Unexpected transformations of 3-(bromoacetyl)coumarin provides new evidence for the mechanism of thiol mediated dehalogenation of α-halocarbonyls
- Magwenzi, Faith N, Khanye, Setshaba D, Veale, Clinton G L
- Authors: Magwenzi, Faith N , Khanye, Setshaba D , Veale, Clinton G L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66200 , vital:28916 , https://doi.org/10.1016/j.tetlet.2017.01.082
- Description: publisher version , The mechanism for the thiol mediated dehalogenation of α-halogenated carbonyls has remained an unresolved problem, despite its ongoing application in synthetic organic chemistry. Nakamura and co-workers first proposed that net dehalogenation occurs via sequential nucleophilic substitutions, while Israel and co-workers concluded that the rate at which dehalogenation occurred suggested that dehalogenation proceeds in a single concerted step. In this study, we investigated the debromination and nucleophilic substitution of 3-(bromoacetyl)coumarin with a variety of thiophenols, whose electron donating or withdrawing natures resulted in large variations in the degree of nucleophilic substitution and dehalogenation products, respectively. Results from these experiments, in addition to an unexpected formation of thioether containing dibenzo[b,d]pyran-6-ones from a Robinson annulation, has provided new evidence for this disputed mechanism.
- Full Text: false
- Date Issued: 2017
- Authors: Magwenzi, Faith N , Khanye, Setshaba D , Veale, Clinton G L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66200 , vital:28916 , https://doi.org/10.1016/j.tetlet.2017.01.082
- Description: publisher version , The mechanism for the thiol mediated dehalogenation of α-halogenated carbonyls has remained an unresolved problem, despite its ongoing application in synthetic organic chemistry. Nakamura and co-workers first proposed that net dehalogenation occurs via sequential nucleophilic substitutions, while Israel and co-workers concluded that the rate at which dehalogenation occurred suggested that dehalogenation proceeds in a single concerted step. In this study, we investigated the debromination and nucleophilic substitution of 3-(bromoacetyl)coumarin with a variety of thiophenols, whose electron donating or withdrawing natures resulted in large variations in the degree of nucleophilic substitution and dehalogenation products, respectively. Results from these experiments, in addition to an unexpected formation of thioether containing dibenzo[b,d]pyran-6-ones from a Robinson annulation, has provided new evidence for this disputed mechanism.
- Full Text: false
- Date Issued: 2017
Indolyl-3-ethanone-α-thioethers: a promising new class of non-toxic antimalarial agents
- Svogie, Archibald L, Isaacs, Michelle, Hoppe, Heinrich C, Khanye, Setshaba D, Veale, Clinton G L
- Authors: Svogie, Archibald L , Isaacs, Michelle , Hoppe, Heinrich C , Khanye, Setshaba D , Veale, Clinton G L
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66233 , vital:28920 , https://doi.org/10.1016/j.ejmech.2016.02.056
- Description: publisher version , The success of chemotherapeutics in easing the burden of malaria is under continuous threat from ever-evolving parasite resistance, including resistance to artemisinin combination therapies. Therefore, the discovery of new classes of antimalarials which inhibit new biological targets is imperative to controlling malaria. Accordingly, we report here the discovery of indolyl-3-ethanone-α-thioethers, a new class of antimalarial compounds with encouraging activity. Synthesis of a focused library of compounds revealed important insight into the SAR of this class of compounds, including critical information regarding the position and chemical nature of substituents on both the thiophenol and indole rings. This investigation ultimately led to the discovery of two hit compounds (16 and 27) which exhibited nano molar in vitro antimalarial activity coupled to no observable toxicity against a HeLa cell line.
- Full Text: false
- Date Issued: 2016
- Authors: Svogie, Archibald L , Isaacs, Michelle , Hoppe, Heinrich C , Khanye, Setshaba D , Veale, Clinton G L
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66233 , vital:28920 , https://doi.org/10.1016/j.ejmech.2016.02.056
- Description: publisher version , The success of chemotherapeutics in easing the burden of malaria is under continuous threat from ever-evolving parasite resistance, including resistance to artemisinin combination therapies. Therefore, the discovery of new classes of antimalarials which inhibit new biological targets is imperative to controlling malaria. Accordingly, we report here the discovery of indolyl-3-ethanone-α-thioethers, a new class of antimalarial compounds with encouraging activity. Synthesis of a focused library of compounds revealed important insight into the SAR of this class of compounds, including critical information regarding the position and chemical nature of substituents on both the thiophenol and indole rings. This investigation ultimately led to the discovery of two hit compounds (16 and 27) which exhibited nano molar in vitro antimalarial activity coupled to no observable toxicity against a HeLa cell line.
- Full Text: false
- Date Issued: 2016
Facile synthesis and biological evaluation of assorted indolyl-3-amides and esters from a single, stable carbonyl nitrile intermediate
- Veale, Clinton G L, Edkins, Adrienne L, de la Mare, Jo-Anne, de Kock, Carmen, Smith, Peter J, Khanye, Setshaba D
- Authors: Veale, Clinton G L , Edkins, Adrienne L , de la Mare, Jo-Anne , de Kock, Carmen , Smith, Peter J , Khanye, Setshaba D
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66221 , vital:28919 , https://doi.org/10.1016/j.tetlet.2015.02.090
- Description: publisher version , The synthesis of biologically relevant amides and esters is routinely conducted under complex reaction conditions or requires the use of additional catalysts in order to generate sensitive electrophilic species for attack by a nucleophile. Here we present the synthesis of different indolic esters and amides from indolyl-3-carbonyl nitrile, without the requirement of anhydrous reaction conditions or catalysts. Additionally, we screened these compounds for potential in vitro antimalarial and anticancer activity, revealing 1H-indolyl-3-carboxylic acid 3-(indolyl-3-carboxamide)aminobenzyl ester to have moderate activity against both lines.
- Full Text: false
- Date Issued: 2015
- Authors: Veale, Clinton G L , Edkins, Adrienne L , de la Mare, Jo-Anne , de Kock, Carmen , Smith, Peter J , Khanye, Setshaba D
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66221 , vital:28919 , https://doi.org/10.1016/j.tetlet.2015.02.090
- Description: publisher version , The synthesis of biologically relevant amides and esters is routinely conducted under complex reaction conditions or requires the use of additional catalysts in order to generate sensitive electrophilic species for attack by a nucleophile. Here we present the synthesis of different indolic esters and amides from indolyl-3-carbonyl nitrile, without the requirement of anhydrous reaction conditions or catalysts. Additionally, we screened these compounds for potential in vitro antimalarial and anticancer activity, revealing 1H-indolyl-3-carboxylic acid 3-(indolyl-3-carboxamide)aminobenzyl ester to have moderate activity against both lines.
- Full Text: false
- Date Issued: 2015
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