during the development of a new regiospecific synthetic methodology for 1,5 dihydroxy- 9,lo-anthraquinone, it was observed that (anthrufin) preparative tlc of 1,2,3,4,5,6,7,8-octahydro-9,lo-dihyd roxy- 1,5-anthracenedione on silica gel produced a well-defined 1:l complex of the dione and an aerial oxidation product of it, the quinone dimethide 1,2,3,4,5,6,7- hexahydro-9,lo-dihydroxy-1 ,5-anthra...

During the development of a new regiospecific synthetic methodology for 1,5 dihydroxy- 9,lO-anthraquinone, it was observed that (anthrufin) preparative TLC of 1,2,3,4,5,6,7,8-octahydro-9,lO-dihyd roxy- 1,5-anthracenedione on silica gel produced a well-defined 1:l complex of the dione and an aerial oxidation product of it, the quinone dimethide 1,2,3,4,5,6,7- hexahydro-9,lO-dihydroxy-1 ,5-...

Troglitazone (TGZ) was the first glitazone used for the treatment of type II diabetes mellitus. TGZ undergoes an oxidative chroman ring-opening reaction to form a quinone product. Recently, cytochrome P450 (P450) was shown to be able to catalyze the formation of TGZ quinone. TGZ quinone was the major metabolite formed by dexamethasone-induced rat liver microsomes or myeloperoxidase (MPO) incuba...

Electrochemical characterization of topa quinone (6-hydroxydopa quinone), the organic cofactor of copper-containing amine oxidases, has been performed with the aid of spectroscopy and ab initio energy minimization technique. Topa quinone exhibits a totally reversible cyclic voltammogram at a mercury electrode, which is ascribed to a two-step one-electron conversion between topa quinone and topa...

The natural product hybrids quinone-mucocin and quinone- squamocin D were synthesized. In these hybrids, the butenolide unit of the annonaceous acetogenins mucocin and squamocin D is exchanged for the quinone moiety of the natural complex I substrate ubiquinone. For both syntheses, a modular, highly convergent approach was applied. Quinone-mucocin was constructed out of a tetrahydropyran (THP) ...

ortho-Quinones are produced in vivo through the oxidation of catecholic substrates by enzymes such as tyrosinase or by transition metal ions. Neuromelanin, a dark pigment present in the substantia nigra and locus coeruleus of the brain, is produced from dopamine (DA) and norepinephrine (NE) via an interaction with cysteine, but it also incorporates their alcoholic and acidic metabolites. In thi...

Quinone oxidoreductases are a class of membrane enzymes that catalyse the oxidation or reduction of membrane-bound quinols/quinones. The conversion of quinone/quinol by these enzymes is difficult to study because of the hydrophobic nature of the enzymes and their substrates. We describe some biochemical properties of quinones and quinone oxidoreductases and then look in more detail at two model...

Quinone molecules are intracellular electron-transport carriers, as well as critical intra- and extracellular signals. However, transcriptional regulation of quinone signaling and its molecular basis are poorly understood. Here, we identify a thiol-stress-sensing regulator YodB family transcriptional regulator as a central component of quinone stress response of Staphylococcus aureus, which we ...

[reaction: see text] A short synthesis of (+/-)-brazilin is reported. This synthesis uses several interesting and underutilized transformations including a regioselective dirhodium-catalyzed aryl C-H insertion, a regioselective IBX phenol --> o-quinone oxidation, a tautomerization of an o-quinone to a p-quinone methide, and an intramolecular aryl cyclization with a p-quinone methide.

Quinone(di)imines are nitrogen analogues of quinones in which one or both quinone oxygens are replaced by an imino group. A series of quinone(di)imines with antitumor activity has been studied for its in vitro chemical reactivity, metabolism, acute toxicity to primary cultured rat hepatocytes, and growth-inhibitory activity with Chinese hamster ovary (CHO) cells. The quinone(di)imines exhibited...