Stereochemical and mechanistic aspects of dioxygenase-catalysed benzylic hydroxylation of indene and chromane substrates
作者:Derek R. Boyd、Narain D. Sharma、Nigel I. Bowers、Rosemary Boyle、John S. Harrison、Kyoung Lee、Timothy D. H. Bugg、David T. Gibson
DOI:10.1039/b300898c
日期:2003.4.14
Toluene dioxygenase (TDO)-catalysed benzylic hydroxylation of indene substrates (8, 16 and 17), using whole cell cultures of Pseudomonas putida UV4, was found to yield inden-1-ol (14 and 22) and indan-1-one bioproducts (15 and 23). The formation of these bioproducts is consistent with the involvement of carbon-centred radical intermediates. TDO-catalysed oxidation of indenes 8 and 16 also gave cis-diols 13 and 18 respectively. TDO and naphthalene dioxygenase (NDO), used as both whole-cell preparations and as purified enzymes, were found to catalyse the benzylic hydroxylation of chromane 30, deuteriated (±)-chromane 30DDDDDDD and enantiomers (4S)-30DDDDDDD and (4R)-30DDDDDDD to yield (4R)- and (4S)-chroman-4-ols 31/31DDDDDD respectively. The mechanism of benzylic hydroxylation of chromane 30/30DDDDDDD involves the stereoselective abstraction of a pro-R
(with TDO) or a pro-S
(with NDO) hydrogen atom at C-4 and a marked preference for retention of configuration.
Mechanism of the Enantioselective Oxidation of Racemic Secondary Alcohols Catalyzed by Chiral Mn(III)−Salen Complexes
作者:M. Kevin Brown、Megan M. Blewett、James R. Colombe、E. J. Corey
DOI:10.1021/ja103103d
日期:2010.8.18
clarify the mechanism and origin of the enantioselectivity of the oxidation of racemicsecondaryalcoholscatalyzed by chiral Mn(III)-salen complexes using HOBr, Br(2)/H(2)O/KOAc or PhI(OAc)(2)/H(2)O/KBr as a stoichiometric oxidant. Key points of the proposed pathway include (1) the formation of a Mn(V)-salen dibromide, (2) its subsequent reaction with the alcohol to give an alkoxy-Mn(V) species, and
The reactions of flavin analogues and other heterocycles as models for bacterial bioluminescence
作者:F. McCapra、P.D. Leeson、V. Donovan、G. Perry
DOI:10.1016/s0040-4020(01)87387-7
日期:1986.1
The reactions of 10a-peroxyflavins have been examined to increase understanding of the oxidative and chemiluminescent reactions catalysed by the flavin co-enzymes. A remarkable series of structural requirements in the peroxides used has been uncovered, and in addition to serving as models for the mechanism of bacterial luciferase, they constitute a set of new chemiluminescent reactions.
Structural Effects on the β-Scission Reaction of Alkoxyl Radicals. Direct Measurement of the Absolute Rate Constants for Ring Opening of Benzocycloalken-1-oxyl Radicals
The absoluterateconstants for β-scission of a series of benzocycloalken-1-oxyl radicals and of the 2-(4-methylphenyl)-2-butoxyl radical have been measured directly by laser flash photolysis. The benzocycloalken-1-oxyl radicals undergo ring opening with rates which parallel the ring strain of the corresponding cycloalkanes. In the 1-X-indan-1-oxyl radical series, ring opening is observed when X =