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1.
Org Lett ; 2021 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-33528266

RESUMO

A new, efficient approach toward the preparation of 2-aryl-2,3-dihydrobenzofuran scaffolds through the Cu/SPDO-catalyzed [3 + 2] cycloaddition between quinone ester and styrene derivatives has been developed. The procedure features excellent enantioselectivities (up to 99% ee), high yields (up to 96%), and broad substrate tolerance. Additionally, asymmetric synthesis of natural corsifurans A and B from commercially available starting materials has also been achieved in two or three steps using this reaction as a key transformation.

2.
Angew Chem Int Ed Engl ; 60(13): 7061-7065, 2021 03 22.
Artigo em Inglês | MEDLINE | ID: mdl-33369843

RESUMO

A challenging direct asymmetric catalytic aerobic oxidative cross-coupling of 2-naphthylamine and 2-naphthol, using a novel CuI /SPDO system, has been successfully developed for the first time. Enantioenriched 3,3'-disubstituted NOBINs were achieved and could be readily derived to divergent chiral ligands and catalysts. This reaction features high enantioselectivities (up to 96 % ee) and good yields (up to 80 %). The DFT calculations suggest that the F-H interactions between CF3 of L17 and H-1,8 of 2-naphthol, and the π-π stacking between the two coupling partners could play vital roles in the enantiocontrol of this cross-coupling reaction.

3.
Nat Prod Bioprospect ; 2020 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-33146865

RESUMO

Three previously undescribed cytochalasins, named xylariasins A‒C (1‒3), together with six known ones (4‒9) were isolated from Xylaria sp. CFL5, an endophytic fungus of Cephalotaxus fortunei. The chemical structures of all new compounds were elucidated on the basis of extensive spectroscopic data analyses and electronic circular dichroism calculation, as well as optical rotation calculation. Biological activities of compounds 1, 4‒9 were evaluated, including cytotoxic, LAG3/MHC II binding inhibition and LAG3/FGL1 binding inhibition activities. Compounds 6 and 9 possessed cytotoxicity against AGS cells at 5 µM, with inhibition rates of 94% and 64%, respectively. In addition, all tested isolates, except compound 6, exhibited obvious inhibitory activity against the interaction of both LAG3/MHC II and LAG3/FGL1. Compounds 1, 5, 7, and 8 inhibited LAG3/MHC II with IC50 values ranging from 2.37 to 4.74 µM. Meanwhile, the IC50 values of compounds 1, 7, and 8 against LAG3/FGL1 were 11.78, 4.39, and 7.45 µM, respectively.

4.
J Org Chem ; 85(18): 11968-11974, 2020 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-32803967

RESUMO

Previously, we have finished the total synthesis of lycojaponicumin A (2) via development of an efficient synthetic strategy using semipinacol rearrangement as a key step. In order to further demonstrate the generality of this synthetic route, herein, we report the total synthesis of another fawcettimine-type alkaloid sieboldine A (1) from the same intermediate, which possesses an A/B/D tricyclic ring system and vicinal quaternary centers of 1. The synthesis features late-stage site-selective redox reactions, Schmidt glycosylation cyclization, and highly selective transformations.

5.
Angew Chem Int Ed Engl ; 59(49): 21954-21958, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32851781

RESUMO

A tandem Bischler-Napieralski/semipinacol rearrangement reaction has been developed for the purpose of assembling a bis(spirocyclic) indole framework, a privileged structural unit of aspidofractinine-type monoterpenoid indole alkaloids, and was used in combination with a subsequent Mannich reaction to expeditiously construct the central bridged bicyclo[2.2.1]heptane ring system of these molecules with contiguous quaternary centers. The development of this novel strategy culminated in the collective total synthesis of four aspidofractinine alkaloids.

6.
Org Lett ; 22(13): 4995-5000, 2020 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-32610934

RESUMO

A copper-catalyzed direct asymmetric coupling of C2 sterically-hindering-group-substituted indoles with quinone and naphthoquinone esters was developed by using the spirocyclic pyrrolidine oxazoline (SPDO) ligand, which was accomplished by metal catalysis for the first time. Diverse structures of axially chiral 3-arylindoles were obtained with good to high enantioselectivities in good to high yields. This protocol can be expanded to implement ß-coupling with naphthoquinone esters, providing an alternative way to prepare ß-substituted derivatives of both naphthols and naphthoquinones.

7.
Org Lett ; 22(10): 3775-3779, 2020 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-32330061

RESUMO

The efficient total synthesis of lycojaponicumin A (1) has been accomplished for the first time. The remarkable features of this novel strategy include the following: (1) rapid construction of tricyclic intermediate 4 through a regio- and stereoselective semipinacol ring expansion, which simplified the construction of rings A and B of 1; (2) the subsequent regio- and stereoselective formation of the highly strained rings C-E of 1 through a tandem oxa-hetero [3 + 2] cycloaddition/N-cycloalkylation.

8.
Angew Chem Int Ed Engl ; 59(22): 8471-8475, 2020 05 25.
Artigo em Inglês | MEDLINE | ID: mdl-32124524

RESUMO

An enantioselective aldehyde α-alkylation/semipinacol rearrangement was achieved through organo-SOMO catalysis. The catalytically generated enamine radical cation serves as a carbon radical electrophile that can stereoselectively add to the alkene of an allylic alcohol and initiate ensuing ring-expansion of cyclopropanol or cyclobutanol. This tandem reaction enables the production of a wide range of nonracemic functionalizable α-quaternary-δ-carbonyl cycloketones in high yields and excellent enantioselectivity from simple aldehydes and allylic alcohols. As a key step, the intramolecular reaction was also successfully applied in the asymmetric total synthesis of (+)-cerapicol.

9.
Org Lett ; 22(5): 2076-2080, 2020 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-32096637

RESUMO

A novel one-pot semipinacol rearrangement/Michael addition/Henry reaction of vinylogous α-ketols with nitroolefins has been achieved through the promotion of two Lewis acids, namely, TMSOTf and TiCl4, at temperatures between 0 and -78 °C. A range of synthetically challenging polyfunctionalized 6-5-5 and 7-5-5 fused tricyclic carbocycles bearing up to five continuous stereocenters, including one quaternary carbon center, are rapidly constructed in moderate to good yields with good to high diastereoselectivities in most cases.

10.
Chem Commun (Camb) ; 56(1): 121-124, 2020 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-31793962

RESUMO

A facile and environmentally benign KI(cat.)/NaBO3·4H2O oxidation system has been developed for the tandem oxidative aminocyclization/coupling of tryptamines, affording a series of 3a,3a'-bispyrrolidino[2,3-b]indolines with high efficiency (up to 94% yield). This reaction features an electrophilic "I+" mechanism, which is importantly quite different from and milder than the typical radical-involving process, and can be readily amplified for the total synthesis of (+)-WIN 64821.

11.
J Org Chem ; 84(19): 12664-12671, 2019 10 04.
Artigo em Inglês | MEDLINE | ID: mdl-31498620

RESUMO

The catalytic asymmetric total syntheses of the biologically important and therapeutically valuable Amaryllidaceae alkaloids (-)-galanthamine and (-)-lycoramine have been divergently achieved from commercially available 3-butyn-1-ol. A newly developed spirocyclic pyrrolidine (SPD)-catalyzed enantioselective Robinson annulation rapidly constructs the key cis-hydrodibenzofuran core, which bears an all-carbon quaternary stereocenter of the target molecules with an excellent stereoselective control. Additionally, the current asymmetric synthetic strategy provides an alternative approach toward the syntheses of (-)-galanthamine and its analogues.


Assuntos
Alcaloides de Amaryllidaceae/síntese química , Galantamina/síntese química , Pirrolidinas/química , Compostos de Espiro/química , Alcaloides de Amaryllidaceae/química , Catálise , Galantamina/química , Estrutura Molecular , Estereoisomerismo
12.
Angew Chem Int Ed Engl ; 58(36): 12491-12496, 2019 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-31293063

RESUMO

An enantioselective sulfenylation/semipinacol rearrangement of 1,1-disubstituted and trisubstituted allylic alcohols was accomplished with a chiral Lewis base and a chiral Brønsted acid as cocatalysts, generating various ß-arylthio ketones bearing an all-carbon quaternary center in moderate to excellent yields and excellent enantioselectivities. These chiral arylthio ketone products are common intermediates with many applications, for example, in the design of new chiral catalysts/ligands and the total synthesis of natural products. Computational studies (DFT calculations) were carried out to explain the enantioselectivity and the role of the chiral Brønsted acid. Additionally, the synthetic utility of this method was exemplified by an enantioselective total synthesis of (-)-herbertene and a one-pot synthesis of a chiral sulfoxide and sulfone.

13.
Nat Commun ; 10(1): 3394, 2019 07 29.
Artigo em Inglês | MEDLINE | ID: mdl-31358765

RESUMO

The proline-type organocatalysts has been efficiently employed to catalyze a wide range of asymmetric transformations; however, there are still many synthetically useful and challenging transformations that remain unachievable in an asymmetric fashion. Herein, a chiral bifunctional organocatalyst with a spirocyclic pyrrolidine backbone-derived containing fluoro-alkyl and aryl sulfonamide functionalities, are designed, prepared, and examined in the asymmetric Mannich/acylation/Wittig reaction sequence of 3,4-dihydro-ß-carboline with acetaldehyde, acyl halides, and Wittig reagents. As a result, the spirocyclic pyrrolidine trifluoromethanesulfonamide catalyst can facilitate this versatile sequence as demonstrated by 18 examples displaying excellent enantioselectivity (up to 94% ee), as well as moderate to good yields (up to 54% over 3 steps). As a practical application, the asymmetric total synthesis of naucleofficine I (1a) and II (1b) in ten steps have been accomplished.

14.
Nat Commun ; 10(1): 2507, 2019 06 07.
Artigo em Inglês | MEDLINE | ID: mdl-31175289

RESUMO

(‒)-Morphine, which is selected as an essential medicine by World Health Organization, is widely applied in the treatment of the pain-related diseases. Due to its synthetically challenging molecular architecture and important clinical role, extensive synthetic studies of morphine-type alkaloids have been conducted. However, catalytic asymmetric total synthesis of (‒)-morphine remains a long-standing challenge. Here, we disclose an efficient enantioselective total synthesis of (‒)-morphine in a longest linear sequence of 16 steps. The key transformation features a highly enantioselective Robinson annulation enabled by our spiro-pyrrolidine catalyst to rapidly construct the densely functionalized cis-hydrodibenzofuran framework containing vicinal stereocenters with an all-carbon quaternary center. This asymmetric approach provides an alternative strategy for the synthesis of (‒)-morphine and its analogues.


Assuntos
Analgésicos Opioides/síntese química , Morfina/síntese química , Benzofuranos/síntese química , Carbono , Estereoisomerismo
15.
Angew Chem Int Ed Engl ; 58(32): 11023-11027, 2019 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-31131524

RESUMO

A novel chiral 1,5-N,N-bidentate ligand based on a spirocyclic pyrrolidine oxazoline backbone was designed and prepared, and it coordinates CuBr in situ to form an unprecedented catalyst that enables efficient oxidative cross-coupling of 2-naphthols. Air serves as an external oxidant and generates a series of C1 -symmetric chiral BINOL derivatives with high enantioselectivity (up to 99 % ee) and good yield (up to 87 %). This approach is tolerant of a broader substrates scope, particularly substrates bearing various 3- and 3'-substituents. A preliminary investigation using one of the obtained C1 -symmetric BINOL products was used as an organocatalyst, exhibiting better enantioselectivity than the previously reported organocatalyst, for the asymmetric α-alkylation of amino esters.

16.
Org Lett ; 21(8): 2536-2540, 2019 04 19.
Artigo em Inglês | MEDLINE | ID: mdl-30945551

RESUMO

The first examples of electrochemical trifluoromethylation and sulfonylation/semipinacol rearrangements of allylic alcohols were developed using cheap and stable RSO2Na (R = CF3, Ph) as reagents. Various ß-trifluoromethyl and sulfonated ketones were obtained in moderate to excellent yields. This strategy provides a facile, direct, and complementary approach to construct all-carbon quaternary stereocenters. In addition, the reaction has the advantages of being chemical oxidant-free and metal-free and has safe and mild reaction conditions.

17.
Chem Commun (Camb) ; 55(26): 3789-3792, 2019 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-30864584

RESUMO

A facile and efficient method to form a chiral multi-substituted 3H-spiro[benzofuran-2,1'-cyclopentane] structural unit has been developed via a one-pot [3+2] cyclization/semipinacol rearrangement cascade. A catalysis system of Cu(ii)/BOX has been used to efficiently construct a key stereogenic center via a cyclization between substituted benzoquinones and allylic alcohols affording the desired products in good yields and with excellent enantioselectivities and diastereoselectivities (21 examples; up to 67% yields; up to 92% ee and up to >20 : 1 dr). This method provides an alternative strategy for the synthesis of the corresponding bioactive molecules containing spiro[benzofurancyclopentane] skeleton units.

18.
Angew Chem Int Ed Engl ; 57(40): 13192-13196, 2018 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-30126040

RESUMO

An efficient oximation method has been developed on the basis of NO+ -initiated semipinacol rearrangement and subsequent proton elimination. The procedure enabled the rapid construction of a series of oximes and oxime ethers with spiro quaternary stereocenters from allylic silyl ethers. Additional features of this reaction include wide substrate tolerance as well as the commercial availability of the safe nitrosation reagent NOBF4 . The key N-heterotricyclic cores of three natural alkaloids, tuberostemoninol B, (+)-quebrachidine, and an insecticide, were also constructed efficiently by this method.

19.
J Am Chem Soc ; 140(32): 10099-10103, 2018 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-30067344

RESUMO

A novel chiral spirocyclic amide (SPA)-derived triazolium organocatalyst has been designed and demonstrated to effect asymmetric homo- and heterodialkylations of various bisoxindoles, enabling enantioselective construction of vicinal all-carbon quaternary stereocenters. These reactions feature excellent enantio- and diastereoselectivities (up to 99% ee and >20:1 dr) as well as good to high yields (up to 89% over two steps). As an application of this methodology, the first asymmetric total synthesis of (-)-chimonanthidine has been achieved.

20.
Org Lett ; 20(14): 4227-4230, 2018 07 20.
Artigo em Inglês | MEDLINE | ID: mdl-29969276

RESUMO

A new and modular electrophilic trifluoromethylthiolation/semipinacol rearrangement of allylic silyl ethers has been developed under mild conditions. This approach allows the formation of a number of ß-SCF3 carbonyl compounds with a cyclic and all-carbon quaternary center framework in moderate to good yields. It should be noted that this achievement is a metal-free process and just requires the use of simple acetyl chloride as an acidic promoter. Additionally, an interesting H-migration in competition with aryl-migration process was revealed.

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