- Fluorogenic Ubiquinone Analogue for Monitoring Chemical and Biological Redox Processes
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We report herein the synthesis and characterization of a fluorogenic analogue of ubiquinone designed to reversibly report on redox reactions in biological systems. The analogue, H2B-Q, consists of the redox-active quinone segment found in ubiquinone, 2,3-dimethoxy-1,4-benzoquinone, coupled to a boron-dipyrromethene (BODIPY) fluorophore segment that both imparts lipophilicity in lieu of the isoprenyl tail of ubiquinone, and reports on redox changes at the quinone/quinol segment. Redox sensing is mediated by a photoinduced electron transfer intramolecular switch. In its reduced dihydroquinone form, H2B-QH2 is highly emissive in nonpolar media (quantum yields 55-66%), while once oxidized, the resulting quinone H2B-Q emission is suppressed. Cyclic voltammetry of H2B-Q shows two reversible, 1-electron reduction peaks at -1.05 V and -1.37 V (vs ferrocene) on par with those of ubiquinone. Chemical reduction of H2B-Q by NaBH4 resulted in >200 fold emission enhancement. H2B-QH2 is shown to react with peroxyl radicals, a form of reactive oxygen species (ROS) as well as to cooperatively interact with chromanol (the active segment of α-tocopherol). Kinetic analysis further shows the antioxidant reactivity of the nonfluorescent intermediate semiquinone. We anticipate that the H2B-Q/H2B-QH2 off/on reversible couple may serve as a tool to monitor chemical redox processes in real-time and in a noninvasive manner.
- Greene, Lana E.,Godin, Robert,Cosa, Gonzalo
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p. 11327 - 11334
(2016/11/05)
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- Synthetic studies on naturally occurring coumarins. II. Synthesis of 6,7-dimethoxy- and 7,8-dimethoxy-5-[(E)-3-oxo-1-butenyl]coumarins
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In connection with studies on the structure elucidation of the so-called Reisch's coumarin isolated from Toddalia asiatica, syntheses of two coumarins (4 and 5) were accomplished via the routes shown in Charts 2 and 3, respectively. Melting points and NMR data of the synthesized coumarins (4 and 5) and of related coumarins (5-methoxysuberenon, toddalenone, and Reisch's coumarin) are given in Table I, suggesting that so-called Reisch's coumarin might be 4.
- Ishii,Ishikawa,Wada,Miyazaki,Kaneko,Harayama
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p. 2614 - 2619
(2007/10/02)
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