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1.
J Org Chem ; 86(3): 2135-2157, 2021 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-33433196

RESUMO

A concise and diastereoselective construction of the ABCD ring system of spirochensilide A is described. The key steps of this synthesis are a semipinacol rearrangement reaction to stereoselectively construct the AB ring system bearing two vicinal quaternary chiral centers and a Co-mediated Pauson-Khand reaction to form the spiro-based bicyclic CD ring system. This chemistry leads to the stereoselective synthesis of 13(R)-demethyl spirochensilide A, paving the way for the first asymmetric total synthesis of (-)-spirochensilide A.

2.
J Org Chem ; 86(3): 2158-2172, 2021 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-33481592

RESUMO

The final phase of the total synthesis of (-)-spirochensilide A is described. A tungsten-mediated cyclopropene-based Pauson-Khand reaction was developed to form the spiral CD ring system with desired stereochemistry at the C13 quaternary center. Other important steps enabling completion of this synthesis included an intermolecular aldol condensation to link the ABCD core with the EF fragment and a Cu-mediated 1,4-addition to stereoselectively install the C21 stereogenic center. The chemistry developed for this total synthesis of (-)-spirochensilide A (1) will aid the synthesis of polycyclic natural products bearing this unique spiral ring system.

3.
J Org Chem ; 83(13): 6907-6923, 2018 07 06.
Artigo em Inglês | MEDLINE | ID: mdl-29508620

RESUMO

The asymmetric total synthesis of lancifodilactone G acetate was accomplished in 28 steps. The key steps in this synthesis include (i) an asymmetric Diels-Alder reaction for formation of the scaffold of the BC ring; (ii) an intramolecular ring-closing metathesis reaction for the formation of the trisubstituted cyclooctene using a Hoveyda-Grubbs II catalyst; (iii) an intramolecular Pauson-Khand reaction for construction of the sterically congested F ring; (iv) sequential cross-metathesis, hydrogenation, and lactonization reactions for installation of the anomerically stabilized bis-spiro ketal fragment of lancifodilactone G; and (v) a Dieckmann-type condensation reaction for installation of the A ring. The strategy and chemistry developed for the total synthesis will be useful in the synthesis of other natural products and complex molecules.

4.
J Am Chem Soc ; 139(40): 13989-13992, 2017 10 11.
Artigo em Inglês | MEDLINE | ID: mdl-28870073

RESUMO

The enantioselective synthesis of (-)-pavidolide B (1) was achieved in a linear sequence of 10 steps. The key steps are (a) an enantioselective organocatalytic cyclopropanation; (b) a radical-based cascade annulation for the regio- and diastereo-selective synthesis of the highly functionalized lactone 3 bearing the characteristic tricyclic core and seven contiguous stereocenters;


Assuntos
Produtos Biológicos/síntese química , Diterpenos/síntese química , Animais , Antozoários/química , Produtos Biológicos/química , Catálise , Ciclização , Diterpenos/química , Modelos Moleculares , Estereoisomerismo
5.
Org Lett ; 19(15): 3986-3989, 2017 08 04.
Artigo em Inglês | MEDLINE | ID: mdl-28726426

RESUMO

Novel oxazaborolidines activated by the strong acid triflimide or AlBr3 form cationic chiral catalysts. These are effective catalysts for highly regio- and enantioselective Diels-Alder reactions using substituted (E)-4-oxopent-2-enoates as dienophiles.

6.
J Am Chem Soc ; 139(16): 5732-5735, 2017 04 26.
Artigo em Inglês | MEDLINE | ID: mdl-28391693

RESUMO

Asymmetric total synthesis of structurally intriguing and highly oxygenated lancifodilactone G acetate (7) has been achieved for the first time in 28 steps from a cheap commodity chemical, 2-(triisopropylsiloxy)-1,3-butadiene.


Assuntos
Acetatos/síntese química , Triterpenos/síntese química , Acetatos/química , Cristalografia por Raios X , Modelos Moleculares , Conformação Molecular , Triterpenos/química
7.
Chem Asian J ; 11(9): 1414-24, 2016 05 06.
Artigo em Inglês | MEDLINE | ID: mdl-26991420

RESUMO

The enantioselective synthesis of the fully functionalized BCDE tetracyclic ring system of propindilactone G (A) is reported. Several synthetic methods were developed and applied to achieve this goal, including: 1) an asymmetric Diels-Alder reaction in the presence of Hayashi's catalyst for the synthesis of optically pure key intermediate 3; 2) an intramolecular Pauson-Khand reaction (PKR) for the stereoselective synthesis of the BCDE ring with an all-carbon chiral quaternary center at the C13 position by using the TMS-substituted acetylene as the substrate; and 3) Pd-catalyzed reductive hydrogenolysis for the stereoselective synthesis of the fully functionalized BCDE tetracyclic ring system. The chemistry developed herein provided a greater understanding of the total synthesis propindilactone G (A) and its analogues.


Assuntos
Compostos Heterocíclicos de 4 ou mais Anéis/síntese química , Triterpenos/síntese química , Catálise , Reação de Cicloadição , Compostos Heterocíclicos de 4 ou mais Anéis/química , Modelos Moleculares , Estrutura Molecular , Estereoisomerismo , Triterpenos/química
8.
Chem Asian J ; 11(9): 1425-35, 2016 05 06.
Artigo em Inglês | MEDLINE | ID: mdl-26991640

RESUMO

Two independent synthetic approaches were evaluated for the final phase of the asymmetric total synthesis of propindilactone G (1). The key steps that led to the completion of the asymmetric total synthesis included: 1) an intermolecular oxidative heterocoupling reaction of enolsilanes to link the core structure to the side chain; 2) an intermolecular Wittig reaction for the formation of the α,ß,γ,δ-unsaturated ester; and 3) a regio- and stereoselective OsO4 -catalyzed dihydroxylation of an α,ß,γ,δ-unsaturated enone, followed by an intramolecular lactonization reaction to afford the final product. These reactions enabled the synthesis of (+)-propindilactone G in only 20 steps. As a consequence of our synthetic studies, the structure of (+)-propindilactone G has been revised. Furthermore, the direct oxidative coupling strategy for ligation of the core of propindilactone G with its side chain may find application in the syntheses of other natural products and complex molecules.


Assuntos
Ésteres/síntese química , Cetonas/química , Triterpenos/síntese química , Produtos Biológicos/síntese química , Produtos Biológicos/química , Ésteres/química , Modelos Moleculares , Estrutura Molecular , Estereoisomerismo , Triterpenos/química
9.
Chem Asian J ; 11(9): 1406-13, 2016 05 06.
Artigo em Inglês | MEDLINE | ID: mdl-26991268

RESUMO

Our first-generation synthetic study towards the total synthesis of propindilactone G (1) and its analogues is reported. The key synthetic steps were an intramolecular Pauson-Khand reaction (PKR) and a vinylogous Mukaiyama reaction (VMAR). The stereoselective synthesis of the CDE ring moiety with an all-carbon quaternary center through a PKR was difficult, whilst a VMAR afforded a product with the opposite stereochemistry at the C20 position on the side chain. These results led us to redesign our synthetic strategy for the total synthesis of compound 1.


Assuntos
Triterpenos/síntese química , Modelos Moleculares , Conformação Molecular , Estereoisomerismo , Triterpenos/química
10.
J Am Chem Soc ; 137(32): 10120-3, 2015 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-26181605

RESUMO

A concise total synthesis of (+)-propindilactone G, a nortriterpenoid isolated from the stems of Schisandra propinqua var. propinqua, has been achieved for the first time. The key steps of the synthesis include an asymmetric Diels-Alder reaction, a Pauson-Khand reaction, a Pd-catalyzed reductive hydrogenolysis reaction, and an oxidative heterocoupling reaction. These reactions enabled the synthesis of (+)-propindilactone G in only 20 steps. As a consequence of our synthetic studies, the structure of (+)-propindilactone G has been revised.


Assuntos
Triterpenos/síntese química , Catálise , Técnicas de Química Sintética , Reação de Cicloadição , Oxirredução , Paládio/química , Schisandra/química , Triterpenos/química
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