771-16-4

Water-induced asymmetric ring opening: Enantio-enriched 2-hydroxy-1-tetralones are formed from oxabicyclic alkenes through a novel RhI-catalyzed domino reaction. The proposed mechanism involves water-induced asymmetric ring opening to generate chiral trans-1,2-diol intermediates and subsequent enantioselective isomerization (see scheme). Copyright

Benzene-cis- and trans-1,2-dihydrodiols undergo acid-catalyzed dehydration at remarkably different rates: kcis/ktrans = 4500. This is explained by formation of a β-hydroxycarbocation intermediate in different initial conformations, one of which is stabilized by hyperconjugation amplified by an aromatic no-bond resonance structure (HOC6H6 + HOC6H5 H+). MP2 calculations and an unfavorable effect of benzoannelation on benzenium ion stability, implied by pKR measurements of -2.3, -8.0, and -11.9 for benzenium, 1-naphthalenium, and 9-phenanthrenium ions, respectively, support the explanation.

Reported in this paper is the first example of a biomimetic iron complex, ([FeII(TPA)(NCMe)2]2+ (TPA = tris(2-pyridylmethyl)amine), that catalyses the cis-dihydroxylation of an aromatic double bond, mimicking the action of

The phdABCD gene cluster in a marine bacterium Nocardioides sp. strain KP7 codes for the multicomponent enzyme phenanthrene dioxygenase. phdA encoding an iron-sulfur protein large subunit alpha, phdB encoding its small subunit beta, phdC encoding ferredoxin, and phdD encoding ferredoxin reductase, were replaced in such a way that the termination codons of the preceding open reading frames were overlapped with the initiation codons of the following genes. This manipulated phdABCD gene cluster was positioned downstream of the thiostrepton-inducible promoter PtipA in a high-copy-number vector pIJ6021, and introduced into the gram-positive, soil-inhabiting, filamentous bacterium Streptomyces lividans. The recombinant S. lividans cells converted phenanthrene into a cis-diol form, which was determined to be cis-3,4-dihydroxy-3,4-dihydrophenanthrene by its UV spectral data as well as HPLC property, using the authentic sample for comparison. This biotransformation proceeded very efficiently; 200 microM and 2 mm of phenanthrene were almost completely converted to its cis-diol form in 6 h and 32 h, respectively. In addition, the S. lividans cells carrying the phdABCD gene cluster were found to transform 1-methoxynaphthalene to two products, which were identified to be 8-methoxy-2-naphthol in addition to 8-methoxy-1,2-dihydro-1,2-naphthalenediol by their EI-MS, 1H- and 13C-NMR spectral data.

1,2-dihydroxynaphthalenes are produced by bioconversion of the corresponding hydrocarbons using Escherichia coli recombinant strains containing the naphthalene dioxygenase and dehydrogenase genes cloned from pseudomonas fluorescens N3. Conversions are lead by a two step procedure without isolation of the dihydrodiol intermediate. Conversion rates depend on the position and nature of the naphthalene substituent.

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1,2-Naphthaquinone, 5-bromo-1,2-naphthaquinone and dibenzanthracene-3,4-quinone in the form of dibromo-intermediates were reduced to a mixture of cis- and trans-diols by the action of sodium borohydride in ethanol.An alternative synthesis of trans-3,4-dihydroxy-3,4-dihydrodibenzanthracene is also reported.

Terminal-ring trans-dihydro diol metabolites have been implicated as the ultimate carcinogenic forms of polycyclic aromatic hydrocarbons.Synthesis of these dihydro diols from the related polycyclic phenols in two steps via oxidation to the corresponding o-quinones with either Fremy's salt or phenylseleninic anhydride followed by stereospecific reduction with lithium aluminum hydride is described.The non-K-region quinones and trans-dihydro diols of naphthalene, anthracene, phenanthrene, benzanthracene, benzopyrene, and 7,12-dimethylbenzanthracene are synthesized via this approach.Although poor yields (1-4percent) were previously reported for the reduction of non-K-region quinones, an improved experimental procedure has been developed which affords the trans-dihydro diols free of the isomeric cis-dihydro diols in generally good yields.Major byproducts are the corresponding hydroquinones, previously undetected, and the related tetrahydro diols.The latter are the major products of reduction of the poorly soluble quinones of benzopyrene and benzanthracene and are shown to arise through further reduction of the dihydro diols.Since the tetrahydro diols are convertible to dihydro diols and the hydroquinones are reoxidizable to quinones, good overall conversions of quinones to dihydro diols are attainable. trans-3,4-Dihydroxy-3,4-dihydro-7,12-dimethylbenzanthracene synthesized in these studies is the most potent tumorigenic hydrocarbon metabolite tested to date.