Reaction of Lithium Aluminum Hydride with Elemental Selenium:  Its Application as a Selenating Reagent into Organic Molecules

Ishihara, Hideharu; Koketsu, Mamoru; Fukuta, Yoshihisa; Nada, Futoshi

doi:10.1021/ja005800o

Cited by 116 publications

(60 citation statements)

References 23 publications

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“…[14] Elemental Se was reduced with NaBH 4 in iPrOH and added to a mixture of N-(dichloromethylene)-N-methylmethanaminium chloride and the desired phenol in CH 2 Cl 2 . It was found that the formation of O-aryl selenocarbamates was sensitive to the choice of solvent, base, temperature, concentration, and the stoichiometry of the reagents.…”

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confidence: 99%

Conversion of Phenols into Selenophenols: Seleno Newman–Kwart Rearrangement

et al. 2013

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Conversion of Phenols into Selenophenols: Seleno Newman–Kwart Rearrangement

et al. 2013

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“…quently, LiAlHSeH (1 eq) 5) was added to the reaction mixture. The reaction mixture was further stirred at 0°C for 3 h. Assay of Tyrosinase Activity Tyrosinase activity was measured by determining its dopa oxidase activity using a modification of the method reported by Shono et al 6) Test substances were dissolved in MeOH to 1 mM, 500 mM, 100 mM, or 10 mM.…”

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confidence: 99%

Inhibition of Tyrosinase Activity by N,N-Unsubstituted Selenourea Derivatives

Koketsu

Lee

et al. 2005

Biological & Pharmaceutical Bulletin

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Melanin formation is the most important determinant of mammalian skin color. Melanin is secreted by melanocyte cells, which are distributed in the basal layer of the dermis. 1) One of the roles of melanin is to protect the skin and underlying tissues from UV-induced skin injury. However, excessive melanin production in the skin has negative hyperpigmenting effects such as melasma, freckles, and senile lentigines. The synthesis of melanin starts with the conversion of the amino acid L-tyrosine to L-dopa (3,4-dihydroxyphenylalanine), the subsequent oxidation of L-dopa then yields dopaquinone. Tyrosinase is the key enzyme in the biosynthesis of melanin, and participates in the oxidation of tyrosine to L-dopa, and of dopa to dopaquinone. 2,3) Therefore, tyrosinase inhibitors are accepted as important constituents of cosmetics and as depigmenting agents in cases of hyperpigmentation. 4) In this study, we investigated inhibitory effects of N,N-unsubstituted selenourea derivatives on mushroom tyrosinase and their depigmenting effect in melan-a cells. MATERIALS AND METHODS General MethodsMelting points were determined using a Yanagimoto micromelting point apparatus. IR spectra were obtained using a Perkin-Elmer 1600 spectrometer, and 1 H-and 13 C-NMR spectra were recorded on a JEOL-JNMa400 (400 MHz) spectrometer. Mass spectra were obtained using a Shimadzu 9020-DF mass spectrometer, and UV spectra using a Molecular Devices E09090 microplate reader.Materials Mushroom tyrosinase, L-dopa (3-(3,4-dihydroxyphenyl)-L-alanine), and kojic acid (5-hydroxy-2-(hydroxymethyl)-4H-pyran-4one) were purchased from Aldrich Chemical; Inc. (U.S.A.). Solvents used for organic syntheses were redistilled. All other chemicals and solvents were of analytical grade and used without further purification.Typical procedure for preparation of N,N-unsubstituted selenourea derivatives, 1 M HCl (2 eq) in diethyl ether was added to N,N-dimethylcyanamide (1 eq) of THF solution. The reaction mixture became milky white suspension from colorless solution in less than 30 s and then was stirred at 0°C for 2 h. The compound was formed in situ. Subsequently, LiAlHSeH (1 eq) 5) was added to the reaction mixture. The reaction mixture was further stirred at 0°C for 3 h. Assay of Tyrosinase Activity Tyrosinase activity was measured by determining its dopa oxidase activity using a modification of the method reported by Shono et al. 6) Test substances were dissolved in MeOH to 1 mM, 500 mM, 100 mM, or 10 mM. 120 ml of L-dopa (8 mM, dissolved in 67 mM phosphate buffer, pH 6.8) and 40 ml of either the same buffer or test sample were added to each well of a 96-well microplate, and then 40 ml of mushroom tyrosinase (125 U) This study investigated inhibitory effects of N,N-unsubstituted selenourea derivatives on tyrosinase activity. Three types of N,N-unsubstituted selenoureas derivatives exhibited inhibitory effect on dopa (3,4-dihydroxyphenylalanine) oxidase activity of mushroom tyrosinase. Compound D at a concentration of 200 m mM exhibited 55.5% of inhibition on dop...

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“…• C for 1 h under an argon atmosphere and then further stirred at room temperature for 3 h. LiAlHSeH [7] was added to the mixture. After the usual workup, N,N-dimethylselenobenzamide (2a) was obtained as …”

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confidence: 99%

“…LiAlHSeH was prepared in accordance with a previously described procedure [7]. The 77 Se chemical shifts were expressed in ppm deshielded with respect to neat Me 2 Se in CDCl 3 .…”

Section: Experimental Generalmentioning

confidence: 99%