chemistry of prenylated caged xanthones h12PCB78i, the occurrence of sesquiterpene coumarins h12PR77i, and the medicinal properties of the xanthone mangiferin h12MRME412i have been reviewed. An overview on the asymmetric syntheses of flavanones and chromanones h12EJO449i, on the synthesis and reactivity of flavones h12T8523i and xanthones h12COC2818i, on the synthesis and biosynthesis of biocoumarins h12T2553i, and on the synthesis and applications of flavylium compounds h12CSR869i has been discussed. The most recent developments in the synthesis and applications of sultones, a very important class of sulfur compounds, were reported h12CR5339i. A review on xanthene-based fluorescent probes for sensing cations, anions, bio- logical species, and enzyme activity has described the spiro-ring-opening approach with a focus on the major mechanisms controlling their luminescence behavior h12CR1910i. The design and synthesis of other derivatives to be used as sensors of gold species h12CC11229i and other specific metal cations h12PC823i have also been described. Recent advances related to coumarin-derived fluorescent chemosen- sors for metal ions h12COC2690i and to monitoring in vitro analysis and cellular imaging of monoamine oxidase activity h12CC6833i have been discussed. The study of various organic chromophores allowed the synthesis of novel dica- tionic phloroglucinol-type bisflavylium pigments h12SL2053i, and the optical and spectroscopic properties of several synthetic 6-aryldibenzo[b,d]pyrylium salts were explored h12TL6433i. Discussion of specific reactions leading to O- and S-membered heterocyclic compounds covers intramolecular radical cyclization h12S2475i and asymmetric enamine and dienamine catalysis h12EJO865i, oxa-Michael h12CSR988i and dom- ino Knoevenagel–hetero-Diels–Alder (hDA) reactions h12T5693i, and the versatility in cycloadditions as well as nucleophilic reactions using o-quinones h12CSR1050i. The use of specific reagents relevant to this chapter includes molecular iodine h12CEJ5460, 12COS561i, samarium diiodide–water for selective reductive transfor- mations h12CC330i, o-quinone methides as versatile intermediates h12CEJ9160i, InCl3 as catalyst h12T8683i, and gold and platinum p-acid mediated insertion of alkynes into carbon–heteroatom s-bonds h12S3401i. The remainder of this chapter discusses the most studied transformations on O- and S-6-membered heterocycles.
- Six-membered ring systems: with O and/or S atomsPublication . Santos, Clementina M.M.; Silva, ArturThe synthesis of O- and S-6-membered heterocycles was actively pursued in 2015. Special emphasis is given to the synthesis of natural oxygen derivatives. The chemistry of -oxoesters in the synthesis of O-, S-, and S,Oheterocycles (15CR151) and of copper-catalyzed C‒H functionalization reactions to prepare O-heterocycles has been discussed (15CR1622). Reviews on natural occurrence and biological properties of xanthone dimers (15NPR6); natural occurrence, synthesis, and biological activities of dihydrocoumarins (15OPP1); synthesis and structure–activity relationship of natural and synthetic peloruside analogs (15CC4750) and of coumarin derivatives (15EJM(101)476, 15NPR1472); and synthesis and bioactivities of 1,4-benzodioxane lignans (15NPR1369) and of chroman-4-ones (15EJM(93)539) have appeared. The synthesis and reactivity of 6-(trifluoromethyl)-2H-pyran-2-ones (15JFC36) and of furochromen- 4-ones (15EJM(90)633); synthesis and physical properties of π-expanded coumarins (15JMCC1421); and isolation, biosynthesis, synthesis, and biological activities of naphthopyranones (15NPR578) were also reviewed. An overview on unconventional terpene cyclases and their impact on biomimetic biosynthesis of terpenoids bearing pyran and chroman moieties (15AGE2604) and the chemical features, synthesis, and biological properties of mangiferin and derivatives have appeared (15MRMC582). The background and implications of natural antimalarial artemisinin in traditional Chinese medicine (15NPR1617) as well as its synthesis, biosynthesis and large-scale production (15NPR359) have been highlighted.
- Epoxidation of 2-Styrylchromone derivativesPublication . Santos, Clementina M.M.; Silva, Artur; Cavaleiro, José; Patonay, Támas; Lévai, Albert2-Styrylchromones constitute a small group of natural heterocyclic compounds with significant biological properties. Certain natural and synthetic hydroxyl derivatives have shown important pharmacological and mainly antioxidant activities [1 ,2]. We are interested in the design of new 2-styrylchromones analogues containing hydroxyl groups at C-3 and in the Ca=C~ systems because they could increase the antioxidation activity of these type of compounds [2]. Our first approach is the preparation of epoxy systems and then we will try to open the epoxy ring to give the desired hydroxyl derivatives. We studied the epoxidation of 2-styryl-chromones 1 with hydrogen peroxide and iodosylbenzene using [salen Mn(lll)] as catalyst, and the epoxy products 2 were obtained in moderate yields. Since the best results were obtained with iodosylbenzene, we applied oxidant to compounds 3 in order to prepare 4. In this communication, we will report the synthetic details and the structural characterisation of the epoxides 3 and 4.
- Six-membered ring systems: with O and/or S atomsPublication . Santos, Clementina M.M.; Silva, ArturThe most important achievements on the synthesis of O- and S-6-membered heterocycles published in 2021 are reviewed. This personal overview is focused on the developments made on the synthesis of a large variety of natural compounds, specific reactions, and reagents for the preparation of natural and synthetic pyrans, chromenes and chromans, isochromenes and isochromans, pyranones, coumarins and isocoumarins, chromones and chromanones, xanthenes and xanthones, thiopyrans and analogues, dioxanes, trioxanes, tetraoxanes, dithiins, and also oxathianes.
- A novel route for the synthesis of 2,3-DiarylxanthonesPublication . Santos, Clementina M.M.; Silva, Artur; Cavaleiro, JoséChemically, xanthones are oxygenated heterocyclic compounds with a dibenzo-け-pirone nucleus [1]. Natural derivatives have several types of substituents in different positions of their nucleus, which can be associated to the pharmacological properties presented by this class of compounds [2]. Xanthones bearing aryl substituents are scarce and no natural derivatives have been reported with the 2,3-diaryl substitution pattern. Recently, we have reported the synthesis of several 2,3-diarylxanthones, starting from 3-bromo-2-methylchromone.
- Synthesis of Benzo[a]naphtho[2,3-c]xanthones from 2-styrylchromonesPublication . Tomé, Sara; Patoilo, Diana; Santos, Clementina M.M.; Silva, Artur2-Styrylchromones, a small group of natural occurring chromones vinylogues of flavones (2-phenylchromones) have been ex tensively studied (both by synthesis and transformations)111 due to their known important biological activities. 121 Following our interest in 2-styrylchromones and exploiting its reactivity as synthons in the preparation of other type of compounds, we studied their reactivity as dienophile in the Diels-Alder reaction with ortho-benzoquinodimethanesY1 Another field of interest of our research group is the chemistry of xanthones. 141 This class of oxygen-containing heterocyclic compounds is also associated with a broad spectrum of pharmacological propertiesY1 The interesting biological profile of benzoxanthones 161 is an example that the tricyclic core of xanthones may represent a promising key in medicinal chemistry. In this communication we present a route towards the synthesis of benzo[a]naphtho[2,3-c]xanthones from 2-styrylchromones. Here we discuss the experimental procedures and reaction mechanisms of the Diels-Alder transformation of 2-styrylchromone 1 into the oxidized cycloadduct 3 and its subsequent photoinduced electrocyclization and oxidation that gave access to the desired benzo[a] naphtho[2,3- c]xanthone 4.
- Anti-inflammatory potencial of 2-Styrylchromones regarding their interference with arachidonic acid metabolic pathwaysPublication . Gomes, Ana Sara; Fernandes, Eduarda; Silva, Artur; Santos, Clementina M.M.; Pinto, Diana; Cavaleiro, José; Lima, José Costa
- Synthesis and evaluation of the antiradicalar activity of polyhydroxy-2-styrylchromonesPublication . Santos, Clementina M.M.; Silva, Artur; Cavaleiro, JoséRecent studies have ascribed the cause of several acute and degenerative diseases, including cell aging and carcinogenesis, to the production of free radicals. As a consequence of this, a large number of investigations have been carried out in order to find new, safe and potent antioxidants and to elucidate the corresponding mechanism of action. The evaluation of antioxidant VS. antiradicalar activity of phenolic compounds, either of natural or synthetic origin, is nowadays an important area of research in the field of food and medicinal sciences. We report here the synthesis of severa I new polyhydroxy-2-styrylchromones 1 starting from 2'-hydroxyacetophenones and cinnamic acid derivatives. The diversity of the substitution pattern, which includes the presence of hydroxyl substituents in 5,7,3' and 4' positions of their skeleton and also a 2,3-double bond was taken into consideration. The evaluation of the antiradicalar efficacy of all synthesised 2-styrylchromones 1 was also carried out by a non-enzymatic method and was performed by the DPPH radical method. 1 The experimental procedures for the synthesis, for the evaluation of the antiradicalar activity and for the structural characterisation of all synthesised compounds will be presented and discussed.
- Síntese de novas cromonas e xantonas com atividade captadora de espécies reativas de oxigénioPublication . Proença, Carina; Albuquerque, Hélio; Santos, Clementina M.M.; Silva, Artur; Cavaleiro, José; Fernandes, EduardaAs cromonas são compostos heterocíclicos oxigenados resultantes da fusão de um anel benzénico com um anel γ-pirona. Vários derivados de cromonas têm sido testados em diferentes sistemas biológicos, apresentando diferentes atividades com potencial aplicação terapêutica. Estes compostos demonstraram atividade anti-inflamatória, antitumoral, antimicrobiana, atividade protetora do sistema nervoso central e preventiva de doenças cardiovasculares, assim como atividade antioxidante [1]. As xantonas são igualmente compostos heterocíclicos oxigenados e cuja estrutura de base é a dibenzo-γ-pirona. Esta classe de compostos também tem despertado um grande interesse devido às diversas atividades biológicas que apresenta, nomeadamente atividade antimicrobiana, antitrombótica, anti-inflamatória, antialérgica, antitumoral e ainda reconhecida atividade antioxidante [2]. Entre as atividades biológicas que estas duas classes de compostos apresentam, destaca-se a elevada atividade antioxidante quer em sistemas in vitro quer em sistemas in vivo. Por este motivo, é importante o aprofundamento dos estudos de atividade antioxidante deste tipo de compostos. Assim, nesta comunicação apresentar-se-á a síntese de novo de 1-arilxantonas hidroxiladas e dos seus percursores (E,E)-2-(4-arilbuta-1,3-dien-1-il)-4H-cromen-4-onas, obtidos por condensação de 2-metilcromonas, apropriadamente substituídas com o 3,4-dimetoxicinamaldeído. Após clivagem dos grupos protectores, as xantonas e cromonas hidroxiladas resultantes foram purificadas e submetidas a ensaios in vitro para avaliar a capacidade de captação de espécies reativas de oxigénio (ERO), nomeadamente do radical anião superóxido (O2•-) e do peróxido de hidrogénio (H2O2). Relativamente à capacidade captadora de O2•-, as cromonas estudadas apresentaram maior atividade que as xantonas, não demonstrando, no entanto, serem compostos muito ativos. Em relação à capacidade de captação de H2O2, as xantonas revelaram-se mais ativas que as cromonas, apresentando um efeito dependente da concentração. Os resultados obtidos permitem aprofundar os conhecimentos sobre a relação estrutura/atividade captadora de ERO, contribuindo assim para o desenvolvimento de novos derivados de cromonas e xantonas com potencial antioxidante.