- N-Alkylation of 2-methoxy-10H-phenothiazine revisited. A facile entry to diversely N-substituted phenothiazine-coumarin hybrid dyes
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N-Alkylation of 2-methoxy-10H-phenothiazine, a valuable building block for the synthesis of bioactive compounds and reaction-based fluorescent probes, has been revisited aimed at introducing a substituent easily convertible into cationic or zwitterionic side chains. We focused our attention on the 3-dimethylaminopropyl group since its derivatization through reactions with various alkyl halides or sultones is a well-established and effective way to enhance polarity of diverse hydrophobic molecular scaffolds. This two-step functionalization approach was applied to the synthesis of novel phenothiazine-coumarin hybrid dyes whose spectral features, especially their NIR-I emission, have been determined in aqueous media with the ultimate goal of identifying novel fluorescent markers for bioanalytical applications, including fluorogenic detection of reactive oxygen species (ROS) through selective S-oxidation reaction of phenothiazine scaffold.
- Quesneau, Valentin,Renault, Kévin,Laly, Myriam,Jenni, Sébastien,Ponsot, Flavien,Romieu, Anthony
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- Photodegradation of 2-chloro substituted phenothiazines in alcohols
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The mechanisms that trigger the phototoxic response to 2- chlorophenothiazine derivatives are still unknown. To better understand the relationship between the molecular structure of halogenated phenothiazines and their phototoxic activity, their photophysics and photochemistry were studied in several alcohols. The photodestruction quantum yields were determined under anaerobic conditions using monochromatic light (313 nm). Absorption- and emission-spectroscopy, 1H- and 13C-NMR and GC-MS were used to characterize the photoproducts and reference compounds. An electron transfer mechanism had been previously proposed by Bunce et al. (J. Med. Chem. 22, 202-204) to explain the large difference between the photodestruction quantum yield of 2-chlorpromazine (φ = 0.46) and 2-chlorphenothiazine (φ = 0.20). According to these authors, the alkylamino chain transfers an electron to the phenothiazine moiety. Our results demonstrate that this mechanism is incorrect, because the photodestruction quantum yields of all chlorinated derivatives of this study are the same under the same conditions of solvent and irradiation wavelength. The quantum yield has no dependence on the 10-substituent, but it depends on the solvent. The percentage of each photoproduct, on the other hand, strongly depends on that substituent, but not very much on the solvent. Finally, it is demonstrated that the phototoxic effect of chlorinated phenothiazines is not related to the photodechlorination, although both processes share the same transient.
- Garcia, Carmelo,Pinero, Luis,Oyola, Rolando,Arce, Rafael
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experimental part
p. 160 - 170
(2009/04/10)
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- Cation Radicals of Phenothiazines. Part 4. Electron Transfer Between Aquamanganase(III) and N-Alkylphenothiazines
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The kinetics of electron transfer between aquamanganase(III) and N-alkylphenothiazines, giving rise to the corresponding cation radicals, has been investigated in the range 0.20-1.50 mol dm-3 HClO4 at different temperatures.The main reaction path has been assigned to the unhydrolysed species Mn(3+)(aq), and there is a dependence of the rate constants on the corresponding reduction potentials.
- Pelizzetti, Ezio
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p. 484 - 486
(2007/10/02)
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