An unexpected reaction pathway in the synthesis of the ABCE framework of strychnine-type alkaloids – A multidisciplinary study

Šoral, Michal; Markus, Jozef; Doháňošová, Jana; Šoralová, Stanislava; Dvoranová, Dana; Chyba, Andrej; Moncóľ, Ján; Berkeš, Dušan; Liptaj, Tibor

doi:10.1016/j.molstruc.2016.08.014

Cited by 4 publications

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“…It is noteworthy that the reaction is highly stereoselective and in all cases, only one diastereomer of spirocylic product 24c was observed. A related result with allyl group instead of CH 2 OTBS was published by us recently using the same base in THF, but the dr. of the spiroindolenine obtained was only of 91:9 . Furthermore, due to the high steric hindrance of N ‐chloroacetyl function and O ‐silyl protecting group configuration, the NMR spectrum of 24c is a mixture of rotamers (see Supporting Information for details).…”

Section: Resultsmentioning

confidence: 99%

Indolylglycines Backbones in the Synthesis of Enantiopure 3,3‐Spiroindolenines, Indolyl Tetracyclic Hemiaminals, and 3‐Indolyl‐maleimides Frameworks

et al. 2019

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This paper describes the synthesis of novel N‐substituted 3‐indolylglycines (3IGs), in high yields and optical purity via three‐component Mannich reaction (3CR) of indole and free glyoxylic acid in the presence of primary and secondary aliphatic amines. By using this efficient approach, a series of racemic 3‐indolylglycines (3IGs) as well as the optically pure (S)‐3‐indolylglycine ((S)‐3IG) in multigram synthesis using (R‐1‐phenylethylamine ((R)‐α‐PEA) as chiral pool were synthetized. In parallel investigations, 3IGs were used as the starting material for the highly stereoselective synthesis of spiroindolenines bearing three controlled contiguous stereogenic centers. Despite our expectations, the N‐chloroacetyl esters of 3IGs did not provide the expected spiroindolenine derivatives but led us to the discovery of a new methodology for the preparation of 3‐indolylmaleimides (3IMs); compounds known for their broad range of important biological and fluorescence activities.

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Section: Resultsmentioning

confidence: 99%

Indolylglycines Backbones in the Synthesis of Enantiopure 3,3‐Spiroindolenines, Indolyl Tetracyclic Hemiaminals, and 3‐Indolyl‐maleimides Frameworks

et al. 2019

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5‐(Cyano)dibenzothiophenium Triflate: A Sulfur‐Based Reagent for Electrophilic Cyanation and Cyanocyclizations

Golz

Alcarazo

2019

Angewandte Chemie

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The synthesis of 5-(cyano)dibenzothiophenium triflate 9,p repared by activation of dibenzo [b,d]thiophene-5oxide with Tf 2 Oa nd subsequent reaction with TMSCN is reported, and its reactivity as electrophilic cyanation reagent evaluated. The scalable preparation, easy handling and broad substrate scope of the electrophilic cyanation promoted by 9, which includes amines,thiols,silyl enol ethers,alkenes,electron rich (hetero)arenes and polyaromatic hydrocarbons,i llustrate the synthetic potential of this reagent. Importantly,Lewis acid activation of the reagent is not required for the transfer process. We additionally report herein biomimetic cyanocyclization cascade reactions,w hich are not promoted by typical electrophilic cyanation reagents,demonstrating the superior ability of 9 to trigger challenging transformations.Scheme 5. Reaction scope of the electrophilic cyanation-Povarov cascade. Reagents, conditions: a) 9 (1.0-1.5 equiv),r .t.,CH 2 Cl 2 ,3 -36 h; b) 9 (1.5 equiv), r.t.,C H 2 Cl 2 ,1 1-36 h. a Diasteromeric mixture (8:1 ratio);t he second diasteromer only differs in the configuration of the carbon marked (*). Molecular structures of compounds 65 and 70 in the solid state. Anisotropic displacement shown at 50 %p robability level. Only selected hydrogen atoms are shown. [24] Angewandte Chemie

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5‐(Cyano)dibenzothiophenium Triflate: A Sulfur‐Based Reagent for Electrophilic Cyanation and Cyanocyclizations

Golz

Alcarazo

2019

Angew Chem Int Ed

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The synthesis of 5‐(cyano)dibenzothiophenium triflate 9 , prepared by activation of dibenzo[b,d]thiophene‐5‐oxide with Tf 2 O and subsequent reaction with TMSCN is reported, and its reactivity as electrophilic cyanation reagent evaluated. The scalable preparation, easy handling and broad substrate scope of the electrophilic cyanation promoted by 9 , which includes amines, thiols, silyl enol ethers, alkenes, electron rich (hetero)arenes and polyaromatic hydrocarbons, illustrate the synthetic potential of this reagent. Importantly, Lewis acid activation of the reagent is not required for the transfer process. We additionally report herein biomimetic cyanocyclization cascade reactions, which are not promoted by typical electrophilic cyanation reagents, demonstrating the superior ability of 9 to trigger challenging transformations.

show abstract

An unexpected reaction pathway in the synthesis of the ABCE framework of strychnine-type alkaloids – A multidisciplinary study

Cited by 4 publications

References 28 publications

Indolylglycines Backbones in the Synthesis of Enantiopure 3,3‐Spiroindolenines, Indolyl Tetracyclic Hemiaminals, and 3‐Indolyl‐maleimides Frameworks

Indolylglycines Backbones in the Synthesis of Enantiopure 3,3‐Spiroindolenines, Indolyl Tetracyclic Hemiaminals, and 3‐Indolyl‐maleimides Frameworks

5‐(Cyano)dibenzothiophenium Triflate: A Sulfur‐Based Reagent for Electrophilic Cyanation and Cyanocyclizations

5‐(Cyano)dibenzothiophenium Triflate: A Sulfur‐Based Reagent for Electrophilic Cyanation and Cyanocyclizations

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