The 24th International Electronic Conference on Synthetic Organic Chemistry, 2020
In this work, the synthesis of thiohydantoins from L-amino acids and isothiocyanates was studied,... more In this work, the synthesis of thiohydantoins from L-amino acids and isothiocyanates was studied, using a high purity method based on the Edman cycle. This process, expected to occur through the Michael addition to a series of 1,4-naphthoquinone derivatives did not lead to the expected final product, rather leading to a colored mixture of compounds, where EPR spectra showed that some of them presented unpaired electrons, indicating that an electron transfer pathway was also involved in the reaction mixture. Detected organic radicals proved to be stable albeit with the use of different experimental conditions. Voltammetric results indicated that the reactions led to the formation of electroactive species, probably derived by homogeneous electron transfer between the reactive quinone moieties and the oxidizable urea functions within the hydantoin species.
We previously showed that microwave assisted synthesis is the best method for the synthesis of na... more We previously showed that microwave assisted synthesis is the best method for the synthesis of naphthoquinone amino acid and chloride-naphthoquinone amino acid derivatives by a complete evaluation of reaction conditions such as stoichiometry, bases, and pH influence. Following the same strategy, we synthesized chloride and non-chloride tyrosine, valine, and tryptophan-naphthoquinones achieving 85–95%, 80–92%, and 91–95% yields, respectively. The cyclic voltammetry profiles showed that both series of naphthoquinone amino acid derivatives mainly display one redox reaction process. Overall, chloride naphthoquinone amino acid derivatives exhibited redox potential values (E1/2) more positive than non-chloride compounds. The six newly synthesized compounds were tested in HPV positive and negative as well as in immortal and tumorigenic cell lines to observe the effects in different cellular context simulating precancerous and cancerous status. A dose-response was achieved to determine the ...
We performed an extensive analysis about the reaction conditions of the 1,4-Michael addition of a... more We performed an extensive analysis about the reaction conditions of the 1,4-Michael addition of amino acids to 1,4-naphthoquinone and substitution to 2,3-dichloronaphthoquinone, and a complete evaluation of stoichiometry, use of different bases, and the pH influence was performed. We were able to show that microwave-assisted synthesis is the best method for the synthesis of naphthoquinone–amino acid and chloride–naphthoquinone–amino acid derivatives with 79–91% and 78–91% yields, respectively. The cyclic voltammetry profiles showed that both series of naphthoquinone–amino acid derivatives mainly display one quasi-reversible redox reaction process. Interestingly, it was shown that naphthoquinone derivatives possess a selective antitumorigenic activity against cervix cancer cell lines and chloride–naphthoquinone–amino acid derivatives against breast cancer cell lines. Furthermore, the newly synthetized compounds with asparagine–naphthoquinones (3e and 4e) inhibited ~85% of SiHa cell p...
A new and efficient protocol to prepare 2-(R-anilino)-1,4-naphthoquinones in quantitative yields ... more A new and efficient protocol to prepare 2-(R-anilino)-1,4-naphthoquinones in quantitative yields is presented. This synthesis occurs under mild conditions by reacting the corresponding aniline and 1,4-naphthoquinone in the presence of a bentonitic clay. The role of the clay is explained in terms of a reaction mechanism in which an activated complex is formed by the reaction of 1,4-naphthoquinone with Lewis acid sites of the clay. Based on the chemical composition of the clay, with Fe 3+ sites, the last step of the mechanism is proposed to involve an oxidationreduction reaction. Keywords 2-Anilino-1,4-naphthoquinone Á Bentonitic clay Á Lewis acid Á Brönsted acid Á Acidic clay Á Fe +3
The 24th International Electronic Conference on Synthetic Organic Chemistry, 2020
In this work, the synthesis of thiohydantoins from L-amino acids and isothiocyanates was studied,... more In this work, the synthesis of thiohydantoins from L-amino acids and isothiocyanates was studied, using a high purity method based on the Edman cycle. This process, expected to occur through the Michael addition to a series of 1,4-naphthoquinone derivatives did not lead to the expected final product, rather leading to a colored mixture of compounds, where EPR spectra showed that some of them presented unpaired electrons, indicating that an electron transfer pathway was also involved in the reaction mixture. Detected organic radicals proved to be stable albeit with the use of different experimental conditions. Voltammetric results indicated that the reactions led to the formation of electroactive species, probably derived by homogeneous electron transfer between the reactive quinone moieties and the oxidizable urea functions within the hydantoin species.
We previously showed that microwave assisted synthesis is the best method for the synthesis of na... more We previously showed that microwave assisted synthesis is the best method for the synthesis of naphthoquinone amino acid and chloride-naphthoquinone amino acid derivatives by a complete evaluation of reaction conditions such as stoichiometry, bases, and pH influence. Following the same strategy, we synthesized chloride and non-chloride tyrosine, valine, and tryptophan-naphthoquinones achieving 85–95%, 80–92%, and 91–95% yields, respectively. The cyclic voltammetry profiles showed that both series of naphthoquinone amino acid derivatives mainly display one redox reaction process. Overall, chloride naphthoquinone amino acid derivatives exhibited redox potential values (E1/2) more positive than non-chloride compounds. The six newly synthesized compounds were tested in HPV positive and negative as well as in immortal and tumorigenic cell lines to observe the effects in different cellular context simulating precancerous and cancerous status. A dose-response was achieved to determine the ...
We performed an extensive analysis about the reaction conditions of the 1,4-Michael addition of a... more We performed an extensive analysis about the reaction conditions of the 1,4-Michael addition of amino acids to 1,4-naphthoquinone and substitution to 2,3-dichloronaphthoquinone, and a complete evaluation of stoichiometry, use of different bases, and the pH influence was performed. We were able to show that microwave-assisted synthesis is the best method for the synthesis of naphthoquinone–amino acid and chloride–naphthoquinone–amino acid derivatives with 79–91% and 78–91% yields, respectively. The cyclic voltammetry profiles showed that both series of naphthoquinone–amino acid derivatives mainly display one quasi-reversible redox reaction process. Interestingly, it was shown that naphthoquinone derivatives possess a selective antitumorigenic activity against cervix cancer cell lines and chloride–naphthoquinone–amino acid derivatives against breast cancer cell lines. Furthermore, the newly synthetized compounds with asparagine–naphthoquinones (3e and 4e) inhibited ~85% of SiHa cell p...
A new and efficient protocol to prepare 2-(R-anilino)-1,4-naphthoquinones in quantitative yields ... more A new and efficient protocol to prepare 2-(R-anilino)-1,4-naphthoquinones in quantitative yields is presented. This synthesis occurs under mild conditions by reacting the corresponding aniline and 1,4-naphthoquinone in the presence of a bentonitic clay. The role of the clay is explained in terms of a reaction mechanism in which an activated complex is formed by the reaction of 1,4-naphthoquinone with Lewis acid sites of the clay. Based on the chemical composition of the clay, with Fe 3+ sites, the last step of the mechanism is proposed to involve an oxidationreduction reaction. Keywords 2-Anilino-1,4-naphthoquinone Á Bentonitic clay Á Lewis acid Á Brönsted acid Á Acidic clay Á Fe +3
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