Stereochemical and mechanistic aspects of dioxygenase-catalysed benzylic hydroxylation of indene and chromane substrates.
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 30D and enantiomers (4S)-30D and (4R)-30D to yield (4R)- and (4S)-chroman-4-ols 31/31D respectively. The mechanism of benzylic hydroxylation of chromane 30/30D 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.
Boyd
Derek R
DR
School of Chemistry, Queen's University of Belfast, Belfast, UK BT9 5AG. dr.boyd@qub.ac.uk
Sharma
Narain D
ND
Bowers
Nigel I
NI
Boyle
Rosemary
R
Harrison
John S
JS
Lee
Kyoung
K
Bugg
Timothy D
TD
Gibson
David T
DT
D002839:Chromans / Q000378:metabolism*; D006900:Hydroxylation; D007192:Indenes / Q000378:metabolism*; D010105:Oxygenases / Q000378:metabolism*; D016958:Pseudomonas putida / Q000201:enzymology; D013379:Substrate Specificity
D002839:Chromans; D007192:Indenes; C093581:indene; D010105:Oxygenases; C023172:toluene dioxygenase