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1.
Angew Chem Int Ed Engl ; 62(3): e202212444, 2023 01 16.
Artigo em Inglês | MEDLINE | ID: mdl-36377924

RESUMO

Ring-opening transformations of donor-acceptor (D-A) cyclopropanes enable the rapid assembly of complex molecules. However, the enantioselective formation of chiral quaternary stereocenters using substrates bearing two different acceptors remains a challenge. Herein, we describe the first palladium-catalyzed highly diastereo- and enantioselective (3+2) cycloaddition of vinyl cyclopropanes bearing two different electron-withdrawing groups, a subset of D-A cyclopropanes. The key to the success of this reaction is the remote stereoinduction through hydrogen bond from chiral ligands, which thereby addressed the aforementioned challenge. A variety of chiral five-membered heterocycles were produced in good yields and with high stereoselectivity (up to 99 % yields, 99 : 1 er and >19 : 1 dr). In-depth mechanistic investigations, including control experiments and theoretical calculations, revealed the origin of the stereoselectivity and the importance of H-bonding in stereocontrol.


Assuntos
Ciclopropanos , Paládio , Paládio/química , Reação de Cicloadição , Catálise , Estereoisomerismo , Ciclopropanos/química
2.
J Am Chem Soc ; 144(41): 18778-18783, 2022 10 19.
Artigo em Inglês | MEDLINE | ID: mdl-36194507

RESUMO

We achieved a concise total synthesis of salimabromide by using a novel intramolecular radical cyclization to simultaneously construct the unique benzo-fused [4.3.1] carbon skeleton and the vicinal quaternary stereocenters. Other notable transformations include a tandem Michael/Mukaiyama aldol reaction to introduce most of the molecule's structural elements, along with hidden information for late-stage transformations, an intriguing tandem oxidative cyclization of a diene to form the bridged butyrolactone and enone moieties spontaneously, and a highly enantioselective hydrogenation of a cycloheptenone derivative (97% ee) that paved the way for the asymmetric synthesis of salimabromide.


Assuntos
Carbono , Compostos Heterocíclicos de 4 ou mais Anéis , Estereoisomerismo , Ciclização , Compostos Heterocíclicos de 4 ou mais Anéis/química
3.
J Am Chem Soc ; 144(13): 5750-5755, 2022 04 06.
Artigo em Inglês | MEDLINE | ID: mdl-35289615

RESUMO

Daphenylline is a structurally unique member of the triterpenoid Daphniphyllum natural alkaloids, which exhibit intriguing biological activities. Six total syntheses have been reported, five of which utilize aromatization approaches. Herein, we report a concise protecting-group-free total synthesis by means of a novel intramolecular oxidative dearomatization reaction, which concurrently generates the critical seven-membered ring and the quaternary-containing vicinal stereocenters. Other notable transformations include a tandem reductive amination/amidation double cyclization reaction, to assemble the cage-like architecture, and installation of the other two chiral stereocenters via a highly enantioselective rhodium-catalyzed challenging hydrogenation of the diene intermediate (90% e.e.) and an unprecedented remote acid-directed Mukaiyama-Michael reaction of the complex benzofused cyclohexanone (13:1 d.r.).


Assuntos
Alcaloides , Ciclização , Estresse Oxidativo , Estereoisomerismo
4.
J Am Chem Soc ; 142(28): 12039-12045, 2020 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-32584568

RESUMO

With the aid of a class of newly discovered Trost-type bisphosphine ligands bearing a chiral cycloalkane framework, the Pd-catalyzed decarboxylative dearomative asymmetric allylic alkylation (AAA) of benzofurans was achieved with high efficiency [0.2-1.0 mol% Pd2(dba)3/L], good generality, and high enantioselectivity (>30 examples, 82-99% yield and 90-96% ee). Moreover, a diversity-oriented synthesis (DOS) of previously unreachable flavaglines is disclosed. It features a reliable and scalable sequence of the freshly developed Tsuji-Trost-Stoltz AAA, a Wacker-Grubbs-Stoltz oxidation, an intra-benzoin condensation, and a conjugate addition, which allows the efficient construction of the challenging and compact cyclopenta[b]benzofuran scaffold with contiguous stereocenters. This strategy offers a new avenue for developing flavagline-based drugs.

5.
J Am Chem Soc ; 138(23): 7268-71, 2016 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-27244042

RESUMO

7,20-Diisocyanoadociane, a scarce marine metabolite with potent antimalarial activity, was synthesized as a single enantiomer in 13 steps from simple building blocks (17 linear steps). Chemical synthesis enabled identification of isocyanoterpene antiplasmodial activity against liver-stage parasites, which suggested that inhibition of heme detoxification does not exclusively underlie the mechanism of action of this class.


Assuntos
Antimaláricos/síntese química , Fígado/parasitologia , Nitrilas/síntese química , Plasmodium falciparum/efeitos dos fármacos , Pirenos/síntese química , Antimaláricos/química , Antimaláricos/farmacologia , Heme/metabolismo , Estrutura Molecular , Nitrilas/química , Nitrilas/farmacologia , Pirenos/química , Pirenos/farmacologia , Estereoisomerismo
6.
Org Biomol Chem ; 13(29): 8029-36, 2015 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-26119264

RESUMO

The soraphens are natural products that exhibit a molecular structure different from what would have been expected by following its polyketidal assembly line. The most significant differences are the presence of a hemiketal instead of a trisubstituted double bond and a double bond at C9 and C10 where a saturated carbon chain was expected. We were interested in the biological activity of the soraphens with architectures as described by the polyketide synthase since we hypothesized that these modifications reflect the evolutionary optimization of the soraphens. Herein we describe four additional derivatives of the so-called paleo-soraphens and their biological profiling to provide a picture of the hypothetical evolutionary optimization of this family of natural products. The syntheses required a unified and convergent strategy and their biological profiling was performed with the aid of impedance measurements. The results of these biological experiments are consistent with the proposed evolutionary optimization of the soraphens.


Assuntos
Macrolídeos/síntese química , Macrolídeos/farmacologia , Animais , Linhagem Celular , Análise por Conglomerados , Impedância Elétrica , Cinética , Macrolídeos/química , Camundongos , Conformação Molecular , Estereoisomerismo
7.
Nat Prod Rep ; 31(4): 563-94, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24595879

RESUMO

The vinylogous Mukaiyama aldol reaction (VMAR) allows efficient access to larger segments for complex natural product synthesis, primarily polyketides, through the construction of vicinal hydroxyl and methyl groups as well as di and tri-substituted double bonds in one single operation. In this review, we will highlight stereoselective protocols that have been used in natural product synthesis and cluster them into the four groups that can be obtained from different silyl ketene acetals or enol ethers. At the beginning, an overview on different stereoselective VMARs is presented; disregarding their applications in total syntheses.


Assuntos
Aldeídos/química , Produtos Biológicos/síntese química , Produtos Biológicos/química , Estrutura Molecular , Estereoisomerismo
8.
Angew Chem Int Ed Engl ; 52(51): 13549-52, 2013 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-24346938

RESUMO

Synthesis can provide molecules such as paleo-soraphens A and B that are genetically encoded but not obtained from the natural source. Although it is unclear whether this is part of an evolutionary process or the consequence of the chemical synthesis, the biological evaluation of these genetically encoded natural products can shed light on how natural products are structurally optimized with respect to their biological profile.


Assuntos
Macrolídeos/síntese química , Sequência de Aminoácidos , Produtos Biológicos , Macrolídeos/química , Policetídeos/química
9.
Chemistry ; 15(12): 2742-6, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19204966

RESUMO

Economical approach: The first organocatalytic asymmetric intramolecular hydroarylation of phenol- and aniline-derived enals offers one of the most straightforward and atom-economic approaches to enantioriched chromans and tetrahydroquinolines (up to 96% ee; see scheme).


Assuntos
Aldeídos/química , Compostos de Anilina/química , Cromanos/síntese química , Quinolinas/síntese química , Catálise , Cromanos/química , Técnicas de Química Combinatória , Estrutura Molecular , Quinolinas/química , Estereoisomerismo
10.
Chem Commun (Camb) ; (28): 4251-3, 2009 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-19585037

RESUMO

A useful Michael addition reaction using nitroalkanes as the nucleophile and 4-oxo-enoates as the Michael acceptor has been disclosed, and the reaction allows expedient access to functionalized chiral gamma-keto esters in high yields and excellent enantioselectivities (up to 98% ee), with a low catalyst loading.


Assuntos
Alcanos/química , Butiratos/química , Nitrocompostos/química , Compostos Orgânicos/química , Catálise , Cristalografia por Raios X , Modelos Moleculares , Estereoisomerismo
11.
Biochem Pharmacol ; 155: 61-70, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29940173

RESUMO

The 'neurotrophic sesquiterpenes' refer to a group of molecules derived from the Illicium genus of flowering plant. They display neurotrophic effects in cultured neuron preparations and have been suggested to be cognitive enhancers and potential therapeutics for neurodegenerative disorders and dementias. Recent synthetic advances generated sufficient quantities of jiadifenolide for in vivo investigation into its biological effects. Jiadifenolide did not induce convulsions in mice nor did it enhance or diminish convulsions induced by pentylenetetrazole. Other negative allosteric modulators of GABAA receptors, picrotoxin, tetramethylenedisulfotetramine (TETS), and bilobalide all induced convulsions. Either i.p. or i.c.v. dosing generated micromolar plasma and brain levels of jiadifenolide but only small effects on locomotion of mice. However, jiadifenolide decreased d-amphetamine-induced hyperlocomotion in mice, an antipsychotic-like drug effect. Jiadifenolide did not significantly alter body temperature or behavior in the forced-swim test in mice. Molecular simulation data suggested a potential site in the pore/M2 helix region that is at an overlapping, yet lower position than those observed for other 'cage convulsant' compounds such as TETS and picrotoxin. We hypothesize that a position nearer to the entrance of the pore channel may allow for easier displacement of jiadifenolide from its blocking location leading to lower potency and lower side-effect liability. Like jiadifenolide, memantine (Namenda), one of the few drugs used in the symptomatic treatment of dementias, occupies a unique site on the NMDA receptor complex that creates low binding affinity that is associated with its reduced side-effect profile. Given the potential therapeutic applications of jiadifenolide and its relatively inert effects on overt behavior, the possibility of clinical utility for jiadifenolide and related compounds becomes intriguing.


Assuntos
Convulsivantes/metabolismo , Convulsivantes/farmacologia , Progressão da Doença , Doenças Neurodegenerativas/metabolismo , Sesquiterpenos/metabolismo , Sesquiterpenos/farmacologia , Animais , Convulsivantes/química , Relação Dose-Resposta a Droga , Células HEK293 , Humanos , Locomoção/efeitos dos fármacos , Locomoção/fisiologia , Masculino , Camundongos , Fatores de Crescimento Neural/química , Fatores de Crescimento Neural/metabolismo , Fatores de Crescimento Neural/farmacologia , Ligação Proteica/efeitos dos fármacos , Ligação Proteica/fisiologia , Estrutura Secundária de Proteína , Agitação Psicomotora/metabolismo , Sesquiterpenos/química
12.
Zhonghua Nei Ke Za Zhi ; 46(3): 229-32, 2007 Mar.
Artigo em Chinês | MEDLINE | ID: mdl-17547808

RESUMO

OBJECTIVE: To study the clinical classification and characteristics as well as prognosis of mushroom poisoning. METHODS: We retrospectively analyzed 191 papers published domestically for 3466 cases of mushroom poisoning from 1995 to 2004 and studied the Xinqiao Hospital data of 172 cases of mushroom poisoning treated from 1980 through 2004. We made a retrospective investigation and clinical classification of all the 3638 cases of mushroom poisoning. RESULTS: Among the 3638 patients, clinical manifestations as gastroenteritis were found in 571, all of them were cured. The most common symptoms were those of acute renal failure being found in 1450 cases; 1414 were cases (97.5%) and 36 died (2.5%). Symptoms of toxic hepatitis were found in 1010 cases, 841 were cases (83.3%) and 169 died (16.7%). Psychoneurological disorder was manifested in 214 cases; 197 were cases (92.1%) and 17 died (7.9%). Erythrolysis was found in 73 cases; 71 were cases (97.3%) and 2 died (2.7%). The therapeutic effect and prognosis of mushroom poisoning with different clinical manifestation varied very significantly (P < 0.001). Of the 320 cases clinically unclassified, multiple organ dysfunction syndrome was found in 222 cases; 98 were cases (44.1%) and 124 died (55.9%). Definite classification could not be made in 98 cases; 90 were cases (91.8%) and 8 died (8.2%). CONCLUSIONS: The clinical classification of mushroom poisoning was usually of four types as described in the textbooks or special articles, but it should be of five types according to the analysis of the data of the present study, i.e. gastroenteritis type, acute renal failure type, toxic hepatitis type, psychoneurological disorder type and erythrolysis type. It is not clear whether there is a mixed type or not. Further investigation is needed in this respect.


Assuntos
Intoxicação Alimentar por Cogumelos/classificação , Intoxicação Alimentar por Cogumelos/diagnóstico , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Criança , Pré-Escolar , Feminino , Humanos , Lactente , Masculino , Pessoa de Meia-Idade , Intoxicação Alimentar por Cogumelos/epidemiologia , Prognóstico , Estudos Retrospectivos
13.
Zhonghua Yi Xue Za Zhi ; 87(4): 223-7, 2007 Jan 23.
Artigo em Chinês | MEDLINE | ID: mdl-17425863

RESUMO

OBJECTIVE: To observe whether bone mesenchymal stem cells (MSCs) have the potential to transdifferentiate into functional hepatocyte-like cells in the special "niche" as well as the therapeutic feasibility to repair damaged liver in mice. METHODS: 20 nude mice were randomly divided into four groups (n = 5 in each group): Group A: 1.0 ml/kg of carbon tetrachloride (CCl(4)) (dissolved in olive oil by ratio of 1:1) was injected into the peritoneum of mice twice a week for 5 weeks. GFP-positive MSCs (1 x 10(6) cells) were injected into the caudal tail vein 1 week after the first dose of CCl(4); Group B: treated with CCl(4) as in A, but received the same volume of saline; Group C: normal nude mice with GFP-positive MSCs Transplanted in the same way as in A. Group D: normal controls. 4 weeks after the cell transplantation, all animal subjects were killed. Liver function tests (LFT), histology of HE and Masson staining as well as double immunofluorescent staining for GFP and albumin were studied in all groups. RESULTS: The hepatic fibrosis in group A & B confirmed the success of model for liver damage and there was no marked difference in the percent of the area occupied by collagen between two groups (10.5 +/- 1.5 vs 12.7 +/- 1.6, t = -2.238, P > 0.05). GFP-positive MSCs were mainly observed around portal area or interspace of lobules in group A. Some of GFP-positive cells also express albumin (35% +/- 7%). While in group B, C or D, there is no such findings. The level of serum albumin in group A was higher than that in group B (24.4 g/L +/- 3.3 g/L vs 18.6 g/L +/- 2.9 g/L, P < 0.05) while the level of ALT was also different between two groups (121 U/L +/- 21 U/L vs 192 U/L +/- 29 U/L, P < 0.05). CONCLUSION: The stimulus of persistent liver damage might enhances the migration of MSCs to the liver, in which some of the MSCs have the potential to transdifferentiate into hepatocyte-like cells. Transplantation of MSCs might amend the damaged tissue of host liver to a certain extent.


Assuntos
Diferenciação Celular , Hepatopatias/cirurgia , Transplante de Células-Tronco Mesenquimais/métodos , Células-Tronco Mesenquimais/citologia , Animais , Tetracloreto de Carbono , Transdiferenciação Celular , Células Cultivadas , Doença Hepática Induzida por Substâncias e Drogas , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Hepatopatias/fisiopatologia , Testes de Função Hepática , Células-Tronco Mesenquimais/metabolismo , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Nus , Camundongos Transgênicos , Microscopia Confocal , Microscopia de Fluorescência , Distribuição Aleatória
14.
Org Lett ; 7(20): 4543-5, 2005 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-16178579

RESUMO

[reaction: see text] Readily tunable and bifunctional L-prolinamides as novel organocatalysts have been developed, and their catalytic activities were evaluated in the direct asymmetric Aldol reactions of various aromatic aldehydes and cyclohexanone. High isolated yields (up to 94%), enantioselectivities (up to 99% ee), and anti-diastereoselectivities (up to 99:1) were obtained under the optimal conditions.


Assuntos
Aldeídos/química , Desenho de Fármacos , Prolina/análogos & derivados , Catálise , Cicloexanonas/química , Estrutura Molecular , Prolina/química , Estereoisomerismo
15.
Nat Chem ; 7(7): 604-7, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26100810

RESUMO

Development of a biologically active secondary metabolite into a useful medicine requires continuous access to meaningful quantities of material. Although any chemical synthesis is broadly useful for its versatility, identification of a synthesis route that can be economically scaled represents a greater challenge. Here we report a concise synthesis of the neurotrophic trace metabolite (-)-jiadifenolide and its production on a gram-scale. The brevity of the route and the structural similarity of a key intermediate to many potent Illicium terpenes make chemical synthesis the unquestionable method for accessing and modifying these potential therapeutics.


Assuntos
Sesquiterpenos/síntese química , Estrutura Molecular , Estereoisomerismo
16.
Org Lett ; 12(24): 5636-9, 2010 Dec 17.
Artigo em Inglês | MEDLINE | ID: mdl-21080696

RESUMO

A highly enantioselective organocatalytic intermolecular conjugate addition of oximes to ß-nitroacrylates has been developed. The highly functionalized adducts obtained are valuable precursors for asymmetric synthesis, as demonstrated by the synthesis of ß(2,2)-amino acids and oxazolidin-2-ones.


Assuntos
Acrilatos/química , Aminoácidos/química , Compostos de Nitrogênio/química , Oximas/química , Catálise , Cristalografia por Raios X , Modelos Moleculares , Estrutura Molecular , Estereoisomerismo
17.
Org Lett ; 11(17): 3946-9, 2009 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-19653671

RESUMO

An atom-economic organocatalytic asymmetric Michael reaction of alpha,beta,beta-trisubstituted olefins has been successfully developed. The reaction exhibits excellent enantioselectivities under low loading of catalysts, and the conjugate addition products are valuable for the synthesis of novel beta(2,2)-amino acids and beta-peptides.


Assuntos
Alcenos/química , Aminoácidos/síntese química , Nitrocompostos/química , Peptídeos/síntese química , Aminoácidos/química , Catálise , Técnicas de Química Combinatória , Estrutura Molecular , Peptídeos/química , Estereoisomerismo
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