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.
利用Pseudomonas putida UV4的全细胞培养物,通过甲苯双加氧酶(TDO)催化的苄位羟基化反应,对茚类底物(8、16和17)进行处理,得到了茚-1-醇(14和22)和茚满-1-酮生物产物(15和23)。这些生物产物的形成与碳中心自由基中间体的参与相符。TDO催化的氧化反应对茚8和16也分别产生了顺式二醇13和18。无论是作为全细胞制剂还是纯化酶,TDO和萘双加氧酶(NDO)都被发现能催化色满30、氘代(±)色满30DDDDDDD及其对映体(4S)-30DDDDDDD和(4R)-30DDDDDDD的苄位羟基化反应,分别生成(4R)-和(4S)-色满-4-醇31/31DDDDDD。色满30/30DDDDDDD的苄位羟基化机制涉及在C-4位上选择性地抽取一个对-R(与TDO)或对-S(与NDO)的氢原子,并有明显的构型保留倾向。