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1.
J Ethnopharmacol ; 247: 112223, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31553926

RESUMO

ETHNOPHARMACOLOGICAL RELEVANCE: Arecae semen has been used as vermifuge and digestant in traditional Chinese medicine (TCM) for more than one thousand years. However, the toxicity effect of areca semen and its underlying mechanism are still unclear. THE AIM OF THE STUDY: This study was aimed to investigate the toxicity of arecae semen and to explore its mechanisms by serum metabolomics. MATERIALS AND METHODS: The male Wistar rats were divided into the control group and treated group (n = 6 in each group), which were given by gavage with distill water or arecae semen aqueous extract (ASAE) once a day for 30 days, respectively. Serum samples were collected from all the rats after treatment of 7-day, 14-day and 30-day for metabolomics analysis. Moreover, biochemistry analysis and histopathological examination were performed at the end of study. RESULTS: The phenomenon of diarrhea, less physical activity, tremors and body curl up were observed in the treated group. Additionally, the body weights of treated rats were significantly decreased compared with control rats from the 8th day after oral administration. Except the level of creatinekinase (CK) in the treated group significantly increased compared with the control group, there were no differences on biochemistry parameters and histopathological test in the two groups. Combined with the methods of principal component analysis (PCA), orthogonal projection to latent structure-discrimination analysis (OPLS-DA) and available databases, the treated and control rats were clearly distinguished from each other and 19 metabolites were identified as the potential biomarkers in the arecae semen treated rats. The identified biomarkers indicated that there were perturbations of the phospholipid metabolism, amino acid metabolism and fat acid metabolism in the treated group. CONCLUSIONS: This indicated that arecae semen possessed certain cardiotoxicity and inhibited the normal growth in Wistar male rats. In addition, the metabolomics approach is a useful tool to study the toxicity in TCM.

2.
Org Lett ; 2019 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-31793792

RESUMO

The asymmetric aminomethylation reaction of 3-diazooxindoles with electronic-rich arenes and N,O-acetals cooperatively catalyzed by achiral dirhodium complex and chiral phosphoric acid is reported. The reaction provides a novel method for the facile synthesis of chiral 3-aminomethyl oxindoles with an all-carbon quaternary center in good yields (82-98%) with high to excellent enantioselectivities (up to 97% ee). The transformation proceeds through a convergent addition of a reactive zwitterionic intermediate with a chiral methylene iminium generated in situ via asymmetric counteranion-directed catalysis (ACDC). This work represents the first asymmetric aminomethylation method of mixed 3,3'-bisindoles with structural diversity.

3.
J Org Chem ; 2019 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-31702914

RESUMO

A zinc-catalyzed intermolecular alkyne-carbonyl metathesis reaction of ynamides with isatins followed by an amide to ester conversion has been developed, which produces the indolone derivatives with a fully substituted alkene species in good to high yields. The salient features of this reaction include the following: mild reaction conditions, an inexpensive zinc catalyst, a broad substrate scope, the excellent regiocontrol and stereoselectivity, and amenable to the gram scale.

4.
Org Biomol Chem ; 17(45): 9792-9798, 2019 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-31701982

RESUMO

Norstatine derivatives are of important value in pharmaceutical science. However, their catalytic asymmetric synthesis is rare. We developed a sustainable method via chiral phosphoric acid (CPA)-[Rh(OAc)2]2 co-catalyzed multi-component reactions (MCR) of diazoacetates with alcohol/water and imines. This method allows us to synthesize a library of 45 norstatines with excellent enanotioselectivites and broad substrate scope which includes anti-α-aryl-norstatines 11-1, anti-α-alkyl-norstatines 11-2, syn-α-hydro-norstatines 11-3 and syn-α-aryl-norstatines 11-4. The sustainability of this method lies in the reliable scalability, improved safety, and reusable [Rh(OAc)2]2 catalyst. The synthetic value of norstatine derivatives was demonstrated by preparing oxazolinone 14, ezetimibe analogue 15, and Taxol C-13 chain 16. Mechanistic study reveals that the synergetic catalysis of CPA and [Rh(OAc)2]2 is essential to maintain chemo- and enantioselectivity. Control experiments support the mechanism where the reactions proceed through the trapping of hyper-reactive oxonium ylides with imines. Shortly, we report herein the sustainable catalytic enantioselective synthesis of both syn- and anti-norstatine derivatives. We believe that this method might shed light on the sustainable synthesis of norstatine derivative-based drug candidates.

5.
iScience ; 21: 499-508, 2019 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-31710965

RESUMO

A gold-catalyzed 6-endo-dig carbocyclization of alkyne with the pendent diazo group is reported. It provides an expeditious approach for the synthesis of multi-functionalized naphthalene derivatives under mild conditions. Mechanistic studies suggest that a vinyl gold carbene is generated as the key intermediate in this cascade transformation that smoothly delivers naphthalene products through an unprecedented stepwise aromatization or an intermolecular aromatic substitution process. The unique endocyclic vinyl species is inaccessible with other precursors; thus, novel carbene cascade transformations could be envisioned with the current catalytic model. Functional groups, such as alkenyl, hydroxyl, amino, and carboxyl groups, remain untouched under these conditions. In addition, the utility of these generated 2-carboxyl naphthalenes is illustrated by the synthesis of chiral 1,2'-binaphthalene ligands and π-conjugated polycyclic hydrocarbons (CPHs).

6.
Dalton Trans ; 48(37): 13907-13911, 2019 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-31469132

RESUMO

Monomeric methyl metaphosphate (CH3OPO2), a highly electrophilic phosphorylating intermediate in chemical oligonucleotide synthesis, has been generated in the gas phase by high-vacuum flash pyrolysis (1000 K) of methyl 2-butenylphosphonate. In addition to the unambiguous characterization using IR spectroscopy in solid N2-, Ar-, and Ne-matrices, the formation CH3OPO2 in the photooxidation of the prototypical phosphinidene oxide CH3PO by O2 with 18O-isotope scrambling has been observed in the solid N2-matrix (15 K).

7.
Chem Commun (Camb) ; 55(45): 6393-6396, 2019 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-31090758

RESUMO

A copper-catalyzed [4+1]-annulation of 2-vinylindoles with diazoacetates has been developed that provides a straightforward access to the dihydrocyclopenta[b]indoles bearing two contiguous all-carbon quaternary centers in good yields. Mechanistic studies indicate that the reaction goes through a concerted and asynchronous annulation process via the key zwitterionic intermediate.

8.
Org Lett ; 21(9): 3328-3331, 2019 05 03.
Artigo em Inglês | MEDLINE | ID: mdl-30994354

RESUMO

A chiral dirhodium-carboxylates-catalyzed asymmetric nitrene/alkyne metathesis (NAM) cascade reaction of alkyne-tethered sulfamates has been developed, which provides a general access to the synthesis of tricyclic N-heterocycles in good yields and excellent enantioselectivity. The chiral dirhodium catalyst not only promotes the nitrene/alkyne metathesis (NAM) to generate the key α-imino metal carbene intermediate but also is responsible for the observed asymmetric induction in the terminating [2,3]-sigmatropic rearrangement of oxonium ylide species.

9.
Org Lett ; 21(6): 1813-1817, 2019 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-30840467

RESUMO

An efficient gold(I)-catalyzed carbocyclization reaction for the synthesis of isomycin derivatives from propargyl diazoacetates has been developed. The suggested cyclization pathway delineated the first example of a vinyl gold carbenoid species generated in situ from gold(I)-catalyzed 1,2-acyloxy migration and intercepted by a cross-coupling reaction with the remaining tethered diazo functionality. The use of protic additives was essential to regulating the reaction outcome by fine-tuning the catalytic preference of the gold(I) complex.

10.
Org Biomol Chem ; 17(9): 2326-2330, 2019 02 27.
Artigo em Inglês | MEDLINE | ID: mdl-30734821

RESUMO

A copper-catalyzed selective cascade reaction of alkyne-tethered diazo compounds is reported for the direct and efficient construction of dihydrocyclohepta[b]indole skeletons under mild reaction conditions. A vinyl copper carbene is the key intermediate, which is generated in situ via carbene/alkyne metathesis (CAM) and terminated with the Buchner reaction.

11.
Angew Chem Int Ed Engl ; 58(16): 5241-5245, 2019 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-30785666

RESUMO

Gold-catalyzed oxidations of alkynes by N-oxides offer direct access to reactive α-oxo gold carbene intermediates from benign and readily available alkynes instead of hazardous diazo carbonyl compounds. Despite various versatile synthetic methods developed based on this strategy, one of the hallmarks of α-oxo carbene/carbenoid chemistry, that is, the Wolff rearrangement, has not been realized in this context. This study discloses the first examples that show the Wolff rearrangement can be readily realized by α-oxo gold carbenes oxidatively generated from TBS-terminated alkynes (TBS=tert-butyldimethylsilyl). The thus-generated silylketenes can be either isolated pure or subsequently trapped by various internal or external nucleophiles in one pot to afford α-silylated carboxylic acids, their derivatives, or TBS-substituted allenes.

12.
Org Lett ; 21(2): 369-372, 2019 01 18.
Artigo em Inglês | MEDLINE | ID: mdl-30596509

RESUMO

A novel gold-catalyzed oxidative cyclization/aldol addition of homopropargyl alcohols with isatins has been developed that provides an effective access to the 3-hydroxyoxindoles in high yields under mild reaction conditions with high diastereoselectivities. In comparison with disclosed transformations of alkyne oxidations via an α-oxo gold carbene route, this is the first example of an aldol-type interception of an ylide (or its enolate form) intermediate with alkyne as a safe and readily available nondiazo carbene precursor.

13.
J Am Chem Soc ; 141(4): 1473-1478, 2019 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-30624920

RESUMO

A novel enantioselective aminomethylation reaction of diazo compound, alcohol and α-aminomethyl ether enabled by asymmetric counteranion-directed catalysis is disclosed that offers an efficient and convenient access to furnish optically active α-hydroxyl-ß-amino acids in high yield with high to excellent enantioselectivities. Control experiments and DFT calculations indicate that the transformation proceeds through trapping the in situ generated enol intermediate with methylene iminium ion, and the asymmetric induction was enabled by chiral pentacarboxycyclopentadiene anion via H-bonding and electrostatic interaction.

14.
Org Biomol Chem ; 16(45): 8677-8685, 2018 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-30387481

RESUMO

Metal carbene, as a reactive intermediate, has shown versatile applications in modern organic synthesis. One of the priorities in this area is exploration of stable carbene precursors with structural diversity. Catalytic carbene/alkyne metathesis (CAM) with readily available and stable materials, such as α-carbonyl diazo compounds, provides an effective approach for the in situ generation of vinyl carbene intermediates, which is difficult to directly access with other carbene precursors. Thus, novel cascade transformations involving the CAM process for the straightforward construction of polycyclic frameworks have been well documented. Challenges including side reaction control and asymmetric catalysis in this area need to be explored. This review will summarize the recent advances in this field and be divided by the type of the terminating carbene reactions.

15.
Artigo em Inglês | MEDLINE | ID: mdl-30375130

RESUMO

An enantioselective Mannich-type reaction of 3-butynol and nitrones is described, which affords dihydrofuran-3-ones in good yields and with excellent enantioselectivities. The reaction is initiated by gold-catalyzed alkyne oxidation and modification of the resulting gold carbene species with a tethered hydroxy group to form enolate species; the reaction terminates with an enantioselective Mannich-type addition with the assistance of chiral phosphoric acid (CPA) and hydrogen bonding. This novel pattern of alkyne transformation involving chemical bond cleavage, and a fragment modification and reassembly process, provides an atom- and step-economic method, and is the first example of cooperative asymmetric catalysis in gold-catalyzed alkyne oxidations via an α-oxo gold carbene route.

16.
J Org Chem ; 83(21): 13243-13255, 2018 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-30284824

RESUMO

Herein, a copper-catalyzed intramolecular cascade reaction of conjugated enynones to deliver substituted 1 H-indenes is reported. The inexpensive and less toxic copper salt served as the only catalyst in the transformation, affording the 3-(2-furyl)-substituted 1 H-indenes in good to excellent yields under mild reaction conditions with broad functional group tolerance and making it highly appealing for synthetic organic chemistry. Notably, detailed DFT calculations have been carried out to elucidate that the reaction undergoes a copper-mediated 5- exo-dig cyclization of enynones to afford copper-(2-furyl)-carbene intermediate, followed by diene-carbene cyclization (one step but involving 6π cyclization of Cu-carbene and reductive elimination) and 1,5-hydrogen shift to provide the 1 H-indenes.

17.
J Am Chem Soc ; 140(42): 13604-13608, 2018 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-30301345

RESUMO

A rare oxyphosphinidene (Me-OP) has been generated in the triplet ground state through either photolysis (266 nm) or flash-vacuum pyrolysis (FVP, 700 °C) of methoxydiazidophosphine MeOP(N3)2. Upon ArF laser irradiation (193 nm), an unprecedented isomerization from Me-OP to the long-sought methylphosphinidene oxide (Me-PO) occurs in cryogenic Ne- and N2-matrices. Alternatively, the latter can be efficiently generated through photolysis (193 nm) or FVP (ca. 700 °C) of methylphosphoryl diazide MeP(O)(N3)2, in which the elusive nitrene intermediate MeP(O)(N3)N in the triplet ground state has been also observed by IR (with 15N-labeling) and EPR (| D/ hc| = 1.545 cm-1 and | E/ hc| = 0.003 95 cm-1) spectroscopy.

18.
Org Lett ; 20(17): 5332-5335, 2018 09 07.
Artigo em Inglês | MEDLINE | ID: mdl-30148636

RESUMO

A novel gold-catalyzed water-mediated carbene cascade reaction of propargyl diazoacetates has been developed. Mechanistic investigation indicates that this reaction is initiated by gold-catalyzed gold-carbene formation followed by an unprecedented 6- endo-dig carbocyclization with tethered alkyne through an oxonium ylide intermediate, terminated by a ß-H elimination/protodeauration process to give the aromatized furan products in good to high yields with broad substrate generality. Notably, the proposed gold-carbene intermediates are verified by interception experiments.

19.
J Ginseng Res ; 42(3): 277-287, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29983609

RESUMO

Background: Temperature is an essential condition in red ginseng processing. The pharmacological activities of red ginseng under different steam temperatures are significantly different. Methods: In this study, an ultrahigh-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry was developed to distinguish the red ginseng products that were steamed at high and low temperatures. Multivariate statistical analyses such as principal component analysis and supervised orthogonal partial least squared discrimination analysis were used to determine the influential components of the different samples. Results: The results showed that different steamed red ginseng samples can be identified, and the characteristic components were 20-gluco-ginsenoside Rf, ginsenoside Re, ginsenoside Rg1, and malonyl-ginsenoside Rb1 in red ginseng steamed at low temperature. Meanwhile, the characteristic components in red ginseng steamed at high temperature were 20R-ginsenoside Rs3 and ginsenoside Rs4. Polar ginsenosides were abundant in red ginseng steamed at low temperature, whereas higher levels of less polar ginsenosides were detected in red ginseng steamed at high temperature. Conclusion: This study makes the first time that differences between red ginseng steamed under different temperatures and their ginsenosides transformation have been observed systematically at the chemistry level. The results suggested that the identified chemical markers can be used to illustrate the transformation of ginsenosides in red ginseng processing.

20.
J Org Chem ; 83(16): 9125-9136, 2018 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-29882666

RESUMO

An unprecedented transition-metal-free tandem bicyclization of diaryl alkynes has been disclosed, which provides a streamlined access to a range of polycyclic 2 H-indazoles in high to excellent yields. The salient features of this reaction include readily available starting materials, good functional group compatibility, mild reaction conditions, no column chromatography, high bond-formation efficiency, and ease in further transformations. Notably, this is the first example for the synthesis of 2 H-indazoles with in situ generated diazonium salt as the nitrogen source, and a mechanistic rationale involving an acid-promoted tandem diazonium salt formation/bicyclization process is discussed.

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